Clad material for electric contacts and method for producing the clad material

Abstract

The present invention is a clad material for an electric contact, including a base material composed of a Cu-based, precipitation-type age-hardening material, and a contact material composed of an Ag alloy bonded to the base material. On a bonded interface between the contact material and the base material, a width of a diffusion region including Ag and Cu is 2.0 μm or shorter. The clad material is produced by bonding each other the contact material and the base material having undergone solutionizing and age-hardening beforehand, suppressing the diffusion region from expanding after bonding. The present invention is capable of providing an electric contact, which achieves higher conductivity, without sacrificing property of the Cu-based, precipitation-type age-hardening material.

Claims

1. A clad material for an electric contact, comprising: a base material composed of a Cu-based, precipitation-based age-hardening material; and a contact material composed of an Ag alloy bonded to the base material, whereinafter, on a bonded interface between the contact material and the base material, a width of a diffusion region including Ag and Cu is from 0.1 μm to 2.0 μm.

2. The clad material for an electric contact according to claim 1, whereinafter the Ag alloy constituting the contact material has an Ag concentration ranging from 10 mass % to 95 mass % inclusive, and contains at least one element selected from a group composed of Ni, Pd, Cu, Au, and Pt.

3. The clad material for an electric contact according to claim 2, whereinafter the Cu-based, precipitation-based age-hardening material is one of a Cu—Ni—Si based alloy, a Cu—Ni—Si—Mg based alloy, a Cu—Be based alloy, a Cu—Fe based alloy, a Cu—Fe—Ni based alloy, a Cu—Sn—Cr—Zn based alloy, and a Cu—Cr—Mg based alloy.

4. The clad material for an electric contact according to claim 2, whereinafter the Ag alloy constituting the contact material is one of an Ag—Cu—Ni based alloy, an Ag—Ni based alloy, an Ag—Pd based alloy, an Ag—Pd—Cu based alloy, an Ag—Pd—Cu—Pt—Au based alloy, and an Ag—Au—Cu—Pt based alloy.

5. The clad material for an electric contact according to claim 4, whereinafter the Cu-based, precipitation-based age-hardening material is one of a Cu—Ni—Si based alloy, a Cu—Ni—Si—Mg based alloy, a Cu—Be based alloy, a Cu—Fe based alloy, a Cu—Fe—Ni based alloy, a Cu—Sn—Cr—Zn based alloy, and a Cu—Cr—Mg based alloy.

6. The clad material for an electric contact according to claim 1, whereinafter the Cu-based, precipitation-based age-hardening material is one of a Cu—Ni—Si based alloy, a Cu—Ni—Si—Mg based alloy, a Cu—Be based alloy, a Cu—Fe based alloy, a Cu—Fe—Ni based alloy, a Cu—Sn—Cr—Zn based alloy, and a Cu—Cr—Mg based alloy.

7. The clad material for an electric contact according to claim 1, wherein the width of the diffusion region including Ag and Cu is from 0.9 μm to 2.0 μm.

8. A method for producing the clad material for an electric contact according to claim 1, the method comprising the steps of: bonding the base material and the contact material to produce a rough clad material; subjecting the rough clad material to an anneal-heat treatment at a temperature falling within a range from −200° C. to −100° C. inclusive from a recrystallization temperature of the base material; and processing the heat-treated rough clad material.

9. A method for producing the clad material for an electric contact according to claim 2, the method comprising the steps of: bonding the base material and the contact material to produce a rough clad material; subjecting the rough clad material to an anneal-heat treatment at a temperature falling within a range from −200° C. to −100° C. inclusive from a recrystallization temperature of the base material; and processing the heat-treated rough clad material.

10. A method for producing the clad material for an electric contact according to claim 4, the method comprising the steps of: bonding the base material and the contact material to produce a rough clad material; subjecting the rough clad material to an anneal-heat treatment at a temperature falling within a range from −200° C. to −100° C. inclusive from a recrystallization temperature of the base material; and processing the heat-treated rough clad material.

11. A method for producing the clad material for an electric contact according to claim 6, the method comprising the steps of: bonding the base material and the contact material to produce a rough clad material; subjecting the rough clad material to an anneal-heat treatment at a temperature falling within a range from −200° C. to −100° C. inclusive from a recrystallization temperature of the base material; and processing the heat-treated rough clad material.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

(1) FIG. 1 is a view illustrating a process for producing a clad material for electric contact, according to one embodiment.

(2) FIG. 2 is SEM pictures and results of EDS analysis on bonded interfaces, according to Example 1 and Comparative Example 1.

