Joining method, joint structure, electronic device, method for manufacturing electronic device and electronic part

Abstract

A joint structure that includes a first metal member, a second metal member, and a joint portion sandwiched between the first metal member and the second metal member. At least a Cu-M-Sn intermetallic compound is dispersed in the joint portion, M is at least one of Ni and Mn, and neither a Cu.sub.3Sn layer nor a Cu.sub.6Sn.sub.5 layer is present on at least one of interfaces between the joint portion and the first metal member and the second metal member.

Claims

1. A joint structure comprising: a first metal member; a second metal member; and a joint portion sandwiched between the first metal member and the second metal member, wherein at least a Cu-M-Sn intermetallic compound is dispersed in the joint portion, M is at least one of Ni and Mn, and neither a Cu.sub.3Sn layer nor a Cu.sub.6Sn.sub.5 layer is present on a first interface between the joint portion and the first metal member and a second interface between the joint portion and the second metal member, and a material of at least one of the first metal member and the second metal member is a CuMn or a CuNi alloy.

2. An electronic device in which the first metal member having at least a surface of a first metal is joined to the second metal member having at least a surface of a second metal with the joint portion sandwiched therebetween, wherein the joint portion has the joint structure according to claim 1.

3. An electronic part comprising: a first electrode; a second electrode; and a joining material in contact with a first surface of the first electrode and a second surface of the second electrode, the joining material including a joining metal of Sn or an alloy containing Sn in an amount of 70% by weight or more, wherein the first surface of the first electrode in contact with the joining material is a CuMn alloy or a CuNi alloy which forms an intermetallic compound with the joining metal, and has a lattice constant difference of 50% or more from the intermetallic compound, and neither a Cu.sub.3Sn layer nor a Cu.sub.6Sn.sub.5 layer is present on a first interface between the joining material and the first electrode and a second interface between the joining material and the second electrode.

4. The electronic part according to claim 3, wherein the first surface of the first electrode in contact with the joining material is a CuMn alloy containing Mn in a proportion of 5 to 30% by weight or a CuNi alloy containing Ni in a proportion of 5 to 30% by weight.

5. The electronic part according to claim 3, wherein the first surface of the first electrode in contact with the joining material is a CuMn alloy containing Mn in a proportion of 10 to 15% by weight or a CuNi alloy containing Ni in a proportion of 10 to 15% by weight.

Description

BRIEF EXPLANATION OF THE DRAWINGS

(1) FIGS. 1(a), 1(b) and 1(c) are drawings schematically showing a behavior in joining by a joining method of an example of the present invention, wherein FIG. 1(a) is a drawing showing a state before heating, FIG. 1(b) is a drawing showing a state where heating is initiated and a joining material is melted, and FIG. 1(c) is a drawing showing a state where heating is continued and an intermetallic compound of a low melting point metal composing the joining material and at least one of a first metal member and a second metal member is formed.

(2) FIGS. 2(a) and 2(b are drawings showing a behavior of solder in soldering by using a conventional solder paste, wherein FIG. 2(a) is a view showing a state before heating and FIG. 2(b) is a view showing a state after the completion of a soldering step.

(3) FIG. 3 is a drawing showing a joint structure in which a laminar intermetallic compound is formed on an interface in joining by using a conventional solder paste.

DETAILED DESCRIPTION OF THE INVENTION

(4) Examples of the present invention will be shown below, and characteristics of the present invention will be described in more detail.

Example 1

(5) In this example, as shown in FIG. 1(a) to FIG. 1(c), a first metal member 11a made of a first metal was joined to a second metal member 11b made of a second metal by using a joining material 10 predominantly made of a low melting point metal having a lower melting point than the first metal and the second metal.

(6) In this example, as the low melting point metal composing the joining material, as shown in Table 1A and Table 1B, Sn-3Ag-0.5Cu, Sn, Sn-3.5Ag, Sn-0.75Cu, Sn-0.7Cu-0.05Ni, Sn-5Sb, Sn-2Ag-0.5Cu-2Bi, Sn-57Bi-1Ag, Sn-3.5Ag-0.5Bi-8In, Sn-9Zn, Sn-8Zn-3Bi, Sn-10Bi, Sn-20Bi, Sn-30Bi, or Sn-40Bi was used.

(7) In the above expression of the low melting point metal composing the joining material, for example, Sn-3Ag-0.5Cu represents an alloy (Sn alloy) in which the low melting point metal material contains Ag in an amount of 3% by weight and Cu in an amount of 0.5% by weight and the rest is Sn. Therefore, Sn-40Bi among the above-mentioned low melting point materials is a material of a comparative example which does not meet the requirement of the present invention that Sn or an alloy containing Sn in an amount of 70% by weight or more.

(8) As the first metal member and the second metal member, as shown in Table 1A and Table 1B, a metal member made of Cu-10Ni, Cu-10Mn, Cu-12Mn-4Ni, Cu-10Mn-1P, Cu or Cu-10Zn was used.

