JPH0562467B2 - - Google Patents

Description

[Detailed description of the invention]

BACKGROUND AND OBJECTS OF THE INVENTION The present invention relates to a method for manufacturing lead frame materials for semiconductor devices. Conventionally, semiconductor devices have been manufactured by die-bonding the semiconductor element to the element mounting part of a lead frame made by punching and molding material, then wire bonding the electrodes of the semiconductor element and the lead part of the lead frame, and then coating the semiconductor element with mold resin. It was sealed and made into a product. Such conventional methods require a lead frame plated with Ag, Au, or the like. This is die bonding, wire bonding,
Since each process such as coating and sealing is performed in the atmosphere, the surface of the lead frame made of Cu may be oxidized, which may lead to poor connections between the lead frame and elements and wires, so prevent this from happening. Therefore, predetermined portions are coated with Au, Ag, etc., which have strong oxidation resistance and high conductivity. However, this has some drawbacks. In other words, not only are Au and Ag expensive, but the plating liquid used to plate them is highly toxic, and the plating itself is prone to defects.
If stripe plating, spot plating, etc. are performed to reduce the amount of Au and Ag used, the process becomes even more complicated. The object of the present invention is to eliminate the drawbacks of the prior art described above and provide a lead frame material that is oxidation resistant even during various heat treatments during the manufacturing process of semiconductor devices. [Summary of the Invention] According to the present invention, the above-mentioned object is to form a thin alloy layer on the surface of a base material whose surface is made of Cu or a Cu alloy by diffusion and penetration of a different metal, and then to roll the material. This is achieved through processing. In this case, the base material may be made entirely of a Cu-based material such as oxygen-free copper or phosphor bronze, or may be an iron-based material coated with a Cu-based material. The thickness of the dissimilar metal coating formed on the surface of the base material before heat diffusion treatment varies depending on the thickness of the base material and the type of dissimilar metal, but it is required to be at least 100 angstroms (0.01μ), and the maximum 10μ, but 0.5~
1μ is appropriate. If the thickness of this dissimilar metal coating is too thin, the oxidation resistance effect will decrease even if an alloy layer is formed, and if it is too thick, brittle compounds may be formed between it and the base metal. The alloy layer may become irregular or the surface condition may become non-uniform. This dissimilar metal coating can be formed using vacuum evaporation, sputtering, ion plating, etc., but the heating and diffusion treatment is performed in a vacuum, an inert gas atmosphere, or a reducing atmosphere. The heating conditions at that time include the base material, type of coating,
Although it varies depending on the thickness etc., the heating temperature needs to be below the melting point of the base material. The heating time varies depending on the shape of the base material, but if the material is rolled out and subjected to continuous heat treatment, it will take 10 seconds or more, and if it is coiled, it will take 10 minutes or more. After this diffusion heat treatment, rolling processing is performed.
By performing this rolling process, a material with appropriate strength and a smooth surface can be obtained. [Example] Next, an example of the present invention will be described. Example 1 A thin film of pure aluminum was formed on the surface of an oxygen-free copper strip with a width of 600 mm, a thickness of 0.8 mm, and a length of 2000 m by sputtering in an argon gas of 10 ^-3 torr, and then a thin film of 1 to 2% Heat treatment was performed at 550°C for 30 seconds using a continuous annealing furnace in a reducing atmosphere containing CO gas.
This copper strip was further rolled to 0.4 mm, its hardness was adjusted, and the width was slit to 40 mm. As shown in Figure 1, a lead frame material 1 having a thin alloy layer 2 formed by diffusion of Al on the surface was formed. Obtained. Table 1 shows the relationship between the Al thin film before heat diffusion treatment, oxidation resistance, and wire bonding properties. , wire bonding properties are both good.

[Table] Example 2 Sn was applied to the surface of an oxygen-free copper strip having the same shape as in Example 1.
After forming a thin film by vacuum deposition (resistance heating), it was heat-treated at 230°C for 1 hour and then at 600°C for 2 hours using an annealing furnace in a reducing atmosphere containing 1 to 2% CO gas. This copper strip was further rolled to 0.4 mm and then slit to a width of 40 mm to obtain a lead frame material. Table 2 shows the Sn thin film before heat treatment, oxidation resistance,
The relationship between wire bonding properties is shown. Samples with Sn of 0.1μ or more have good oxidation resistance and wire bonding properties. but
Samples with more than 10μ of Sn were not shown, but
After the heat diffusion treatment, the surface roughness worsened and the bonding properties also deteriorated.

[Table] [Effects of the Invention] As described above, the material according to the present invention forms a thin alloy layer on the surface by diffusion and penetration of dissimilar metals, and prevents oxidation during various heat treatments during the manufacturing process of semiconductor devices. Because of this, it does not require plating with precious metals such as Cu and Ag, and has the advantage of omitting the complicated process associated with plating, and being less expensive without being subject to specific regulations. Note that Cu is a metal with poor adhesion to various resins, but by forming an alloy layer with Al, Zn, etc. on the surface, it is possible to improve adhesion while retaining the characteristics of Cu. becomes.

[Brief explanation of the drawing]

The figure is an explanatory view showing an example of a lead frame material according to the present invention. 1: lead frame material, 2: alloy layer.

Claims (1)

[Scope of Claims] 1. After coating a different metal on the surface of a base material whose surface is made of copper or a copper alloy, the base material is heated to diffuse and infiltrate the different metal into the surface of the base material, and then, A method for manufacturing a lead frame material for semiconductor devices having oxidation resistance, the method comprising rolling the base material. 2 Different metals include Al, Sn, Ni, Si, Mn, Pb, Ti,
The first material is at least one of Zr and Cr.
Manufacturing method described in section. 3. The manufacturing method according to item 1 or 2, wherein the thickness of the dissimilar metal before diffusion and penetration is 0.01 to 10 μm.