JPS63118051A - Fe-ni alloy or fe-ni-co alloy having superior heat resistance in noble metal plating - Google Patents

Abstract

PURPOSE:To improve the heat resistance of an Fe-Ni or Fe-Ni-Co alloy during noble metal plating by regulating the work degenerated surface layer of the alloy to a thin layer of a specified thickness. CONSTITUTION:An Fe-Ni or Fe-Ni-Co alloy ingot is hot rolled, cold rolled and subjected to cold rolling including annealing. The thickness of the work degenerated surface layer is regulated to <=5mum by selecting conditions during the final cold rolling and the kind of lubricating oil used. When the alloy is plated with a noble metal at a high temp., the resulting plating does not tarnish because the alloy has superior heat resistance.

Description

[Detailed Description of the Invention] The present invention relates to alloys used for applying precious metal plating, and more specifically, Fe-Ni alloys useful for applying noble metal plating with excellent heat resistance. The present invention relates to alloys and Fe-Ni-Co alloys.

Prior art In general, Fe alloys such as 42 alloy, Kovar alloy, amber, etc.
-Ni alloys and Fe-Ni-Co alloys are widely used as various sealing materials including IC lead frames due to their low thermal expansion properties. and,
These alloys are often used after being plated with a noble metal such as Au or ferrite. For example, when used as an IC lead frame, the wire bonding part and the wire bonding part are plated with a precious metal such as Ag or Ag. This plating is performed to ensure bonding strength with the semiconductor cord and adhesion strength with the bonding wire.

However, these precious metal plated lead frames
Since heat is applied under various conditions during the assembly process for semiconductor parts, the heat resistance of plating is important. For example, heat of up to about 450° C. is applied in the bonding process for bonding semiconductor elements. In this case, if the heat resistance of the plating is poor, the plating surface will discolor and oxides of the material elements will form on the plating surface, resulting in poor adhesion between the wire and the plating during wire bonding. There is.

Also, generally speaking, increasing the thickness of precious metal plating improves the heat resistance of the plating, but in recent years, due to the demand for lower costs, the thickness of the plating has been reduced to reduce the amount of precious metal used. , there is a tendency to promote the so-called saving of precious metals.

Therefore, the heat resistance of noble metal plating on the above alloys has become more important than ever, and Fe-Ni alloys and Fe-Ni-Co alloys, which have excellent heat resistance for noble metal plating, are becoming more important than ever.
There is a growing demand for alloys.

Under these circumstances, Fe-Ni alloys have recently been developed as a technology to improve the heat resistance of the plating mentioned above.
- It has been proposed to increase the (200) surface strength of the old yarn alloy to 40% or more (Japanese Patent Application Laid-open No. 73356/1983).

However, recrystallization collection of Fe-Ni alloy! The 1Jll weave is (200), and it is very easy to develop and is difficult to disappear even by cold working, so in many working cases, the (200) surface strength of Re-Ni alloys is 40% or more. For example, when the above alloy is recrystallized by rolling at a high working rate, the (200) plane strength reaches 90%, and even if this alloy material is subjected to various final temper rolling, the (200) plane strength is becomes more than 40%.

In other words, the (200) plane strength of the Fe-Ni alloy is 40
% or more is not special, and it has been found that even if the above-mentioned processing is performed to increase the (200) surface strength to 40% or more, the heat resistance of the plating is not improved. Therefore, at present, a technology for improving the heat resistance of noble metal plating on alloys has not yet been established.

The present invention was developed in view of the above-mentioned situation, and it is possible that when a Re-Ni alloy or a Fe-N1-Co alloy plated with a precious metal is exposed to high temperatures, the plating will be removed. It is an object of the present invention to provide an Fe-Ni alloy and a Fe-Ni-Co alloy that do not cause discoloration and can form a so-called glaze with excellent heat resistance.

The present invention will be explained in detail below.

Main skin ■Bottom Features of the present invention include Fe-Ni alloy or Fe-Ni alloy.
- The thickness of the process-affected layer on the surface of the Co-based alloy is 5 μm or less.

The term "process-affected layer" here refers to a surface layer that has undergone changes in the surface that occur when a metal article is subjected to some kind of mechanical surface treatment, and is a layer that undergoes surface changes that occur when a metal article is subjected to some kind of mechanical surface treatment. It can be measured by observing 'lJim. However, in order to more quantitatively measure this process-affected layer, a microhardness tester is used, and the layer is determined to have a hardness different from the base material by 10 or more μIIV, and the layer is determined using the above measurement method in combination.

F for Solving the Problems The present inventors investigated the improvement of the heat resistance of noble metal plating on the above-mentioned alloy, and found that when a process-affected layer is formed on the surface of the alloy material to a certain value or more, the heat resistance of the plating decreases. We have obtained knowledge that there is significant deterioration. That is, it has been found that when the thickness of the process-affected layer on the surface of the alloy material exceeds 5 μm, the heat resistance of the heat applied thereto is significantly deteriorated.

