BONDING WIRE FOR SEMICONDUCTOR DEVICE

Abstract

A bonding wire for a semiconductor device includes a Cu alloy core material and a Pd coating layer formed on a surface thereof. Containing an element that provides bonding reliability in a high-temperature environment improves the bonding reliability of the ball bonded part in high temperature. Furthermore, making an orientation proportion of a crystal orientation <100> angled at 15 degrees or less to a wire longitudinal direction among crystal orientations in the wire longitudinal direction 30% or more when measuring crystal orientations on a cross-section of the core material in a direction perpendicular to a wire axis of the bonding wire, and making an average crystal grain size in the cross-section of the core material in the direction perpendicular to the wire axis of the bonding wire 0.9 to 1.5 m provides a strength ratio of 1.6 or less.

Claims

1. A bonding wire for a semiconductor device, the bonding wire comprising: a Cu alloy core material; and a Pd coating layer formed on a surface of the Cu alloy core material, wherein when measuring crystal orientations on a cross-section of the core material in a direction perpendicular to a wire axis of the bonding wire, a crystal orientation <100> angled at 15 degrees or less to a wire longitudinal direction has a proportion of 30% or more among crystal orientations in the wire longitudinal direction, an average crystal grain size in the cross-section of the core material in the direction perpendicular to the wire axis of the bonding wire is 0.9 m or more and 1.5 m or less, and the bonding wire contains one or more elements selected from Co, Rh, Ir, Ni, Pd, Pt, Ag, Au, Zn, Al, In, Sn, P, As, Sb, Bi, Se and Te.

2. The bonding wire for a semiconductor device according to claim 1, wherein a strength ratio defined by the following Equation (1) is 1.1 or more and 1.6 or less:
Strength ratio=ultimate strength/0.2% offset yield strength.(1)

3. The bonding wire for a semiconductor device according to claim 1, wherein a thickness of the Pd coating layer is 0.015 m or more and 0.150 m or less.

4. The bonding wire for a semiconductor device according to claim 1, further comprising an alloy skin layer containing Au and Pd on the Pd coating layer.

5. The bonding wire for a semiconductor device according to claim 4, wherein a thickness of the alloy skin layer containing Au and Pd is 0.050 m or less.

6. The bonding wire for a semiconductor device according to claim 1, wherein the bonding wire contains at least one element selected from Ni, Zn, Rh, In, Ir and Pt, and a concentration of the at least one element in total is 0.011% by mass or more and 2% by mass or less relative to the entire wire.

7. The bonding wire for a semiconductor device according to claim 1, wherein the bonding wire contains one or more elements selected from As, Te, Sn, Sb, Bi and Se, a concentration of the elements in total is 0.1 ppm by mass or more and 100 ppm by mass or less relative to the entire wire, and Sn10 ppm by mass; Sb10 ppm by mass; and Bi1 ppm by mass.

8. The bonding wire for a semiconductor device according to claim 1, wherein the bonding wire further contains at least one element selected from B, P, Mg, Ca and La, and a concentration of each of the at least one element is 1 ppm by mass or more and 200 ppm by mass or less relative to the entire wire.

9. The bonding wire for a semiconductor device according to claim 1, wherein Cu is present at an outermost surface of the bonding wire.

10. The bonding wire for a semiconductor device according to claim 1, wherein the Cu alloy core material contains a metallic element of Group 10 of the Periodic Table of Elements in a total amount of 0.1% by mass or more and 3.0% by mass or less, and a concentration of Cu at an outermost surface of the wire is 1 at % or more.

Description

EXAMPLES

[0078] The bonding wires according to embodiments of the present invention will be described in detail below with reference to examples.

Working Examples 1 to 59 and Comparative Examples 1 to 16

[0079] (Manufacture of Sample)

[0080] First, the following describes a method for manufacturing a sample. For Cu as a raw material of a core material, Cu with a purity of 99.99% by mass or more and containing inevitable impurities as the remainder was used. For Au, Pd, Ni, Zn, Rh, In, Ir and Pt, the ones with a purity of 99% by mass or more and containing inevitable impurities as the remainder were used. Additive elements to the core material (Ni, Zn, Rh, In, Ir and Pt) are mixed so that the wire or the core material will have a desired composition. Regarding the addition of Ni, Zn, Rh, In, Ir and Pt, they can be mixed singly. Alternatively, they may be mixed so as to be a desired amount using a Cu master alloy containing the additive elements manufactured in advance if the element has a high melting point as a single body or if the element is added in an infinitesimal amount. Working examples 27 to 47 further contain one or more of Ga, Ge, As, Te, Sn, Sb, Bi, Se, B, P, Mg, Ca and La.

[0081] The Cu alloy as the core material was manufactured to give a wire diameter of a few millimeters by continuous casting. The obtained alloy with a diameter of a few millimeters was drawn to manufacture a wire with a diameter of 0.3 to 1.4 mm. A commercially available lubricant was used for the wire drawing, and a wire drawing speed was 20 to 150 m/min. In order to remove an oxide film on a surface of wire, pickling treatment with hydrochloric acid or the like was performed, and a Pd coating layer was formed by 1 to 15 m so as to cover the entire surface of the Cu alloy as the core material. Furthermore, for some wires, an alloy skin layer containing Au and Pd was formed by 0.05 to 1.5 m on the Pd coating layer. For the formation of the Pd coating layer and the alloy skin layer containing Au and Pd, electroplating was used. A commercially available semiconductor plating solution was used for a plating solution. Thereafter, wire drawing was performed mainly using dies with an area reduction rate of 10 to 21%, and furthermore, one to three pieces of heat treatment were performed at 200 to 500 C. during the wire drawing to perform working to a diameter of 20 m. After working, heat treatment was performed so that breaking elongation would finally be about 5 to 15%. A method of heat treatment was performed while successively sweeping the wire and was carried out while flowing an N.sub.2 or Ar gas. A wire feeding speed was 10 to 90 m/min, a heat treatment temperature was 350 to 500 C., and a heat treatment time was 1 to 10 seconds.

[0082] (Method of Evaluation)

[0083] The contents of Ni, Zn, Rh, In, Ir, Pt, Ga, Ge, As, Te, Sn, Sb, Bi, Se, B, P, Mg, Ca and La in the wire were analyzed as the concentrations of the elements contained in the entire bonding wire using an ICP emission spectrometer.

[0084] For the concentration analysis of the Pd coating layer and the alloy skin layer containing Au and Pd, Auger electron spectrometry was performed while trimming the bonding wire from its surface in the depth direction by sputtering or the like. From an obtained concentration profile in the depth direction, a thickness of the Pd coating layer, a maximum concentration of Pd in the Pd coating layer and a thickness of the alloy skin layer containing Au and Pd were determined.

[0085] The orientation proportion of the crystal orientation <100> angled at 15 degrees or less to the wire longitudinal direction among the crystal orientations in the wire longitudinal direction in the cross-section of the core material in the direction perpendicular to the wire axis of the bonding wire was calculated by observing crystal orientations of an observation surface (that is, the cross-section of the core material in the direction perpendicular to the wire axis) by EBSD. For the analysis of EBSD measurement data, exclusive software (OIM analysis manufactured by TSL Solutions, for example) was used. The average crystal grain size in the cross-section of the core material in the direction perpendicular to the wire axis was calculated by observing the crystal orientations on the observation surface by EBSD. For the analysis of EBSD measurement data, exclusive software (OIM analysis manufactured by TSL Solutions, for example) was used. The crystal grain size was obtained by performing an arithmetic mean on an equivalent diameter of crystal grains contained in a measurement area (the diameter of a circle equivalent to an area of a crystal grain; a circle-equivalent diameter).

[0086] The 0.2% offset yield strength and the ultimate strength were evaluated by performing a tensile test with an inter-mark distance of 100 mm. A universal material test machine Type 5542 manufactured by Instron was used for a tensile test apparatus. The 0.2% offset yield strength was calculated using exclusive software installed in the apparatus. A load at the time of breaking was determined to be the ultimate strength. The strength ratio was calculated from the following Equation (1)

Strength ratio=ultimate strength/0.2% offset yield strength.(1)

[0087] The evaluation of the wedge bondability in the wire bonded part was determined by performing 1,000 pieces of bonding on wedge bonding parts of a BGA substrate and by the occurrence frequency of peeling of the bonded parts. The used BGA substrate was plated with Ni and Au. In this evaluation, assuming bonding conditions more rigorous than normal, a stage temperature was set to 150 C., which was lower than a general set temperature range. In the evaluation, a case in which 11 or more failures occurred was determined to be problematic to be marked with a symbol of cross, a case of 6 to 10 failures was determined to be practicable but somewhat problematic to be marked with a symbol of triangle, a case of 1 to 5 failures was determined to be no problem to be marked with a symbol of circle, and a case in which no failure occurred was determined to be excellent to be marked with a symbol of double circle in the column wedge bondability in Tables 1 to 4.

[0088] The bonding reliability of the ball bonded part in a high-temperature and high humidity environment or a high-temperature environment was determined by manufacturing a sample for bonding reliability evaluation, performing HTS evaluation, and evaluating the bonding longevity of the ball bonded part. The sample for bonding reliability evaluation was manufactured by performing ball bonding onto an electrode, which has been formed by forming an alloy of Al-1.0% Si-0.5% Cu as a film with a thickness of 0.8 m on a Si substrate on a general metallic frame, using a commercially available wire bonder and sealing it with a commercially available epoxy resin. A ball was formed while flowing an N.sub.2 5% H.sub.2 gas at a flow rate of 0.4 to 0.6 L/min, and its size was within the range of a diameter of 33 to 34 m.

[0089] For the HTS evaluation, the manufactured sample for bonding reliability evaluation was exposed to a high-temperature environment with a temperature of 200 C. using a high-temperature thermostatic device. A shear test on the ball bonded part was performed every 500 hours, and a time until a value of shear strength became half of the initial shear strength was determined to be the bonding longevity of the ball bonded part. The shear test after the high-temperature and high-humidity test was performed after removing the resin by acid treatment and exposing the ball bonded part.

