BONDING WIRE FOR SEMICONDUCTOR DEVICE

Abstract

A bonding wire for a semiconductor device includes a Cu alloy core material and a Pd coating layer on a surface of the Cu alloy core material, and contains Ga and Ge of 0.011 to 1.2% by mass in total, which is able to increase bonding longevity of the ball bonded part in the high-temperature, high-humidity environment, and thus to improve the bonding reliability. The thickness of the Pd coating layer is preferably 0.015 to 0.150 m. When the bonding wire further contains one or more elements of Ni, Ir, and Pt in an amount, for each element, of 0.011 to 1.2% by mass, it is able to improve the reliability of the ball bonded part in a high-temperature environment at 175 C. or more. When an alloy skin layer containing Au and Pd is further formed on a surface of the Pd coating layer, wedge bondability improves.

Claims

1. A bonding wire for a semiconductor device, comprising: a Cu alloy core material; and a Pd coating layer formed on a surface of the Cu alloy core material, wherein the bonding wire contains Ga, and a concentration of Ga relative to the entire wire is 0.025% by mass or more and 1.5% by mass or less.

2. 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.

3. 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.

4. The bonding wire for a semiconductor device according to claim 3, wherein a thickness of the alloy skin layer containing Au and Pd is 0.0005 m or more and 0.050 m or less.

5. The bonding wire for a semiconductor device according to claim 1, wherein the bonding wire further contains one or more elements selected from Ni, Ir, and Pt, and a concentration of each of the elements relative to the entire wire is 0.011% by mass or more and 1.2% by mass or less.

6. The bonding wire for a semiconductor device according to claim 1, wherein the Cu alloy core material contains Pd, and a concentration of Pd contained in the Cu alloy core material is 0.05% by mass or more and 1.2% by mass or less.

7. 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, and Mg, and a concentration of each of the elements relative to the entire wire is 1 ppm by mass or more and 100 ppm by mass or less.

8. The bonding wire for a semiconductor device according to claim 1, in a measurement result when measuring crystal orientations on a surface of the bonding wire, a crystal orientation <111> angled at 15 degrees or less to a longitudinal direction has a proportion of 30% or more and 100% or less among crystal orientations in the longitudinal direction of the bonding wire.

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

Description

EXAMPLES

[0057] The following specifically describes the bonding wire according to an embodiment of the present invention with reference to examples.

[0058] (Sample)

[0059] First, the following describes a method for manufacturing a sample. Cu as a raw material of the core material with a purity of 99.99% by mass or more and containing inevitable impurities as the remainder was used. Ga, Ge, Ni, Ir, Pt, Pd, B, P, and Mg with a 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 target composition. Regarding the addition of Ga, Ge, Ni, Ir, Pt, Pd, B, P, and Mg, although they can be mixed singly, or 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.

[0060] The Cu alloy as 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 a 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 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 the wire surface, pickling treatment with sulfuric acid was performed, and the 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 partial wires, the 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 causing a N.sub.2 or Ar gas to flow 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 causing the N.sub.2 or Ar gas to flow. 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.

[0061] By adjusting the working rate after forming the Pd coating layer or after forming the Pd coating layer and the alloy skin layer containing Au and Pd, there was adjusted the proportion (areal percentage) of the crystal orientation <111> angled at 15 degrees or less to the longitudinal direction among the crystal orientations in the longitudinal direction of the bonding wire, in a measurement result when measuring crystal orientations on the surface of the bonding wire.

[0062] 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 the Pd concentration was 50 at % or more and the Au concentration was less than 10 at % was determined to be the Pd coating layer, and a region in which the Au concentration on the surface of the Pd coating layer was in the range of 10 at % or more was determined to be the alloy skin layer. The thicknesses and compositions of the coating layer and the alloy skin layer are listed in Tables 1 and 2. The concentration of Pd in the Cu alloy core material was measured by a method that exposes a wire section and performs line analysis, point analysis, or the like on the exposed wire section by an electron probe micro analyzer installed in a scanning electron microscope. For the method for exposing the wire section, 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 in which the bonding wire was dissolved 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.

