JPH045849A - Manufacture of lead frame - Google Patents

Abstract

PURPOSE:To perform multiple pins by chemical etching by etching a metal plate, suspending it on the way, covering one side with an etching resistant film, etching it from the other side to pass therethrough, and forming a lead. CONSTITUTION:Photosensitive resin patterns 12 are formed on both side surfaces of a metal plate 10. Using them as masks the plate 10 is etched from both sides with etchant, stopped on the way, and an etching resistant film 14 is formed on one side. The material is desirably formed of the same as the resin of the pattern 12. It is etched from the other side to pass through an etching groove to form a predetermined lead. Then, the pattern 12 and the film 14 are removed, and a predetermined lead frame is obtained.

Description

[Detailed description of the invention] (Industrial application field) The present invention relates to a method for manufacturing a lead frame.

(Prior Art) There are two methods of manufacturing lead frames for semiconductor devices: a press processing method and a chemical etching method.

In the case of the conventional etching process, the steps shown in FIG. 5 were used.

That is, as shown in FIG. 5(a), a photosensitive resin pattern 12 for a mask corresponding to the lead frame pattern is formed on the front and back surfaces of the metal plate 10, and then, as shown in FIG. Etched from both sides, then the same figure (C1
As shown in FIG. 2, the photosensitive resin pattern 12 was removed and a predetermined lead frame was formed.

(Problems to be Solved by the Invention) However, when chemical etching is used, the problem of side etching cannot be avoided.

For this reason, the photosensitive resin pattern 12 should have a lead width that takes into account the above side etching! However, after the etching grooves penetrate from both sides, side etching becomes even more intense, making it difficult to control the etching rate. Therefore, there is a problem that dimensional accuracy varies.

In the case of chemical etching, the etching is inevitably isotropic, so the spacing between the leads is generally limited to the thickness of the material, and cannot be made any narrower than that, so there is a limit to increasing the number of bins. .

SUMMARY OF THE INVENTION The present invention has been made to solve the above-mentioned problems, and its purpose is to provide a method for manufacturing a lead frame that can be manufactured in a large number of bins by chemical etching.

(Means for Solving the Problems) An object of the present invention is to form a predetermined photosensitive resin pattern on both sides of a metal plate in a method of manufacturing a lead frame in which a predetermined pattern is formed by etching from both sides of a metal plate. using the photosensitive resin pattern as a mask, etching at least one side of the metal plate, stopping the etching on the one side halfway, and covering the one side of the metal plate with a film having etching resistance; This is achieved by a lead frame manufacturing method characterized in that the other surface is then further or newly etched to form a predetermined lead pattern, and the photosensitive resin pattern and film are removed.

Further, it is preferable that the film is formed so as to fill the etched grooves.

(Embodiment) A preferred embodiment of the present invention will be described below with reference to the accompanying drawings.

First, as shown in FIG. 1(a), a photosensitive resin pattern 12 is formed by applying a photosensitive resin on both sides of a metal plate 10 and exposing it to light using a mask.

Next, as shown in the same figure (b), a photosensitive resin pattern 12 is formed.
Using this as a mask, etching is performed from both sides of the metal plate 10 using an etching solution such as a ferric chloride aqueous solution or a cupric chloride aqueous solution.

Next, the feature of the present invention is that, as shown in FIG. 1C, etching is stopped before both etching grooves penetrate through, and an etching-resistant film 14 is formed on one side of the metal plate 1o. do.

The film 14 was applied with a photosensitive resin coated and cured, a thermosetting resin coated and cured, or a dry film made of a photosensitive resin formed into a sheet and cured. The material is preferably one that can be removed simultaneously with the same removal solution when the photosensitive resin pattern 12 is dissolved and removed in a subsequent process.

For example, it is preferable to use the same material as the photosensitive resin pattern 12.

The film 14 may be a film-like material such as vinyl that simply covers one side of the metal plate 10, but it is particularly preferable that it also fill the etched grooves. For this purpose, it is best to use a film obtained by applying a photosensitive resin liquid or a thermosetting resin liquid to fill the etching grooves and then hardening the film as described above. Of course, only the inside of the etching groove may be filled.