[0090] A tester manufactured by DAGE was used for a shear tester for the HTS evaluation. An average value of measurement values of 10 ball bonded parts randomly selected was used for the value of the shear strength. In the above evaluation, the bonding longevity being less than 500 hours was determined to be impracticable to be marked with a symbol of cross, being 500 hours or more and less than 1,000 hours was determined to be practicable but desired to be improved to be marked with a symbol of triangle, being 1,000 hours or more and less than 3,000 hours was determined to be practically no problem to be marked with a symbol of circle, and being 3,000 hours or more was determined to be especially excellent to be marked with a symbol of double circle in the column HTS in Tables 1 to 4.

[0091] For the evaluation of ball formability (FAB shape), a ball before performing bonding was collected and observed, and the presence or absence of voids on a surface of the ball and the presence or absence of deformation of the ball, which is primarily a perfect sphere, were determined. The occurrence of any of the above was determined to be faulty. The formation of the ball was performed while blowing an N.sub.2 gas at a flow rate of 0.5 L/min in order to reduce oxidation in a melting process. The size of the ball was 34 m. For one condition, 50 balls were observed. A SEM was used for the observation. In the evaluation of the ball formability, a case in which five or more failures occurred was determined to be problematic to be marked with a symbol of cross, a case of three or four failures was determined to be practicable but somewhat problematic to be marked with a symbol of triangle, a case of one or two failures was determined to be no problem to be marked with a symbol of circle, and a case in which no failure occurred was determined to be excellent to be marked with a symbol of double circle in the column FAB shape in Tables 1 to 4.

[0092] The bonding longevity of the ball bonded part in the high-temperature and high-humidity environment with a temperature of 130 C. and a relative humidity of 85% can be evaluated by the following HAST evaluation. For the HAST evaluation, the manufactured sample for bonding reliability evaluation was exposed to a high-temperature and high-humidity environment with a temperature of 130 C. and a relative humidity of 85% using an unsaturated type pressure cooker tester and was biased with 5 V. A shear test on the ball bonded part was performed every 48 hours, and a time until a value of shear strength became half of the initial shear strength was determined to be the bonding longevity of the ball bonded part. The shear test after the high-temperature and high-humidity test was performed after removing the resin by acid treatment and exposing the ball bonded part.

[0093] A tester manufactured by DAGE was used for a shear tester for the HAST evaluation. An average value of measurement values of 10 ball bonded parts randomly selected was used for the value of the shear strength. In the above evaluation, the bonding longevity being less than 144 hours was determined to be impracticable to be marked with a symbol of cross, being 144 hours or more and less than 288 hours was determined to be practically no problem to be marked with a symbol of circle, being 288 hours or more and less than 384 hours was determined to be excellent to be marked with a symbol of double circle, and being 384 hours or more was determined to be especially excellent to be marked with a symbol of a pair of double circles in the column HAST in Tables 1 to 4.

[0094] The evaluation of a crushed shape of the ball bonded part was determined by observing the ball bonded part from immediately above after bonding and evaluating by its circularity. For a bonding counterpart, an electrode in which an Al-0.5% Cu alloy was formed as a film with a thickness of 1.0 m on a Si substrate was used. The observation was performed using an optical microscope, and 200 sites were observed for one condition. Being elliptic with large deviation from a perfect circle and being anisotropic in deformation were determined to be faulty in the crushed shape of the ball bonded part. In the above evaluation, a case in which one to three failures was determined to be no problem to be marked with a symbol of circle, and a case in which a favorable perfect circle was obtained for all was determined to be especially excellent to be marked with a symbol of double circle in the column crushed shape in Tables 1 to 4.

TABLE-US-00001 TABLE 1 Crystal structure Mechanical Thick- <100> characteristics ness Pro- 0.2% Coating layer of portion Average Offset Additive element (% by mass) Pd alloy of crystal Ultimate yield Strength M.sub.A Thick- maximum skin wire C grain strength strength ratio Wire quality M.sub.A in ness concentration layer section size {circle around (1)} {circle around (2)} {circle around (1)}/{circle around (2)} Wedge FAB Crushed No. Ni Pt Zn Rh In Ir total Other (m) (at %) (m) (%) (m) (mN/m.sup.2) bondability HTS shape HAST shape Working 1 0.7 0.7 0.015 97 92 1.1 0.19 0.16 1.19 Example 2 1.2 1.2 0.050 100 72 0.9 0.22 0.17 1.29 3 1.0 1.0 0.100 100 71 1.0 0.24 0.16 1.50 4 0.5 0.5 0.150 100 72 1.1 0.29 0.24 1.21 5 0.1 0.1 0.015 98 75 1.2 0.30 0.22 1.36 6 0.03 0.03 0.050 100 63 1.3 0.31 0.20 1.55 7 1.1 0.3 1.4 0.100 100 75 1.0 0.33 0.28 1.18 8 1.2 0.8 2.0 0.150 100 65 0.9 0.34 0.27 1.26 9 0.1 0.7 0.8 0.015 98 51 1.2 0.35 0.22 1.59 10 0.6 0.1 0.05 0.75 0.100 100 97 1.2 0.33 0.30 1.10 11 0.8 0.8 0.3 1.9 0.150 100 80 1.1 0.34 0.28 1.21 12 0.05 0.05 0.05 0.15 0.015 99 70 1.2 0.35 0.22 1.59 13 0.3 1.0 1.0 1.4 0.015 97 54 1.0 0.35 0.23 1.52 14 0.5 0.5 0.015 98 0.0005 91 1.1 0.20 0.18 1.11 15 1.2 1.2 0.050 100 0.0010 70 0.9 0.21 0.17 1.24 16 0.7 0.7 0.100 100 0.0100 69 1.1 0.22 0.15 1.47 17 0.3 0.3 0.150 100 0.0500 70 1.2 0.28 0.24 1.17 18 0.1 0.1 0.015 98 0.0005 76 1.2 0.29 0.22 1.32 19 0.05 0.05 0.050 100 0.0010 64 1.3 0.30 0.19 1.58 20 0.5 0.3 0.8 0.100 100 0.0100 74 1.1 0.33 0.28 1.18 21 1.2 0.1 1.3 0.150 100 0.0500 64 1.2 0.34 0.26 1.31 22 0.01 0.7 0.71 0.015 99 0.0005 50 1.1 0.35 0.23 1.52 23 0.6 0.1 0.05 0.75 0.050 100 0.0010 98 1.0 0.30 0.20 1.50 24 0.8 0.8 0.3 1.9 0.100 100 0.0100 85 0.9 0.33 0.29 1.14 25 0.05 0.05 0.05 0.15 0.150 100 0.0500 74 1.3 0.34 0.25 1.36 26 0.3 1.0 0.1 1.4 0.015 97 0.0100 51 0.9 0.35 0.25 1.40

TABLE-US-00002 TABLE 2 Thick- Mechanical characteristics ness Crystal structure 0.2% Coating layer of <100> Average Offset Additive element (% by mass) Pd alloy Proportion crystal Ultimate yield Strength M.sub.A Thick- maximum skin of wire C grain strength strength ratio Wire quality M.sub.A in ness concentration layer section size {circle around (1)} {circle around (2)} {circle around (1)}/{circle around (2)} Wedge FAB Crushed No. Ni Pt Zn Rh In Ir total other (m) (at %) (m) (%) (m) (mN/m.sup.2) bondability HST shape HAST shape Working 27 0.7 0.7 Gn: 0.007 0.100 100 88 0.9 0.22 0.18 1.22 Example 28 1.1 1.1 Ge: 0.008 0.050 100 75 1.0 0.25 0.17 1.47 29 0.7 0.7 As: 0.003 0.050 100 72 1.0 0.30 0.21 1.43 30 1.2 1.2 Te: 0.001 0.150 100 67 1.2 0.31 0.24 1.29 31 0.5 0.5 Sn: 0.0007 0.015 96 66 1.0 0.29 0.22 1.32 32 0.05 0.05 Sb: 0.0008 0.050 100 74 1.1 0.35 0.29 1.21 33 1.0 1.0 Bi: 0.00008 0.100 100 80 1.1 0.31 0.22 1.41 34 0.8 0.8 Se: 0.0001 0.100 100 92 0.9 0.27 0.19 1.42 35 0.05 0.05 Gn: 0.003 0.100 100 72 1.2 0.30 0.19 1.58 Te: 0.0008 36 0.08 0.08 Gn: 0.003 0.150 100 0.0050 55 1.3 0.33 0.25 1.32 Sb: 0.0007 37 0.1 0.1 As: 0.001 0.150 100 0.0100 82 1.1 0.32 0.25 1.28 Se: 0.001 38 0.08 0.08 B: 0.0008 0.050 100 74 1.1 0.34 0.23 1.48 39 1.2 1.2 P: 0.004 0.050 100 77 1.2 0.29 0.20 1.45 40 0.05 0.05 Mg: 0.005 0.100 100 91 1.0 0.33 0.28 1.18 41 0.5 0.5 Ca: 0.003 0.015 95 68 1.0 0.23 0.19 1.21 42 0.1 0.1 La: 0.003 0.100 100 0.0100 91 0.9 0.26 0.21 1.24 43 0.05 0.05 P: 0.006 0.050 100 0.0050 68 1.1 0.29 0.19 1.53 B: 0.0008 44 0.6 0.6 P: 0.003 0.015 100 0.0100 57 1.3 0.33 0.24 1.38 Ca: 0.001 45 0.5 0.5 B: 0.015 0.100 100 0.0100 90 0.9 0.25 0.21 1.19 46 0.5 0.5 P: 0.02 0.050 100 0.0050 67 1.1 0.28 0.19 1.47 47 0.5 0.5 La: 0.018 0.015 100 0.0100 56 1.3 0.33 0.24 1.38 48 0.011 0.011 0.015 98 75 1.0 0.21 0.18 1.17 49 0.011 0.011 0.050 100 72 1.0 0.19 0.16 1.19 50 0.011 0.011 0.100 100 67 1.2 0.23 0.19 1.21 51 0.011 0.011 0.150 100 66 1.0 0.22 0.18 1.22 52 0.011 0.011 0.050 100 74 1.1 0.21 0.18 1.17 53 0.011 0.011 0.100 100 80 0.9 0.23 0.2 1.15

