JPH0425338B2 - - Google Patents

Description

[Detailed description of the invention]

[Industrial Application Field] The present invention relates to an improved copper alloy for electronic devices,
In particular, strength, workability, electrical conductivity (thermal conductivity), corrosion resistance,
It has excellent heat resistance and is suitable for manufacturing miniaturized precision parts. [Conventional technology] Electronic equipment, especially semiconductors (IC, transistors)
Copper alloys with excellent strength, workability, corrosion resistance, and conductivity are required for leads, connectors, switches, contact springs, etc. Cu-Be alloys and Cu-Ti alloys with excellent strength are known as such alloys, but these are expensive and Cu-Ni-
Sn-based spinodal alloys have low electrical conductivity of less than 10% IACS and poor workability, and the same is true for Cu-Ni-Al alloys. In addition, Corson alloys, such as Cu-Ni-Si, are alloys that have both strength and conductivity, but in order to obtain these properties, a combination of solution treatment and aging is essential, and they tend to be expensive. Furthermore, this alloy has a serious drawback as a copper alloy for electronic devices in that its bondability with solder (Sn and Sn-Pb alloys) deteriorates over time, impairing reliability. By adding Mg to Corson alloy, Cu-Ni-Si-
Although it is disclosed in US Pat. No. 4,594,221 that various properties are improved as a Mg-based
is an easily oxidizable element and requires atmospheric melting and casting, which increases costs. Furthermore, it was reported in Japanese Patent Publication No. 124254/1983 and Japanese Patent Publication No. 60/1989 that Cu-Ni-Si-Sn alloy, which is a Corson alloy with Sn added, is suitable for terminals, connectors, and lead materials.
Although it is disclosed in Japanese Patent No. 43448, it is not sufficient to meet the required properties desired for these uses, and it is necessary to improve strength, workability, solderability, and plating adhesion. The phosphor bronze for springs that is currently widely used is 60
Although it has a strength of ~80Kg/ ^mm2 , its electrical conductivity is ~10~
It has a low IACS of 15%, and it is a major practical drawback in terms of aging deterioration of solder joint strength and susceptibility to corrosion cracking. Therefore, Cu-Fe alloys such as C194
Alloys and C195 alloys are used in some cases, but their use is limited because their strength is around 45 to 65 kg/mm ² and their workability is poor. [Problems to be Solved by the Invention] In recent years, electronic devices have become smaller and more highly integrated, and it is strongly desired that Cu alloys used in these devices have improved strength and conductivity. In addition, it is inexpensive for large quantities, and in order to meet the trend toward surface mounting, solder joint strength and adhesion reliability of Sn and Sn-Pb alloy plating are also required. In order to meet these demands and replace conventional alloys, alloys with higher performance and lower cost are required. (1) Alloys with a higher balance of strength and electrical conductivity, for example, strength 50-100 Kg/mm ² and electrical conductivity 10-
Having the characteristics of 30% IACS. (2) It is cheap in terms of cost, for example, the alloy components are cheap and the manufacturing process is simple. (3) Excellent workability, corrosion resistance, and stress corrosion cracking resistance. (4) The solder joint strength and the adhesion of Sn and Sn-Pb alloy plating are stable over a long period of time. (5) In addition to Sn and Sn-Pb alloys for electronic equipment applications,
Plating materials such as Au, Ag, and Ni are often used, and the plating properties of these materials are also excellent. etc. are required. [Means for Solving the Problems] In view of this, the present invention has been developed as a result of various studies, and has been developed to provide a miniaturized precision component that has particularly excellent strength, workability, electrical conductivity (thermal conductivity), corrosion resistance, heat resistance, etc. We have developed a copper alloy for electronic devices that is especially suitable for semiconductor (IC, transistor, etc.) lead frames and connectors. That is, one of the aspects of the present invention is that Sn exceeds 4.0 wt% (hereinafter wt% is abbreviated as %) and 7.0% or less, and any one or more of Ni, Co, and Cr is contained in a total of 1.0 to 6.0% (however, Ni
1.0% or more and less than 3.5%) and more than 0.2% and less than 2.0% Si, and O ₂ content is included in the unavoidable impurities.
50ppm or less, the S content is 20ppm or less, and the average precipitate particle size is 10μm or less, with the balance consisting of Cu and unavoidable impurities, preferably
