JPH0339446A - High strength low expansion fe-ni alloy - Google Patents

Abstract

PURPOSE:To obtain the alloy having a low thermal expansion coefficient and excellent strength and press workability and suitable as a lead frame material for IC by adding small amounts of Be and S to an Fe-Ni series alloy having specified compsn. CONSTITUTION:An Fe-Ni series alloy ingot constituted of, by weight, 30 to 55% Ni, <2.0% Co, <1% Mn, <0.5% Si, 0.01 to 2.0% Be, <5.0% Cu, 0.003 to 0.050% S, <0.1% C, <0.1% O, <0.1% N and the balance Fe is subjected to hot forging, hot rolling and annealing, is thereafter to cold rolling into final sheet thickness and is furthermore to aging treatment, by which the Fe-Ni series alloy material having a low thermal expansion coefficient, high strength and excellent press workability and suitable as a lead frame material for IC can be obtd.

Description

Detailed Description of the Invention "Field of Industrial Application" The present invention relates to an Fe-Ni alloy suitable as a lead frame material for IC, etc.
By adding specific amounts of Be and S to an alloy containing specific amounts of Si and Cu, it is made to have high strength and a low coefficient of thermal expansion, and also has improved press workability.

"Conventional Technology" In recent years, the development of highly integrated large-scale integrated circuits (LSI) and very large-scale integrated circuits (VLSI) has become active. Silicon devices are becoming larger and the amount of heat generated when energized is increasing. Therefore, if there is a large difference in coefficient of thermal expansion between the silicon element and the lead frame, there is a risk that the silicon element will be subjected to thermal stress. Therefore, for lead frame materials for LSIs and VLSIs, it is particularly necessary to bring the coefficient of thermal expansion close to that of silicon elements.

For this reason, lead frame materials have traditionally been made of 4-Fe-Ni alloy, which has a low coefficient of thermal expansion and is intended to alleviate the thermal stress that acts on silicon elements.
2 A l1oy (42%N i-F e)
5-119156 etc.), Kovar (29% Ni-1
7% Co-Fe) and low expansion Kovar (29%
Ni-13%Co-F eX JP-A-59-198741
No.) are known.

``Problem to be solved by the invention'' However, as lead frames such as IC5LSI have recently increased in number of pins, the width of the leads has become smaller, so the material strength of the leads tends to be insufficient. There was a problem in that the reeds were susceptible to deformation due to external forces. Furthermore, with the recent increase in the size of ICs, LSIs, etc., and the miniaturization of packaging, the sealing resin and leads have become damaged due to heat history during the assembly process in surface mount type lead frames and lead frames with large chip sizes. A problem has arisen in which cracks occur between the frame and the frame, and these cracks cause malfunctions of ICs and LSIs.

Therefore, the inventors of the present application first proposed in Japanese Patent Application No. 63-315646 as an alloy with improved lead strength, and after this proposal, Fe and Ni were proposed as an alloy with improved resin adhesion. Co, Mn, Si, and Cu
We have also proposed an alloy in which a small amount of Be is added to an alloy containing a predetermined amount of Be. This proposed alloy has 30-55% Ni
, Co 2.0% or less, M n 1% or less, St 0.5%
Below, Be 0.01 to 0.05%, Cu 5.0% or less,
The remainder has a composition of Fe.

These proposed alloys have both high strength and low expansion, and are also alloys with excellent resin adhesion. However, when this alloy was considered for use in a multi-pin lead frame produced by press working, there was a problem in that it had poor press workability due to its high strength compared to the conventional 42A11oy.

The present invention has been made to solve the above problems,
The present invention aims to provide a high-strength, low-expansion Fe-Ni alloy that exhibits a low coefficient of thermal expansion close to that of silicon elements, has high strength, and has excellent press workability.

