JPS587707B2 - Manufacturing method of etched products - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for obtaining a processed product by applying a corrosion-resistant film only to a predetermined portion of the surface of a metal plate and selectively chemically etching the film.

For example, a metal conductive plate for semiconductor integrated circuits as an etched product is called a lead frame, and as shown in FIG. It has a metal strip 2 having a shape.

A box-shaped portion surrounded by the tips of each metal strip 2 is a table 3 on which a wafer chip is placed.

Although the illustrated example shows only one lead frame, a large number of lead frames are usually obtained from a single metal plate, which is called multi-sided mounting.

This selective etching of the metal plate 1 involves forming a corrosion-resistant film on the surface of the metal plate 1 using a photographic method using an exposure mask having a shape corresponding to the lead frame (not strictly speaking), and then chemical etching. However, side etching is unavoidable in chemical etching.

Figure 2a shows the shape of the normal corrosion-resistant film 4 by enlarging a part of the lead frame, but when the metal plate 1 coated with this type of corrosion-resistant film 4 is chemically etched, it becomes as shown in Figure 2b. Metal plate 1 with side etching and covered with a corrosion-resistant film
The side surface of the corrosion-resistant film 4 is gouged out, making it slightly smaller in size than the corrosion-resistant film 4.

The amount of side etching is determined by the etching method and etching solution, but in the case of lead frames, the thickness of the metal plate 1 is 0. The thickness is 2 mm to 0.3 mm, which is rather thick to be etched, and this results in a large amount of side etching.

Especially regarding the tip of the metal strip 2 in FIG. 2b,
This part is an important part for electrically connecting with the terminals of the integrated circuit, and it was a total problem that this tip was severely gouged out by side etching and lost its shape.

In particular, with the recent development of integrated circuits, the number of terminals has increased, and lead frames with 64 or more metal strips 2 have appeared, and with the increase in the number of lead frames, the pattern accuracy required for each metal strip 2 has also increased. It's expensive.

The present invention has been devised in consideration of the above circumstances, and the shape of the corrosion-resistant film for forming the tip of the metal strip is such that the width increases from near the tip toward the tip and is adjacent to the tip. It is formed by interconnecting a metal strip with a corrosion-resistant film.

To explain the embodiment in more detail with reference to FIG. The corrosion-resistant films 5' and 5'' are connected to each other to form a bridge portion 7.

The portion of the metal plate 1 covered by the bridge portion 7 is either narrowed in width as a whole or removed from the main body of the metal strip 6 so that the portion of the metal plate 1 covered by the bridge portion 7 disappears by side etching during chemical etching. In this case, the portions of the bridge portion 7 corresponding to the piers are made thinner.

Since the corrosion-resistant film 5 having the shape as shown in FIG. 3a particularly prevents chipping at the tip of the metal strip, a metal strip 6 having a square sharp tip can be obtained as shown in FIG. 3b. It is something that can be done.

To explain this point in more detail with reference to FIG. 4, the area indicated by broken lines and hatching in the corrosion-resistant coating 8 on the metal plate 1 is the expected shape of the metal strip 9 remaining after etching. Although this also makes it clear how much the corrosion resistant film 8 is gouged out by the side etching, the shape of the corrosion resistant film 8 is actually determined to have a wide width taking into account the width of the side etching.

That is, the width d protruding from the side surface of the metal strip 9 corresponds to the width of the side etching.

Since side etching tends to be particularly noticeable at the tip of the metal strip 9, the width of the corrosion-resistant film 9 is increased toward the tip, and the bridge portion 10 is formed with piers 11 that are thin enough to be eliminated by side etching. It is good to place it.

According to this embodiment, when chemical etching is performed, the bridge portion 10 separates and falls off from the tip of the metal strip 9 just before the etching end point.

Due to this bridge portion 10, the tip end of the metal strip 9 has a good rectangular shape, and shape defects can be prevented.

Furthermore, the etching end point can be visually detected by the falling off of the bridge portion 10.

Of course, this assumes that the width of the pier 11 is adjusted so that it disappears just before the etching end point.
The width can be appropriately determined empirically.

As described above, according to the method for producing etched products of the present invention, not only can the shapes of the tips of the parallel metal strips be adjusted, but also the etching can be completed properly by observing the disappearing or falling off of the bridges. It is possible to know the timing and contributes to the stability of the quality of the obtained product.

Furthermore, during etching, the parallel metal strips are connected by the bridge, which prevents the tip from bending, which has the additional effect of making it easier to handle during etching.

[Brief explanation of the drawing]

Figure 1 is a plan view showing an example of a lead frame, which is a type of etched product, and Figures 2a and 2b are plan views showing the shape of a conventional corrosion-resistant film and the shape of a metal plate etched with it. , FIGS. 3a and 3b are plan views showing the shape of the corrosion-resistant film of the present invention and the shape of the metal plate etched with it, and FIG. 4 shows the relationship between the shape of the corrosion-resistant film of the present invention and side etching. It is an explanatory diagram. 1... Metal plate, 2, 6, 9... Metal strip, 3... Stand, 4, 5, 8... Corrosion resistant film,
7, 10... Bridge section, 11... Bridge pier.

Claims (1)

[Claims] 1. In a method of applying a corrosion-resistant film to a predetermined part of the surface of a metal plate and selectively chemically etching it to obtain a processed product, the shape of the corrosion-resistant film for forming parallel metal strips is determined from the vicinity of the tip of the metal strip. The width of the corrosion-resistant film is increased toward the tip, and a bridge section is provided that is connected to the corrosion-resistant film of the adjacent metal strip.The width of the entire bridge section or the width of the bridge pier is narrowed, and side etching is performed to form the metal plate. A method for manufacturing an etched product, characterized in that the part is made to disappear.