JPS63132466A - Material for lead frame - Google Patents

Abstract

PURPOSE:To obtain a lead frame excellent in conductivity and tensile strength, by coating at least one side surface of an amorphous alloy foil with Cu or Cu alloy. CONSTITUTION:Single surface or both surfaces of amorphous alloy 1 are coated with Cu or Cu alloy 1 and made composite. By making composite material of amorphous alloy and Cu, the following defects can be improved while superior characteristics of amorphous alloy are maintained; low conductivity, durability for repeated bending, blanking property, and soldering property. Suitable thickness of amorphous alloy is 20-50mum. In the case of thickness less than or equal to 20mum, the strength and toughness are not sufficient. In the case of thickness more than 50mum, the alloy becomes fragile. The thickness of Cu or Cu alloy for making composite is 2-20mum. From economical view-point, Fe-base alloy is desirable for the composition of amorphous alloy.

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention relates to a lead frame material that is a component of a pancage of an IC (integrated circuit) or the like.

(Prior Art) Lead frames used for IC and transistor chips are made of special alloy foil (or thin plate).

Previously, for example, Nikkei Mechanical E, January 985 issue 82-8
As explained on page 7, the so-called 4 of Fe42Ni
Two types of alloys, 2-alloy and Cu-based alloy, have become mainstream as practical materials. Although Fe-42Ni alloy is superior to Cu alloy in terms of strength and thermal expansion properties,
It is inferior to Cu alloy in electrical conductivity, thermal conductivity, etc. On the other hand, Cu alloys exhibit excellent electrical conductivity and thermal conductivity, but have the drawback of low strength. There is also the cheapest lead frame material that uses iron foil, but it is easy to contract and lacks functional reliability, so it is a low-quality material.
In its original state, it is limited to the manufacturing materials of C.

These materials have been used in packages that take advantage of their respective characteristics, but as ICs become more highly integrated, the current materials are no longer able to adequately support them. For example, there is a need to improve material strength by dissipating heat and increasing the number of bottles.

One way to deal with this situation is to improve the alloy components, and other attempts have been made to create a cladding of two or more types of materials. Among these, improvements in alloy components have mainly been made in Cu alloys. About 1% of a different element is added to increase the strength while maintaining CuO's high conductivity. However, due to restrictions on the amount added, dramatic improvements in strength have not been achieved so far. In addition, Fe4 is used as a cladding material.
Clad materials of 2Ni alloy and Cu alloy are being put into practical use, but aside from their properties, they have the drawback of high material costs due to manufacturing difficulties.

(Problems to be Solved by the Invention) An object of the present invention is to provide a novel lead frame material that has both high conductivity and high strength characteristics that can respond to the trends of higher integration of ICs and smaller packages.

(Means for Solving the Problems) The lead frame material of the present invention is characterized in that it uses a ribbon of amorphous alloy as a base material, and at least one surface thereof is coated with Cu or a Cu alloy.

Amorphous alloys are produced from melts by ultra-quenching, and have various characteristic properties due to their structure (random atomic arrangement).

For example, it exhibits high strength and high corrosion resistance that cannot be obtained with conventional crystalline metals (alloys). However, when viewed as a lead frame material, Cu has poor conductivity, punching workability, and solderability.
Its inferiority compared to alloys prevented its practical use as a standalone material.

The present invention utilizes the high strength of amorphous alloy foil while
In order to impart high conductivity to the amorphous alloy 1, as shown in FIG.
This is a composite material coated with u-alloy 2. Although plating is often used as a composite method, other methods such as cladding may also be used.

By making a composite of amorphous alloy and Cu (or Cu alloy), the excellent characteristics of amorphous alloy are retained, while the disadvantages of low conductivity, repeated bendability, punchability, and solderability are significantly improved. be done.

The preferred thickness of the amorphous alloy is 20 μm to 50 μm.
It is. If it is less than 20 μm, the strength and toughness will be insufficient;
If it exceeds m, it becomes brittle and the repeated bendability becomes insufficient even when Cu (or Cu alloy) is composited. For these reasons, the thickness of the amorphous alloy that serves as the base material is set in the range of 20 to 50 mm.
It was set as μm.

The thickness of Cu or Cu alloy to be composited is at least 2μ
m is required. For applications where electrical conductivity and punchability are important, it is preferable to make the thickness of Cu (or Cu alloy) relatively large. In addition, the thickness of Cu is 20 μm (one side)
If the thickness exceeds this, the cost will increase if plating is used, so it is desirable to keep the thickness below this.