[0063] The configurations of the respective samples manufactured according to the above procedure are listed in the following tables. Table 1 lists working examples, and Table 2 list comparative examples. In Table 2, figures out of the range of the present invention are underlined.

TABLE-US-00001 TABLE 1 Wire characteristics Component content Film thickness of In wire In wire (% by mass) alloy skin layer Areal percentage (% by mass) (in core material (% In wire Film thickness of containing of surface crystal Quality evaluation results Ga and by mass) for Pd) (ppm by mass) Pd coating layer Au and Pd orientation FAB Wedge Crushed Test No Ga Ge Ge in total Ni Ir Pt Pd B P Mg (m) (m) <111> (%) HAST HTS shape bondability shape Leaning Working 1 0.020 0.020 0.15 68 Example 2 0.025 0.025 0.015 0.0005 94 3 0.500 0.500 0.1 0.0005 89 4 1.500 1.500 0.05 0.001 62 5 0.011 0.011 0.1 0.001 48 6 0.025 0.025 0.05 0.08 92 7 0.300 0.300 0.05 0.01 59 8 1.500 1.500 0.1 0.01 44 9 0.015 0.011 0.026 0.05 0.001 95 10 0.010 0.015 0.025 0.015 0.01 93 11 0.020 0.005 0.025 0.1 0.003 62 12 0.012 0.015 0.027 0.15 0.0005 55 13 0.050 0.070 0.120 0.015 0.0005 79 14 0.016 0.050 0.066 0.015 0.001 53 15 0.050 0.600 0.650 0.05 0.01 33 16 0.600 0.850 1.450 0.05 0.003 67 17 0.002 0.800 0.802 0.05 0.003 33 18 0.030 0.030 0.50 0.15 0.001 69 19 0.030 0.030 1.20 0.15 0.003 41 20 0.030 0.030 0.50 0.05 85 21 0.030 0.030 1.20 0.1 0.01 58 22 0.030 0.030 0.50 0.05 0.01 97 23 0.030 0.030 1.20 0.1 0.01 73 24 0.030 0.030 0.50 0.015 0.0005 65 25 0.030 0.030 1.20 0.1 0.01 72 26 0.030 0.030 7 0.015 0.01 98 27 0.030 0.030 100 0.015 0.001 94 28 0.030 0.030 7 0.1 0.01 62 29 0.030 0.030 100 0.015 0.08 68 30 0.030 0.030 7 0.05 0.01 49 31 0.030 0.030 100 0.05 0.05 40 Working 32 0.030 0.030 0.80 0.15 0.01 83 Example 33 0.030 0.030 1.20 0.05 0.003 88 34 0.030 0.030 0.80 0.05 0.01 82 35 0.030 0.030 1.20 0.15 0.001 94 36 0.030 0.030 0.80 0.15 0.08 92 37 0.030 0.030 1.20 0.15 0.001 87 38 0.030 0.030 0.80 0.015 0.003 85 39 0.030 0.030 1.20 0.1 0.003 68 40 0.030 0.030 6 0.015 0.08 65 41 0.030 0.030 100 0.15 0.0005 42 42 0.030 0.030 6 0.1 0.001 88 43 0.030 0.030 100 0.05 0.01 57 44 0.030 0.030 6 0.15 0.0005 38 45 0.030 0.030 100 0.05 0.01 76 46 0.500 0.500 0.90 30 0.05 0.003 76 47 0.500 0.500 0.90 30 0.05 84 48 0.500 0.500 0.90 30 0.05 0.003 95 49 0.500 0.500 0.90 30 0.05 0.003 84 50 0.500 0.500 0.90 50 0.05 0.003 