(9) In the sample Nos. 16 and 17 in Table 1B, different materials were used for the first metal material and the second metal material. That is, in the sample No. 16, Cu-10Ni was used for the first metal material (upper metal material) and Cu-10Mn was used for the second metal member (lower metal member), and in the sample No. 17, Cu was used for the first metal member (upper metal member) and Cu-10Mn was used for the second metal member (lower metal member).

(10) In this example, in joining the first metal member and the second metal member described above to each other with a joining material predominantly made of the low melting point metal, a joining material shaped into a plate was located between the first metal member and the second metal member and reflowed at 250 C. for 30 minutes under a load to join the first metal member to the second metal member.

(11) Here, in reference to FIG. 1(a) to FIG. 1(c), a joining method in this example will be described below.

(12) First, as shown FIG. 1(a), a joining material 10 shaped into a plate is positioned between a first metal member 11a and a second metal member 11b.

(13) Next, in this state, the joining material is reflowed at 250 C. for 15 minutes under a load to melt the low melting point metal (Sn or a Sn alloy) composing the joining material 10, as shown in FIG. 1(b). Then, by further keeping on heating for a predetermine time (15 minutes) (that is, by reflowing at 250 C. for 30 minutes), the low melting point metal composing the joining material 10 is melted and reacted with the first metal and/or the second metal respectively composing the first metal member 11a and the second metal member 11b to produce an intermetallic compound 12 (FIG. 1(c)).

(14) Thereby, a joined body in which the first metal member is joined to the second metal member by the joining material containing an intermetallic compound solidified after the reflow is obtained.

(15) It was confirmed that a Cu-M-Sn (M is nickel and/or Mn) intermetallic compound exists in a state of being dispersed in the joining material in accordance with the joining method of the present invention.

(16) [Evaluation of Characteristics]

(17) The joined bodies thus obtained were used as samples, and their characteristics were measured and evaluated by the following methods.

(18) <Joint Strength>

(19) With respect to the joint strength, shear strength of the obtained joined body was measured by using a bonding tester and evaluated.

(20) Measurement of the shear strength was carried out at a lateral push rate of 0.1 mm/s.sup.1 under conditions of room temperature and 260 C.

(21) A sample having a shear strength of 20 Nmm.sup.2 or more was rated as (excellent), and a sample having a shear strength of 2 Nmm.sup.2 or less was rated as x (defective).

(22) The measured joint strength (room temperature, 260 C.) of the samples and the results of evaluation are collectively shown in Table 1A and Table 1B.

(23) <Evaluation of Remaining Component>

(24) A portion of about 7 mg of the joining material (reaction product) containing an intermetallic compound solidified after the reflow was cut off, and analyzed at a temperature rise rate of 5 C./min at a measurement temperature of 30 C. to 300 C. in a nitrogen atmosphere using Al.sub.2O.sub.3 as a reference by using differential scanning calorimetry (DSC). The amount of the remaining low melting point metal component was quantified from an endothermic quantity of an endothermic melting peak at a melting temperature of the low melting point metal component in the resulting DSC chart and the content (% by volume) of the remaining low melting point metal was determined. The case where the content of the remaining low melting point metal was 0 to 3% by volume was rated as (excellent), the case where it was more than 3% by volume and 30% by volume or less was rated as (good), and the case where it was more than 30% by volume was rated as x (defective).

(25) The content of the remaining low melting point metal and the results of evaluation are collectively shown in Table 1A and Table 1B.

(26) <Flow Out Percent Defective (%)>

(27) The obtained joined bodies were sealed with an epoxy resin, left standing in an environment of 85% in relative humidity, and heated in the reflow condition of a peak temperature of 260 C. to determine an incidence rate of flow out defective in which the joining material was remelted and flown out. The flow out percent defective was determined from this result and evaluated.

(28) The case where the flow out percent defective of the joining material was 0 to 10% was rated as (excellent), the case where it was more than 10% and 50% or less was rated as (good), and the case where it was more than 50% was rated as x (defective).

(29) The flow out percent defective and the results of evaluation are collectively shown in Table 1A and Table 1B.

(30) <Existence or Non-Existence of Cracks and Joint Strength after Thermal Shock Test>

(31) The obtained joined bodies (samples) were subjected to a test in which a cycle of respectively holding a sample for 30 minutes under the temperature conditions of 40 C. and +85 C. is repeated a thousand times, and then production of cracks of each sample was observed. Then, the existence or non-existence of production of cracks was evaluated.

(32) Further, the joint strength of the samples after the thermal shock test was evaluated in the same way as in the above test. A sample having a shear strength of 20 Nmm.sup.2 or more was rated as (excellent), a sample having a shear strength of 10 Nmm.sup.2 or more and less than 20 Nmm.sup.2 was rated as (good), and a sample having a shear strength of less than 10 Nmm.sup.2 was rated as x (defective).

(33) The existence or non-existence of cracks and joint strength after the thermal shock test and the results of evaluation are collectively shown in Table 1A and Table 1B. The production of cracks was evaluated not because the crack itself is problematic but because it is a factor for deteriorating the joint strength.