Amorphous alloy foil of the present invention - Cu (or Cu alloy)
Since a composite material originally provides the excellent electrical and thermal properties of Cu to an amorphous metal and improves the mechanical strength, which is a weak point of Cu alloys, the higher the purity of Cu, the better. Alloying is a means to increase the strength of Cu at the expense of electrical conductivity. Therefore, when using a Cu alloy, it is best to use one with as few impurities as possible, and the content of additional elements should be 1% by weight or less. is desirable. Sn as an additive element.

Zn, P, etc. are good.

The composition of the amorphous alloy used in the present invention is preferably an Fe-based alloy represented by FeaXbMe in consideration of economic efficiency. Here, X is Cr, Mo, or W.

One or more of Ti, Nb, Ni, and Co,
M is B.

It represents one or more of C1P, St+Ge. The content is a: 60-90 (same below at%)
, b: .

0-20. c: preferably in the range of 10 to 35. However, a+b+c=100. The addition of element X is selected from the above range depending on the requirements for improvement of mechanical properties and corrosion resistance, coefficient of thermal expansion, and magnetic properties. The semimetal (M) needs to be added in an amount of 10 to 35 at% as an element necessary for forming an amorphous state.

Next, a specific example of means for coating an amorphous alloy with Cu will be shown below. ´ Amorphous alloys are metals with properties similar to glass, and have a strong passive film on their surfaces, so they have traditionally been
Metal plating on this alloy was considered impossible. Also,
Even if this passive film is removed and metal plating is applied, if a large amount of hydrogen enters the material, it will cause hydrogen embrittlement and will be destroyed just by hitting it, just like breaking glass.

This is because an amorphous alloy is a metal that easily absorbs hydrogen, so much so that it can also be used as a hydrogen storage alloy.If a large amount of hydrogen atoms generated during the plating process are absorbed into this alloy,
It causes hydrogen embrittlement and easily breaks, making it difficult to maintain the shape of the sheet.

In addition, amorphous alloys that have undergone hydrogen embrittlement deteriorate physically and cannot be used, but they also lose their electrical properties, so plating work on this alloy does not cause hydrogen embrittlement, unlike metal plating on general metals. It is important to be careful.

Plating on amorphous alloy foil can be performed as follows. First, an amorphous alloy foil was placed in an acidic activation bath containing the following acid components and additives in an appropriate combination at room temperature for 30 min.
Chemically polish by soaking for 2 to 7 minutes.

1) Hydrochloric acid 3-20% by weight, (11) Sulfuric acid 2-30% by weight, (iii) Citric acid 2-15% by weight, (iv) Acetic acid 0
~3% by weight, (v) nitric acid 2-10% by weight, (vl) nonionic or amphoteric surfactant 0.1-0.3
wt%, (vi) amine corrosion inhibitor 0-0.15 wt%, (v
ii) 2-pyrrolidone or its N-alkyl derivative, e.g. N-ethyl [or methyl-2-pyrrolidone) 0 to 2% by weight, (1K) acetylenic glycol (e.g., 2-pentyne-1,4-diol, 2-pyrrolidone) -butyne-1,4-diol) 0 to 10% by weight, and then the chemically polished amorphous alloy foil is electrolytically activated using an electrolytic bath having a composition that appropriately combines the acid components and additives listed below. do.

(i) Phosphoric acid 2-20% by weight, (11) Sulfuric acid 2-30% by weight, (iii) Citric acid 2-15% by weight, (iv) Acetic acid 0
~5% by weight, (v) nonionic or amphoteric surfactant 0.1-0.3% by weight, (vl) amine corrosion inhibitor 0-0.15% by weight, (v
i) 2-pyrrolidone or its N-alkyl derivative 0-
20% by weight, electrolytic activation uses an amorphous alloy as a cathode, for example, a platinum-plated titanium anode, at a current density of 1 to 1 at room temperature.
This is achieved by electrolyzing at 7A, /dmz for 30 seconds to 5 minutes.

In order to prevent the electrolytically activated amorphous alloy foil from forming a passive film on the amorphous alloy surface again,
Move to the plating process as quickly as possible, and by plating C
Coat with u or Cu alloy.

The plating method itself may be performed by a conventional method. For example, Cu plating can be performed using an acidic copper sulfate bath, a copper birophosphate bath, or the like.