TABLE-US-00003 TABLE 3 Thick- ness Coating layer of Additive element (% by mass) Pd alloy M.sub.A Thick- maximum skin M.sub.A in ness concentration layer No. Ni Pt Zn Rh In Ir total other (m) (at %) (m) Working 54 0.02 0.02 0.015 97 Example 55 0.02 0.02 0.05 100 56 0.02 0.02 0.1 100 57 0.02 0.02 0.15 100 58 0.02 0.02 0.05 100 59 0.02 0.02 0.1 100 Mechanical characteristics Crystal structure 0.2% <100> Average Offset Proportion crystal Ultimate yield Strength of wire C grain strength strength ratio Wire quality section size {circle around (1)} {circle around (2)} {circle around (1)}/{circle around (2)} Wedge FAB Crushed No. (%) (m) (mN/m.sup.2) bondability HTS shape HAST shape Working 54 30 1 0.31 0.24 1.29 Example 55 41 1 0.33 0.22 1.50 56 49 1.2 0.28 0.19 1.47 57 52 1.3 0.32 0.27 1.19 58 60 1.4 0.22 0.18 1.22 59 74 1.5 0.25 0.20 1.25

TABLE-US-00004 TABLE 4 Additive element Ni Pd Pt Zn Rh In Ir Gn Ge (% by mass) As Te Sn Sb Bi Se No. (Amount in core material for Pd (% by mass)) (ppm by mass) Com- 1 0.7 parative 2 1.2 0.8 Example 3 0.6 0.1 4 0.03 5 0.1 0.7 6 0.8 7 0.7 1.2 8 1.1 9 0.05 0.05 0.05 10 0.05 1.2 0.9 11 1 1.1 1.1 12 0.05 1.3 1.1 13 1 1.1 1.2 0.8 14 0.05 0.05 1.1 0.9 1.2 15 16 Thick- Mechanical characteristics ness Crystal structure 0.2% Pd coating layer of <100> Average Offset Pd alloy Proportion crystal Ultimate yield Strength Thick- maximum skin of wire C grain strength strength ratio Wire quality ness concentration layer section size {circle around (1)} {circle around (2)} {circle around (1)}/{circle around (2)} Wedge FAB Crushed No. (m) (at %) (m) (%) (m) (mN/m.sup.2) bondability HTS shape HAST shape Com- 1 0.015 98 50 0.8 0.35 0.32 1.09 X parative 2 0.150 100 29 1.7 0.29 0.16 1.81 X Example 3 0.100 100 51 0.7 0.28 0.26 1.08 X 4 0.050 100 25 0.9 0.21 0.12 1.75 X 5 0.015 96 20 1.1 0.30 0.17 1.76 X 6 0.150 100 21 1.6 0.35 0.19 1.84 X 7 0.050 100 22 1.0 0.21 0.12 1.75 X 8 0.100 100 25 1.6 0.30 0.18 1.67 9 0.015 97 28 1.8 0.34 0.20 1.70 10 0.015 98 22 0.8 0.20 0.19 1.05 X 11 0.15 100 23 0.7 0.26 0.24 1.08 X 12 0.1 100 25 0.9 0.35 0.21 1.67 13 0.05 100 23 1.1 0.31 0.19 1.63 14 0.015 96 22 1.6 0.24 0.14 1.71 X 15 0.15 100 92 1.1 0.21 0.12 1.75 X X X 16 0.05 100 45 1.4 0.34 0.21 1.62 X X

[0095] (Evaluation Results)

[0096] The bonding wires according to Working Examples 1 through 59 each include a Cu alloy core material and a Pd coating layer formed on a surface of the Cu alloy core material, and a thickness of the Pd coating layer is in the preferable range of 0.015 to 0.150 m. All of them exhibit favorable FAB shape. Further, these bonding wires contain at least one element selected from Ni, Zn, Rh, In, Ir and Pt and a concentration of the elements in total is 0.011 to 2% by mass relative to the entire wire, and with this configuration, they achieve favorable high-temperature reliability of the ball bonded part in the HTS evaluation.

[0097] In the working examples, the area reduction rate at the time of wire drawing was 10% or more, and the heat treatment temperature after wire drawing was a low temperature of 500 C. or less, whereby, the crystal orientation <100> angled at 15 degrees or less to the wire longitudinal direction among the crystal orientations in the wire longitudinal direction could be 30% or more when measuring crystal orientations on the cross-section of the core material in the direction perpendicular to the wire axis of the bonding wire, and the average crystal grain size in the cross-section of the core material in the direction perpendicular to the wire axis of the bonding wire could be 0.9 to 1.5 m. Consequently, the strength ratio (=ultimate strength/0.2% offset yield strength) in all cases was in the range of 1.1 to 1.6 even though the wire contained Ni, Zn, Rh, In, Ir and Pt. Consequently, the wedge bondability was favorable in all cases.

[0098] In contrast, in Comparative Examples 4 through 7 and 12 through 14, the heat treatment temperature was a high temperature of 600 C. or more, whereby the <100> orientation proportion in the wire longitudinal direction was less than 30%. In Comparative Examples 2, 6, 8, 9 and 14, the heat treatment temperature was a high temperature of 620 C. or more, whereby the <100> orientation proportion in the wire longitudinal direction was less than 30%, and the average crystal grain size in the cross-section of the core material was more than 1.5 m. Consequently, in all Comparative Examples 2, 4 through 9 and 12 through 14, the strength ratio was more than 1.6, and the wedge bondability was faulty or problematic.

[0099] In Comparative Examples 1 and 3, the average crystal grain size in the cross-section of the core material was less than 0.9 m, the strength ratio was less than 1.1, and the wedge bondability was faulty in both cases because the die area reduction rate was less than 10%. In Comparative Examples 10 and 11, the <100> orientation proportion in the wire longitudinal direction was less than 30%, and the average crystal grain size in the cross-section of the core material was less than 0.9 m, and the wedge bondability was faulty in both cases. In Comparative Example 15, the average crystal grain size was 0.9 to 1.5 m and the <100> orientation proportion in the wire longitudinal direction was 30% or more, but all of HTS, HAST and wedge bondability were faulty because the element that provides bonding reliability in a high-temperature environment was not contained therein. In Comparative Example 16, HTS and HAST were faulty because the element that provides bonding reliability in a high-temperature environment was not contained therein.

Working Examples 2-1 to 2-44

(Sample)

[0100] First, the following describes a method for manufacturing a sample. For Cu as a raw material of the core material, Cu with a purity of 99.99% by mass or more and containing inevitable impurities as the remainder was used. For Ga, Ge, Ni, Ir, Pt, Pd, B, P and Mg, the ones with purity of 99% by mass or more and containing inevitable impurities as the remainder were used. Ga, Ge, Ni, Ir, Pt, Pd, B, P and Mg as additive elements to the core material are mixed so that the wire or the core material will have a desired composition. Regarding the addition of Ga, Ge, Ni, Ir, Pt, Pd, B, P and Mg, they can be mixed singly. Alternatively, they may be mixed so as to be a desired amount using a Cu master alloy containing the additive elements manufactured in advance if the element has a high melting point as a single body or if the element is added in an infinitesimal amount.

[0101] The Cu alloy as the core material was manufactured by charging raw materials into a carbon crucible worked into a cylindrical shape with a diameter of 3 to 6 mm, heating and melting the raw materials at 1,090 to 1,300 C. in vacuum or in an inert atmosphere such as an N.sub.2 or Ar gas using a high-frequency furnace, and performing furnace cooling. The obtained alloy with a diameter of 3 to 6 mm was drawn to be worked into a diameter of 0.9 to 1.2 mm, and a wire with a diameter of 300 to 600 m was manufactured by successively performing wire drawing using dies. A commercially available lubricant was used for the wire drawing, and a wire drawing speed was 20 to 150 m/min. In order to remove an oxide film on a surface of wire, pickling treatment with sulfuric acid was performed, and a Pd coating layer was formed by 1 to 15 m so as to cover the entire surface of the Cu alloy as the core material. Furthermore, for some wires, an alloy skin layer containing Au and Pd was formed by 0.05 to 1.5 m on the Pd coating layer. For the formation of the Pd coating layer and the alloy skin layer containing Au and Pd, electroplating was used. A commercially available semiconductor plating solution was used for a plating solution. Heat treatment at 200 to 500 C. and wire drawing were then repeatedly performed to be worked into a diameter of 20 m. After working, heat treatment was performed while flowing an N.sub.2 or Ar gas so that breaking elongation will finally be about 5 to 15%. A method of heat treatment was performed while successively sweeping the wire and was performed while flowing an N.sub.2 or Ar gas. A wire feeding speed was 20 to 200 m/min, a heat treatment temperature was 200 to 600 C., and a heat treatment time was 0.2 to 1.0 second.