"Means for Solving the Problems" In order to solve the problems described above, the present invention provides Ni 30
~55% Co 2.0% or less Mn 1% or less Si 0.5% or less Be 0.01-2.0% Cu 5.0% or less S 0.003-0.050% C0. It has a composition of t% or less 0 0.1% or less N 0.1% or less balance Fe and unavoidable impurities. In addition, as unavoidable impurities, AI 0.1% or less, Mg 0.1% or less, Ca 0.1
% or less, and may contain 0.5% or less of Cr.

"Function" The amount of Be and S added to the alloy containing predetermined amounts of Fe, Ni, Co, Mn, Si, and Cu is small, and since the main component of the alloy is an alloy with a low coefficient of thermal expansion, it is suitable for lead frames. A low coefficient of thermal expansion suitable for materials such as these is ensured. In addition, by adding a small amount of Be, a Be0 layer is generated on the surface of the material, and this Be0 layer improves the adhesion with the sealing resin, making it possible to obtain an alloy with higher strength than conventional Fe-Ni alloys. I can do it.

Furthermore, by adding a small amount of S, fine sulfides are uniformly dispersed within the structure, so press workability is improved while maintaining high strength. Furthermore, if the amounts of C10 and N added exceed 0.1% each, hot workability deteriorates, which is not preferable.

The present invention will be explained in more detail below.

In the alloy of the present invention, Ni (nickel) is 30 to 5
5%, Go (cobalt) 2.0% or less, Mn (manganese) 1% or less, Si (silicon) 0.5% or less, Be
(beryllium) 0.01-2.0%, Cu (copper) 5%
．． 0% or less, S (sulfur) 0.003-0.050%
, C (carbon) at 0.1% or less, O (oxygen) at 0.1% or less, and N (nitrogen) at 0.01% or less.

In these compositions, the contents of Ni, Go, Mn, and Si are determined by the high-strength, low-expansion Fe-N, which the present inventors have previously applied for in Japanese Patent Application No. 63-315646.
Alloys described in i-alloys and their production methods,
Alternatively, it is based on the alloy composition proposed by the inventors of the present invention after the above proposal. In addition, in the alloy of the present invention, as unavoidable impurities, A1 (aluminum) 0.1% or less, Mg (magnesium) 0.1% or less,
Ca (calcium) 0% or less, Cr (chromium) 0.5
There is no problem even if it contains less than %.

In the above composition, if the Ni content is other than 30 to 55%, it is not preferable because the lead frame material will not be able to obtain a thermal expansion coefficient adapted to the thermal expansion coefficient of the silicon element, etc. to which the lead frame material is applied. If it exceeds 2.0%, the coefficient of thermal expansion becomes too large, which is not preferable. Also, B
If the content of e is less than 0.01%, a BeO oxide film will not be formed and the adhesion with the sealing resin will become insufficient, which is not preferable. It should be noted that even if the Be content exceeds 2.0%, there will be no further strength improvement effect, and it will be expensive and e.g.
Since the addition of Be increases costs unnecessarily, the amount of Be added is preferably 2.0% or less. Furthermore, Si is used as a deoxidizing agent, but if the content exceeds 0.5%, it will cause the alloy to become brittle, which is disadvantageous.Also, Mn improves forgeability and is used as a deoxidizing agent, but if the content exceeds 0.5%, it will cause the alloy to become brittle. If it exceeds 1.0%, it is not preferable because it deteriorates bendability. Further, if the Cu content exceeds 5.0%, the thermal expansion becomes too large, which is inappropriate. S is used to improve press workability by dispersing fine sulfides within the structure, but 0.00
If it is less than 3%, the effect cannot be obtained, and if it exceeds 0.050%, hot workability is deteriorated, which is inappropriate. Furthermore,
When the additive amounts of C, N, and O exceed 0.1%, hot workability decreases.

An example of a method for manufacturing an alloy having the above composition will be described below.

