JPH08209271A - Copper alloy for electronic equipment excellent in solder joining strength and its production - Google Patents

Abstract

PURPOSE: To produce a copper alloy for electronic equipment excellent in solder joining strength by preparing a copper alloy in which each content of Ni, Co, Cr, Si, Sn and P is prescribed. CONSTITUTION: The ingot of a copper alloy contg., by weight, >1 to 4% Ni or Ni and Co, >1.0 to 2% Cr, 0.2 to 1.5% Si and 1.1 to 3% Sn, furthermore contg. total >=5% of one or more kinds among <=0.3% P, <=0.3% B, <=5% Zn, <=1% Mn, <=0.2% Mg and <=0.5% Zr, and the balance Cu is cast. This cast ingot is subjected to hot working at >=650 deg.C and is immediately cooled to about <=350 deg.C at the rate of >=10 deg.C/sec to suppress the precipitation of compounds, by which working under low loads is made possible. Next, it is subjected to >=70% cold working and is subjected to heat treatment at 400 to 600 deg.C, therefore, by the operation of working strains, homogeneous and fine precipitation is swiftly executed. Thus, the copper alloy excellent in solder joining strength and suitable for electronic equipment can be obtd.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a copper alloy for electronic equipment having excellent solder joint strength, and more particularly to a copper alloy suitable for a small and high-density semiconductor lead frame and a method for producing the same.

[0002]

2. Description of the Related Art Cu-Sn based phosphor bronze is used as a copper alloy for electronic equipment, and a spring for a connector or a switch,
It is widely used for terminals, semiconductor lead frames, lead wires and the like. Although this alloy is excellent in strength and workability, its conductivity is as low as 10 to 25% IACS, so that it cannot be used for applications requiring conductivity and thermal conductivity. Therefore, for applications requiring electrical conductivity and thermal conductivity, a Cu-Fe system such as C194 (Cu-2.4wt% Fe-0.12wt% Zn-P
Alloy) (hereinafter wt% is abbreviated as%), C195 (Cu-1.5%
Fe-0.8% Co-0.6% Sn-P alloy) is used. This alloy has a strength of 45-55 kg / mm ² , conductivity of 50-65%
4 shows the characteristics of IACS.

[0003] In electronic equipment, miniaturization and densification are remarkable, and the required properties of alloys are constantly required to be high performance. Particularly, semiconductors are most remarkable and occupy the most important industrial position. For example, in a mass-produced plastic mold semiconductor, a DIP type 100 mil
The copper alloy is used in large quantities as a frame having two-way leads at a pitch. Recently, SOP, FP, as new surface mount type semiconductor packages that can be made smaller
PLCC has been developed. In particular, since PLCC uses a frame with leads of 50 mil pitch in four directions, it can be mounted in a higher density than a conventional DIP type. Also F
P is similar, SOP is bidirectional lead but 50mil
This is a surface mounting method using a thin pitch lead frame.

[0004]

The lead frame and the like used in the above-mentioned new electronic equipment are required to have a higher balance of high strength and workability as well as further improvement in conductivity, and furthermore, to have an isotropic mechanical property. Is required. That is, the characteristics of the sheet strip in the rolling direction and the width direction, especially the difference in processing characteristics, are fatal defects in lead frames such as PLCC which require high precision. However, the above-mentioned phosphor bronze and Cu-Fe alloys cannot satisfy these required characteristics, and at present, C
150 (Cu-0.1% Zr alloy) and Cu-2% Sn-0.1
Percent Cr alloy is used, the strength former exhibits a conductivity of about 90% IACS is only about 40 kg / mm ^2, the latter is intensity of about 50~55kg / mm ² also conductivity Is 30 ~
Only 40% IACS.

[0005] For this reason, copper alloys for electronic equipment are excellent in both conductivity and strength, have high isotropic workability, ie, press moldability, and are important for the reliability of surface mount components. Improvement in bonding strength is desired. For example, in surface mounting in which soldering is performed on the surface without using a through hole of a printed circuit board, the deterioration with time of the bonding strength is fatal. It is also required to have sufficient plating resistance and corrosion resistance, for example, stress corrosion cracking caused by ammonia.

[0006]

As a result of various studies in view of the above, the present invention has been made, and as a result, various improvements have been made to electrical and thermal conductivity, mechanical strength, precision workability, solder joint strength and the like, and a method for producing the same. Was developed.

That is, the copper alloy for electronic equipment of the present invention contains Ni or Ni and Co in an amount of more than 1% and less than 4%, Cr: more than 1.0% and less than 2%, Si: 0.2-1.5%, Sn: 1.1-3%. In addition, P: 0.3% or less, B: 0.3% or less, Zn: 5%
Hereinafter, Mn: 1% or less, Mg: 0.2% or less, Zr: 0.5
% Or less, and one or two or more of them are contained in a total of 5% or less, with the balance being Cu.