Since the process-affected layer does not have a clean crystal lattice, if plating is applied on top of this layer, the electroplated particles will be deposited unevenly on the surface of the alloy material, creating a porous plating layer. Since such plating is porous, when heat is applied, Fe, which is a metal element in the base material, tends to diffuse to the surface, and oxidation of Fe occurs on the surface, causing discoloration.

As mentioned above, a process-affected layer is likely to be formed when metal is processed, and in fact it is formed during all processes, but it is only when the thickness exceeds a certain level that it affects the heat resistance of the plating. This is limited to cases where the thickness exceeds 5 μM, and there is virtually no effect on the plating heat resistance if the thickness is 5 μm or less.

Therefore, in the present invention, the thickness of the process-affected layer on the surface is reduced to 5 μm.
Fe-Ni alloys and Fe-Ni-Co
The alloy is used as a base material for noble metal plating, but in order to make the work-affected layer as thin as 5 μm or less, it is necessary to use lubricated rolling when rolling, for example. Care must be taken because the thickness of the process-affected layer changes greatly by selecting the rolling conditions and the type of lubricating oil. Specifically, the rolling speed is high, the rolling oil with high viscosity is used, and a large amount of rolling oil is preferably supplied, and the diameter of the work roll is preferably large.

In the present invention, the Fe-Ni alloy used as the base material for plating includes a Fe-Ni alloy containing 30 to 85% Ni;
and alloys in which up to 10% of other elements are added to the alloy, and Fe-Ni-Co alloys include Ni2O
-50%, 0010-30% Fe-Ni-Co based alloys, and alloys in which up to 10% of other elements are added to the alloys.

As described above, the present invention is based on F
By reducing the thickness of the process-affected layer on the surface of e-Ni alloys and Fe-Ni-Co alloys to 5μ or less, the heat resistance of precious metal plating on these alloys can be improved.
This can be said to be useful in significantly increasing the usefulness of the alloy as the above-mentioned sealing material.

? (2) The present invention and its effects will be concretely explained below with reference to Examples.

Example 1 A 42 alloy ingot having the following composition was manufactured in a high frequency vacuum melting furnace.

CO,004 (wt%) Mn O, 61 Si 0.16 S O,002 Ni 41.33 The remainder is Fe and inevitable impurities.

This ingot was hot rolled at 1100℃ to a thickness of 4f.
fis plate, and then cold-rolled to a thickness of 1.51 mm. This plate was further annealed at 750°C for 1 hour, then cold rolled to a thickness of 0.35mm, and then rolled again at 750°C.
It was annealed at ℃ for 1 hour. The alloy material obtained in this way is finally cold rolled to a thickness of 0.25m+n, and at that time, dry rolling or normal rolling oil (Lotus CC
), various pass schedules,
Process-affected layers of various thicknesses were formed on the surface of the alloy material by rolling under the conditions of rolling speed and roll diameter.

Next, the thickness of the process-affected layer of these materials was measured by observing the metal structure by etching and using a microhardness meter (μIIV, Ig
) was used in conjunction with measurements of the base material and 10 or more different layers. The results are shown in Table 1.

Next, these alloy materials having process-affected layers of various thicknesses were plated with Au to a thickness of 1.0 μm using a conventional method, and then heated in the air to a temperature of 450°C for 5 minutes to remove the plating. The presence or absence of surface discoloration was visually observed.

The results are shown in Table 1.

Table 1 As shown in Table 1, when the process-affected layer on the surface of the alloy material exceeds 5 μm, discoloration of the plating occurs.
It can be seen that when the temperature is less than aa, no discoloration is observed even when heated, and excellent heat resistance is exhibited.

Example 2 An ingot of a Fe-Ni-Co alloy having the following composition was manufactured in a high-frequency vacuum melting furnace.

CO,009 (wt%) Mn 0.43 Si 0.10 S O,001 Ni 29.35 Co 16.75 The remainder was Fe and unavoidable impurities.

This ingot was rolled according to the same procedure as described in Example 1 to form work-affected layers of various thicknesses.

Next, the thickness of the work-affected layer of each alloy material on which the work-affected layer was formed in this way was measured in the same manner as in Example 1, and then Au plating was applied to the alloy material in the same manner as in Example 1. After heating, the presence or absence of discoloration of the plating surface was visually observed. The results are shown in Table 2.

Table 2 As shown in Table 2, Fe-Ni-Co alloys exhibit good plating heat resistance when the thickness of the damaged layer is 5 μm or less, but when the thickness exceeds 5 μm, discoloration of the plating occurs. You will be able to do it.

Claims (1)

[Claims] (1) An alloy with excellent noble metal plating heat resistance, characterized in that the thickness of the process-affected layer on the surface of the Fe-Ni alloy or Fe-Ni-Co alloy is 5 μm or less.