JP2836904B2 - Lead frame manufacturing method - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to a method for manufacturing a lead frame.

(Prior Art) There are two methods of manufacturing a lead frame for a semiconductor device: a method by press working and a method by chemical etching.

Conventionally, in the case of a method using an etching process, the process is performed according to the process shown in FIG.

That is, as shown in FIG. 1A, a photosensitive resin pattern 12 for a mask corresponding to a lead frame pattern is formed on the front and back of a metal plate 10, and then, as shown in FIG. Etching was performed from both sides, and then the photosensitive resin pattern 12 was removed and formed into a predetermined lead frame as shown in FIG.

(Problems to be Solved by the Invention) However, the problem of side etching cannot be avoided when performing chemical etching. For this reason, the photosensitive resin pattern 12 is formed to be wider than the lead width l to be obtained in consideration of the above-mentioned side etching, so that a predetermined lead width is obtained at the end of the etching. After penetrating, the side etching becomes more intense, so that it becomes difficult to control the etching rate, and there is a problem that dimensional accuracy varies.

Thus, in the case of chemical etching, since isotropic etching is inevitable, the interval between the leads is generally limited to the thickness of the material, and the distance between the leads cannot be narrowed further. .

SUMMARY OF THE INVENTION The present invention has been made in order to solve the above-mentioned problem, and an object of the present invention is to provide a method for manufacturing a lead frame capable of increasing the number of pins by chemical etching.

(Means for Solving the Problems) A method for manufacturing a lead frame according to the present invention includes the following steps.

That is, in a method of manufacturing a lead frame in which a predetermined lead pattern is formed by etching from both surfaces of a metal plate, a step of forming a photosensitive resin pattern corresponding to the predetermined lead pattern of the lead frame on both surfaces of the metal plate; Using a photosensitive resin pattern as a mask, etching at least one side of the metal plate halfway to form an etching groove; and forming an inner lead of a lead frame among the etching grooves formed on one side of the metal plate. Covering the etching groove formed along the region with a film having etching resistance, and further etching the photosensitive resin pattern and the etching groove on one side of the metal plate not covered with the film having etching resistance. At the same time as etching, the photosensitive resin pattern A step of forming an etching groove by further or newly etching the other side of the metal plate, forming a predetermined lead pattern by penetrating the metal plate with the etching groove from both sides, and forming the photosensitive resin from the lead pattern. Removing the pattern and the film having etching resistance.

Hereinafter, a preferred embodiment of the present invention will be described with reference to the accompanying drawings.

First, as shown in FIG. 1A, a photosensitive resin pattern 12 is formed on both surfaces of a metal plate 10 by applying a photosensitive resin and exposing using a mask.

Next, as shown in FIG.
Is used as a mask, etching is performed from both sides of the metal plate 10 with an etching solution such as an aqueous ferric chloride solution or an aqueous cupric chloride solution.

Next, as a feature of the present invention, FIG.
As shown in (1), the etching is stopped before both etching grooves pass through, and an etching-resistant film 14 is formed on one side of the metal plate 10.

As the film 14, a photosensitive resin was applied and cured, a thermosetting resin was applied and cured, or a photosensitive resin was formed into a sheet and a dry film was applied. It is preferable to use a material that can be removed simultaneously with the same removing liquid when dissolving and removing the photosensitive resin pattern 12 in a later step. For example, the same material as the photosensitive resin pattern 12 is preferable.

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

After the film 14 is formed on one side as described above, etching is continued from the other side as shown in FIG. 4D, and the leads are formed through the etching grooves.

Next, a predetermined lead frame is obtained by removing the photosensitive resin pattern 12 and the film 14 (FIG. 3E).

In this embodiment, etching from one side is completely stopped halfway. Therefore, as shown in FIG. 2, the side etching on one side is slight, and the margin of the photosensitive resin pattern 12 in consideration of the side etching may be small. At this stage, since one side of the metal plate 10 is covered with the film 14 and the etching is continued from the other side, the one side covered with the film 14 is not etched at all when the other side is etched. Therefore, the etching of the lead frame can be completed while the initially planned lead width 1 on one side is maintained at a predetermined width.