Further, the production method of the present invention is characterized in that Ni or Ni and Co are used.
More than 1% and less than 4%, Cr: more than 1.0% and less than 2%,
Si: 0.2 to 1.5%, Sn: 1.1 to 3%, P: 0.3% or less, B: 0.3% or less, Zn: 5% or less, M
n: 1% or less, Mg: 0.2% or less, Zr: 0.5% or less, including any one or more of 5% or less in total;
After hot working the alloy consisting of the remaining Cu at 650 ° C or higher,
Cool to 350 ° C or less at a rate of 10 ° C / sec or more, and then
The feature is that after 70% or more of cold working is applied, heat treatment is performed at 400 to 600 ° C.

As described above, according to the present invention, Ni or Ni and Co is more than 1% and less than 4%, Cr: more than 1.0% and less than 2%, and S is S.
i: 0.2 to 1.5%, Sn: 1.1 to 3%, P: 0.3% or less, B: 0.3% or less, Zn: 5% or less,
Mn: 1% or less, Mg: 0.2% or less, Zr: 0.5% or less, containing any one or more kinds in total of 5% or less, with the balance being Cu.
Thus, hot working is desirably performed at 700 ° C. or more.

[0010] Immediately after the processing, a cool air or a water shower is blown to cool at least 10 ° C / sec to at least 350 ° C. It is made by subjecting this to 70% or more surface reduction processing by cold working and then heat-treating at 400-600 ° C. The heat treatment time depends on the actual conditions, but it varies from 10 minutes to 6 minutes.
Time is enough. After heat treatment, if necessary, processing or intermediate annealing may be performed to finish to the desired dimensions.
It is effective to improve mechanical properties, especially elongation and workability, by releasing at least a part of work strain by heat treatment at a low temperature of ~ 350 ° C.

The alloy of the present invention is made of Ni ₂ Si, Cr ₃ Si, C
Fine particles such as r ₅ Si ₂ are uniformly dispersed and precipitated,
A precipitation of r, NiP, NiB, CrP, etc. is also added, and a Cu-Sn alloy in which the solid solution Si in the Cu matrix is reduced as much as possible, or components such as Zn, Mn, B, Zr, Mg, etc. are uniformly added thereto. By incorporating, the tensile strength of 50 ~
70 kg / mm and ² or more, the conductivity also 20 to 40% IAC
It is S.

Thus, the content of Ni as a reinforcing component is 1
% And 4% or less, and the Cr content over 1.0% and 2% or less does not result in sufficient strengthening below the lower limit and above the upper limit, not only the workability is impaired, but also the conductivity is lowered. This is because the The same effect can be obtained even if a part of Ni is replaced by Co. However, Co is significantly more expensive than Ni.

The Si content as the above-mentioned compound precipitation component is
The reason for setting the content to 0.2 to 1.5% is that if the amount is less than the lower limit, sufficient strengthening cannot be obtained, and if the amount exceeds the upper limit, the conductivity is significantly reduced. That is, excess Si from the stoichiometry not only becomes a solid solution element and lowers the conductivity of the alloy but also causes a deterioration with time of the solder joint strength.
An amount close to the stoichiometric amount of i + Cr, especially below the stoichiometric amount (the stoichiometry of Si relative to Ni is about 1 / 5.18,
Is about 1 / 5.5). The above-mentioned two types of Si compounds not only facilitate uniform and fine precipitation, but also have a stoichiometric N content.
Among i and Cr, Ni has higher affinity than Cr and Ni ₂
It becomes Si, and excess Cr precipitates as elemental Cr, which acts secondarily to improve the strength of the alloy and does not cause a decrease in conductivity. If Cr is not used together, the excess Si or unreacted Si remains in the Cu matrix as a solid solution, which not only greatly reduces the conductivity but also causes the temporal deterioration of the solder joint strength.

The reason why the Sn content is limited to 1.1 to 3% is as follows.
Sn promotes solid solution strengthening and promotes homogeneous precipitation and dispersion of the precipitates, and improves the strength, elongation, workability, etc. of the alloy in combination with the dispersion strengthening effect. However, when the content is less than 1.1%, sufficient strength is obtained. If it exceeds 3%, the conductivity is greatly reduced.

Next, the subcomponents of the alloy of the present invention are within the ranges of P: 0.3% or less, B: 0.3% or less, Zn: 5% or less, Mn: 1% or less, Mg: 0.2% or less, Zr: 0.5% or less. The reason why the total amount of any one or more of them is 5% or less is to further improve the strength of the alloy.

In particular, P and B act as deoxidizers and form a compound with Ni and Cr inevitably liberated, not only strengthening the alloy but also improving the solderability, but their contents are 3% each. If it exceeds, the conductivity decreases. Zn and Mn also act as deoxidizing agents and strengthen the alloy to improve solderability. In particular, Mn improves hot workability, but when both exceed the upper limit, the electrical conductivity decreases. Mg and Zr improve the strength and bending workability by the crystal refining action, and also precipitate compounds with P and the like, and contribute to the improvement of the strength. However, when both exceed the upper limit, the conductivity and the elongation decrease. However, the total content of these subcomponents is 5% or less, and if the content exceeds this range, the conductivity is significantly reduced.