(34) In Table 1A and Table 1B, the following items are shown:

(35) type (composition) of the low melting point metal composing the joining material,

(36) composition and the lattice constant of metals (a first metal and a second metal) composing the first metal member and the second metal member (in Tables 1A and 1B, the first metal and the second metal are the same metal in the sample Nos. 1 to 15 and different metals in the sample Nos. 16 and 17),

(37) type and the lattice constant of an intermetallic compound produced by the reaction of the low melting point metal composing the joining material with the first metal and/or the second metal (in examples, the lattice constant was evaluated based on a axis),

(38) lattice constant difference which is a difference between the lattice constant of the intermetallic compound and the lattice constant of the first metal and/or the second metal, and

(39) existence or non-existence of a laminar intermetallic compound such as Cu.sub.3Sn and Cu.sub.6Sn.sub.5 formed on the interface between the first metal member and/or the second metal member made of a metal having a lattice constant difference of 50% or more from the intermetallic compound and the joint portion (joining material including an intermetallic compound) which is solidified after reflow and joins the first metal member to the second metal member in the joint portion.

(40) TABLE-US-00001 TABLE 1A Composition and Lattice Composition of Joint Strength and Low Melting Constant of First Metal Intermetallic Compound Existence or Evaluation Point Metal and Second Metal Produced Lattice Non-existence of (Room Temperature) Composing Lattice Lattice Constant Laminar Joint Sample Joining Constant a Constant a Difference Intermetallic Strength No. Material Composition (nm) Composition (nm) (%) Compound (Nmm.sup.2) Evaluation 1 Sn3Ag0.5Cu Cu10Ni 0.357 Cu.sub.2NiSn 0.597 67 None 28 2 Sn3Ag0.5Cu Cu10Mn 0.367 Cu.sub.2MnSn 0.617 68 None 28 3 Sn Cu10Mn 0.367 Cu.sub.2MnSn 0.617 68 None 29 4 Sn3.5Ag Cu10Mn 0.367 Cu.sub.2MnSn 0.617 68 None 27 5 Sn0.75Cu Cu10Mn 0.367 Cu.sub.2MnSn 0.617 68 None 27 6 Sn15Bi Cu10Mn 0.367 Cu.sub.2MnSn 0.617 68 None 27 7 Sn0.7Cu0.05Ni Cu10Mn 0.367 Cu.sub.2MnSn 0.617 68 None 28 8 Sn5Sb Cu10Mn 0.367 Cu.sub.2MnSn 0.617 68 None 30 9 Sn2Ag0.5Cu2Bi Cu10Mn 0.367 Cu.sub.2MnSn 0.617 68 None 29 10 Sn30Bi Cu10Mn 0.367 Cu.sub.2MnSn 0.617 68 None 29 Flow Out Percent Thermal Shock Test and Joint Strength and Defective and Evaluation Evaluation Content of Remaining Evaluation Existence (260 C.) Low Melting Point Flow Out or Non- Joint Metal and Evaluation Percent existence Joint Sample Strength Content Defective of Crack Strength No. (Nmm.sup.2) Evaluation (%) Evaluation (%) Evaluation Production (Nmm.sup.2) Evaluation 1 25 0 0 None 26 2 24 0 0 None 25 3 24 0 0 None 26 4 22 0 0 None 26 5 24 0 0 None 25 6 26 0 0 None 24 7 24 0 0 None 26 8 26 0 0 None 28 9 26 0 0 None 25 10 25 15 20 Slightly 17 existed

(41) TABLE-US-00002 TABLE 1B Composition and Lattice Composition of Joint Strength and Low Melting Constant of First Metal Intermetallic Compound Existence or Evaluation Point Metal and Second Metal Produced Lattice Non-existence of (Room Temperature) Composing Lattice Lattice Constant Laminar Joint Sample Joining Constant a Constant a Difference Intermetallic Strength No. Material Composition (nm) Composition (nm) (%) Compound (Nmm.sup.2) Evaluation 11 Sn3.5Ag0.5Bi8In Cu10Mn 0.367 Cu.sub.2MnSn 0.617 68 None 28 12 Sn9Zn Cu10Mn 0.367 Cu.sub.2MnSn 0.617 68 None 27 13 Sn8Zn3Bi Cu10Mn 0.367 Cu.sub.2MnSn 0617 68 None 27 14 Sn3Ag0.5Cu Cu12Mn4Ni 0.367 Cu.sub.2MnSn 0.617 68 None 28 15 Sn3Ag0.5Cu Cu10Mn1P 0.367 Cu.sub.2MnSn 0.617 68 None 29 16 Sn3Ag0.5Cu Cu10Ni 0.352 Cu.sub.2NiSn 0.597 67 None 28 (first) Cu10Mn 0.367 Cu.sub.2MnSn 0.617 68 (second) 17 Sn3Ag0.5Cu Cu (first) 0.361 Cu.sub.3Sn 0.432 20 Existed 26 (upper side) Cu10Mn 0.367 Cu.sub.2MnSn 0.617 68 Did not exist (second) (lower side) 18 Sn3Ag0.5Cu Cu 0.361 Cu.sub.3Sn 0.432 20 Existed 25 19 Sn3Ag0.5Cu Cu10Zn 0.359 Cu.sub.3Sn 0.432 20 Existed 31 20 Sn40Bi Cu10Mn 0.359 Cu.sub.3Sn 0.432 20 Existed 28 Flow Out Percent Thermal Shock Test and Joint Strength and Defective and Evaluation Evaluation Content of Remaining Evaluation Existence (260 C.) Low Melting Point Flow Out or Non- Joint Metal and Evaluation Percent existence Joint Sample Strength Content Defective of Crack Strength No. (Nmm.sup.2) Evaluation (%) Evaluation (%) Evaluation Production (Nmm.sup.2) Evaluation 11 24 0 0 None 27 12 25 0 0 None 26 13 24 0 0 None 23 14 23 0 0 None 25 15 23 0 0 None 24 16 25 0 0 None 24 17 24 0 0 Existed 15 only on upper side 18 0.1 X 31 X 75 X Existed 5 X 19 1.8 X 34 X 70 X Existed 7 X 20 2.0 X 32 X 71 X Existed 8 X

