JPH04155951A - Lead frame material for semiconductor device - Google Patents

Abstract

PURPOSE:To obtain an inexpensive lead frame material which has small mean thermal expansion coefficient at ambient and high temperatures, large thermal conductivity and strength, excellent direct bondability with low cost by employing a clad material in which copper is disposed at both sides of Fe-42%Ni alloy. CONSTITUTION:A 42 alloy clad material 1 is made of three layers of copper/42 alloy/copper clad with coppers 3, 4 at both sides thereof so as to hold the 42 alloy 2 therebetween. After one 42 alloy plate and two pure copper plates are degreased and polished, the two pure copper plates are superposed on both side surfaces of the 42 alloy plate, rolled under pressure by a cold rolling method so that its pressing rate becomes 55% to be integrated, its composite material is heated at 450 deg.C for about 30min to be thermally diffused, and rolling and heat treatments are then repeated to obtain a 42 alloy clad material of 0.2mm thick in which finish rolling is eventually performed at 20%.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a lead frame material for semiconductor devices such as ICs and LSIs.

[Conventional technology]

Lead frame materials for semiconductor devices such as ICs and LSIs have excellent thermal conductivity and electrical conductivity, as well as high strength, especially tensile strength, good repeat bendability, a relatively small coefficient of thermal expansion, and plating properties. .

Good solderability is required, and conventionally Fe-42%Ni alloy (hereinafter referred to as 42 alloy) has been mainly used.

However, due to the increase in the size of semiconductor chips due to the high integration of semiconductor devices, the need to deal with the generation of heat.

Furthermore, there is a need for materials with high thermal conductivity and a coefficient of thermal expansion close to that of semiconductor chips. In addition, in the case of direct bonding, in which wires such as Au wires and Cu wires are directly bonded to lead frames, the oxides of added components such as Ni, Cr, and Sn are exposed on the surface of steel alloy lead frames, resulting in poor bonding reliability. Therefore, a lead frame suitable for direct bonding is required. .

Conventionally, a cladding material (hereinafter referred to as amber clad material) consisting of three layers of wire/umber/rope, in which copper is placed on both sides of amber (Fe-36%Ni alloy), has been used as a lead frame material that meets these demands. It has been proposed (Hitachi Cable & 3 (19J13-12) pp. 57-60).

Since amber has the lowest coefficient of thermal expansion among the Fe-Ni systems, an amber clad material in which both sides of amber are clad with copper is said to have a small coefficient of thermal expansion and high thermal conductivity.

[□Problem that the invention seeks to solve]

However, the coefficient of thermal expansion of amber clad material is small only in the temperature range around room temperature, and the coefficient of thermal expansion increases rapidly at high temperatures. For this reason, when the semiconductor chip is heated to the solder melting temperature (approximately 300° C.) during die bonding, cracks may occur in the semiconductor chip due to the difference in thermal expansion coefficient with the lead frame. Further, the amber clad material does not necessarily have satisfactory thermal conductivity and strength, and since it is a special alloy, it is not easy to obtain and has problems such as high cost.

This invention was made to solve the above-mentioned conventional problems, and has a small average coefficient of thermal expansion at room temperature to high temperature, high thermal conductivity and strength, and allows direct bonding, making it low cost. The object of the present invention is to obtain a lead frame material for semiconductor devices.

[Means to solve the problem] A lead frame material for semiconductor devices according to the present invention.

It is made of a cladding material (hereinafter referred to as 42 alloy cladding material) in which copper is arranged on both sides of an Fs-42% Ni alloy.

42 alloy is Fe-N with 5g% Fe and 42% Ni by weight.
It is an alloy widely used as a material for electrical and electronic devices, and is easily available and low cost.6 The copper disposed on both sides is preferably pure copper, especially oxygen-free copper.

The 42 alloy clad material used in the present invention is copper/42 alloy/copper clad on both sides of the 42 alloy.
It is a cladding material consisting of three layers of copper. 42 alloy and copper are bonded together by pressure welding and metal diffusion, making the entire material an integrated material.

The composition ratio of copper:42 alloy:copper (volume ratio to the entire cladding material) is preferably 1:(1 to 10):1.

The 42 alloy clad material is made by degreasing and polishing the 42 alloy and copper, stacking copper on both sides of the 42 alloy, and rolling and welding them together using a cold rolling method at a reduction rate of 50 to 60%. The composite was heated at 400-500°C for about 30 minutes to perform diffusion heating to diffuse the 42 alloy and the steel into each other, followed by repeated rolling and heat treatment, followed by 20-4
By applying 0% finish rolling, a cladding material having desired strength is manufactured. The thickness of the 42 alloy clad material is preferably 0.2 to 0.15 mm.

The cladding material obtained in this way is made by integrating the 42 alloy and the copper on both sides, and has excellent thermal and electrical conductivity, high strength, good repeat bendability, a small coefficient of thermal expansion, and good plating and solderability. Good direct bonding properties. In particular, it has a lower average coefficient of thermal expansion, higher thermal conductivity, and higher strength than amber clad materials at room temperature to high temperatures, particularly from 30 to 300°C.

Such a rad material is used as a lead frame material as it is or after being subjected to arbitrary processing, and is processed into a predetermined shape by punching, etching, etc. to form a lead frame.

〔Example〕

Embodiments of the present invention will be described below with reference to the drawings.

FIG. 1 is a perspective view showing a lead frame material for a semiconductor device according to an embodiment of the present invention.
This is a cladding material consisting of three layers of copper/42 alloy/copper, with copper (3) and copper (4) clad on both sides of the 42 alloy (2) sandwiching it.

After degreasing and polishing one 42 alloy plate and two pure steel plates.

Two pure copper plates were stacked on both sides of a 42 alloy plate, and they were rolled and welded together using a cold rolling method with a reduction ratio of 55%, and the composite was heated at 450°C for about 30 minutes to perform diffusion heating. After that, rolling and heat treatment were repeated to obtain a 42 alloy clad material having a thickness of 0.2 mm and which had been subjected to final 20% finish rolling.

The composition ratio of copper/42 alloy/copper in the 42 alloy cladding material is 1;
(1 to 10):1, we obtained a 42 alloy clad material by changing the thickness of the 42 alloy plate and pure copper plate, measured its physical properties, and compared the results with amber clad material with the same composition ratio. Shown in 1.

Table 1 From the above results, it can be seen that the 42 alloy clad material has a smaller average coefficient of thermal expansion at room temperature to high temperature, and higher thermal conductivity and tensile strength than the amber clad material.

〔Effect of the invention〕

As described above, according to the present invention, since the 42 alloy clad material is used, the average coefficient of thermal expansion at room temperature to high temperature is small, the thermal conductivity and strength are high, and the direct bonding property is excellent, resulting in a low cost lead. Frame material is obtained.

[Brief explanation of drawings]

FIG. 1 is a perspective view showing a lead frame material for a semiconductor device according to an example. (1)...42 alloy clad material, (2)...42 alloy, (3), (4)...copper.

Claims (1)

[Claims] (1) A lead frame material for a semiconductor device characterized by being made of a cladding material in which copper is arranged on both sides of a Fe-42%Ni alloy.