JPS60258441A - Alloy for lead frame - Google Patents

Abstract

PURPOSE:To improve the electric conductivity, heat conductivity and strength by adding prescribed percentages of Zn, Co and Y or a rare earth element to Cu. CONSTITUTION:This alloy for a lead frame consists of, 10-40wt% Zn, 0.1- 9wt% Co, 0.01-5wt% Y or rare earth element and the balance Cu. Sm, Pr or misch metal is used as the rare earth element. The alloy is used in the manufacture of IC, LSI or the like and has superior electric conductivity, heat conductivity and strength.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to an alloy for lead frames used in ICs, LSIs, etc.

[Conventional technology]

In recent years, semiconductor technology has made remarkable progress, and in the very near future, VLSI memory devices will be manufactured in large quantities.

Kovar was first used as an alloy for lead frames used in ICs, LSIs, etc., followed by 42 alloy,
52 alloy etc. came to be used. And L.S.
With the development of ultra-integrated circuits such as I, alloys with excellent electrical conductivity, thermal conductivity, and strength have come to be required, and currently iron alloys and copper alloys have approximately the same ratio. used in

The relationship between electrical conductivity, which is a major element in alloys for lead frames, and strength is such that as electrical conductivity increases, strength generally decreases. The subject of research is how to keep it low.

Various methods have been studied to maintain high electrical conductivity and strength, among which a combination treatment with spinodal decomposition and other mechanisms is considered to be the best method.

For example, Cu--Ni alloys were conventionally considered to be completely solid solution alloys, but spinodal decomposition occurs by adding special elements or by performing treatments.

Although copper alloys generally have the property that the Young's modulus decreases when other elements are added, in Cu-Ni spinodal alloys, the addition of the above elements improves the Young's modulus and suppresses the decrease in electrical conductivity. be able to.

Therefore, when a Cu-Ni alloy is subjected to a combined process of spinodal decomposition treatment and strengthening mechanism, for example, the strength can be increased to 60 kg/x.
*2. It can achieve an electrical conductivity of 80%, which is an extremely excellent value for an alloy for LSI lead frames at the time of its origin, and is also suitable for an alloy for VLSI lead frames. be.

Furthermore, the alloy for lead frames is required to have a small coefficient of thermal expansion. In general, iron-based alloys have a small coefficient of thermal expansion, while copper-based alloys have a large coefficient of expansion. However, copper-based alloys are used as alloys for lead frames because their thermal conductivity is approximately 10 times that of iron-based alloys.

Therefore, the biggest challenge in the future is how to lower the coefficient of thermal expansion of copper-based alloys.

[Problems to be solved by the present invention]

The present invention has been made based on the above-mentioned viewpoints, and its purpose is to have excellent electrical conductivity, thermal conductivity, strength, etc., and to be usable not only in LSI but also in VLSI, etc. The present invention aims to provide an alloy for lead frames.

[Means for solving problems]

Therefore, the gist of the present invention is to contain 10 to 40% Zn and 0.1 to 9% Co by weight percentage (the same applies hereinafter).
and 0.01 to 5% Y or rare earth elements, especially S m-
.

At least one type of Y or rare earth element selected from Pr, minosu metal, etc., and the remainder is Cu excluding impurities.
It exists in an alloy consisting of.

[For production]

By using the alloy configured as above, it is possible to maintain high electrical conductivity, thermal conductivity, strength, etc., and it can function satisfactorily as an alloy for not only LSI but also VLSI lead frames. It is.

〔Example〕

Hereinafter, the details of the present invention will be specifically explained with reference to the graph shown in FIG. 1 of the drawings.

FIG. 1 is a graph showing the characteristics of the lead frame alloy according to the present invention.

The method for manufacturing the alloy for lead frames according to the present invention includes Zn of 10 to 40% by weight percentage (hereinafter the same);
0.1-9% CO and 0.1-5% Sm, Pr.

At least one kind of Y or a rare earth element selected from miso metal, etc., and the remainder is Cu, and the above raw materials are high-frequency melted in the atmosphere and then cast into a mold to form an ingot. This ingot is subjected to decomposition treatment at 900° C. to 1050° C. for about 3 hours, and then hot or cold rolled.

In the case of hot rolling, the ingot is rolled at a temperature of about 900°C to 1050°C for 10 minutes, depending on the size of the ingot, before entering the next step.
After the solution treatment is performed for about 1 minute to 1 hour, the next aging step is carried out, and the material is aged at 200 to 800°C.

Thereafter, it is cold rolled to the final thickness, and finally formed by punching or the like.

In addition, each of the above-mentioned solution treatments involve heating and holding at a predetermined temperature, refining, and then cooling and quenching by cooling with water or oil. Moreover, the above-mentioned aging may be multi-stage aging or continuous temperature-lowering aging, if necessary.

Figure 1 of the drawing shows the electrical conductivity and tensile strength when measured at room temperature after being held at each aging temperature for 1 hour, preferably by normal quenching, and the black and white circles indicate 35%Z, respectively.
Figure 2 shows the tensile strength and electrical conductivity of an n-5%Co-1%Sm-balance Cu alloy.