(3) FIG. 3 is a view illustrating a conventional process for producing a clad material for electric contact.

MODE FOR CARRYING OUT THE INVENTION

(4) Embodiments of the present invention will now be described hereinafter. In the embodiments, a plurality of kinds of Ag alloys each serving as a contact material and a plurality of kinds Cu-based, precipitation-type age-hardening materials each serving as a base material were prepared to produce clad materials (inlay type clad materials). The Ag alloys used in the embodiments and served as contact materials (Table 1) and the Cu-based, precipitation-type age-hardening materials used in the embodiments and served as base materials are illustrated below (Table 2). Among the base materials in Table 2, B1, B2, B3, and B4 represent the Cu-based, precipitation-type age-hardening materials with higher strength. Meanwhile, B5, B6, B7, and B8 represent the Cu-based, precipitation-type age-hardening materials with moderate strength. In first to third embodiments described below, contact materials and base materials were appropriately selected from among the materials. Clad materials were thus produced and evaluated.

(5) TABLE-US-00001 TABLE 1 Contact material Composition (wt %) Symbol Constitution Ag Cu Ni Pd Au Pt Zn Sm In S1 Ag—Cu—Ni based 93. 6 0.5 — — — — — — S2 alloy 92. 6 0.5 — — — 1 — — S3 90 8 0.5 — — — 1 0.5 — S4 Ag—Ni based alloy 90 — 10 — — — — — — S5 85 — 15 — — — — — — S6 Ag—Pd based 70 — — 30 — — — — — S7 alloy 50 — — 50 — — — — — S8 67 — 1 30 — — — — 2 S9 Ag—Pd—Cu—Pt—Au 30 14 1 35 10 10 — — — based alloy S10 Ag—Au—Cu—Pt 10 14 1 — 70 5 — — — based alloy S11 Ag—Pd—Cu based 40 16.5 — 43 — 0.5 — — — alloy

(6) TABLE-US-00002 TABLE 2 Base material (Cu based age-hardening material) Composition (wt %) Symbol Constitution Cu Ni Be Fe Si P Mg Cr Sn Zn Co Mn B1 Cu—Ni—Si based Rest 1.99 — — 0.48 — — — — — — 0.07 alloy (Corson of the based) composition B2 Cu—Ni—Si—Mg 2.7  — — 0.53 — 0.12 — — — — — based alloy (Corson based) B3 Cu—Be based — 0.32 — — — — — — — 0.5 — B4 alloy (Beryllium — 1.89 — — — — — — — 0.3 — copper based) B5 Cu—Fe based — — 2.35 — 0.07 — — — 0.12 — — alloy B6 Cu—Fe—Ni based 0.12 — 2.2  — 0.02 — — 0.05 — — — alloy B7 Cu—Sn—Cr—Zn — — — — — — 0.26 0.26 0.22 — — based alloy B8 Cu—Cr—Mg — — — — — 0.25 0.1  — — — — based alloy

(7) First embodiment: Combinations of contact materials and base materials used for producing clad materials in the embodiment are illustrated in Table 3. Table 3 illustrates recrystallization temperatures of the base materials and temperature conditions for aging performed before press-fitting with the contact materials, in addition to compositions of the contact materials and the base materials.

(8) TABLE-US-00003 TABLE 3 Base material Contact Base Recrystallization material material temperature Aging Example 1 S7 B1 700° C. After solutionizing at 700° C., aging at 450° C. Example 2 S5 B5 650° C. After solutionizing at 600° C., aging at 450° C. Example 3 S1 B3 750° C. After solutionizing at 750° C., aging at 450° C.

(9) A process for producing a clad material, according to the embodiment, is illustrated in FIG. 1. In the embodiment, the tape-shaped precipitation-type age-hardening materials having been subjected to an aging treatment beforehand and the tape-shaped contact materials, described in Table 1, were rolled and press-fitted. After the press-fitting, the tape-shaped rough clad materials were allowed to pass through a heating furnace heated at a temperature of 550° C. (reducing atmosphere) (1.0 m/min) to undergo anneal-heat treatment. The rough clad materials were rolled, were allowed to undergo again anneal-heat treatment, and were finally rolled. After the final rolling, the clad materials (each having a plate thickness of 0.1 mm) underwent slit processing. The tape-shaped clad materials each having a width of 18 mm were produced (Examples 1 to 3).

COMPARATIVE EXAMPLES 1 to 3

(10) Clad materials were produced through the conventional production process described in FIG. 3. That is, contact materials and base material were respectively clad-bonded to each other, and were subjected to solutionizing and age-heat treatment. The clad materials for electric contact were thus produced. Conditions for the solutionizing and the aging treatment in the comparative examples were identical to the conditions in the examples in Table 1. Other processing conditions were also identical to the processing conditions in the embodiment.