[0102] For the concentration analysis of the Pd coating layer and the alloy skin layer containing Au and Pd, the analysis was performed using an Auger electron spectroscopic apparatus while sputtering the bonding wire from its surface in the depth direction with Ar ions. The thicknesses of the coating layer and the skin alloy layer were determined from an obtained concentration profile (the unit of the depth was in terms of SiO.sub.2) in the depth direction. A region in which a concentration of Pd was 50 at % or more and a concentration of Au was less than 10 at % was determined to be the Pd coating layer, and a region in which a concentration of Au was in a range of 10 at % or more on a surface of the Pd coating layer was determined to be the alloy skin layer. The thicknesses of the coating layer and the alloy skin layer and a maximum concentration of Pd are listed in Tables 5 and 6. The concentration of Pd in the Cu alloy core material was measured by a method that exposes a cross-section of wire and performs line analysis, point analysis, or the like on the exposed cross-section of wire by an electron probe micro analyzer installed in a scanning electron microscope. For the method for exposing the cross-section of wire, mechanical polishing, ion etching, or the like was used. For the concentrations of Ga, Ge, Ni, Ir, Pt, B, P and Mg in the bonding wire, a solution obtained by dissolving the bonding wire with a strong acid was analyzed using an ICP emission spectrometer or an ICP mass spectrometer, and they were detected as the concentrations of the elements contained in the entire bonding wire.

[0103] The configurations of the respective samples manufactured according to the above procedure are listed in the following Tables 5 and 6.

TABLE-US-00005 TABLE 5 Coating layer Additive element Pd M.sub.B M.sub.B M.sub.A Other Thick- maximum Ga Ge in Ni Pd Pt Ir B P Mg ness concentration No. (% by mass) total (% by mass) (ppm by mass) (m) (at %) Working 2-1 0.020 0.020 0.15 100 Example 2-2 0.025 0.025 0.015 98 2-3 0.500 0.500 0.1 100 2-4 1.500 1.500 0.05 100 2-5 0.011 0.011 0.1 100 2-6 0.025 0.025 0.05 100 2-7 0.300 0.300 0.05 100 2-8 1.500 1.500 0.1 100 2-9 0.015 0.011 0.026 0.05 100 2-10 0.050 0.600 0.650 0.05 100 2-11 0.600 0.850 1.450 0.05 100 2-12 0.002 0.800 0.802 0.05 100 2-13 0.030 0.030 0.50 0.15 100 2-14 0.030 0.030 1.20 0.15 100 2-15 0.030 0.030 0.50 0.05 100 2-16 0.030 0.030 1.20 0.1 100 2-17 0.030 0.030 0.50 0.05 100 2-18 0.030 0.030 1.20 0.1 100 2-19 0.030 0.030 0.50 0.015 96 2-20 0.030 0.030 1.20 0.1 100 2-21 0.030 0.80 0.15 100 2-22 0.030 1.20 0.05 100 Thick- Mechanical characteristics ness Crystal structure 0.2% of <100> Average Ulti- Offset alloy Proportion crystal mate yield Strength skin of wire C grain strength strength ratio Wire quality layer section size {circle around (1)} {circle around (2)} {circle around (1)}/{circle around (2)} Wedge FAB Crushed No. (m) (%) (m) (mN/m.sup.2) bondability HTS shape HAST shape Leaning Working 2-1 91 1.1 0.20 0.19 1.05 Example 2-2 0.0005 71 1.2 0.23 0.17 1.35 2-3 0.0005 70 0.9 0.25 0.18 1.39 2-4 0.001 71 1.0 0.30 0.23 1.30 2-5 0.001 74 1.1 0.31 0.23 1.35 2-6 0.08 62 1.1 0.32 0.25 1.28 2-7 0.01 74 1.3 0.34 0.26 1.31 2-8 0.01 64 1.0 0.35 0.30 1.17 2-9 0.001 50 1.2 0.34 0.22 1.55 2-10 0.01 96 0.9 0.21 0.19 1.11 2-11 0.003 79 1.0 0.22 0.16 1.38 2-12 0.003 69 1.0 0.23 0.19 1.21 2-13 0.001 53 1.1 0.30 0.19 1.58 2-14 0.003 90 1.2 0.27 0.25 1.08 2-15 70 1.2 0.28 0.21 1.33 2-16 0.01 68 1.0 0.29 0.25 1.16 2-17 0.01 69 1.1 0.32 0.26 1.23 2-18 0.01 75 1.3 0.33 0.25 1.32 2-19 0.0005 63 1.2 0.34 0.28 1.21 2-20 0.01 73 1.0 0.31 0.23 1.35 2-21 0.01 63 1.0 0.34 0.29 1.17 2-22 0.003 51 1.0 0.21 0.14 1.50

TABLE-US-00006 TABLE 6 Coating layer Additive element Pd M.sub.B M.sub.B M.sub.A other Thick- maximum Ga Ge in Ni Pd Pt Ir B P Mg ness concentration No. (% by mass) total (% by mass) (ppm by mass) (m) (at %) Working 2-23 0.030 0.030 0.80 0.05 100 Example 2-24 0.030 0.030 1.20 0.15 100 2-25 0.030 0.030 0.80 0.15 100 2-26 0.030 0.030 1.20 0.15 100 2-27 0.030 0.030 0.80 0.015 97 2-28 0.030 0.030 1.20 0.1 100 2-29 0.500 0.500 0.90 30 0.05 100 2-30 0.500 0.500 0.90 30 0.05 100 2-31 0.500 0.500 0.90 50 0.05 100 2-32 0.500 0.500 0.90 50 0.15 100 2-33 0.500 0.500 0.90 10 0.15 100 2-34 0.500 0.500 0.90 10 0.15 100 2-35 0.800 0.500 1.300 0.50 15 0.015 99 2-36 0.080 1.200 1.280 0.50 15 0.15 100 2-37 1.300 0.050 1.350 0.50 100 0.15 100 2-38 0.300 0.500 0.800 0.50 100 0.015 96 2-39 0.080 0.040 0.120 0.50 30 0.015 98 2-40 1.000 0.100 1.100 0.50 30 0.15 100 2-41 0.050 0.015 98 2-42 0.050 0.015 96 2-43 1.000 0.1 100 2-44 1.000 0.1 100 Thick- Mechanical characteristics ness Crystal structure 0.2% of <100> Average Offset alloy Proportion crystal Ultimate yield Strength skin of wire C grain strength strength ratio Wire quality layer section size {circle around (1)} {circle around (2)} {circle around (1)}/{circle around (2)} Wedge FAB Crushed No. (m) (%) (m) (mN/m.sup.2) bondability HTS shape HAST shape Leaning Working 2-23 0.01 97 1.2 0.24 0.22 1.09 Example 2-24 0.001 84 0.9 0.29 0.20 1.45 2-25 0.08 73 1.0 0.30 0.23 1.30 2-26 0.001 50 1.1 0.28 0.18 1.56 2-27 0.003 87 1.3 0.34 0.23 1.48 2-28 0.003 76 1.1 0.30 0.22 1.36 2-29 0.003 66 0.9 0.26 0.21 1.24 2-30 65 1.2 0.29 0.24 1.21 2-31 0.003 92 1.2 0.32 0.29 1.10 2-32 0.01 72 1.2 0.33 0.25 1.32 2-33 0.001 54 1.1 0.31 0.2 1.55 2-34 0.01 81 1.0 0.25 0.17 1.47 2-35 0.003 73 1.2 0.33 0.25 1.32 2-36 0.01 76 1.3 0.29 0.22 1.32 2-37 0.01 91 0.9 0.26 0.24 1.08 2-38 0.003 67 1.0 0.23 0.2 1.15 2-39 0.001 91 1.1 0.33 0.3 1.10 2-40 0.05 67 1.2 0.29 0.25 1.16 2-41 57 1.1 0.29 0.19 1.53 2-42 98 1.0 0.26 0.23 1.13 2-43 75 1.0 0.35 0.26 1.35 2-44 69 1.2 0.21 0.18 1.17

[0104] (Method of Evaluation)

[0105] A crystal structure was evaluated on a surface of wire as an observation surface. Electron backscattered diffraction (EBSD) method was used as a method of evaluation. The EBSD method is characterized in that it can observe crystal orientations on an observation surface and can graphically show an angle difference of the crystal orientations between adjacent measurement points. Further, the EBSD method can relatively easily observe the crystal orientations with high accuracy even for a thin wire like the bonding wire.

[0106] Care should be taken when performing EBSD with a curved surface like the wire surface as an observation subject. When a region with a large curvature is measured, measurement with high accuracy is difficult. However, a bonding wire to be measured is fixed to a line on a plane, and a flat part near the center of the bonding wire is measured, whereby measurement with high accuracy can be performed. Specifically, the following measurement region will work well. The size in the circumferential direction is 50% or less of the wire diameter with the center in the wire longitudinal direction as an axis, whereas the size in the wire longitudinal direction is 100 m or less. Preferably, the size in the circumferential direction is 40% or less of the wire diameter, whereas the size in the wire longitudinal direction is 40 m or less, whereby measurement efficiency can be improved by reducing a measurement time. In order to further improve accuracy, it is desirable that three or more points be measured to obtain average information with variations taken into account. The measurement sites may be apart from each other by 1 mm or more so as not to be close to each other.

[0107] As for the orientation proportion of the crystal orientation <100> angled at 15 degrees or less to the wire longitudinal direction among the crystal orientations in the wire longitudinal direction in the cross-section of the core material in the direction perpendicular to the wire axis of the bonding wire and the average crystal grain size (m) in the cross-section of the core material in the direction perpendicular to the wire axis, they were obtained by the same method as Working Examples 1 to 59. As for 0.2% offset yield strength and ultimate strength, they were evaluated by the same method as Working Examples 1 to 59 and a strength ratio was calculated by the above-mentioned equation (1).

[0108] The bonding reliability of the ball bonded part in a high-temperature and high humidity environment or a high-temperature environment was determined by manufacturing a sample for bonding reliability evaluation, performing HAST and HTS evaluation, and evaluating the bonding longevity of the ball bonded part in each test. The sample for bonding reliability evaluation was manufactured by performing ball bonding onto an electrode, which has been formed by forming an alloy of Al-1.0% Si-0.5% Cu as a film with a thickness of 0.8 m on a Si substrate on a general metallic frame, using a commercially available wire bonder and sealing it with a commercially available epoxy resin. A ball was formed while flowing an N.sub.2+5% H.sub.2 gas at a flow rate of 0.4 to 0.6 L/min, and its size was within the range of a diameter of 33 to 34 m.