To manufacture the alloy, first, raw materials are blended to have the composition as described above, and then vacuum melting is performed in an atmosphere of Ar gas or the like to avoid contamination with impurities to obtain an ingot having the composition as described above.

Next, this ingot is forged at 1200 to 1400°C, and then rolled to a desired shape, for example, a desired thickness, preferably at a processing rate of 70% or less, and
Repeated annealing treatment at 100°C is performed. Then, during the final rolling process, the processing rate is preferably set to about 50% or less, and after the final rolling process, for the purpose of age hardening treatment,
Heat treatment is preferably performed in a temperature range of 700° C. for 5 hours or less to obtain a plate material with a desired thickness.

The alloy manufactured as described above is mainly composed of Fe-Ni-based low thermal expansion coefficient alloy and by adding a small amount of Be, it maintains a thermal expansion coefficient close to that of silicon elements while maintaining a thermal expansion coefficient similar to that of conventional silicon elements. A lead frame material having higher strength than Fe-Ni alloy can be obtained. Also, due to the effect of added Be, a Be0 layer is formed on the surface of the material, and this Be
Since the 0 layer improves the adhesion with the resin material, when a lead frame is constructed and sealed with resin, the adhesion between the sealing resin and the lead frame is improved, which has the effect of preventing TC and LSI malfunctions. There is. Furthermore, since the addition of S improves the press workability, there is an effect that when forming a lead frame of a desired shape by press work, it can be easily processed.

"Example" Each raw material was blended to have the composition shown in Table 1 below, each blend was melted in a vacuum atmosphere of 80 Torr containing Ar gas to create an ingot, and then this ingot was heated at 1200 to 1400 °C Hot forged with
Next, rolling processing performed at a processing rate of 70% or less and 800 to 1
The annealing process of heating to 100°C and slow cooling is repeated, the final rolling process is performed at a processing rate of 50% or less to complete the rolling process, and then the aging process of heating to 500°C for 2 hours is performed to reduce the thickness to 0. A plate of .15 am was obtained. The average coefficient of thermal expansion of this plate-shaped body was measured, and the results are shown in Table 2 below.

(Hereafter, margin) No. ! table Table 2 As shown in Table 2, alloy sample N of the present invention.

Nos. 3 to 6 have low thermal expansion coefficients comparable to those of silicon elements.

Next, a press workability evaluation test was conducted using the aforementioned samples Nos. 1 to 6. Samples No. 1 and No. 6 were pressed with a mold to break, and the ratio of the sheared surface thickness and plate thickness of the press-broken surface as shown in FIG. 1 was measured. The results are shown in Table 3.

Table 3 As is clear from Table 3, sample No. of the invention product
Samples No. 3 to No. 6 showed smaller values than samples No. 1 and No. 2 of the comparative example, and it became clear that the press workability was improved. In addition, sample No. 2 containing 0.002% S
Sample No. 3, which contained 0.003% S, showed a large numerical improvement rate. Therefore S
It is clear that the content of 0.003% or more is required.

"Effects of the Invention" As explained above, according to the present invention, Fe, Ni and c
By adding a small amount of Be and S to a low expansion coefficient alloy containing predetermined amounts of O, Mn, Si, and Cu, it maintains a thermal expansion coefficient close to that of silicon elements, and has a higher strength than conventional alloys. An alloy with good adhesion can be provided. Moreover, since a small amount of S is added, an alloy with improved press workability can be provided. Further, since only a small amount of expensive e is added, it can be obtained at low cost.

[Brief explanation of drawings]

FIG. 1 is a sectional view for explaining the press workability evaluation test method.

Claims (1)

[Claims] Ni 30-55% (weight%, same below) Co2.0% or less Mn 1% or less Si0.5% or less Be0.01~2.0% Cu5.0% or less S0.003~0.050% C0.1% or less 0.1% or less N0.1% or less Balance Fe and unavoidable impurities A high-strength, low-expansion Fe-Ni alloy having the composition.