After forming the film 14 on one side as described above,
As shown in d), etching is continued from the other side, and both etching grooves are penetrated to form a predetermined lead.

Next, a predetermined lead frame is obtained by removing the photosensitive resin pattern 12 and the film 14 (FIG. 4(e)).

In this embodiment, etching from one side is completely stopped midway through. Therefore, as shown in FIG. 2, side etching on one side is slight, and the amount of photosensitive resin pattern 12 that takes into account this side etching may also be small. At this stage, one side of the metal plate 10 is coated with the film 14 and etching is continued from the other side, so when etching this other side, the film 14 is coated.
One side covered with step 4 is not etched at all. Therefore, the etching of the lead frame can be completed while the initially planned lead width 2 on one side is maintained at a predetermined width.

In this case, by filling the film 14 up to the inside of the etching groove, the wall surface of the etching groove on one side will remain in the film 14 even after the image etching groove has penetrated, as shown by the broken line in FIG.
New side etching progresses because it is covered with
A predetermined lead width a is ensured.

In this way, etching is stopped at the stage where a shallow etching groove is formed on one side, and the lead width at this stopped stage can be maintained at almost the final lead width l, so that adjacent leads can be brought closer together. Can increase the number of pins.

Note that the amount of etching on the other side is larger than that of the conventional side etching, and the cross section of the lead becomes trapezoidal as shown in Figure 3. However, in the case of a lead frame for a semiconductor device, the bonding area (lead width) on the upper surface As long as the width of the other side can be secured with a bonding tool during wire bonding, there will be no problem unless the width is particularly acute. do not have.

Furthermore, in a lead frame for a semiconductor device, the part where the lead pattern is particularly dense is the part of the inner lead surrounding the semiconductor element, so the part on which the film 14 is formed as described above may be at least the part of the inner lead. ,
A portion of the outer lead where a wide distance between the leads can be ensured may be etched from both sides at the same time as usual.

FIG. 4 shows another embodiment.

In this example, after the photosensitive resin pattern 12 is formed as shown in FIG. 5(a), etching is first performed from only one side as shown in FIG. 2(b), and this etching is stopped midway. Then, a film 14 is formed on one side to cover it, and then, as shown in FIG. 3(d), new etching is performed from the other side to form a predetermined lead.

In this embodiment as well, the side etching on one side, which becomes the bonding area, can be minimized and the leads can be brought close together, allowing for a large number of pins.

Although various preferred embodiments of the present invention have been described above, the present invention is not limited to the above-mentioned embodiments, and it goes without saying that many modifications can be made without departing from the spirit of the invention. be.

(Effects of the Invention) As described above, according to the present invention, a metal plate is etched from at least one side, the etching on the one side is stopped halfway, and the other side is covered with a film having etching resistance. Although the lead is formed by x'y etching to penetrate the lead, the lead width is determined by the first shallow etching, and in the second etching from the other side, the side on which the film is formed is Since side etching is not performed, the etching rate can be easily controlled, dimensional accuracy is improved, and the number of pins can be increased.

[Brief explanation of drawings]

Fig. 1 is a process diagram of an embodiment of the method of the present invention, and Fig. 2 is a process diagram of an embodiment of the method of the present invention.
An explanatory diagram showing the state of side etching during the next etching. Fig. 3 is an explanatory diagram showing the state of side etching during the second etching when the film is formed into the etching groove. Fig. 4 is a process diagram showing another example, No. 5
The figure shows a process diagram of a conventional method. DESCRIPTION OF SYMBOLS 10... Metal plate, 12... Photosensitive resin bottle pattern, 14... Film.

Claims (1)

[Claims] 1. A method for manufacturing a lead frame in which a predetermined pattern is formed by etching from both sides of a metal plate, which comprises forming a predetermined photosensitive resin pattern on both sides of the metal plate, and forming the photosensitive resin pattern on both sides of the metal plate. As a mask, at least one side of the metal plate is etched, the etching on the one side is stopped midway, and the one side of the metal plate is coated with an etching-resistant film, and then the other side is further or newly etched. 1. A method for manufacturing a lead frame, comprising etching to form a predetermined lead pattern, and removing the photosensitive resin pattern and film. 2. A method for manufacturing a lead frame, characterized in that the inside of the etching groove is filled with the film.