JPH01169959A - Manufacture of clad belt for ic lead frame - Google Patents

Abstract

PURPOSE:To improve the irregularity of oxidation quantity and the solder wettability of base metal belt surface, and increase the quality, by rolling the base metal belt surface by using a dull-skin roll in the process to perform clad rolling and finish rolling. CONSTITUTION:After a base metal belt surface is subjected to wire brush polishing, clad rolling and finish rolling which follows the clad rolling are performed. In the above process, the base metal belt surface is, at least once, subjected to rolling by using a dull-skin rolling. The dull-skin rolling is a roll whose surface roughness is more than or equal to Ra 0.10mum. Thereby, the irregularity of oxidation quantity and the wettability of the base metal belt surface are improved, and the quality is increased.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a method of manufacturing a cladding band used in a lead frame of a semiconductor integrated circuit (IC).

[Conventional technology]

A typical example of cladding material used as an IC lead frame is 42% Ni-Fe alloy (base material) + A1 foil (
It is used in glass-ceramic packages (Sardip).

In the production of cladding materials, conventionally, for example, Japanese Patent Application Laid-Open No. 57-
As disclosed in No. 121265, wire brush polishing is generally performed on the surface of the base metal strip prior to cladding.

The effect of wire brush polishing is not only to clean and activate the metal surface, but also to form a hardened layer on the metal surface as disclosed in JP-A No. 62-72489, and to prevent new surfaces from forming when cracks occur during rolling. It is said that it also has the effect of encouraging the appearance of the fruit.

[Problem that the invention seeks to solve]

However, in the wire brush polishing described above, it is difficult to treat only the cladding portion with high precision, and polishing is performed over almost the entire surface of the base material other than the cladding portion. The wire traces caused by this polishing were not completely eliminated by clad rolling and subsequent finish rolling, and were carried over into the final product. As a result, the surface properties of the wire brush polished surface and the unpolished surface are different, resulting in an imbalance in the degree of coloring on the upper and lower surfaces of the material, that is, the thickness of the oxide film, during the heating process during IC package mounting. There is a need for a cladding material that has the same surface properties on both sides of the base metal strip.

As a means to make the surface properties of both surfaces the same, it is also possible to perform wire brush polishing on the non-clad surface in the same manner as on the clad surface, but this method does not work.

In addition to increasing the number of steps, the wire-brush polished surface is microscopically non-uniform and forms a thick oxide film, which causes solder wettability to deteriorate more easily than non-polished surfaces. . Furthermore, if the diameter of the wire is excessively large, it may become a starting point for bending and breaking.

An object of the present invention is to provide a method for manufacturing a cladding band for an IC lead frame, which improves the non-uniform surface caused by wire brush polishing and has the same surface properties on both sides of the base metal band.

[Means for Solving the Problems] The present invention involves wire-brush polishing the surface of the base metal strip, and then rolling it using a dull roll at least once during the steps of clad rolling and subsequent finish rolling. This is a method of manufacturing a cladding band for an IC lead frame.

In the present invention, after wire brush polishing the surface of the base metal strip, a dull skin roll is used at least once during the clad rolling and the subsequent finish rolling to completely eliminate the effects of wire brush polishing. This is to erase the scratches and to obtain the same surface texture on both sides.

In the present invention, a dull skin roll has a surface roughness of Ra
O, refers to rolls of 10 μm or more. However, if the surface roughness is made too rough, problems such as surface roughness of the clad metal strip and easy oxidation of the base metal strip occur, so Ra is preferably set to 0.25 μm or less. Note that the dull skin roll may be used at least once in the rolling process after cladding, so it can be used as a clad roll or in the subsequent finish rolling. Also, depending on the process, a heat treatment process such as softening annealing or diffusion annealing may be added during the process.
Examples] Below, one example according to the present invention will be shown.

(Example 1) A strip of Fe-42%Ni alloy (0.32 m
+++X35, Oan width) was used as the adherend, and a pure aluminum strip (10μ thick x 10.Own width) was used.

First, as a cladding pretreatment, the cladding side surface of the base metal was polished with a wire brush, and then aluminum strips were stacked and cladding rolling was performed using a dull skin roll with a surface roughness of Ra = 0.20 μm. A cladding band with a thickness of .254 mm was obtained (No. 1 in Table 1).

(Example 2) Using the same material as in Example 1, the cladding side surface of the base material was polished with a wire brush in the same manner, and then aluminum strips were stacked and the cladding was rolled using a bright skin roll with a surface roughness of Ra = 0.05 μm. Then, the surface roughness is Ra=0.
Finish rolling with a 20μm dull roll to give a roll of 0.25
A 4 nm thick cladding band was obtained (Table 1 No. 2).

(Example 3) Using the same material as in Example 1, the cladding side surface of the base material was polished with a wire brush in the same manner, and then aluminum strips were stacked and the cladding was rolled using a bright skin roll with a surface roughness of Ra = 0.05 μm. Then, in step 1, the surface roughness is Ra=0.
．． Finish rolling (1) is performed with a 20 μm dull roll,
Finally, finish rolling (2) was performed using a bright skin roll with Ra=0.05 μm to obtain a 0.254 mm thick cladding band (Table 1, No, 3).

As a comparative example, only the clad side surface of the base material was polished with a wire brush in the same manner as in the example, and then Ra = 0.05.
Ra = = 0.0 after clad rolling and finish rolling using only the μ proverbial bright skin roll (No. 4 in Table 1) and wire brush polishing on both sides of the base material.
Cladding rolling using only 5μm bright skin rolls,
Finish rolling (1), finished rolling (2) (first
Table No. 5) is shown.

Each of the obtained clad bands was subjected to atmospheric heating at 530°C for 5 minutes, and the solder wettability of both sides of the base metal band was evaluated.

Or, after treating the surface with chlorine-based flux for solder wettability, evaluate the wettability by immersing it in a eutectic solder bath heated to 240°C for 5 seconds, and those showing a wetted area of 951 or more on the evaluated surface are considered good. I judged it.

Table 1 shows the results. As is clear from Table 1, all five cladding bands obtained according to the present invention exhibit good solder wettability. On the other hand, in Comparative Example No. 4, the wire brush polished surface caused poor solder wetting. Also, no.

No. 5 has deteriorated solder wettability.

Furthermore, when observing the front and back surfaces of the cladding band, the oxide film of the cladding band according to the present invention has the same film quality on the front and back sides and is a uniform film, whereas Comparative Example No. 4 has oxidation on the front and back surfaces. The film was heterogeneous, and the oxide film thickness on the wire brush polished surface was thicker and non-uniform than that of the present invention.

Furthermore, although Comparative Examples No. 5 and 5 have the same quality on the front and back surfaces, No.
Similar to the wire brush polished surface of No. 4, the oxide film was thick and non-uniform.

〔Effect of the invention〕

According to the present invention, it is possible to improve the variation in the amount of oxidation on the surface of the cladding material and the solder wettability, which have been problems in the past, and to obtain a cladding band of good quality.

Claims (1)

[Claims] Manufacture of a clad strip for an IC lead frame, characterized in that after wire brush polishing the surface of the base metal strip, rolling is performed using a dull roll at least once during the steps of clad rolling and subsequent finish rolling. Method.