Ni1.0% or more and less than 3.5%, Co1.5% or less, Cr0.05~
Total of one or more types within a range of 0.8%
It is contained so that (Ni+Co+Cr)/Si=2 to 8 at 1.0 to 6.0%, the O ₂ content is 30 ppm or less, the S content is 10 ppm or less, and the average precipitate particle size is 3 μm or less. Another aspect of the present invention is Sn more than 4.0% and less than 7.0%, and a total of 1.0 to 6.0% of any one or more of Ni, Co, and Cr (however, Ni is 1.0% to less than 3.5%) and,
Contains more than 0.2% Si and 2.0% or less, and further Zn 5.0% or less, Mn 5.0% or less, Al 2.0% or less, Fe 2.0% or less,
Ti0.8% or less, Zr0.8% or less, Ag0.3% or less,
Mg 0.3% or less, Be 0.3% or less, In 0.3% or less,
Ca0.3% or less, P0.3% or less, B0.3% or less, Y0.3%
Below, any one or two or more types within the range of La 0.3% or less, Te 0.3% or less, Ce 0.3% or less for a total of 5.0%
The O ₂ content in unavoidable impurities, including:
50ppm or less, the S content is 20ppm or less, and the average precipitate particle size is 10μm or less, with the balance consisting of Cu and unavoidable impurities, preferably
Ni1.0% or more and less than 3.5%, Co1.5% or less, Cr0.05~
Total of one or more types within a range of 0.8%
It is contained so that (Ni+Co+Cr)/Si=2 to 8 at 1.0 to 6.0%, the O ₂ content is 30 ppm or less, the S content is 10 ppm or less, and the average precipitate particle size is 3 μm or less. The alloy of the present invention is produced by hot working and cold working an ingot that has been melted and cast with the above composition. For example, the ingot is heated to 700 to 1000℃, hot rolled or hot extruded, finished at 650℃ or higher, immediately cooled with water, and preferably cooled to 400℃ or lower at a rate of 10℃/sec or higher. do. The surface is cleaned by milling, shaving, or pickling, and then processed by cold rolling, drawing, etc.
Heat treatment at 350-700℃ for at least 5 minutes,
Finished using a combination of cold working. Furthermore, higher properties can be obtained by combining heat annealing at 200 to 550°C, tension leveler, tension annealing, etc. after the final cold working. Furthermore, the alloy of the present invention can be directly cold worked into an ingot and then heat treated. [Function] The copper alloy of the present invention has a strength of 50 to 100, depending on the composition.
Kg/mm ² , elongation 3-20%, electrical conductivity 10-40% IACS properties. Such a copper alloy of the present invention is Cu-Sn.
Silicon compounds of Ni, Co, and Cr, namely Ni _x Si _y , Co _x Si _y , and Cr _x Si _{y ,} are dispersed and precipitated in the uniform solid solution alloy matrix, making it possible to improve strength and conductivity. Particularly, Cr is partially precipitated as metallic Cr alone.
However, the reason why the composition of the copper alloy of the present invention is limited as described above is as follows. The reason for limiting the Sn content as above is that if the content is less than the lower limit, the strength is insufficient, and if it exceeds the upper limit, greater strength cannot be obtained, which is not only uneconomical, but also due to excessive Sn. Hot workability decreases,
Serious impediment to productivity. Since Ni, Co, Cr groups and Si are combined and precipitated in a stoichiometric ratio, it is desirable that the ratio (weight) of the two is in the range of about 2 to 8:1, and free uncombined Si and
Ni and Co reduce conductivity and are harmful to solder joint strength. Cr has an advantage in this respect, but
The strength improvement effect is less than that of Ni. However, the reason why the Si content and the total content of one or more of Ni, Co, and Cr are limited as above is that sufficient effects cannot be obtained when each is below the lower limit, and when the upper limit is exceeded, the content is high. This is because not only is this inconvenient because it impedes workability at high temperatures, but also solder wettability and the like are reduced. In particular, the Ni content should be 1.0% or more and less than 3.5%, and the Co content should be reduced.
It is desirable that the Cr content be 1.5% or less and the Cr content be 0.05 to 0.8%.
If it is less than the lower limit, there is no effect, and if it exceeds the upper limit, hot workability and solderability will be reduced. Although Cr strengthens the steel and improves hot rolling properties and heat resistance, although it is not as strong as Ni, it has no effect below the lower limit, and when it exceeds the upper limit, it significantly deteriorates castability, impairs productivity, and increases costs. easy. Although Co is not as strong as Ni, it is inferior in cost performance when the high cost is taken into consideration. However, it is extremely effective for heat resistance, especially for preventing crystal coarsening at high temperatures, and for practical purposes, it is desirable to add it within a range of 1.5% or less. Next, the O ₂ content was set to 5 ppm or less because of Cr and Si.