(42) As shown in Table 1A and Table 1B, with respect to the joint strength at room temperature, both of samples of examples of sample Nos. 1 to 17 which meet the requirements of the present invention and samples of comparative examples of sample Nos. 18 to 20 which do not meet the requirements of the present invention exhibited a joint strength of 20 Nmm.sup.2 or more, and were found to have practical strength.

(43) On the other hand, with respect to the joint strength at 260 C., while the samples of comparative examples of sample Nos. 18 to 20 exhibited insufficient joint strength of 2 Nmm.sup.2 or less, the samples of examples of sample Nos. 1 to 17 had a joint strength of 10 Nmm.sup.2 or more, and were found to have practical strength.

(44) Further, with respect to the content of the remaining low melting point metal (remaining component evaluation), it was found that in the samples of comparative examples of sample Nos. 18 to 20, the content of the remaining low melting point metal was larger than 30% by volume, and on the other hand, in all of the samples of examples of sample Nos. 1 to 17, the content of the remaining low melting point metal could be made 30% by volume or less, and particularly in all of the samples of examples of sample Nos. 1 to 9 and 11 to 17 in which Sn or an alloy containing Sn in an amount of 85% by weight or more was used as a low melting point metal, the content of the remaining low melting point metal was 0% by volume.

(45) Further, with respect to the flow out percent defective of the joining material, it was found that in the samples of comparative examples of sample Nos. 18 to 20, the flow out percent defective was 70% or more, and on the other hand, in all of the samples of examples of sample Nos. 1 to 17, the flow out percent defective was 20% or less, and particularly all of the samples of examples of sample Nos. 1 to 9 and 11 to 17, in which Sn or an alloy containing Sn in an amount of 85% by weight or more was used as a low melting point metal, had high heat resistance as the flow out percent defective was 0%.

(46) It was found that the samples of examples of sample Nos. 1 to 17 had similar high heat resistance irrespective of the type of the low melting point metal.

(47) Further, the samples of examples of sample Nos. 1 to 17 which satisfy the requirements of the present invention include:

(48) samples in which metals composing the first metal member and the second metal member are the same metal and a metal containing CuMn as a base (Cu-12Mn-4Ni, Cu-10Mn-1P, etc.) like the samples of sample Nos. 1 to 15,

(49) samples in which the first metal member and the second metal member are respectively made of different metals and both metal members have the above-mentioned lattice constant difference of 50% or more like the sample of sample No. 16, and

(50) samples in which the first metal member and the second metal member are respectively made of different metals and one of the metal members has the above-mentioned lattice constant difference of less than 50% like the sample of sample No. 17, and any of these samples was similarly found to have high heat resistance.

(51) Further, in the samples of comparative examples of sample Nos. 18 to 20, production of cracks was found after the 1000 cycle test in the observation of the sample after the thermal shock test. The cracks were produced principally within a Cu.sub.3Sn layer and a Cu.sub.6Sn.sub.5 layer (intermetallic compound layer) formed at an interface between the joining material and the first metal member and/or the second metal member, at an interface between the intermetallic compound layer and the first metal member and/or the second metal member, and at an interface between the intermetallic compound layer and the joining material.

(52) Meanwhile, in the samples of examples of sample Nos. 1 to 9 and 11 to 16, production of cracks was not found. On the other hand, in the sample of the example of sample No. 10, since the content of Sn in the low melting point metal was 70% by weight, an intermetallic compound firstly produced had a low diffusion rate though the intermetallic compound was Cu.sub.2MnSn. Thus, an intermetallic compound such as Cu.sub.6Sn.sub.5 or Cu.sub.3Sn, but not a laminar compound, was segregated at a part of the interface between the joining material and the first metal member and/or the second metal member. Consequently, microcracks were produced at the interface after the thermal shock, and therefore joint strength was slightly deteriorated.