The 35% Zn-5% Co-1% Sm-balance Cu alloy is
At 200°C to 500°C, it is a spinodal transformation region,
500°C to 800°C is the precipitation region.

C shows spinodal transformation and precipitation.

-Y or a rare earth element compound, and depending on the alloy composition containing Go and Y or rare earth elements, some or all of CO precipitates, and electrical conductivity and strength are improved by spinodal transformation and precipitation. can be significantly improved. Further, when 1 to 10% of Ni or Sn is added to the above-mentioned alloy of the present invention or in place of the above-mentioned Zn, the electrical conductivity decreases, but the tensile strength can be significantly improved.

The phase that precipitates when Y or rare earth elements such as Sm and Pr are added is ferromagnetic, so if the above aging is performed in a magnetic field, elongated precipitates can be obtained in the direction of the magnetic field, and electrical conductivity can be obtained. Both strength and tensile strength can be improved.

That is, the precipitated compound of Go and Y or a rare earth element is, for example, if Sm is used as Y or a rare earth element, Sm2
Co17, SmCo5, Sm2Co7,,
SmCo3, SmCo2.5l11! ] Co4.5
1113 Go etc., especially Sm2 Co17 and SmCo5
A ferromagnetic material of a mixture including or
The above-mentioned G has a strength that was not sufficient with only precipitation.

-The strength is significantly increased by precipitation of Y or rare earth element compound.

Effective conditions for aging in a magnetic field include a magnetic field strength of at least 1,000e to 50,000e, usually 1,000 to 30,000e, aging for about 30 minutes at a temperature of 300 to 500°C, which depends on the alloy composition, and then The aging process is performed in the absence of a magnetic field at a temperature slightly lower than the temperature normally used for aging in a magnetic field.

In this way, the alloy becomes stronger in the direction of the magnetic field treatment. FIG. 2 shows the effective composition range based on the characteristics of the Zn-free alloy that is the basis of the alloy of the present invention.

That is, in Figure 2, when the vertical axis is the composition (%) of Y or rare earth element (RE), and the horizontal axis is the Co composition (%), the figure of merit of the alloy, that is, the electric conductivity, Isovalue curves of figures of merit that are both superior in terms of tensile strength (e.g., ■ [electrical conductivity] + [tensile strength], or usually ■ [electrical conductivity] × [tensile strength]) It shows
At least a part of CO is alloyed with Y or a rare earth element, and in the case of Sm, for example, SmCo5 or Sm2 close to this is formed.
It has high performance in the vicinity where ferromagnetic compounds such as Co17 are precipitated.

From FIG. 2 and the experimental example described above, the preferred composition range for Y or rare earth elements is 0.3 to 3.5%, and the same for Co is 1 to 7%. In the alloy of the present invention, 0.1% Co, 0.01% Y, or rare earth elements and 10% Zn are set as the lower limits because sufficient strength cannot be obtained if any of them is less than these. The reason why 9% Co, 5% Y or a rare earth element, and 40% Zn were used is because if any of them exceeds 9%, the electrical conductivity will decrease.

The alloy of the present invention has 0.1 to 9% Co50.01 to
This is an alloy consisting of 5% Y or rare earth elements, and the remainder is Cu excluding impurities, by substituting part of the Cu with Zn. It is well known that this substitution increases the strength of the Zn-Cu alloy compared to the Cu alloy. This is clear from the Zn-Cu alloy properties.

In addition, as impurities other than metals, oxygen, phosphorus, etc. each have a concentration of 10%.
Although it will be contained at around 0 ppm or less, there will be no particular problem up to this level.

〔Effect of the invention〕

Since the present invention is constructed as described above, it is possible to maintain high electrical conductivity, thermal conductivity, strength, etc., and therefore it can be used as an alloy for lead frames of not only LSI but also VLSI. It can perform a sufficient function.

[Brief explanation of the drawing]

FIG. 1 is a graph showing the characteristics of the alloy for lead frames according to the present invention, and FIG. 2 is a graph showing the relationship between other characteristics and alloy composition. In Figure 1, black circles---35%Zn-5%Go-1%5L11-
Tensile strength of balance Cu alloy White circle---35%Zn
Electrical conductivity of -5%Co -1%Sm-balance Cu alloy Patent applicant Representative of Inoue Japan Co., Ltd. (7
524) Mogami Shotabe

Claims (1)

[Claims] 1) Zn of 10 to 40% by weight percentage (the same applies hereinafter);
An alloy for lead frames consisting of 0.1 to 9% CO, 0.01 to 5% Y or rare earth elements, and the remainder Cu excluding impurities. 2) The lead frame alloy according to claim 1, wherein the rare earth element is SII+. 3) The alloy for a lead frame according to claim 1, wherein the rare earth element is Pr. 4) The alloy for a lead frame according to claim 1, wherein the rare earth element is Mitsushi metal.