This is to suppress deterioration of plating adhesion and strength due to the generation of oxides such as oxides, and it is preferably 30 ppm or less.
The reason why the S content is set to 20 ppm or less is that S condenses at grain boundaries and significantly reduces hot workability, and is preferably 10 ppm or less. In addition, the average precipitate particle size was set to 10 μm or less because
The smaller the particle size of the compound precipitate, the more effective it is in improving strength, and if the particle size exceeds 10 μm, workability and plating adhesion will deteriorate, so it is preferably 3 μm or less. Next, Zn, Mn, Al, Fe, Ti, Zr, Ag, Mg,
The addition of Be, In, Ca, P, B, Y, La, Te, and Ce (hereinafter abbreviated as the third element) all act as deoxidizers and improve the workability and other properties of the alloy. Furthermore
Zn, Mn, Ag, Mg, and Ca improve hot workability and improve long-term stability of solder joint strength and adhesion of Sn and Sn-Pb alloy plating. Also, Al,
Fe, Ti, Zr, Be, In, P, B, Y, La, Te,
Ce suppresses coarse crystal growth and improves bending workability. However, the reason for limiting the content of these third elements as mentioned above is that if the content exceeds this limit, it will lead to a decrease in the conductivity and workability including hot working, and at the same time, it is difficult to obtain a sound ingot. This is because it becomes difficult to maintain the plating and further deteriorates plating adhesion and stress corrosion cracking susceptibility. As semiconductor elements become smaller, lead materials for semiconductor devices also become thinner, so improvements in strength are desired, but good heat dissipation is also required from a reliability perspective. In order to satisfy both of these conditions, the Sn content must be reduced to 2.0.
It is desirable to limit it to ~5.0%. On the other hand, electronic
There is a strong desire for higher packaging density and smaller size for electrical equipment connectors, sockets, springs, terminals, etc.
It is thought that walls will continue to become thinner, and in that case, having high strength is an essential element.
It is desirable to limit the Sn content to 2.5-7.0%. [Examples] The present invention will be described in detail below with reference to Examples. Example (1) The alloy composition shown in Table 1 was blended and melted, and cast into a water-cooled mold to form an ingot with a thickness of 40 mm, width of 80 mm, and length of 250 mm. Heat this to about 850℃ and make it 6mm thick.
It was hot-rolled to 100% and immediately cooled in water. The temperature at the end of hot rolling was approximately 680°C. This was pickled, cold rolled to a thickness of 1.2mm, then heat treated at 600℃ for 2 hours, cold rolled to a thickness of 0.4mm, and further
After heat treatment at 550°C for 2 hours, it was cold rolled to a thickness of 0.25mm. Regarding these, average particle size, tensile strength, elongation, electrical conductivity, bending ratio, solder joint strength, stress corrosion cracking resistance,
Ag plating property was investigated. The results were compared to the conventional alloy phosphor bronze (Sn8.0%, P0.1%, remainder Cu) and
C195 (Fe1.5%, Sn0.6%, Co0.8%, P0.09%, Cu
Table 2 shows a comparison with the remainder). The bendability was determined by bending using a 90° die with various bending radii (R), determining the presence or absence of cracks using a 40x magnification microscope, and determining the minimum R/t without cracking (t is the plate thickness). The bending axis was perpendicular to the rolling direction. The solder joint strength was determined by soldering a lead wire to an area of 9 mm in diameter, aging it at a temperature of 150°C for 300 hours, and then performing a pull test. Stress corrosion cracking is based on JIS C 8306, ammonia 3vol%
A constant load test was conducted under a tensile load of 30 kg/mm ² in an atmosphere of 30 kg/mm 2 , and the time until cracking occurred was measured. Ag plating properties were determined by etching the surface to a thickness of about 1 μm, then applying Ag strike plating and 5 μm thick Ag plating using the following bath, and then heating it at 475°C for 5 minutes in the air, and then checking for swelling. Examined. Ag Strike Metsuki AgCH 30g/ KCN 60g/ Current Density 5A/dm ² hours 15sec Ag Strike Metsuki AgCH 37g/ KCN 58g/ K ₂ CO ₃ 25g/ Current Density 1A/dm ²