[0109] For the HAST evaluation, the manufactured sample for bonding reliability evaluation was exposed to a high-temperature and high-humidity environment with a temperature of 130 C. and a relative humidity of 85% using an unsaturated type pressure cooker tester and was biased with 7 V. A shear test on the ball bonded part was performed every 48 hours, and a time until a value of shear strength became half of the initial shear strength was determined to be the bonding longevity of the ball bonded part. The shear test after the high-temperature and high-humidity test was performed after removing the resin by acid treatment and exposing the ball bonded part.

[0110] A tester manufactured by DAGE was used for a shear tester for the HAST evaluation. An average value of measurement values of 10 ball bonded parts randomly selected was used for the value of the shear strength. In the above evaluation, the bonding longevity being less than 96 hours was determined to be practically problematic to be marked with a symbol of cross, being 96 hours or more and less than 144 hours was determined to be practicable but somewhat problematic to be marked with a symbol of triangle, being 144 hours or more and less than 288 hours was determined to be practically no problem to be marked with a symbol of circle, and being 288 hours or more was determined to be excellent to be marked with a symbol of double circle in the column HAST in Tables 5 and 6.

[0111] For the HTS evaluation, the manufactured sample for bonding reliability evaluation was exposed to a high-temperature environment with a temperature of 200 C. using a high-temperature thermostatic device. A shear test on the ball bonded part was performed every 500 hours, and a time until a value of shear strength became half of the initial shear strength was determined to be the bonding longevity of the ball bonded part. The shear test after the high-temperature and high-humidity test was performed after removing the resin by acid treatment and exposing the ball bonded part.

[0112] A tester manufactured by DAGE was used for a shear tester for the HTS evaluation. An average value of measurement values of 10 ball bonded parts randomly selected was used for the value of the shear strength. In the above evaluation, the bonding longevity being 500 hours or more and less than 1,000 hours was determined to be practicable but be desired to be improved to be marked with a symbol of triangle, being 1,000 hours or more and less than 3,000 hours was determined to be practically no problem to be marked with a symbol of circle, and being 3,000 hours or more was determined to be especially excellent to be marked with a symbol of double circle.

[0113] For the evaluation of ball formability (FAB shape), a ball before performing bonding was collected and observed, and the presence or absence of voids on the ball surface and the presence or absence of deformation of the ball, which is primarily a perfect sphere, were determined. The occurrence of any of the above was determined to be faulty. The formation of the ball was performed while blowing an N.sub.2 gas at a flow rate of 0.5 L/min in order to reduce oxidation in a melting process. The size of the ball was 34 m. For one condition, 50 balls were observed. A SEM was used for the observation. In the evaluation of the ball formability, a case in which five or more failures occurred was determined to be problematic to be marked with a symbol of cross, a case of three or four failures was determined to be practicable but somewhat problematic to be marked with a symbol of triangle, a case of one or two failures was determined to be no problem to be marked with a symbol of circle, and a case in which no failure occurred was determined to be excellent to be marked with Aa symbol of double circle in the column FAB shape in Tables 5 and 6.

[0114] The evaluation of wedge bondability on the wire bonded part was determined by performing 1,000 pieces of bonding on leads of a lead frame and by the occurrence frequency of peeling of the bonded part. An Fe-42 at % Ni alloy lead frame plated with 1 to 3 m Ag was used for the lead frame. In this evaluation, assuming bonding conditions more rigorous than normal, a stage temperature was set to 150 C., which was lower than a general set temperature range. In the evaluation, a case in which 11 or more failures occurred was determined to be problematic to be marked with a symbol of cross, a case of 6 to 10 failures was determined to be practicable but somewhat problematic to be marked with a symbol of triangle, a case of 1 to 5 failures was determined to be no problem to be marked with a symbol of circle, and a case in which no failure occurred was determined to be excellent to be marked with a symbol of double circle in the column wedge bondability in Tables 5 and 6.

[0115] The evaluation of a crushed shape of the ball bonded part was determined by observing the ball bonded part from immediately above after bonding and evaluating by its circularity. For a bonding counterpart, an electrode in which an Al-0.5% Cu alloy was formed as a film with a thickness of 1.0 m on a Si substrate was used. The observation was performed using an optical microscope, and 200 sites were observed for one condition. Being elliptic with large deviation from a perfect circle and being anisotropic in deformation were determined to be faulty in the crushed shape of the ball bonded part. In the above evaluation, a case in which six or more failures occurred was determined to be problematic to be marked with a symbol of cross, a case of four or five failures was determined to be practicable but somewhat problematic to be marked with a symbol of triangle, being one to three was determined to be no problem to be marked with a symbol of circle, and a case in which a favorable perfect circle was obtained for all was determined to be especially excellent to be marked with a symbol of double circle in the column crushed shape in Tables 5 and 6.

[0116] [Leaning]

[0117] To a lead frame for evaluation, 100 pieces of bonding were performed with a loop length of 5 mm and a loop height of 0.5 mm. As a method of evaluation, a wire upright part was observed from a chip horizontal direction, and evaluation was performed based on spacing when spacing between a perpendicular line passing through the center of the ball bonded part and the wire upright part was maximized (leaning spacing). If the leaning spacing was smaller than the wire diameter, leaning was determined to be favorable, whereas if the leaning spacing was larger, the upright part leaned, and the leaning was determined to be faulty. One hundred bonded wires were observed with an optical microscope, and the number of leaning failures was counted. A case in which seven or more failures occurred was determined to be problematic to be marked with a symbol of cross, a case of four to six failures was determined to be practicable but somewhat problematic to be marked with a symbol of triangle, a case of one to three failures was determined to be no problem to be marked with a symbol of circle, and a case in which no failure occurred was determined to be excellent to be marked with a symbol of double circle in the column leaning in Tables 5 and 6.

[0118] (Evaluation Results)

[0119] As shown in Tables 5 and 6, the bonding wires of Working Examples 2-1 through 2-44 each include the Cu alloy core material and the Pd coating layer formed on the surface of the Cu alloy core material, and the bonding wire contains one or more elements selected from Ga and Ge and a concentration of the elements in total is 0.011 to 1.5% by mass relative to the entire wire. It has been revealed that with this configuration the bonding wires of Working Examples 2-1 through 2-44 can obtain the reliability of the ball bonded part in the HAST test in the high-temperature and high-humidity environment with a temperature of 130 C. and a relative humidity of 85%.

[0120] In the working examples of the present invention further including the alloy skin layer containing Au and Pd on the Pd coating layer, it has been revealed that excellent wedge bondability can be obtained when the layer thickness of the alloy skin layer containing Au and Pd is 0.0005 to 0.050 m.

[0121] In the working examples in which the bonding wires further contain at least one element selected from Ni, Ir, Pt and Pd, it has been revealed that the high-temperature reliability of the ball bonded part in the HTS evaluation is further favorable.

[0122] In the working examples in which the bonding wires further contain at least one element selected from B, P and Mg, the crushed shape of the ball bonded part was favorable when a concentration of each of the elements was 1 to 200 ppm by mass relative to the entire wire.

Working Examples 3-1 to 3-50

(Sample)

[0123] First, there will be described a method for manufacturing a sample. For Cu as a raw material of a core material, Cu with a purity of 99.99% by mass or more and containing inevitable impurities as the remainder was used. For As, Te, Sn, Sb, Bi, Se, Ni, Zn, Rh, In, Ir, Pt, Ga, Ge, Pd, B, P, Mg, Ca and La, the ones with a purity of 99% by mass or more and containing inevitable impurities as the remainder were used. As, Te, Sn, Sb, Bi, Se, Ni, Zn, Rh, In, Ir, Pt, Ga, Ge, Pd, B, P, Mg, Ca and La as additive elements to the core material are mixed so that the wire or the core material will have a desired composition. Regarding the addition of As, Te, Sn, Sb, Bi, Se, Ni, Zn, Rh, In, Ir, Pt, Ga, Ge, Pd, B, P, Mg, Ca and La, they can be mixed singly. Alternatively, they may be mixed so as to be a desired amount using a Cu master alloy containing the additive elements manufactured in advance if the element has a high melting point as a single body or if the element is added in an infinitesimal amount.

[0124] The Cu alloy for the core material was manufactured by charging the raw materials into a carbon crucible worked into a cylindrical shape with a diameter of 3 to 6 mm, heating and melting the raw materials at 1,090 to 1,300 C. in vacuum or in an inert atmosphere such as an N.sub.2 or Ar gas using a high-frequency furnace, and performing furnace cooling. The obtained alloy with a diameter of 3 to 6 mm was drawn to manufacture a wire with a diameter of 0.9 to 1.2 mm. Thereafter, a wire with a diameter of 300 to 600 m was manufactured by successively performing wire drawing and the like using a die. A commercially available lubricant was used for the wire drawing, and a wire drawing speed was 20 to 150 m/min. In order to remove an oxide film on a surface of wire, a pickling treatment with hydrochloric acid was performed, and a Pd coating layer was formed by 1 to 15 m so as to cover the entire surface of the Cu alloy as the core material. Furthermore, for some wires, an alloy skin layer containing Au and Pd was formed by 0.05 to 1.5 m on the Pd coating layer. For the formation of the Pd coating layer and the alloy skin layer containing Au and Pd, electroplating was used. A commercially available semiconductor plating solution was used for a plating solution. Heat treatment at 200 to 500 C. and wire drawing were then repeatedly carried out to perform working to a diameter of 20 m. After working, heat treatment was performed while flowing an N.sub.2 or Ar gas so that breaking elongation will finally be about 5 to 15%. A method of heat treatment was performed while successively sweeping the wire and was carried out while flowing an N.sub.2 or Ar gas. A wire feeding speed was 20 to 200 m/min, a heat treatment temperature was 200 to 600 C., and a heat treatment time was 0.2 to 1.0 second.

