JPS60258442A - Alloy for lead frame - Google Patents

Abstract

PURPOSE:To improve the electric conductivity, heat conductivity and strength by adding prescribed percentages of Co and Y or a rare earth element, and the balance Cu. CONSTITUTION:This alloy for a lead frame consists of 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, L'SIs, 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 particularly excellent electrical conductivity, thermal conductivity, and strength have come to be required, and currently iron alloys and copper alloys are almost the same. used in proportions. □ The relationship between electrical conductivity, which is the main element for lead frame alloys, and strength is such that the strength generally decreases as the electrical conductivity increases.In the future, as the electrical conductivity increases, the strength will decrease. The subject of research is how to keep this low.

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

For example, Cυ-Nr alloy was conventionally considered to be a solid solution type alloy, but spinodal decomposition occurs when special elements are added or when a treatment is performed.

Although copper alloys generally have the property that their 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 reduces the decrease in electrical conductivity ( It can be held down.

Therefore, when a Cu-Ni alloy is subjected to a combined treatment of spinodal decomposition treatment and a strengthening mechanism, for example, the strength is 60 kg /
m2, 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 as an alloy for VLSI glue-1” frames. It is a value.

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 that Co of 0.1 to 9% by weight (the same applies hereinafter) and Y of 0.01 to 5%
Or it exists in an alloy consisting of at least one kind of Y or a rare earth element selected from rare earth elements, especially Sm, Pr, miso metal, etc., and the remainder is Cu excluding impurities.

[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 CO of 0.1 to 9% by weight percentage (the same applies hereinafter);
O, OI~5% of at least one Y or rare earth element selected from Sm, Pr, miso metal, etc., and the balance is Cu, and the above raw materials are melted at high frequency in the atmosphere and then cast into a mold. Make it into an ingot.

This ingot is subjected to a drop-off treatment at 900° C. to 1050° C. for about 3 hours, and then hot or cold rolled.

In the case of hot rolling, before proceeding to the next step, solution treatment is performed at a temperature of about 900'C to 1050C for about 10 minutes to 1 hour depending on the size of the ingot, and then the next step is carried out. The material is aged at 200 to 800°C so as to proceed to an aging process. Thereafter, it is cold rolled to the final thickness, and finally formed by punching or the like.

Note that each of the above solution treatment treatments involves heating and holding at a predetermined temperature, and then rapidly 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 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 white and black circles indicate 5% CO, respectively.
-1%Sm-balance Cu alloy tensile strength and electrical conductivity are shown.

The 5%Co-1%Sm-balance Cu alloy was heated at 200℃~5
At 00°C, it is in the spinodal transformation region, and from 500°C
800°C is the precipitation region.

Spinodal transformation and precipitation occur in CO-Y or rare earth element compounds, and depending on the alloy composition containing Co and Y or rare earth elements, some or all of CO precipitates, causing spinodal transformation and precipitation. By doing so, the electrical conductivity and strength can be significantly improved. Also, 10-40% Zn, 1-10% Ni or S
When n or the like is added to the above-mentioned alloy of the present invention, the electrical conductivity decreases, but it becomes possible to significantly improve the tensile strength.

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, SmCo5.51112 CO7, Sm
Co3-, SmCo2 %Sn+43 Co4, S
It is a ferromagnetic material such as m3 Co, especially Sm2 Co17, SmCo5, etc., or a mixture containing them, and the above-mentioned C has a strength that was not sufficient with the conventional precipitation of Co alone.

- The strength is significantly reduced due to the precipitation of Y or rare earth element compounds.
It is something that increases.

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 It is aged 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 (
Become. Therefore, the effective composition range based on the characteristics of the alloy of the present invention is as shown in FIG.

That is, in Figure 2, when the vertical axis is the composition (%) of Y or rare earth element (R), and the horizontal axis is the composition (%) of CO, the figure shows the figure of merit of the alloy, that is, the electrical conductivity. and a figure of merit that is superior in terms of both electrical conductivity and tensile strength (e.g., ■ [electrical conductivity] + [tensile strength], or usually a value such as ■ [electrical conductivity] × [tensile strength]). It shows a curve,
If at least a part of the CO is alloyed with Y or a rare earth element, for example Sm, 5IIIC05 or S close to this is formed.
It has high performance in the vicinity where ferromagnetic compounds such as m2 Cot 7 are precipitated.

From this FIG. 2 and the above experimental example, 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 and 0.1% Co and 0.1% Co and 0.1% Co and 0.1% The reason why we set the lower limit to O1% Y or rare earth elements is that sufficient strength cannot be obtained if either is lower than this, and the reason why we set the upper limit to 9% Co and 5% Y or rare earth elements is because either of them is higher than this. This is because the electrical conductivity becomes low.

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 shown on paper, it is possible to maintain high electrical conductivity, thermal conductivity, strength, etc., and is therefore sufficient as an alloy for lead frames of not only LSI but also VLSI. It can perform a number of functions.

[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 Fig. 1, white circles ---, ---5%C0-1%Sm-remaining C
U alloy tensile strength black circle---5%C0-1%
Button - Residual Cu alloy electrical conductivity patent applicant Inoue Japan Nox Research Institute Agent (7524) Shotabe Mogami

Claims (1)

[Scope of Claims] 1) 0.1 to 9% CO by weight percentage (hereinafter referred to as the following);
An alloy for lead frames consisting of 0.01 to 5% Y or a rare earth element and the remainder Cu excluding impurities. 2) The alloy for lead frames according to claim 1, wherein the rare earth element is Sm. 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 miso metal.