(53) In the sample of the example of sample No. 18, a laminar intermetallic compound was formed at an interface between the joining material and the first metal since Cu was used as a first metal. Consequently, cracks were produced only at the interface between the joining material and the first metal, and therefore joint strength was slightly deteriorated.

(54) Consequently, with respect to the thermal shock resistance, in the samples of comparative examples of sample Nos. 18 to 20 which do not meet the requirements of the present invention concerning the lattice constant difference, etc., the joint strength after the thermal shock test was as low as 5 Nmm.sup.2 (sample No. 18), 7 Nmm.sup.2 (sample No. 19), or 8 Nmm.sup.2 (sample No. 20), but in the samples of sample Nos. 1 to 17 which meet the requirements of the present invention, it was found that the joint strength after the thermal shock test was largely improved compared with that in comparative examples.

(55) Specifically, it was found that in the samples of sample Nos. 1 to 9 and 11 to 16, the joint strength after the thermal shock test was 20 Nmm.sup.2 or more, that in the sample of sample No. 10 (sample in which the content of Sn in the low melting point metal is 70% by weight), the joint strength after the thermal shock test was 17 Nmm.sup.2, and that in the sample of sample No. 17 (sample in which a first metal member (upper metal member) is Cu and a second metal member (lower metal member) is Cu-10Mn), the joint strength after the thermal shock test was 15 Nmm.sup.2, and these joint strengths were smaller than those of the samples of sample Nos. 1 to 9 and 11 to 16 but were at an adequately practicable level.

(56) In addition, in the case of the sample of sample No. 17, while Cu composing the first metal member has a lattice constant difference of less than 50% from an upper intermetallic compound, Cu-10Mn composing the lower second metal member is a metal having a lattice constant difference of more than 50% from the intermetallic compound, and therefore Cu-10Mn reacts quickly with Sn or a Sn alloy which is a low melting point metal in the joining material. Therefore, it is thought that the production of the intermetallic compound on the Cu-10Mn side (second metal side) is prevalent, and a laminar intermetallic compound such as Cu.sub.3Sn or Cu.sub.6Sn.sub.5 at the interface on the Cu side (first metal side), even if this layer is produced, is very small in thickness and the effect on the joint strength after the thermal shock test was small.

(57) In addition, it was confirmed that in the joint portion, a laminar intermetallic compound such as Cu.sub.3Sn or Cu.sub.6Sn.sub.5 was not formed on the interface with the second metal member made of a metal (Cu-10Mn) having a lattice constant difference of more than 50% from the intermetallic compound.

(58) Further, in the case of samples of examples of sample Nos. 1 to 17 which meet the requirements of the present invention, since the low melting point metal (Sn or a Sn alloy) did not remain in the joint portion, it is thought that an intermetallic compound layer did not grow, and therefore cracks were not produced to maintain joint strength even when a joined body obtained after reflow was further subjected to the thermal shock test.

(59) The reason why samples of sample Nos. 1 to 17 satisfying the requirements of the present invention have high heat resistance as described above is probably that CuMn and a CuNi alloy respectively having a lattice constant difference of 50% or more from the intermetallic compounds (Cu.sub.2MnSn and Cu.sub.2NiSn) which CuMn and CuNi form with the low melting point metal composing the joining material are used for at least one of the first metal and the second metal respectively composing the first metal member and the second metal member.

(60) That is, when the intermetallic compound produced has a large lattice constant difference from the first metal composing the first metal member and/or the second metal composing the second metal member, since the reaction is repeated while the intermetallic compound is peeled/dispersed in the melted low melting point metal, it is thought that the production rate of the intermetallic compound outstandingly increases and the laminar intermetallic compound is not formed at the interface.

Example 2

(61) A joining material using Sn as a low melting point metal was used, and a first metal member and a second metal member, respectively made of Cu-10Ni, were joined to each other (samples of sample Nos. 21 to 27 in Table 2).

(62) Similarly, a joining material using Sn as a low melting point metal was used, and a first metal member and a second metal member, respectively made of Cu-10Ni, were joined to each other (samples of sample Nos. 28 to 30 in Table 2).

(63) Thicknesses of the first metal member and the second metal member were set to 0.1 mm.

(64) As the joining material, as shown in Table 2, plate-like joining materials having different thicknesses from 0.266 mm to 1.327 mm were used.

(65) The first metal member was joined to the second metal member under the same conditions as in Example 1 except for the above-mentioned thicknesses.

(66) Then, characteristics of the resulting joined bodies were measured and evaluated in the same way as in Example 1. Specifically, measurement of joint strength, evaluation of the remaining component, evaluation of flow out, and evaluation of existence or non-existence of cracks and measurement of joint strength after a thermal shock test were performed.

(67) In addition, in the evaluation of joint strength in Example 2, a sample having a shear strength of 20 Nmm.sup.2 or more was rated as (excellent), a sample having a shear strength of 2 Nmm.sup.2 or more and less than 20 Nmm.sup.2 was rated as (good), and a sample having a shear strength of less than 2 Nmm.sup.2 was rated as x (defective).

