JPH0784630B2 - Copper alloy for electronic and electric equipment and its manufacturing method - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial field of application] The present invention relates to a copper alloy for electronic / electrical equipment, which has high mechanical strength and is excellent in electrical / thermal conductivity, solderability, plating property and corrosion resistance, and its production. It is about law.

[Conventional technology]

Copper bronze (Cu-Sn based alloy) and brass (Cu-Zn based) are generally used as copper alloys for electronic and electrical equipment used in semiconductor lead frames, various terminals, connector contacts, springs, heat exchangers, various conductors, etc. Alloy), nickel silver (Cu-Ni-Zn alloy), etc. are known. However, brass and nickel silver have a fatal defect called stress corrosion cracking and cannot be applied to applications with high mechanical stress. Phosphor bronze is most widely used because of its high strength and excellent workability, but it uses a large amount of Sn, which has low conductivity and is expensive. Also soldering
Not only does it easily cause the phenomenon of peeling of Sn and Sn alloy plating, but it also possesses stress corrosion cracking, though not as much as brass and nickel silver.

Therefore, in some applications Cu-Fe alloys such as C194 (Cu
-2.3wt% Fe-0.12wt% Zn-P alloy) and C195 (Cu-1.5wt)
% Fe-0.8 wt% Co-0.6 wt% Sn-P alloy) is used. This alloy is not as strong as 6wt% Sn phosphor bronze,
It has a conductivity that is two to three times that of the alloy and is not susceptible to stress corrosion cracking. However, not only is workability inferior, but plating and solderability are insufficient.

[Problems to be solved by the invention]

In recent years, electronic / electrical devices have become smaller, more highly integrated, more sophisticated,
Along with surface mounting, a copper alloy having the following characteristics is required.

(1) Both strength and conductivity (heat conductivity) are high.

(2) Good workability.

(3) Solderability, plating property, bonding property, especially solder joint strength and plating adhesion are high for a long time.

(4) Corrosion resistance, especially no susceptibility to stress corrosion cracking.

(5) Be economical.

[Means for solving problems]

As a result of various investigations in view of the above, the present invention has developed a copper alloy for electronic / electrical devices, which has high mechanical strength, excellent electrical / thermal conductivity, solderability, plating property, and corrosion resistance, and a method for producing the same. is there.

That is, the alloy of the present invention, Cr0.1 ~ 0.75%, Sn0.05 ~ 7.5%, Mg
Or, at least one kind of Ca is 0.0005-0.05%, P0.0001-
0.02%, Zn5% or less, Si0.2% or less, B0.1% or less, RE0.1% or less at least one or more, O ₂ content is limited to 0.0025% or less However, the balance is composed of Cu and unavoidable impurities.

The production method of the present invention is Cr 0.1 to 0.75%, Sn 0.05 to 7.5%, Mg
Or, at least one kind of Ca is 0.0005-0.05%, P0.0001-
0.02% or Zn5% or less, Mn0.5% or less, Si
Alloy casting containing 0.2% or less, B0.1% or less, RE 0.1% or less, at least one kind or more, O ₂ content limited to 0.0025% or less, and balance Cu and unavoidable impurities. A lump,
After heating to 850-950 ℃ and hot working, 850 ℃ to 450 ℃
Pass the temperature range of within 20 minutes to cool, then 400
It is characterized in that cold working including a heat treatment for 5 minutes or more at a temperature of up to 500 ° C. is performed at least once.

[Work]

The alloy of the present invention is an alloy in which Sn is solid-dissolved in Cu and Cr is precipitated and dispersed, and excellent characteristics are obtained by the mutual action of both. In addition, Mg and Ca homogenize the precipitation dispersion of Cr,
Improves practical properties such as bonding, plating, soldering, etching, and workability. These components act effectively within the scope of the present invention, but if the content is less than the lower limit, a sufficient effect cannot be obtained, and if the content exceeds the upper limit, manufacturing defects and reduction in conductivity are brought about. In particular, the characteristics become maximum when the Cr content is 0.2 to 0.4%. Excess Cr
Becomes coarse-grained. Further, Sn is effective for strength and workability, but since it lowers the conductivity, it is desirable to set the Sn content to 0.05 to 0.5% for the purpose of requiring both conductivity and strength. 60-95% IACS is possible and strength is
About 60Kg / mm ² is possible. In particular, when the Sn content is 0.5% or more, if the conductivity is sacrificed, an improvement in strength and workability of about 80 kg / mm ² can be expected.