Next, the present invention will be explained in detail with reference to Examples.

(Example) Example 1 7 per side on both sides of an amorphous alloy foil with an alloy composition of FB7aCrJ+zca, a plate width of 25 mm, and a plate thickness of 26 μm.
Cu plating with a total thickness of 14 μm on both sides was performed by the following method.

First, an amorphous alloy foil was degreased with trichlene, washed, and degreased with alkali, and then chemically polished through an acidic activation bath having the following composition. Polyethylene glycol alkyl ether 0.2% by weight, N-methyl-
5% by weight of 2-pyrrolidone, 1% by weight of 2-butyne-1,4-diol, 0. 1% by weight, 3
5% hydrochloric acid 5% by volume, 85% sulfuric acid 5% by volume, citric acid powder 10% by weight, 90% acetic acid 1% by volume, 68% nitric acid 2% by volume
An acidic activation bath was prepared by adding the mixed acid solution consisting of:

Next, polyethylene glycol alkyl ether 0.
2% by weight, 5% by weight of N-methyl-2-pyrrolidone, 0.1% by weight of amine corrosion inhibitor, 10% by volume of 85% phosphoric acid.
, 85% sulfuric acid 5% by volume, citric acid powder 5% by weight, 90%
It was added to a mixed acid solution consisting of 1% acetic acid and heated to 65°C. The surface of the amorphous alloy foil was activated by passing an electric current through the amorphous alloy foil and the titanium/platinum plated plate as electrodes to 4 volts in the above electrolytic bath.

The activated amorphous alloy foil is immediately treated with 20g of copper sulfate.
/jL citric acid 90 g / 1, sodium citrate 90
A very thin copper strike plating was performed by plating for 10 seconds at a current density of 6A/dm'' in a plating bath of 180 g/l of copper sulfate, 45 g/l of sulfuric acid, i! , 2 A/dm" and 7 minutes to obtain a sinus plating of about 7 μm.

The plate thickness of the obtained Cu-amorphous alloy-Cu composite material was 40 μm, and the measurement results of various properties were as shown in Table 1.

Table 1 Genuine Fe42Ni alloy (thickness 0.2mm).

This chapter Cu-5%Sn alloy (thickness 0.2mm) Here, the electrical conductivity is expressed as [AC5%].

As is clear from the characteristic values shown in Table 1, the plate thickness of the composite material of the present invention is 40 μm, which is about 175 μm compared to the conventional material.
Although it is a thin plate, it is suitable as a lead frame material.

Example 2 Alloy composition is Fe74Mo+oB+zC4, plate width 50mm
Cu plating was applied to both sides of an amorphous alloy foil having a plate thickness of 40 μm to a thickness of 12 μm per side and a total thickness of 24 μm on both sides by the following method.

After activating the surface of the amorphous alloy foil in the same manner as in Example 1, copper strike plating was performed, and copper pyrophosphate (Cu content 36%) 80 g//2, potassium pyrophosphate 3
Using a plating bath containing 00 g/β and 0.2% by volume of ammonia (20% solution), electrolytic plating was carried out at a bath temperature of 60° C. while applying a voltage of 6 to 7 μm to the amorphous alloy foil.

The plate thickness of the obtained Cu-amorphous alloy-Cu composite material was 64 μm, and the measurement results of various properties were as shown in Table 2.

Table 2 The characteristic values in Table 2 show that the material of the present invention is superior in both strength and electrical conductivity compared to the comparative example listed in Table 1 as a lead frame material.

(Effects of the Invention) The composite of the amorphous alloy foil and Cu of the present invention is superior in both electrical conductivity and tensile strength to conventional materials;
It is ideal as a lead frame material to support higher integration of C, smaller and lighter packages, and increased number of pins.

[Brief explanation of the drawing]

FIG. 1 is an explanatory diagram of the material of the present invention, where (al is one-sided coating of Cu (or Cu alloy), ft, is an example of double-sided coating). 1: Amorphous alloy foil, 2: Cu (or Cu alloy) coating layer. Figure 1

Claims (2)

[Claims] (1) C on at least one surface of the amorphous alloy foil
A lead frame material characterized by being coated with u or Cu alloy. (2) The thickness of the amorphous alloy foil is 20 to 50 μm,
The lead frame material according to claim 1, wherein the Cu or Cu alloy has a thickness of 2 to 20 μm on one side.