(68) The case where a ratio of the remaining first metal component was 0 to 3% by volume was rated as (excellent), the case where it was more than 3% by volume and 30% by volume or less was rated as (good), and the case where it was more than 30% by volume was rated as x (defective).

(69) The case where the flow out percent defective of the joining material was 0 to 10% was rated as (excellent), the case where it was more than 10% and 50% or less was rated as (good), and the case where it was more than 50% was rated as x (defective).

(70) With respect to the existence or non-existence of cracks after a thermal shock test, the existence or non-existence of production of cracks was evaluated.

(71) The joint strength (room temperature, 260 C.), the content of the remaining low melting point metal, the flow out percent defective and the existence or non-existence of cracks and joint strength after a thermal shock test of the joined bodies are shown in Table 2.

(72) In Table 2, Proportion (%) in the column First Metal and Second Metal represents the proportion of the total thickness (0.2 mm) of the first metal member (Cu-10Mn) and the second metal member (Cu-10Mn) to the combined value (0.466 mm) of the total thickness (in the sample No. 21, 0.1 mm2=0.2 mm) of the first metal member (Cu-10Mn) and the second metal member (Cu-10Mn) and the thickness (in the sample No. 21, 0.266 mm) of the joining material (Sn).

(73) TABLE-US-00003 TABLE 2 Joint Strength and Joint Strength and Thickness Evaluation Evaluation of (Room Temperature) (260 C.) Joining First Metal and Second Metal Joint Joint Sample Material Thickness Proportion Strength Strength No. (Sn) (mm) Kind (mm) (%) (Nmm.sup.2) Evaluation (Nmm.sup.2) Evaluation 21 0.266 Cu10Mn 0.1 42.9 25 23 22 0.404 Cu10Mn 0.1 33.1 28 24 23 0.467 Cu10Mn 0.1 30.0 30 26 24 0.533 Cu10Mn 0.1 27.1 31 16 25 0.765 Cu10Mn 0.1 20.1 29 11 26 1.066 Cu10Mn 0.1 15.8 27 9 27 1.327 Cu10Mn 0.1 13.1 27 7 28 0.342 Cu10Ni 0.1 36.9 30 27 29 0.467 Cu10Ni 0.1 30.0 33 29 30 1.027 Cu10Ni 0.1 16.3 27 8 Content of Flow Out Percent Thermal Shock Test and Remaining Low Defective and Evaluation Melting Point Evaluation Existence Metal and Evaluation Flow Out or Non- Content Percent existence Joint Sample (% by Defective of Crack Strength No. volume) Evaluation (%) Evaluation Production (Nmm.sup.2) Evaluation 21 0 0 None 24 22 0 0 None 26 23 0 0 None 26 24 11 11 None 28 25 16 14 None 25 26 21 21 None 24 27 26 49 None 23 28 0 0 None 28 29 0 0 None 28 30 23 41 None 24

(74) As shown in Table 2, with respect to the joint strength at room temperature, all of samples of sample Nos. 21 to 30 exhibited a joint strength of 20 Nmm.sup.2 or more, and were found to have adequate joint strength.

(75) Further, with respect to the joint strength at 260 C., each of samples of sample Nos. 21 to 30 has a joint strength of 7 to 26 Nmm.sup.2 that is 2 Nmm.sup.2 or more, and it was found that practicable joining was performed. Particularly, when the first metal and the second metal were Cu-10Mn, the samples of sample Nos. 21 to 23, 28 and 29, in which the proportion of Cu-10Mn was 30% by volume or more, exhibited a joint strength of 23 Nmm.sup.2 or more, and were found to have high strength in high temperature.

(76) Further, with respect to the content of the remaining low melting point metal, it was found that all of the samples of sample Nos. 21 to 30 exhibited a content of the remaining low melting point metal of 30% by volume or less, and particularly in the samples of sample Nos. 21 to 23 in which the proportion of Cu-10Mn is 30% by volume or more and the samples of sample Nos. 28 and 29 in which the proportion of Cu-10Ni is 30% by volume or more, the content of the remaining low melting point metal was 0% by volume.

(77) Further, with respect to the flow out percent defective of the joining material, it was found that all of the samples of sample Nos. 21 to 30 exhibited a flow out percent defective of 50% or less, and particularly in the samples of sample Nos. 21 to 23 in which the proportion of Cu-10Mn is 30% by volume or more and the samples of sample Nos. 28 and 29 in which the proportion of Cu-10Ni is 30% by volume or more, the flow out percent defective was 0% by volume and high heat resistance was obtained.

Example 3

(78) A first metal member and a second metal member, respectively made of metals (CuMn alloys) as shown in sample Nos. 31 to 35 in Table 3, were joined to each other by using a joining material using Sn as a low melting point metal.

(79) A first metal member and a second metal member, respectively made of metals (CuNi alloys) as shown in sample Nos. 36 to 39 in Table 3, were joined to each other by using a joining material using Sn as a low melting point metal.

(80) Thicknesses of the first metal member and the second metal member were set to 0.3 mm.