[0125] For a concentration analysis of the Pd coating layer and the alloy skin layer containing Au and Pd, an Auger electron spectrometry was performed while trimming the bonding wire from its surface in the depth direction by sputtering or the like. From an obtained concentration profile in the depth direction, there were determined a thickness of the Pd coating layer, a thickness of the alloy skin layer containing Au and Pd and a maximum concentration of Pd.

[0126] Concerning Working Examples 3-1 to 3-50, an element selected from As, Te, Sn, Sb, Bi and Se is contained in the core material.

[0127] Concerning Working Examples 3-34 through 3-44, Cu is caused to be present at an outermost surface of the bonding wire. In this regard, a column of Cu concentration at wire surface is provided in Table 7, and results obtained by measuring a surface of the bonding wire by an Auger electron spectroscopic apparatus were entered therein. By selecting a temperature and time for heat treatment of the bonding wire, Cu was caused to be present at an outermost surface at a certain concentration. Concerning Working Examples 3-1 through 3-33 and 3-45 through 3-50, heat treatment conditions that caused Cu not to be present at an outermost surface were applied, and therefore Cu was not detected by the Auger electron spectroscopic apparatus.

[0128] The configurations of the samples manufactured according to the above procedure are listed in Tables 7 and 8.

TABLE-US-00007 TABLE 7 Additive element M.sub.A M.sub.B M.sub.C M.sub.C Ni Pd Pt Zn Rh In Ir Gn Ge As Te Sn Sb Bi Se in (% by mass) No. (ppm by mass) total (Amount in core material for Pd (% by mass)) Working 3-1 0.4 0.4 Example 3-2 1.2 1.2 3-3 12 12 3-4 75 75 3-5 0.1 0.1 3-6 1.2 1.2 3-8 15 15 3-8 98 98 3-9 0.2 0.2 3-10 1.3 1.3 3-11 10 10 3-12 0.1 0.1 3-13 1.2 1.2 3-14 9.8 9.8 3-15 0.3 0.3 3-16 1 1 3-17 0.1 0.1 3-18 1.2 1.2 3-19 4.9 4.9 3-20 99 99 3-21 0.1 0.1 0.05 3-22 4.1 4.1 1.2 3-23 8.1 8.1 0.7 3-24 12 12 0.7 3-25 18 18 0.7 Crystal structure Thick <100> Mechanical characteristics ness- Proportion 0.2% Coating layer of of Average Offset Additive element Pd alloy wire crystal Ultimate yield Strength Other Thick- maximum skin C grain strength strength ratio Wire quality B P Mg Ca La ness concentration layer section size {circle around (1)} {circle around (2)} {circle around (1)}/{circle around (2)} Wedge FAB Crushed No. (ppm by mass) (m) (at %) (m) (%) (m) (mN/m.sup.2) bondability HTS shape HAST shape Leaning Working 3-1 0.1 100 0.01 94 0.9 0.33 0.22 1.50 Example 3-2 0.15 100 0.05 74 1.0 0.29 0.22 1.32 3-3 0.01 100 73 1.1 0.25 0.19 1.32 3-4 0.05 100 0.001 75 1.2 0.22 0.17 1.29 3-5 0.015 98 0.0005 77 1.3 0.32 0.24 1.33 3-6 0.1 100 0.001 65 1.0 0.28 0.23 1.22 3-8 0.15 100 0.003 77 0.9 0.33 0.25 1.32 3-8 0.01 100 0.01 84 1.2 0.31 0.21 1.48 3-9 0.015 97 0.05 98 1.2 0.32 0.21 1.52 3-10 0.05 100 54 1.1 0.29 0.26 1.12 3-11 0.1 100 0.005 50 1.2 0.23 0.21 1.10 3-12 0.15 100 0.001 66 1.0 0.19 0.16 1.19 3-13 0.015 95 0.003 87 1.1 0.30 0.21 1.43 3-14 0.05 100 0.01 93 0.9 0.35 0.22 1.59 3-15 0.1 100 0.05 54 1.1 0.20 0.18 1.11 3-16 0.15 100 0.001 78 1.2 0.30 0.23 1.30 3-17 0.015 99 0.003 65 1.2 0.25 0.20 1.25 3-18 0.05 100 0.01 52 1.3 0.21 0.19 1.11 3-19 0.1 100 0.05 60 1.1 0.26 0.22 1.18 3-20 0.15 100 90 1.2 0.30 0.19 1.58 3-21 0.015 97 55 1.3 0.19 0.17 1.12 3-22 100 0.1 100 0.001 90 0.9 0.32 0.21 1.52 3-23 100 0.1 100 0.003 68 0.9 0.25 0.20 1.25 3-24 50 0.05 100 0.05 60 1.0 0.24 0.20 1.20 3-25 50 0.15 100 0.003 85 1.0 0.30 0.21 1.43

TABLE-US-00008 TABLE 8 Additive element M.sub.A M.sub.B M.sub.C M.sub.C Ni Pd Pt Zn Rh In Ir Ga Ge Other As Te Sn Sb Bi Se in (% by mass) B P No. (ppm by mass) total (Amount in core material for Pd (% by mass)) (ppm by mass) Working 3-26 52 52 0.05 Example 3-27 99 99 0.1 3-28 0.2 0.2 0.1 0.05 3-29 2.5 2.5 1.1 0.05 100 3-30 5.2 5.2 1.1 0.1 100 3-31 21 21 0.7 0.1 50 3-32 41 41 1.1 0.05 3-33 98 98 0.1 0.1 3-34 22 22 3-35 16 16 1.1 0.1 3-36 4.1 4.1 3-37 5.8 5.8 0.7 0.7 3-38 0.7 0.7 3-39 4.8 4.8 1.1 1.1 3-40 2.5 2.5 0.7 0.1 3-41 1.8 1.8 0.1 0.05 3-42 0.5 0.5 1.1 0.05 3-43 0.2 0.2 0.05 0.1 3-44 20 20 0.7 0.02 3-45 1.0 1 3-46 1.5 1.5 3-47 1.2 1.2 3-48 1.0 1 3-49 0.9 0.9 3-50 1.2 1.2 Crystal structure Thick <100> Mechanical characteristics ness- Proportion 0.2% Coating layer of of Average Offset Cu Additive element Pd alloy wire crystal Ultimate yield Strength concentration Other Thick- maximum skin C grain strength strength ratio Wire quality at wire Mg Ca La ness concentration layer section size {circle around (1)} {circle around (2)} {circle around (1)}/{circle around (2)} Wedge FAB Crushed surface No. (ppm by mass) (m) (at %) (m) (%) (m) (mN/m.sup.2) bondability HTS shape HAST shape Leaning (at %) Working 3-26 50 0.1 100 0.0005 72 1.2 0.27 0.21 1.29 Example 3-27 0.01 100 0.01 92 1.1 0.34 0.22 1.55 3-28 0.05 100 0.005 98 1.3 0.25 0.16 1.56 3-29 0.1 100 0.003 65 1.1 0.24 0.20 1.20 3-30 0.1 100 0.001 74 1.1 0.30 0.22 1.36 3-31 0.15 100 0.003 52 1.2 0.23 0.21 1.10 3-32 1 0.05 100 0.05 88 1.0 0.32 0.22 1.45 3-33 0.01 100 0.01 60 1.0 0.21 0.18 1.17 3-34 0.1 100 0.001 87 1.1 0.30 0.21 1.43 5.4 3-35 0.15 100 0.003 65 1.3 0.28 0.24 1.17 5.2 3-36 0.01 100 0.01 54 0.9 0.23 0.21 1.10 10 3-37 0.05 100 0.05 74 1.2 0.29 0.22 1.32 11 3-38 0.1 100 96 1.1 0.29 0.19 1.53 26 3-39 0.15 100 0.0005 66 1.0 0.21 0.17 1.24 28 3-40 0.01 100 88 1.0 0.33 0.23 1.43 1.1 3-41 0.05 100 0.0005 96 1.1 0.31 0.20 1.55 1.4 3-42 0.1 100 0.01 54 0.9 0.26 0.23 1.13 5.2 3-43 0.15 100 0.03 84 1.2 0.32 0.22 1.45 5.5 3-44 0.01 100 0.01 85 1.2 0.29 0.20 1.45 12 3-45 0.1 100 96 1.1 0.29 0.19 1.53 3-46 0.1 100 57 1.0 0.20 0.18 1.11 3-47 0.1 100 77 1.3 0.30 0.23 1.30 3-48 0.1 100 72 0.9 0.28 0.21 1.33 3-49 0.1 100 56 1.2 0.21 0.18 1.17 3-50 0.1 100 61 1.0 0.22 0.18 1.22

[0129] (Method of Evaluation)

[0130] A crystal structure was evaluated with a surface of wire as an observation surface. An electron backscattered diffraction method (EBSD) was used as a method of evaluation. The EBSD method is characterized in that it can observe crystal orientations on an observation surface and graphically shows an angle difference of the crystal orientations between adjacent measurement points. The EBSD method can relatively easily observe the crystal orientations with high accuracy, even for a thin wire like the bonding wire.

[0131] Care should be taken when performing EBSD method with a curved surface like the wire surface as a subject. When a region with a large curvature is measured, measurement with high accuracy is difficult. However, a bonding wire to be measured is fixed to a line on a plane, and a flat part near the center of the bonding wire is measured, whereby measurement with high accuracy can be performed. Specifically, the following measurement region will work well. The size in the circumferential direction is 50% or less of the wire diameter with a center in the wire longitudinal direction as an axis, and the size in the wire longitudinal direction is 100 m or less. Preferably, the size in the circumferential direction is 40% or less of the wire diameter, and the size in the wire longitudinal direction is 40 m or less, whereby measurement efficiency can be improved by reducing a measurement time. In order to further improve accuracy, it is desirable that three or more points are measured to obtain average information with variations taken into account. The measurement sites may be apart from each other by 1 mm or more so as not to be close to each other.