(11) EDS analysis was performed for the clad materials according to the examples and the comparative examples, produced as described above (Analysis device: JSM-7100E made by JEOL Ltd. and Detector: X-ACT made by OXFORD). In the analysis, test pieces were embedded in resin. Samples exposed with cross-sections were thus created. The samples were SEM-observed (power of 4000). As well as, a boundary between each of the contact materials and each of the base materials were line-analyzed through EDS (acceleration voltage: 15 kV). Based on results of the line analysis, widths of diffusion regions were measured. In the measurement, based on an Ag count number around an end (around a surface) of each of the contact material (100%), a point with an Ag count number of 95% was specified as a starting point, and a point with an Ag count number of 5% was specified as an ending point. A gap between the starting point and the ending point was determined as a diffusion region. For the measured widths of diffusion regions, desired five locations were EDS-analyzed, and average values were calculated.

(12) For the clad materials according to the examples and the comparative examples, resistance values were measured to confirm conductive property. The resistance values were measured based on a four-terminal method. As examples of cross-section observation, pictures of cross-sections around bonded interfaces in Example 1 and Comparative Example 1 are illustrated in FIG. 2. Results of measurement on widths of diffusion regions and resistance values are illustrated in Table 4.

(13) TABLE-US-00004 TABLE 4 Contact Electric material Base material Diffused region resistance Example 1 S7 B1 1 μm 0.22 mΩ Comparative 6 μm 0.41 mΩ Example 1 Example 2 S5 B5 1 μm 0.30 mΩ Comparative 6 μm 2.04 mΩ Example 2 Example 3 S1 B3 1.8 μm   0.34 mΩ Comparative 4 μm 0.43 mΩ Example 3

(14) As can be seen from the SEM pictures and the results of EDS analysis in FIG. 2, the diffusion region in Example 1 is narrowed in width. This tendency can also be found in the other examples. The widths of diffusion regions are each 1.8 μm or narrower. In the comparative examples, the diffusion regions all exceed 2 μm. Some of the diffusion regions each have a wider width of 6 μm.

(15) Development of the diffusion regions affects conduction characteristics of the clad materials. Although depending on the kinds of the contact materials and the base materials, it has been confirmed that, with the developed diffusion regions in some of the comparative examples, resistance values tended to increase.

(16) Second embodiment: In the embodiment, the Cu-based, precipitation-type age-hardening materials with higher strength, i.e., B1, B2, B3, and B4, were used as the base materials. Various contact materials were bonded to the base materials. The clad materials were thus produced. A process for producing the clad materials was basically followed to the method in the first embodiment. For aging of the non-clad base materials, processing conditions ordinary known for the materials were applied. For anneal-heat treatment of rough clad materials, a temperature ranging from −200° C. to −100° C. inclusive from each of recrystallization temperatures of the base materials was set.

(17) For the produced clad materials, a method identical to the method in the first embodiment was used to measure widths of diffusion regions. In the embodiment, for evaluating property of the clad materials, strength (tensile strength) and conductivity (IACS) were measured. In measurement of tensile strength, a universal precision tester (AGS-X made by Shimadzu Corporation) was used, and test pieces each having a size of 25.0 mm in length×30 mm in width×0.1 mm in thickness were measured. Tension was measured under a measuring condition, i.e., at a speed of 20 mm/min. Conductivity was measured through the four-terminal method. Specifically, for the test pieces (30 mm in width and 0.1 mm in thickness), measurement was made on a length of 1000 mm (Measuring apparatus: 4338B made by Agilent). For judgment of tensile strength and conductivity, by taking into account that the base materials being applied have higher strength, tensile strength equal to or above 600 MPa was judged to acceptable (“∘”), and conductivity equal to or above 20% IACS was judged to acceptable (“∘”). The results of evaluation on the clad materials produced in the embodiment are illustrated in Table 5.