If Mg and Ca are excessive, manufacturing will be extremely difficult. If the amount is insufficient, the above-mentioned effects cannot be exhibited. Since the alloy structure is finely homogenized by the coexistence of Mg and Ca, the above-mentioned effects are obtained.

The action of the above alloy components is particularly effective at P 0.0001 to 0.02%, preferably 0.0001 to 0.005%, and O ₂ 0.0025% or less, promoting the precipitation of these alloy components, and making the precipitation uniform and fine. However, alloys exceeding this amount are harmful to the uniform precipitation and dispersion of alloy components. Since P can contribute to the flowability of molten metal, 0.0001 to 0.005% is particularly desirable. In particular, coarse precipitation dispersion not only hinders the improvement of strength, but also becomes detrimental to workability, plating properties, solderability, and bondability, and is practically harmful to precision and minute processed parts required for electronic devices such as semiconductors. Becomes

The addition of at least one or more of Zn, Mn, Si, B, and RE further improves the properties and production conditions of the alloy of the present invention. All of these components act as deoxidizers, and It not only works for uniform solid solution and precipitation dispersion of alloy components, but also works effectively for bonding and adhesion of solder and plating. However, if the content of these components exceeds the upper limits, the electrical conductivity is lowered and other problems occur.

The alloy of the present invention is not susceptible to stress corrosion cracking, and properties such as strength can be optimized by the above manufacturing method. That is, the alloy ingot having the above composition is heated to 850 to 950 ° C. and hot worked,
Subsequently, the material is cooled by passing it from 850 ° C to 450 ° C for a period other than 20 minutes, and then heat-treated at a temperature of 400 to 500 ° C for 5 minutes or more at least once to finish it into a desired size by cold working. .

Therefore, the reason why the material is heated to 850 to 950 ° C. and hot worked is that the above-mentioned target homogeneous precipitation dispersion cannot be achieved by the production method of the present invention even if the heating temperature is less than 850 ° C. or exceeds 950 ° C. . Further, after hot working, the material is allowed to pass from 850 ° C. to 450 ° C. within 20 minutes for cooling, because the desired homogeneous precipitation dispersion cannot be achieved if the time exceeds 20 minutes. In addition, the reason why cold working including heat treatment at 400 to 500 ° C. for 5 minutes or more after cooling is to perform uniform precipitation by heating and work into a desired size. This is because it becomes insufficient, and if it exceeds the upper limit, the precipitate becomes coarse. It should be noted that, for uniform precipitation, it is also effective to give an appropriate working strain before heat treatment.

The above-mentioned manufacturing method shows an example of optimizing the above-mentioned action of the alloy of the present invention, and it is of course possible to manufacture the alloy under conditions outside this range. In addition to the above composition, for example, a small amount of Al, Ni,
Co, Ti, Zr, Fe, Mo, W, Ta, Nb, Hf, Ge, Pb, As, Sb, Ga, In, Y, Tl, B
It is also possible to use e, Ba, Cd, Bi, Se, Te, Ru, Ag, Au, Dd, Pt and the like together.

〔Example〕

An alloy ingot (40 mm × 40 mm × 30 mm) having the composition shown in Table 1 was externally cut, heated at 875 ° C. for 15 minutes, and hot-rolled to form a plate having a thickness of 10 mm. The rolling time was about 3 minutes, and the rising temperature was 670 to 700 ° C. Immediately after rolling, this was water-cooled to 100 ° C. or lower. After pickling this, the thickness is 1.2
cold rolled to 450 mm, then heat treated at 450 ° C for 25 minutes, then cold rolled to a thickness of 0.4 mm, again heat treated at 420 ° C for 30 minutes and then cold rolled to a thickness of 0.20 mm, then Heat treatment was performed at 300 ° C for 15 minutes.