[0132] As for the orientation proportion of the crystal orientation <100> angled at 15 degrees or less to the wire longitudinal direction among the crystal orientations in the wire longitudinal direction in the cross-section of the core material in the direction perpendicular to the wire axis of the bonding wire and the average crystal grain size (m) in the cross-section of the core material in the direction perpendicular to the wire axis, they were obtained by the same method as Working Examples 1 to 59. As for 0.2% offset yield strength and ultimate strength, they were evaluated by the same method as Working Examples 1 to 59 and a strength ratio was calculated by the above-mentioned equation (1).

[0133] The bonding reliability of the ball bonded part in a high-temperature and high humidity environment or a high-temperature environment was determined by manufacturing a sample for bonding reliability evaluation, performing HAST and HTS evaluation, and by evaluating the bonding longevity of the ball bonded part in each test. The sample for bonding reliability evaluation was manufactured by performing ball bonding onto an electrode, which has been formed by forming an alloy of Al-1.0% Si-0.5% Cu as a film with a thickness of 0.8 m on a Si substrate on a general metallic frame, using a commercially available wire bonder and sealing it with a commercially available epoxy resin. A ball was formed while flowing an N.sub.2+5% H.sub.2 gas at a flow rate of 0.4 to 0.6 L/min, and its size was a diameter of a range from 33 to 34 m.

[0134] For the HAST evaluation, the manufactured sample for bonding reliability evaluation was exposed to a high-temperature and high-humidity environment of a temperature of 130 C. and a relative humidity of 85% using an unsaturated type pressure cooker tester and was biased with 5 V. A shear test on the ball bonded part was performed every 48 hours, and a time until a value of shear strength became half of the initial shear strength was determined to be the bonding longevity of the ball bonded part. The shear test after the high-temperature and high-humidity test was carried out after removing a resin by acid treatment and exposing the ball bonded part.

[0135] A tester manufactured by DAGE was used for a shear tester for the HAST evaluation. An average value of measurement values on 10 ball bonded parts randomly selected was used for the value of the shear strength. In the above evaluation, the bonding longevity being less than 96 hours was determined to be practically problematic to be marked with a symbol of cross, being 96 hours or more and less than 144 hours was determined to be practicable but somewhat problematic to be marked with a symbol of triangle, being 144 hours or more and less than 288 hours was determined to be practically no problem to be marked with a symbol of circle, being 288 hours or more and less than 384 hours was determined to be excellent to be marked with a symbol of double circle, and being 384 hours or more was determined to be especially excellent to be marked to with a symbol of a pair of double circle in the column HAST in Tables 7 and 8.

[0136] For the HTS evaluation, the manufactured sample for bonding reliability evaluation was exposed to a high-temperature environment of a temperature of 200 C. using a high-temperature thermostatic device. A shear test on the ball bonded part was performed every 500 hours, and a time until a value of shear strength became half of the initial shear strength was determined to be the bonding longevity of the ball bonded part. The shear test after the high-temperature and high-humidity test was performed after removing a resin by acid treatment and exposing the ball bonded part.

[0137] A tester manufactured by DAGE was used for a shear tester for the HTS evaluation. An average value of measurement values on 10 ball bonded parts randomly selected was used for the value of the shear strength. In the above evaluation, the bonding longevity being 500 or more to less than 1,000 hours was determined to be practicable but desirably to be improved to be marked with a symbol of triangle, being 1,000 or more to less than 3,000 hours was determined to be practically no problem to be marked with a symbol of circle, and being 3,000 hours or more was determined to be especially excellent to be marked with a symbol of double circle in the column HTS in Tables 7 and 8.

[0138] For the evaluation of ball formability (FAB shape), a ball before performing bonding was collected and observed, and the presence or absence of voids on a surface of the ball and the presence or absence of deformation of the ball, which is primarily a perfect sphere, were determined. The occurrence of any of the above was determined to be faulty. The formation of the ball was performed while an N.sub.2 gas was blown at a flow rate of 0.5 L/min in order to reduce oxidation in a melting process. The size of the ball was 34 m. For one condition, 50 balls were observed. A SEM was used for the observation. In the evaluation of the ball formability, a case where five or more failures occurred was determined to be problematic to be marked with a symbol of cross, a case of three or four failures was determined to be practicable but somewhat problematic to be marked with a symbol of triangle, a case of one or two failures was determined to be no problem to be marked with a symbol of circle, and a case where no failure occurred was determined to be excellent to be marked with a symbol of double circle in the column FAB shape in Tables 7 and 8.

[0139] The evaluation of wedge bondability on the wire bonded part was determined by performing 1,000 pieces of bonding on leads of a lead frame and evaluating by the occurrence frequency of peeling of the bonded part. An Fe-42 at % Ni alloy lead frame plated with 1 to 3 m Ag was used for the lead frame. In this evaluation, assuming more rigorous bonding conditions than normal, a stage temperature was set to be 150 C., which was lower than a generally set temperature range. In the above evaluation, a case where 11 or more failures occurred was determined to be problematic to be marked with a symbol of cross, a case of 6 to 10 failures was determined to be practicable but somewhat problematic to be marked with a symbol of triangle, a case of 1 to 5 failures was determined to be no problem to be marked with a symbol of circle, and a case where no failure occurred was determined to be excellent to be marked with a symbol of double circle in the column wedge bondability in Tables 7 and 8.

[0140] The evaluation of a crushed shape of the ball bonded part was determined by observing the ball bonded part from immediately above after bonding and evaluating by its circularity. For an object to be bonded with the bonding wire, an electrode in which an Al-0.5% Cu alloy was formed as a film with a thickness of 1.0 m on a Si substrate was used. The observation was performed using an optical microscope, and 200 sites were observed for one condition. Being elliptic with large deviation from a perfect circle and being anisotropic in deformation were determined to be faulty in the crushed shape of the ball bonded part. In the above evaluation, a case where six or more failures occurred was determined to be problematic to be marked with a symbol of cross, a case of four or five failures was determined to be practicable but somewhat problematic to be marked with a symbol of triangle, being one to three was determined to be no problem to be marked with a symbol of circle, and a case where a favorable perfect circle was obtained for all was determined to be especially excellent to be marked with a symbol of double circle in the column crushed shape in Tables 7 and 8.

[0141] [Leaning]

[0142] To a lead frame for evaluation, 100 pieces of bonding were performed with a loop length of 5 mm and a loop height of 0.5 mm. As a method of evaluation, a wire upright part was observed from a chip horizontal direction, and evaluation was performed based on spacing when spacing between a perpendicular line passing through the center of the ball bonded part and the wire upright part was maximized (leaning spacing). If the leaning spacing was smaller than the wire diameter, leaning was determined to be favorable, whereas if the leaning spacing was larger, the upright part leaned, and the leaning was determined to be faulty. One hundred bonded wires were observed with an optical microscope, and the number of leaning failures was counted. A case where seven or more failures occurred was determined to be problematic to be marked with a symbol of cross, a case of four to six failures was determined to be practicable but somewhat problematic to be marked with a symbol of triangle, a case of one to three failures was determined to be no problem to be marked with a symbol of circle, and a case in which no failure occurred was determined to be excellent to be marked with a symbol of double circle in the column leaning in Tables 7 and 8.

[0143] (Evaluation Results)

[0144] The bonding wires according to Working Examples 3-1 through 3-50 each include a Cu alloy core material and a Pd coating layer formed on the surface of the Cu alloy core material, and the bonding wire contains at least one or more elements selected from As, Te, Sn, Sb, Bi and Se, a concentration of the elements in total is 0.1 to 100 ppm by mass relative to the entire wire. It has been revealed that with this configuration the bonding wires according to Working Examples 3-1 through 3-50 can achieve the reliability of the ball bonded part in the HAST test in the high-temperature and high-humidity environment of a temperature of 130 C. and a relative humidity of 85%.

[0145] In the working examples further including an alloy skin layer containing Au and Pd on the Pd coating layer, it has been revealed that excellent wedge bondability can be obtained when a thickness of the alloy skin layer containing Au and Pd is 0.0005 to 0.050 m.

[0146] In Working Examples 3-21 through 3-33, 3-35, 3-37, and 3-39 through 3-44, it has been revealed that the high-temperature reliability of the ball bonded part by the HTS evaluation is favorable because the bonding wire further contains at least one or more elements selected from Ni, Zn, Rh, In, Ir, Pt, Ga and Ge, and a concentration of each of the elements other than Pd is 0.011 to 1.2% by mass relative to the entire wire, and a concentration of Pd contained in the Cu alloy core material is 0.05 to 1.2% by mass.

[0147] In Working Examples 3-22 through 3-26 and 3-29 through 3-32, the FAB shape was favorable and the wedge bondability was favorable when the bonding wire further contains at least one or more elements selected from B, P, Mg, Ca and La, and a concentration of each of the elements is 1 to 100 ppm by mass relative to the entire wire.

[0148] In Working Examples 3-34 through 3-44, the wire contains As, Te, Sn, Sb, Bi and Se, and Cu was present at an outermost surface of the wire. With this configuration, Working Examples 3-34 through 3-44 were a symbol of a pair of double circle or a symbol of double circle in the HAST evaluation results, which revealed the effect of causing Cu to be present at an outermost surface.