【table】

【table】

[Table] As is clear from Tables 1 and 2, alloys Nos. 1 to 3 of the present invention are all C195 (No. 9), which is a conventional alloy.
It is found that all properties are satisfactory when compared with phosphor bronze (No. 10) and phosphor bronze (No. 10). On the other hand, comparative alloy No. 4 with a low Sn content lacks tensile strength, and comparative alloy No. 4 with a high Sn content lacks tensile strength.
No. 5 had poor workability, and rolling was discontinued. Comparative alloy No. 6, which has low Si and Ni contents, not only has insufficient tensile strength but also has high stress corrosion cracking susceptibility, while comparative alloy No. 7, which has high Si and Ni contents, has poor workability. The rolling process was discontinued due to poor performance.
Comparative alloy No. 8, which has a high O ₂ content, had a decrease in strength, plating adhesion, and bendability, and the precipitate grain size was also large. Example (2) The alloy composition shown in Table 3 was blended, and the thickness was 0.25 mm in the same manner as in Example (1).
Same as (1), average particle size, tensile strength, elongation, electrical conductivity, bending ratio, solder joint strength, stress corrosion cracking, Ag
We investigated the stickability. The results were compared to conventional alloys of phosphor bronze (Sn8%, P0.1%, remainder Cu) and C195.
(1.5% Fe, 0.6% Sn, 0.8% Co, 0.09% P, remainder of Cu) is shown in Table 4.

【table】

〔Effect of the invention〕

As described above, the present invention has high performance that greatly exceeds the characteristics of conventional phosphor bronze, and has remarkable industrial effects such as making it possible to miniaturize, increase density, and improve reliability of electronic equipment. It is something that plays.

Claims (1)

[Claims] 1 Sn more than 4.0wt% and 7.0wt% or less, Ni, Co,
A total of 1.0 to 6.0 wt% of one or more of Cr
(However, Ni is 1.0wt% or more and less than 3.5wt%)
Contains more than 0.2wt% Si and less than 2.0wt%, O ₂ content in unavoidable impurities less than 50ppm, and S content less than 50ppm.
A copper alloy for electronic devices consisting of Cu and unavoidable impurities, with an average precipitate particle size of 20ppm or less and 10μm or less. 2 Ni 1.0 wt% or more and less than 3.5 wt%, Co 1.5 wt% or less, and Cr 0.05 to 0.8 wt%, with a total of 1.0 to 6.0 wt% (Ni+Co+
Cr)/Si=2 to 8, O ₂ content is 30 ppm or less, S content is 10 ppm or less, and the average precipitate particle size is 3 μm or less. Copper alloy for use. 3 Sn over 4.0wt% and 7.0wt% or less, Ni, Co,
A total of 1.0 to 6.0 wt% of one or more of Cr
(However, Ni is 1.0wt% or more and less than 3.5wt%)
Contains more than 0.2wt% Si and less than 2.0wt%, and further
Zn5.0wt% or less, Mn5.0wt% or less, Al2.0wt% or less, Fe2.0wt% or less, Ti0.8wt% or less, Zr0.8wt%
Below, Ag0.3wt% or less, Mg0.3wt% or less,
Be 0.3wt% or less, In 0.3wt% or less, Ca 0.3wt% or less, P 0.3wt% or less, B 0.3wt% or less, Y 0.3wt% or less, La 0.3wt% or less, Te 0.3wt% or less, Ce0. 3wt
Total of any one type or two or more types within the range of % or less
A copper alloy for electronic devices, containing 5.0wt% or less, O ₂ content in inevitable impurities of 50ppm or less, S content of 20ppm or less, and average precipitate particle size of 10μm or less, the balance being Cu and inevitable impurities. . 4 Any one or more of Ni 1.0 wt% or more and less than 3.5 wt%, Co 1.5 wt% or less, and Cr 0.05 to 0.8 wt% in a total of 1.0 to 6.0 wt% (Ni + Co +
Cr)/Si=2 to 8, the electronic device has an O ₂ content of 30 ppm or less, a S content of 10 ppm or less, and an average precipitate particle size of 3 μm or less. Copper alloy for use.