(81) As the joining material, a plate-like joining material having a thickness of 0.1 mm was used.

(82) The first metal member was joined to the second metal member under the same conditions as in Example 1 except for the above-mentioned thicknesses.

(83) Then, characteristics of the resulting joined body were measured and evaluated in the same way as in Example 1. Specifically, measurement of joint strength, evaluation of the remaining component, evaluation of flow out, and evaluation of existence or non-existence of cracks and measurement of joint strength after a thermal shock test were performed.

(84) In addition, evaluation of joint strength, evaluation of the content of the remaining low melting point metal and evaluation of the flow out percent defective were performed according to the same criteria as in Example 2.

(85) The joint strength (room temperature, 260 C.), the content of the remaining low melting point metal, the flow out percent defective and the existence or non-existence of cracks and joint strength after a thermal shock test of the joined bodies are shown in Table 3.

(86) TABLE-US-00004 TABLE 3 Joint Strength and Joint Strength and Content of Remaining Evaluation Evaluation Low Melting Point First Metal (Room Temperature) (260 C.) Metal and Evaluation Joining and Second Joint Joint Content Sample Material Metal Strength Strength (% by No. (0.3 mm) (0.1 mm) (Nmm.sup.2) Evaluation (Nmm.sup.2) Evaluation volume) Evaluation 31 Sn Cu5Mn 28 6 19 32 Sn Cu10Mn 27 24 0 33 Sn Cu15Mn 28 25 0 34 Sn Cu20Mn 30 12 9 35 Sn Cu30Mn 31 5 21 36 Sn Cu5Ni 28 8 12 37 Sn Cu10Ni 30 26 0 38 Sn Cu15Ni 29 26 0 39 Sn Cu20Ni 30 12 5 Thermal Shock Test and Flow Out Percent Evaluation Defective and Evaluation Existence Flow Out or Non- Percent existence Joint Sample Defective of Crack Strength No. (%) Evaluation Production (Nmm.sup.2) Evaluation 31 32 None 24 32 0 None 25 33 0 None 25 34 15 None 27 35 35 None 27 36 26 None 26 37 0 None 26 38 0 None 25 39 12 None 27

(87) As shown in Table 3, with respect to the joint strength at room temperature, all of samples of sample Nos. 31 to 39 exhibited a joint strength of 20 Nmm.sup.2 or more, and were found to have adequate joint strength.

(88) Further, with respect to the joint strength at 260 C., each of samples of sample Nos. 31 to 39 was found to have a joint strength of 5 to 26 Nmm.sup.2 which is a practicable joint strength of 2 Nmm.sup.2 or more.

(89) Particularly, the samples of sample No. 32 in which the first metal and the second metal were Cu-10Mn, the sample of sample No. 33 in which the first metal and the second metal were Cu-15Mn, the sample of sample No. 37 in which the first metal and the second metal were Cu-10Ni, and the sample of sample No. 38 in which the first metal and the second metal were Cu-15Ni exhibited a joint strength of 24 Nmm.sup.2 or more, and were found to have high strength in high temperature.

(90) With respect to the content of the remaining low melting point metal, it was found that all of the samples of sample Nos. 31 to 39 exhibited a content of the remaining low melting point metal of 30% by volume or less, and moreover in the sample of sample No. 32 in which the first metal and the second metal were Cu-10Mn, the sample of sample No. 33 in which the first metal and the second metal were Cu-15Mn, the sample of sample No. 37 in which the first metal and the second metal were Cu-10Ni and the sample of sample No. 38 in which the first metal and the second metal were Cu-15Ni, the content of the remaining low melting point metal was 0% by volume.

(91) Further, with respect to the flow out percent defective of the joining material, it was found that all of the samples of sample Nos. 31 to 39 exhibited a flow out percent defective of 35% or less, and moreover in the sample of sample No. 32 in which the first metal and the second metal were Cu-10Mn, the sample of sample No. 33 in which the first metal and the second metal were Cu-15Mn, the sample of sample No. 37 in which the first metal and the second metal were Cu-10Ni and the sample of sample No. 38 in which the first metal and the second metal were Cu-15Ni, the flow out percent defective was 0% and high heat resistance was obtained.

Example 4

(92) In Examples 1 to 3 described above, the plate-like joining material was used as a joining material containing a low melting point metal, but in Example 4, a solder paste obtained by mixing a flux and a low melting point metal (Sn-3Ag-0.5Cu powder) was used, and a first metal member made of Cu and a second metal member made of Cu-10Mn were joined to each other.

(93) In joining, the above-mentioned solder paste was printed on the first metal member made of Cu, and the second metal member made of Cu-10Mn was overlaid thereon, and then reflowing was performed at 250 C. for 30 minutes to join the first metal member to the second metal member.

(94) Then, characteristics of the resulting joined body were measured and evaluated in the same way as in Example 1. Specifically, measurement of joint strength, evaluation of the remaining component, evaluation of flow out, and evaluation of existence or non-existence of cracks and measurement of joint strength after a thermal shock test were performed, and characteristics were evaluated.