(18) TABLE-US-00005 TABLE 5 Constitution of clad material Tensile strength Conductivity Test Contact Base Diffusion Measured Measured No. material material region/μm value/MPa Judgment value/IACS % Judgment 1 S2 B1 1.6 630 ◯ 35 ◯ 2 B2 1.7 730 ◯ 43 ◯ 3 B3 1.8 740 ◯ 43 ◯ 4 B4 1.7 1020 ◯ 21 ◯ 5 S3 B1 1.5 640 ◯ 36 ◯ 6 B2 1.6 740 ◯ 41 ◯ 7 B3 1.6 750 ◯ 44 ◯ 8 B4 1.7 1020 ◯ 20 ◯ 9 S8 B1 1.1 660 ◯ 40 ◯ 10 B2 1.1 780 ◯ 48 ◯ 11 B3 1.1 760 ◯ 46 ◯ 12 B4 1 1090 ◯ 22 ◯ 13 S9 B1 1.2 650 ◯ 39 ◯ 14 B2 1.1 770 ◯ 49 ◯ 15 B3 1.1 760 ◯ 47 ◯ 16 B4 1 1100 ◯ 21 ◯ 17  S10 B1 1.6 650 ◯ 38 ◯ 18 B2 1.7 760 ◯ 48 ◯ 19 B3 1.5 750 ◯ 45 ◯ 20 B4 1.5 1080 ◯ 21 ◯ 21  S11 B1 1.2 640 ◯ 39 ◯ 22 B2 1.1 770 ◯ 48 ◯ 23 B3 1.1 760 ◯ 47 ◯ 24 B4 1 1100 ◯ 22 ◯

(19) According to Table 5, the clad materials for electric contact, produced in the embodiment, each had a width of a diffusion region shorter than 2.0 μm. It has been confirmed that strength and conductivity of the clad materials all reached the acceptance values.

(20) Third embodiment: In the embodiment, the Cu-based, precipitation-type age-hardening materials with moderate strength, i.e., B5, B6, B7, and B8, were used as base materials. Various contact materials were bonded to the base materials. The clad materials were thus produced. A process for producing the clad materials was also basically followed to the method in the first embodiment. Ordinary processing conditions were applied for aging of the base materials. For anneal-heat treatment of rough clad materials, by taking into account recrystallization temperatures of the base materials used, appropriate ranges were set.

(21) For the produced clad materials, a method identical to the method in the first and second embodiments was used to measure widths of diffusion regions. Further, similar to the second embodiment, tensile strength and conductivity (IACS) were measured and evaluated. In the evaluation, with a matter that the base materials being applied have moderate strength taken into account, tensile strength equal to or above 400 MPa was judged to acceptable (“o”), and conductivity equal to or above 60% IACS was judged to acceptable (“0”). The results of evaluation on the clad materials produced in the embodiment are illustrated in Table 6.

(22) TABLE-US-00006 TABLE 6 Constitution of clad material Tensile strength Conductivity Test Contact Base Diffusion Measured Measured No. material material region/μm value/MPa Judgment value/IACS % Judgment 25 S2 B5 1.0 515 ◯ 65 ◯ 26 B6 1.1 445 ◯ 78 ◯ 27 B7 1.0 570 ◯ 69 ◯ 28 B8 1.0 650 ◯ 76 ◯ 29 S4 B5 1.1 520 ◯ 64 ◯ 30 B6 1.0 450 ◯ 78 ◯ 31 B7 1.2 580 ◯ 65 ◯ 32 B8 1.1 650 ◯ 78 ◯ 33 S6 B5 0.9 520 ◯ 67 ◯ 34 B6 0.9 455 ◯ 76 ◯ 35 B7 1.0 570 ◯ 66 ◯ 36 B8 0.9 670 ◯ 77 ◯ 37 S9 B5 1.0 515 ◯ 65 ◯ 38 B6 1.0 450 ◯ 75 ◯ 39 B7 1.0 565 ◯ 65 ◯ 40 B8 1.0 650 ◯ 78 ◯ 41  S10 B5 1.3 520 ◯ 64 ◯ 42 B6 1.5 455 ◯ 76 ◯ 43 B7 1.4 560 ◯ 64 ◯ 44 B8 1.3 645 ◯ 76 ◯ 45  S11 B5 1.1 510 ◯ 67 ◯ 46 B6 0.9 450 ◯ 77 ◯ 47 B7 1.0 575 ◯ 66 ◯ 48 B8 1.0 660 ◯ 78 ◯

(23) According to Table 6, the clad materials for electric contact, produced in the embodiment, each had a width of a diffusion region shorter than 2.0 μm. It has been confirmed that strength and conductivity of the clad materials also all reached the acceptance values.

INDUSTRIAL APPLICABILITY

(24) As described above, in the clad material for electric contact, according to the present invention, the diffusion region on the bonded interface between the contact material and the base material is suppressed from expanding. The present invention is the clad material with the precipitation-type age-hardening material applied as the base material to suppress the diffusion region from expanding, preventing higher conductivity from being inhibited, while keeping higher strength. The present invention is advantageously used as a contact material for various small-sized electronic and electric appliances.