As a production method for realizing the above-mentioned properties of the alloy of the present invention with high productivity in practical use, a melt-cast ingot is hot-worked at 650 ° C. or more and immediately at a speed of 10 ° C./sec or more and at least 350 ° C. or less. By cooling to below, precipitation of the above compound is suppressed, and processing can be performed with a low load force. Then 70
% Or more, and then heat-treating at 400 to 600 ° C., a uniform and fine precipitation is rapidly performed by the action of processing strain. In other words, by precipitating a homogeneous and fine compound as completely as possible, properties essential for electronic equipment applications such as strength, conductivity, workability, and solderability are exhibited to the maximum.

In a conventional precipitation-type alloy, the solution aging treatment is performed at a high temperature of 800 ° C. or more during cold working or at the end, followed by water quenching and then precipitation aging treatment. However, solution quenching is a complicated process. Requires oxidation problems and special equipment. According to the present invention, an alloy having high properties is obtained without the need for a conventional process due to the effect of suppressing the quenching sensitivity by limiting the alloy composition as described above.

Thus, even if the hot working temperature is lower than 650 ° C.,
Even when the cooling rate is less than 10 ° C./sec, coarse precipitation of the above compound occurs, and high properties cannot be obtained even after cold working and heat treatment. On the other hand, if the cold working after the hot working is less than 70%, the working strain is insufficient, and the precipitated compound due to the heat treatment becomes coarse. Further, if the heat treatment temperature is lower than 400 ° C., it takes a long time to precipitate the compound, and if it exceeds 600 ° C., the precipitated compound becomes coarse and the alloy properties are deteriorated.

[0020]

EXAMPLE Alloys having the compositions shown in Table 1 were melt-cast and the surface was machine-finished to form an ingot having a thickness of 50 mm, a width of 150 mm and a length of 510 mm. This was hot-rolled to a thickness of 5.5 mm, immediately cooled by water cooling, pickled, and then cold-rolled. This was heat-treated in an Ar atmosphere. The manufacturing conditions for these are shown in Table 2. Tensile strength of the sheet material thus obtained,
The elongation, conductivity, bending workability, and solder joint strength were examined. Table 3 compares these results with the conventional alloys (C510, C195).
Shown in

The bending workability is bent by a press using a combination device of a 90 ° die with various tip radii (R) and a punch, and the crack in the bent portion is examined, and the minimum R / t (R:
Bending radius, t: plate thickness). The solder joint strength of the eutectic soldered joint with lead at 150 ° C is 300
After aging for a time, the tensile strength was determined by a tensile test.

[0022]

[Table 1]

[0023]

[Table 2]

[0024]

[Table 3]

As apparent from Table 3, the alloys (A to C) of the present invention shown in Table 1 manufactured by the methods Nos. 1 to 3 of the present invention shown in Table 2 were all conventional alloys of C510 (No. 6). ) And C195 (N
Compared to o.7), it was found that the mechanical properties, electrical properties, solder joint strength, and overall properties of homogeneity were excellent.
On the other hand, it can be seen that Comparative Examples Nos. 4 and 5 in which comparative alloys outside the composition range of the alloy of the present invention were produced by the method of the present invention were inferior in various properties.

[0026]

As described above, according to the present invention, the electrical and thermal conductivity, mechanical strength, precision workability, solder joint strength and the like are excellent, and not only the semiconductor lead frame but also the solder joint strength required lead. It is suitable for wires, various terminals, connectors, etc., and contributes significantly to miniaturization and high density of electronic equipment, and it has remarkable industrial effects.

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Masato Asai 500 Kiyotaki Town, Nikko City, Tochigi Prefecture Furukawa Electric Co., Ltd. Nikko Denki Copper Works (72) Inventor Shigeo Shinozaki 500 Kiyotaki Town, Nikko City, Tochigi Prefecture Furukawa Electric Kogyo Co., Ltd. Nikko Electric Copper Works

Claims (2)

[Claims] 1. Ni or Ni and Co exceeding 1 wt% and 4 wt%
% Or less, Cr: more than 1.0 wt% and 2 wt% or less, Si: 0.2
~ 1.5wt%, Sn: 1.1 ~ 3wt%, and P: 0.3
wt% or less, B: 0.3 wt% or less, Zn: 5 wt% or less, M
n: 1 wt% or less, Mg: 0.2 wt% or less, Zr: 0.5 wt%
A copper alloy for electronic equipment which has one or more kinds in the following range and a total of 5 wt% or less, and the balance of Cu is excellent in solder joint strength. 2. Ni or Ni and Co in excess of 1 wt% to 4 wt
% Or less, Cr: more than 1.0 wt% and 2 wt% or less, Si: 0.2
~ 1.5wt%, Sn: 1.1 ~ 3wt%, and P: 0.3
wt% or less, B: 0.3 wt% or less, Zn: 5 wt% or less, M
n: 1 wt% or less, Mg: 0.2 wt% or less, Zr: 0.5 wt%
After hot working at 650 ° C or more, the alloy containing one or two or more kinds in total in the following range is contained at 5% by weight or less, and then cooled to 350 ° C or less at a rate of 10 ° C / sec or more. And then cold-work at least 70%, then 400-600
A method for producing a copper alloy for electronic equipment having excellent solder joint strength, characterized by heat-treating at a temperature of ° C.