Working Examples 4-1 to 4-15

[0149] As raw materials of a bonding wire, Cu with a purity of 99.99% by mass or more and Ni, Pd, Pt, Au, P, B, Be, Fe, Mg, Ti, Zn, Ag and Si as additive elements were used for manufacturing a Cu alloy core material; Pd with a purity of 99.99% by mass or more was used for forming a coating layer; and Au with a purity of 99.99% by mass or more was used for forming a skin alloy layer. Cu and the additive elements were weighed as starting raw materials and then were heated and melted in a high vacuum to obtain a copper alloy ingot with a diameter of about 10 mm. The ingot was then forged, rolled, and subjected to wire drawing to manufacture a Cu alloy wire with a diameter of 500 m. Thereafter, electroplating was performed so as to form a Pd coating layer with a thickness of 1 to 3 m on a surface of the Cu alloy wire and to form an Au skin layer with a thickness of 0.05 to 0.2 m on a surface of the coating layer, thus obtaining a multilayer wire. The final thicknesses of the Pd coating layer and the AuPd skin alloy layer are listed in Table 8. The position at which a concentration of Pd is 50 at % was set to be a boundary between the core material and the coating layer, and the position at which a concentration of Au is 10 at % was set to be a boundary between the coating layer and the skin alloy layer. Continuous wire drawing was then performed with a condition of a wire drawing speed of 100 to 700 m/min and a reduction rate in area of die of 8 to 30% to obtain final wire diameters listed in Table 8. The thickness of the skin alloy layer, the maximum concentration of Au, the surface concentration of Cu, and the thickness of the coating layer were controlled by performing heat treatment two or three times during the wire drawing. Conditions therefor were as follows: a temperature of 500 to 700 C. and a speed of 10 to 70 m/min at a wire diameter of 200 to 250 m; a temperature of 450 to 650 C. and a speed of 20 to 90 m/min at a wire diameter of 70 to 100 m; and when the final wire diameter is thin, additionally a temperature of 300 to 500 C. and a speed of 30 to 100 m/min at a wire diameter of 40 to 70 m. Heat treatment was then performed with a condition of a temperature shown in Table 8 and a speed of 30 to 120 m/min at the final diameters. In order to diffuse Cu to the surface, in one of heat treatments, an oxygen concentration in a heat treatment furnace was set to 0.2 to 0.7%, which was higher than a normal concentration. This heat treatment is preferably performed last, if possible; this is because when wire drawing is repeated after Cu is exposed to the surface, oxidation of Cu is likely to occur. In the heat treatment other than that, the oxygen concentration in the heat treatment furnace was set to less than 0.2%, whereby a stable thickness, composition, and the like were controlled while suppressing excessive oxidation of the skin alloy layer. Bonding wires with a diameter of 15 to 25 m were thus obtained.

[0150] The concentration analysis of the coating layer and the skin alloy layer and the concentration analysis of Ni, Pd, Pt and Au in the Cu alloy core material were performed using an AES apparatus while sputtering with Ar ions from a surface of the bonding wire in the depth direction. The thicknesses of the coating layer and the skin alloy layer were determined from an obtained concentration profile in the depth direction (the unit of the depth was in terms of SiO.sub.2). For the observation of element distribution, there was also performed an analysis with using an EPMA, an EDX apparatus, and the like. A region in which a concentration of Pd was 50 at % or more and a concentration of Au was less than 10 at % was determined to be the coating layer, and a region in which a concentration of Au was in the range of 10 at % or more on a surface of the coating layer was determined to be the skin alloy layer. The thicknesses and compositions of the coating layer and the surface alloy layer are listed in Table 8. The concentrations of P, B, Be, Fe, Mg, Ti, Zn, Ag and Si in the bonding wire were measured by an ICP emission spectrometer, an ICP mass spectrometer, and the like. As for the orientation proportion of the crystal orientation <100> angled at 15 degrees or less to the wire longitudinal direction among the crystal orientations in the wire longitudinal direction in the cross-section of the core material in the direction perpendicular to the wire axis of the bonding wire and the average crystal grain size (m) in the cross-section of the core material in the direction perpendicular to the wire axis, they were obtained by the same method as Working Examples 1 to 59. As for 0.2% offset yield strength and ultimate strength, they were evaluated by the same method as Working Examples 1 to 59 and a strength ratio was calculated by the above-mentioned equation (1).

[0151] For connection of a bonding wire, a commercially available automatic wire bonder was used. A ball was manufactured at a tip of the bonding wire by arc discharge immediately before bonding. The diameter of the ball was selected to be 1.7 times the diameter of the bonding wire. The atmosphere during the manufacture of the ball was nitrogen.

[0152] As objects to be bonded with the bonding wire, Al electrodes with a thickness of 1 m formed on a Si chip, and leads of a lead frame the surface of which is plated with Pd were used. The manufactured ball was ball-bonded to the electrode heated at 260 C., followed by wedge bonding a base part of the bonding wire to the lead heated at 260 C., and forming another ball, thus successively repeating the bonding. A loop length was two kinds: 3 mm and 5 mm, and a loop height was two kinds: 0.3 mm and 0.5 mm.

[0153] For the wedge bondability of the bonding wire, a bondability and a fishtail symmetry were evaluated. Regarding the bondability, 100 bonded parts of the bonding wire being wedge bonded were observed, and peeled bonded parts were counted as NG. Regarding the fishtail symmetry, 100 bonded parts of the bonding wire being wedge bonded were observed, and their symmetry was evaluated. The lengths from the center of a fishtail-shaped crimped part to the left end and the right end were measured, and the difference therebetween was 10% or more was counted as NG. Regarding the bondability and the fishtail symmetry, NG being 0 was determined to be a symbol of double circle, being 1 to 10 was determined to be a symbol of circle, and being 11 or more was determined to be a symbol of cross.

[0154] For the 1st bondability (ball bondability) of the bonding wire, a HTS test, a HAST test and a FAB shape were evaluated. The HTS test was evaluated by the same method as Working Examples 1 to 59. In order to evaluate the soundness of a ball bonding part in the HAST test, a semiconductor device in which bonding has been performed was left in a high-temperature, high-humidity furnace with a temperature of 130 C., a relative humidity of 85% RH, and 5 V, and the device was taken out every 48 hours and was evaluated. As for the evaluation method, the electric resistance was measured, and the resistance being increased was determined to be NG. Time to reach NG state being more than 480 hours was determined to be a symbol of double circle, being 384 hours or more and less than 480 hours was determined to be a symbol of circle, and being less than 384 hours was determined to be a symbol of cross.

[0155] Regarding the FAB shape, 100 FABs were manufactured on the lead frame and were observed with a SEM. A FAB being perfectly spherical was determined to be OK, being eccentric or having a shrinkage cavity was determined to be NG, and their numbers were counted. Regarding the FAB shape, NG being 0 was determined to be a symbol of double circle, being 1 to 5 was determined to be a symbol of circle, being 6 to 10 was determined to be a symbol of triangle, and being 11 or more was determined to be a symbol of cross. Symbols of double circle and circle are passing, whereas a symbol of triangle is passing but somewhat faulty in quality. The concentrations of Ni, Pd and Pt in Table 9 (% by mass *) indicate a concentration in the Cu alloy core material.

TABLE-US-00009 TABLE 9 Additive element Additive Wire M.sub.A M.sub.A element 2 Other diameter Ni Pd Pt in Au Ni P B Be Fe Mg Ti Zn Ag Si No. (mm) (% by mass *) total (% by mass) (% by mass) Working 4-1 15 1.8 1.8 0.0008 Example 4-2 18 0.5 0.5 0.005 0.0006 0.0004 4-3 20 1.3 1.3 0.0001 4-4 23 0.1 0.1 0.002 4-5 23 3.0 3.0 0.005 4-6 25 0.4 0.4 0.0011 0.0011 4-8 25 2.0 0.4 4-8 0.6 0.3 0.005 0.001 4-9 3.0 0.0006 0.0004 4-10 1.0 0.4 0.002 0.001 0.001 4-11 0.9 0.4 0.6 0.003 0.004 0.003 4-12 1.5 4-13 0.8 4-14 1.2 4-15 0.7 Crystal structure <100> Mechanical characteristics Cu Proportion 0.2% concentrated Coating layer Alloy skin layer of Average Offset part Pd Au wire crystal Ultimate yield Strength Outermost Heat Thick- maximum Thick- maximum C grain strength strength ratio surface treatment Wedge bonding ness concentration ness concentration secion size {circle around (1)} {circle around (2)} {circle around (1)}/{circle around (2)} concentration temperature Fishtail FAB No. (m) (at %) (nm) (at %) (%) (m) (mN/m.sup.2) (at %) ( C.) Bondability symmetry HTS shape HAST Working 4-1 48 100 11 55 51 0.9 0.20 0.18 1.11 2.8 485 Example 4-2 66 100 6 34 85 1.1 0.30 0.21 1.43 2.2 475 4-3 66 100 22 61 97 1.2 0.35 0.24 1.46 5.2 510 4-4 90 100 4 18 55 1.0 0.23 0.21 1.10 3.5 510 4-5 73 100 26 60 78 1.2 0.30 0.23 1.30 1.3 485 4-6 30 98 4 27 90 1.3 0.31 0.21 1.48 10 515 4-8 39 99 12 32 65 0.9 0.23 0.19 1.21 1.4 490 4-8 46 100 10 50 78 1.1 0.27 0.20 1.35 2.7 485 4-9 52 100 18 56 69 1.2 0.26 0.21 1.24 2.1 475 4-10 88 100 6 34 77 1.1 0.28 0.21 1.33 5.1 510 4-11 22 96 20 60 74 1.0 0.24 0.19 1.26 1.5 485 4-12 45 100 7 33 65 1.2 0.20 0.17 1.18 9.8 515 4-13 41 100 93 1.2 0.34 0.23 1.48 5.1 510 4-14 60 100 78 1.2 0.30 0.23 1.30 5.3 510 4-15 52 100 80 1.0 0.24 0.17 1.41 5.1 510

[0156] In Working Examples 4-1 through 4-15, the Cu alloy contains one or more elements selected from Ni, Pd and Pt (a metallic element of Group 10 of the Periodic Table of Elements) in an amount of 0.1 to 3.0% by mass in total and a concentration of Cu at an outermost surface of the bonding wire is 1 to 10 at %. With this configuration, Working Examples 4-1 through 4-15 exhibited excellent results in the bondability and fishtail symmetry in the wedge bonded part and exhibited favorable results in HTS, FAB shape and HAST.