In this case, since the film 14 is particularly filled into the etching groove, the wall of the etching groove on one side is covered with the film 14 even after both the etching grooves penetrate as shown by the broken line in FIG. New side etching does not proceed, and a predetermined lead width l is secured.

As described above, the etching is stopped at the stage of the shallow etching groove on one side, and the lead width at this stopped stage can be almost assured to almost the final lead width l. The number of pins can be increased.

In addition, although the etching amount on the other surface side is larger than the conventional one and the side etching proceeds, the cross section of the lead becomes trapezoidal as shown in FIG.
It is sufficient that the bonding area (lead width 1) on the upper surface is secured to a predetermined width, and the width on the other surface does not become particularly acute as long as the receiving width of the bonding tool at the time of wire bonding is secured. As long as there is no problem.

Also, in a lead frame for a semiconductor device, a portion where a lead pattern is particularly dense is a portion of an inner lead surrounding a semiconductor element. Therefore, a portion where a film 14 is formed as described above extends along a portion where an inner lead is formed. The outer lead portion, which is a portion of the formed etching groove and which can secure a wide interval between the leads, is simultaneously etched from both sides as usual.

 FIG. 4 shows another embodiment.

In this embodiment, after the photosensitive resin pattern 12 is formed as shown in FIG. 6A, etching is first performed only from one side as shown in FIG. 6B, and this etching is stopped halfway. Then, a film 14 is formed and covered on one side, and then, as shown in FIG. 4D, another etching is performed from the other side to form a predetermined lead.

Also in the present embodiment, the side etching on one side serving as a bonding area can be reduced as much as possible, and the leads can be brought close to each other, so that the number of pins can be increased.

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

(Effects of the Invention) As described above, according to the present invention, the metal plate is etched from at least one side, and the etching is temporarily stopped halfway, so that the etching groove is formed along the portion where the lead pattern is formed, and The etching groove formed along the portion where the inner lead is formed among the etching grooves is covered with a film having an etching resistance, and the metal plate is further etched and penetrated from one side and the other side to form a lead pattern. Since the inner lead is formed, the lead width of the inner lead is determined by the first shallow etching, and the inner lead forming region on the side where the film is formed is not side-etched by the second etching. Lead frame that facilitates control, improves lead dimensional accuracy, and increases the number of pins Can be provided.

In addition, since the above-mentioned film is not formed in the etching groove formed along the portion where the outer lead is formed on one side of the metal plate, the second etching is performed from both sides of the metal plate as usual, so that manufacturing is easy. is there.

[Brief description of the drawings]

FIG. 1 is a process diagram of an embodiment of the method of the present invention, and FIG.
FIG. 3 is an explanatory view showing the state of side etching at the time of the next etching. FIG. 3 is an explanatory view showing the state of side etching at the time of the second etching when a film is formed up to the inside of the etching groove. Is a process drawing showing another embodiment, and FIG.
The figure shows a process chart according to the conventional method. 10 ... metal plate, 12 ... photosensitive resin pattern, 14 ... film.

Claims (1)

(57) [Claims] 1. A method for manufacturing a lead frame in which a predetermined lead pattern is formed by etching from both surfaces of a metal plate, wherein a photosensitive resin pattern corresponding to the predetermined lead pattern of the lead frame is formed on both surfaces of the metal plate. Using the photosensitive resin pattern as a mask, etching at least one side of the metal plate halfway to form an etching groove; and, among the etching grooves formed on one side of the metal plate, inner leads of a lead frame. Covering an etching groove formed along a portion where a metal plate is formed with a film having etching resistance; and etching one side of the metal plate not covered with the photosensitive resin pattern and the film having etching resistance. Simultaneously etching the groove, using the photosensitive resin pattern as a mask Forming an etching groove by further or newly etching the other surface of the metal plate, and forming a predetermined lead pattern by penetrating the metal plate with the etching groove from both surface sides; Removing the conductive resin pattern and the film having etching resistance.