(95) Consequently, it was found that a joined body having characteristics equal to those of samples of Examples 1 to 3 which meet the requirements of the present invention was obtained.

(96) In examples described above, the present invention has been described taking a case where the whole first metal member is made of the first metal and the whole second metal member is made of the second metal as an example, but it is also possible to employ a constitution in which the first metal and the second metal are metal materials composing plating films formed on the surfaces of the first metal member (electrode body) and the second metal member (electrode body) to be joined to each other, respectively, and at least one of the first metal and the second metal is a metal material having a lattice constant difference of 50% or more from the intermetallic compound.

Example 5

(97) a) In Example 5, a solder paste obtained by mixing a flux and a low melting point metal (Sn-3Ag-0.5Cu powder) was used, and an electronic device having a structure in which a chip capacitor and a surface acoustic wave filter were mounted on a glass epoxy board was manufactured by joining a land electrode (first metal member in the present invention) made of Cu on the glass epoxy board to an external electrode (second metal member in the present invention) made of Cu-10Mn of the chip capacitor (electronic part) and the surface acoustic wave filter (SAW filter) (electronic part).

(98) That is, the electronic device is an electronic device having a structure in which the above first metal member is joined to the above second metal member with a joining material meeting the requirements of the present invention sandwiched therebetween.

(99) In joining the external electrode (second metal member) to the land electrode (first metal member), the above-mentioned solder paste was printed on the first metal member made of Cu of a glass epoxy board, and the external electrode (second metal member) made of Cu-10Mn of the chip capacitor and a SAW filter was overlaid thereon, and then reflowing was performed at 250 C. for 30 minutes to join the first metal member to the second metal member.

(100) The thickness of the first metal member was set to 0.05 mm and the thickness of the second metal member was set to 0.05 mm.

(101) Further, the solder paste was printed on the land electrode by using a metal mask having a thickness of 0.05 mm.

(102) Characteristics of the resulting joined bodies were measured and evaluated in the same way as in Example 1. Specifically, measurement of joint strength, evaluation of the remaining component, evaluation of flow out, and evaluation of existence or non-existence of cracks and measurement of joint strength after a thermal shock test were performed, and characteristics were evaluated.

(103) Evaluation of joint strength, evaluation of the content of the remaining low melting point metal and evaluation of the flow out percent defective were performed according to the same criteria as in Example 2.

(104) The joint strength (room temperature, 260 C.), the content of the remaining low melting point metal, the flow out percent defective and the existence or non-existence of cracks and joint strength after a thermal shock test of the joined bodies are shown in Table 4.

(105) TABLE-US-00005 TABLE 4 Low Melting First Metal and Second Metal Joint Strength and Joint Strength and Point First Metal Second Metal Evaluation Evaluation Metal Member Member (Room Temperature) (260 C.) Composing Made of Made of Joint Joint Joining First Second Strength Strength Material Metal Cu Metal Cu10Nn (Nmm.sup.2) Evaluation (Nmm.sup.2) Evaluation Sn3Ag0.5Cu Electrode External 28 24 of Glass Electrode Epoxy of Chip Board Capacitor External 29 24 Electrode of SAW Filter Content of Flow Out Percent Thermal Shock Test and Low Melting First Metal and Second Metal Remaining Low Defective and Evaluation Point First Metal Second Metal Melting Point Metal Evaluation Existence Metal Member Member and Evaluation Flow Out or Non- Composing Made of Made of Content Percent existence Joint Joining First Second (% by Defective of Crack Strength Material Metal Cu Metal Cu10Nn volume) Rating (%) Evaluation Production (Nmm.sup.2) Evaluation Sn3Ag0.5Cu Electrode External 0 0 None 16 of Glass Electrode Epoxy of Chip Board Capacitor External 0 0 None 18 Electrode of SAW Filter

(106) As shown in Table 4, it was found that also in Example 5, a joined body having characteristics equal to those of samples of Examples 1 to 4 which meet the requirements of the present invention was obtained.

(107) In addition, it is also possible to employ a constitution in which the first metal and the second metal are metal materials composing plating films formed on the surfaces of the first metal member (electrode body) and the second metal member (electrode body) to be joined to each other, respectively, and at least one of the first metal and the second metal is a metal material having a lattice constant difference of 50% or more from the intermetallic compound.

(108) The present invention is not intended to be limited to the above-mentioned examples, and various applications and variations may be made within the scope of the invention regarding types and composition of the low melting point metal composing the joining material, and types and composition of materials composing the first metal member having at least a surface made of a first metal and the second metal member having at least a surface made of a second metal.

(109) Further, various applications and variations may be made also regarding the type of object to be joined by applying the present invention, and conditions in the joining step.

(110) In the present invention, various applications and variations may be made also in other aspects within the scope of the invention.

DESCRIPTION OF REFERENCE SYMBOLS

(111) 10 plate-like joining material 11a first metal member (first metal) 11b second metal member (second metal) 12 Intermetallic compound 64 Laminer intermetallic compound