94 51 0.500 0.500 0.90 50 0.15 0.01 60 52 0.500 0.500 0.90 50 0.1 0.003 45 53 0.500 0.500 0.90 50 0.15 0.003 55 54 0.500 0.500 0.90 10 0.15 0.001 88 55 0.500 0.500 0.90 10 0.15 0.01 97 56 0.500 0.500 0.90 10 0.15 0.001 41 57 0.500 0.500 0.90 10 0.15 0.003 64 Working 58 0.700 0.700 0.50 15 0.1 0.01 58 Example 59 0.700 0.700 0.50 15 0.015 0.001 85 60 0.700 0.700 0.50 15 0.1 0.01 48 61 0.700 0.700 0.50 15 0.1 0.01 64 62 0.700 0.700 0.50 70 0.015 0.001 67 63 0.700 0.700 0.50 70 0.05 0.0005 87 64 0.700 0.700 0.50 70 0.05 0.0005 88 65 0.700 0.700 0.50 70 0.15 0.001 49 66 0.700 0.700 0.50 40 0.05 0.003 72 67 0.700 0.700 0.50 40 0.1 0.001 96 68 0.700 0.700 0.50 40 0.1 0.003 58 69 0.800 0.500 1.300 0.50 15 0.015 0.003 66 70 0.080 1.200 1.280 0.50 15 0.15 0.01 67 71 0.500 0.040 0.540 0.50 15 0.015 0.001 69 72 1.300 0.050 1.350 0.50 100 0.15 0.01 60 73 0.300 0.500 0.800 0.50 100 0.015 0.003 87 74 0.500 0.600 1.100 0.50 100 0.15 0.003 49 75 0.080 0.040 0.120 0.50 30 0.015 0.001 82 76 1.000 0.100 1.100 0.50 30 0.15 0.05 78 77 0.030 0.600 0.630 0.50 30 0.05 0.001 39 78 1.500 1.500 0.40 0.30 10 0.15 0.08 83 79 1.500 1.500 0.40 0.30 23 0.15 0.01 88 80 1.500 1.500 0.40 0.30 30 0.15 0.0005 97 81 1.500 1.500 0.40 0.50 24 0.15 0.01 81 82 1.500 1.500 1.20 15 15 0.1 0.003 72 83 1.500 1.500 1.20 15 30 0.1 0.003 68 84 1.500 1.500 1.20 15 30 0.015 0.0005 78 85 1.500 1.500 0.50 0.50 10 50 0.15 0.05 79 86 1.500 1.500 0.50 0.50 25 50 0.015 0.0005 65 87 1.500 1.500 0.50 0.50 30 50 0.15 0.01 39 Working 88 1.200 1.200 0.80 0.40 15 0.15 95 Example 89 1.200 1.200 0.80 0.40 24 0.05 0.001 87 90 1.200 1.200 0.80 0.40 60 0.1 0.01 66 91 1.200 1.200 0.80 0.40 35 0.15 0.01 64 92 1.200 1.200 0.80 60 8 0.15 0.001 74 93 1.200 1.200 0.80 70 5 0.15 0.01 76 94 1.200 1.200 0.80 80 10 0.15 0.003 47 95 1.200 1.200 0.30 0.60 10 50 0.05 0.0005 84 96 1.200 1.200 0.30 0.60 15 60 0.1 0.01 57 97 1.200 1.200 0.30 0.60 20 70 0.015 0.01 91 98 0.600 0.050 0.650 0.60 0.70 20 0.1 0.0005 41 99 1.100 0.300 1.400 0.60 0.70 60 0.15 87 100 0.800 0.400 1.200 0.60 0.70 100 0.05 0.001 75 101 0.800 0.030 0.830 0.60 0.70 35 0.15 0.003 64 102 0.050 1.100 1.150 1.20 75 0.015 0.001 97 103 0.800 0.060 0.860 1.20 75 0.015 0.05 86 104 0.030 0.800 0.830 1.20 75 0.1 0.01 96 105 0.090 1.300 1.390 0.30 0.40 30 20 0.1 0.01 66 106 0.700 0.700 1.400 0.30 0.40 40 20 0.05 79 107 0.200 0.600 0.800 0.30 0.40 50 20 0.15 0.003 89