In addition to measuring the tensile strength, elongation and conductivity of these, a 90 ° angle V-bending test with various tip radii R was performed and the cracked state of the bent part was examined to find the minimum radius (R) without microcracks. The ratio R / t with the plate thickness (t) was determined. For stress corrosion cracking, the cracking time was determined according to JIS C8306 by the constant load method in 3vol% NH ₃ vapor. The load is the tensile strength
It was set to 50%. Next, a lead wire was soldered to a portion having a diameter of 9 mm by eutectic solder, and after aging at 150 ° C. for 300 hours, a pull test was performed to obtain solder joint strength. Also, Sn-5% Pb alloy plating was applied to a thickness of 7.5μ in a borofluoride bath, and 1
After holding at 05 ° C for 2000 hours, the peeling of the plating layer at the 100 ° angled bending portion was observed under a microscope. Next, after treating with 10% KCN solution, 2.5 μm thick Ag is plated in AgCN bath, and it is heated at 450 ℃ × 5 minutes to simulate the heat history of die bonding, and then at 225 ℃. Then, using Au wire with a wire diameter of 23μ, the first and second bonds were formed by the automatic ultrasonic thermocompression bonding method to form 1,000 1.5 mm loops. This was subjected to a pull test to obtain the bonding yield. It should be noted that anything other than broken wires is peeled off with the second bond,
It was bad. These results are compared with conventional alloys (phosphor bronze, C19
It is shown in Table 2 in comparison with 4).

As is clear from Tables 1 and 2, the alloy No. 1 of the present invention
Compared with the conventional alloy, phosphor bronze (No.12), all of Nos. 5 to 5 have excellent conductivity and corrosion resistance, and excellent soldering and plating reliability. The conventional alloy is C194 (No.13). It is understood that the strength and molding processability are excellent, and the reliability of soldering, plating and bonding is excellent as compared with the above.

On the other hand, Comparative Alloy No. 6 having a insufficient Cr content is inferior in strength, and Comparative Alloy No. 7 having an inadequate Sn and Mg content is inferior in strength as well as inferior plating reliability. In addition, No. 11 lacking Mg has a result that in addition to characteristics such as strength, plating and solderability are also inferior. Comparative alloy N with excess Mg content
In o.8, a normal ingot was not obtained, and the final processing could not be achieved. Further, it is understood that Comparative Alloy No. 9 having an excessive O ₂ content has not only poor moldability but also poor reliability of bonding and plating, and Comparative Alloy No. 10 having an excessive Mn content has poor strength.

〔The invention's effect〕

As described above, according to the present invention, strength, conductivity (heat conductivity),
Moldability and corrosion resistance are excellent, soldering and plating reliability is greatly improved, and for electronic and electrical equipment, for example, semiconductor lead frames, connectors, spring materials such as switches, terminals, heat exchangers, various conductors. As a result, it has an industrially remarkable effect such as miniaturization and high integration of electronic and electric devices.

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Shigeo Shinozaki Inventor, 500 Kiyotaki-cho, Nikko-shi, Tochigi Furukawa Electric Co., Ltd. Nikko Denki Copper Works (72) Masato Asai 500, Kiyotaki-cho, Nikko-shi, Tochigi Furukawa Electric Kogyo Co., Ltd. Nikko Denki Copper Works (56) Reference JP 61-99642 (JP, A) JP 58-123862 (JP, A) JP 60-245752 (JP, A)

Claims (3)

[Claims] 1. Cr 0.1 to 0.75 wt%, Sn 0.05 to 7.5 wt%, 0.0005 to 0.05 wt% of at least one of Mg or Ca, P0.0001 to
Contains 0.02wt%, Zn5wt% or less, Mn0.5wt% or less, Si
0.2 wt% or less, B 0.1 wt% or less, rare earth element (RE) 0.1 wt%
A copper alloy for electronic / electrical devices, containing at least one of the following, limiting the O ₂ content to 0.0025 wt% or less, and the balance Cu and inevitable impurities. 2. A Cr content of 0.2 to 0.4 wt% and a Sn content of 0.05.
The copper alloy for electronic / electrical equipment according to claim 1, wherein the copper alloy is limited to 0.5 wt%. 3. 0.1 to 0.75 wt% Cr, 0.05 to 7.5 wt% Sn, 0.0005 to 0.05 wt% P, at least one of Mg and Ca.
0.02wt% included, Zn5wt% or less, Mn0.5wt% or less, Si0.
2 wt% or less, B 0.1 wt% or less, rare earth element (RE) 0.1 wt% or less at least one or more, O ₂ content is limited to 0.0025 wt% or less, balance Cu and inevitable An alloy ingot made of impurities is heated to 850 to 950 ° C and hot worked, then passed through a temperature range of 850 ° C to 450 ° C within 20 minutes to cool, and then at a temperature of 400 to 500 ° C. A method for producing a copper alloy for electronic and electrical equipment, which comprises performing cold working including at least one heat treatment for 5 minutes or more.