TABLE-US-00002 TABLE 2 Component content In wire In wire (% by mass) (% by mass) (in core material (% In wire Test Ga and by mass) for Pd) (ppm by mass) No Ga Ge Ge in total Ni Ir Pt Pd B P Mg Comparative 1 0.010 0.010 Example 2 0.010 0.010 3 0.010 0.010 4 0.010 0.010 6 0.010 0.010 6 0.010 0.010 7 0.0050 0.0050 0.010 8 0.0050 0.0050 0.010 9 0.0050 0.0050 0.010 Wire characteristics Film Film thickness Areal thickness of of alloy skin percentage of Pd coating layer containing surface crystal Quality evaluation results Test layer Au and Pd orientation FAB Wedge Crushed No (m) (m) <111> (%) HAST HTS shape bondability shape Leaning Comparative 1 0.005 0.001 18 X X Example 2 0.2 0.003 68 X X 3 0.3 0.01 28 X X 4 0.05 0.001 97 X 6 0.2 0.003 56 X X 6 0.005 0.01 22 X X 7 0.3 0.001 56 X X 8 0.05 0.003 22 X 9 0.2 0.01 48 X X

[0064] (Method of Evaluation)

[0065] A crystal structure was evaluated with the wire surface as an observation surface. Electron backscattered diffraction (EBSD) was used as a method of evaluation. EBSD is characterized by observing crystal orientations on the observation surface and enabling an angle difference of the crystal orientations between adjacent measurement points to be illustrated and can observe the crystal orientations with high accuracy while being relatively simple even for a thin wire like the bonding wire.

[0066] Care should be taken when performing EBSD 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 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.

[0067] The proportion of the surface crystal orientation <111> was determined by calculating the areal percentage of the crystal orientation <111> angled at 15 degrees or less to the longitudinal direction among the crystal orientations in the longitudinal direction of the bonding wire with all crystal orientations identified by exclusive software (for example, OIM analysis manufactured by TSL Solutions) as a population.

[0068] 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 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 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 causing a N.sub.2+5% H.sub.2 gas to flow at a flow rate of 0.4 to 0.6 L/min, and its size was in a range of a diameter of 33 to 34 m.

[0069] Concerning 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 when a value of shear strength was half the shear strength initially obtained 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.

[0070] 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 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 to 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 to 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 Table 1.

[0071] Concerning 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 when a value of shear strength was half the shear strength initially obtained 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.

[0072] 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 evaluation, the bonding longevity being 500 hours or more to 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 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.

[0073] Concerning 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. The occurrence of any of the above was determined to be faulty. The formation of the ball was performed while a 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 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 Table 1.

[0074] 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 Table 1.

[0075] The evaluation of a crushed shape of the ball bonded part was determined by observing the ball bonded part after bonding from immediately above and 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 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 Table 1.

[0076] [Leaning]

[0077] 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 Table 1.

[0078] (Evaluation Results)

[0079] The bonding wires according to Working Examples 1 through 107 listed in Table 1 each include the Cu alloy core material and the Pd coating layer formed on the surface of the Cu alloy core material, the bonding wire containing one or more elements selected from Ga and Ge, and the concentration of the elements in total relative to the entire wire being 0.011 to 1.5% by mass. It has been revealed that with this configuration the bonding wires according to Working Examples 1 through 107 can obtain the reliability of the ball bonded part in the HAST test in the high-temperature, high-humidity environment with a temperature of 130 C. and a relative humidity of 850.

[0080] In contrast, in Comparative Examples 1 through 9 listed in Table 2, the reliability of the ball bonded part in the HAST test was not obtained since the concentration of Ga and Ge in total was out of the lower limit. In Comparative Examples 1 and 6, the FAB shape was a symbol of cross since the thickness of the Pd coating layer was out of the lower limit of the preferable range. In Comparative Examples 1, 3, 6, and 8, the leaning was a symbol of triangle since the areal percentage of the <111> crystal orientation was out of the preferable range of the present invention.

[0081] 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 caused by the fact that the layer thickness of the alloy skin layer containing Au and Pd is 0.0005 to 0.050 m.

[0082] 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 by the HTS evaluation is favorable caused by the fact that the concentration of each of the elements other than Pd relative to the entire wire is 0.011 to 1.2% by mass, and the concentration of Pd contained in the Cu alloy core material is 0.05 to 1.2% by mass.

[0083] In the working examples in which the bonding wires further contain at least one element selected from B, P, and Mg, the crushed shaped of the ball bonded part was favorable caused by the fact that the concentration of each of the elements relative to the entire wire was 1 to 100 ppm by mass.