JPH05190719A - Manufacture of multipin lead frame - Google Patents

Abstract

PURPOSE:To stably manufacture a multipin lead frame in which the wire bonding effective width of the inner lead is secured and which is excellent in adhesion with the adhesion with the sealing material of a package, using press and etching in combination. CONSTITUTION:In the manufacture of a lead frame 8, which has at least an outer lead 4 and an inner lead 3 ranging from the outer lead and provided fronting on the periphery of a pad 1, the area to form the inner lead or the top of the inner lead of a metallic plate 9 for formation is thinned, and a photoresist film is provided on the thin part 10, and also photomask patterns for the inner lead or the top of the inner lead are made on one side of the photoresist film, and they are etched from one side, and the outer lead is made with a press.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for manufacturing a multi-pin lead frame.

[0002]

2. Description of the Related Art In a semiconductor device, a semiconductor integrated circuit chip (hereinafter referred to as a chip) is mounted on a pad portion (semiconductor mounting portion), and a chip terminal and an inner lead of a lead frame are formed by wires such as gold wire and aluminum wire. It is manufactured by connecting or directly connecting the inner lead and the chip and encapsulating them with resin or ceramic.

By the way, the semiconductor device is indispensable to electronic equipment applied to all industrial fields, and its technical progress is remarkable, and in order to cope with this, the semiconductor device can be highly functionalized, highly integrated, and miniaturized. It will be more important in the future.

Recently, the lead frame has, for example, one pin.
Those with more than 00 pins are manufactured. As the number of pins increases, the lead width and lead spacing decrease, and the inner lead width and spacing become extremely fine.

Further, in order to make the semiconductor device smaller and thinner, it is necessary to reduce the resin sealing thickness at the time of packaging. On the other hand, this causes a problem that the resin lowers the adhesion to the lead frame. ..

[0006] As one of the methods of manufacturing a multi-pin lead frame, there is a method of using both punching by a press and etching. For example, Japanese Examined Patent Publication No. 3-6663 discloses a method of manufacturing a lead frame in which the inner lead portion and the pad portion are formed by etching and the outer lead portion is formed by pressing. This has the effect of obtaining the advantages of both the fine etching action of etching and the high-speed and highly stable punching action of the press.

Japanese Unexamined Patent Publication No. 63-148667 discloses a method of manufacturing a lead frame in which an outer lead, a dam bar and a guide hole are punched by a press, then positioned with reference to the guide hole and an inner lead portion is formed by etching. Has been done. This has the effect of combining the advantages of pressing and etching.

[0008]

Although the prior art has a corresponding effect, the inner lead etched by etching deeply erodes the back side of the photoresist pattern called side etching, and The width of the inner lead differs depending on the plate thickness direction, and the plate surface side is narrow, and when wire bonding is performed, there are problems such as the need for advanced technology due to welding connection, and impeding the speeding up of welding.

Further, the semiconductor device is required to be thin. By the way, a semiconductor device is manufactured by mounting a chip on a pad portion of a lead frame, connecting a terminal of the chip to a tip portion of an inner lead through a wire or directly, and then sealing with a resin or the like. To reduce the thickness, it is necessary to reduce the resin sealing thickness, but on the other hand, this brings about a decrease in the adhesion strength between the resin and the lead frame. In particular, the inner lead etched by etching has a narrow width on the plate surface side by side etching, which is a problem in a thin semiconductor device.

According to the present invention, when the inner lead or the tip of the inner lead is etched by etching to produce a multi-pin lead frame, the side-etching phenomenon in etching is not adversely affected, and the effective wire bonding width is stably secured. Even if a thin package is used, the adhesion with the sealing material such as resin or plastic is secured,
Further, the outer lead portion is formed by pressing, and it is an object of a manufacturing method that is high in cost instead of using a large number of pins.

[0011]

SUMMARY OF THE INVENTION The gist of the present invention is a method for manufacturing a lead frame, which comprises at least an outer lead portion and an inner lead portion which is continuous with the outer lead portion and faces the pad periphery. The area where the inner lead portion or the inner lead tip portion of the plate is formed is thinned, a photoresist film is provided on the thinned portion, and a photomask pattern of the inner lead portion or the inner lead tip portion is provided on one surface of the photoresist film, A method for manufacturing a multi-pin lead frame is characterized in that an inner lead portion or an inner lead tip portion is formed by etching from the one surface, and the outer lead portion is formed by pressing.

Further, if necessary, when the thinning is performed up to the pad portion forming region, a photoresist is also provided in the region and a photomask pattern is provided on one surface,
It is formed by etching from the one surface.

[0013]

In the present invention, when the lead frame is manufactured by using both etching and press working, the inner lead portion or the inner lead tip forming region is thinned by etching, and the photoresist is provided on the thin portion surface and one surface thereof is provided. Since a photomask pattern is formed and etching is performed from one surface to form the inner lead portion or the inner lead tip portion, there is no side etching on the other surface side, the lead width is not narrowed, and the bonding work is facilitated.
Also, the plate thickness is thin, but the side end surface of the inner lead has a wider lead width as described above, which exists along the longitudinal direction of the lead, and the lead width in the plate thickness direction changes. Therefore, even if it is a thin type, it does not drop out because it strongly adheres to the sealing material when packaged. In addition, the outer lead part, whose lead width and spacing are not as fine as the inner lead, is formed at high speed and with high accuracy because it is formed by a die without pressing, and the cost is not high in place of multiple pins. There is an effect.

[0014]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be described below in detail with reference to the drawings based on an embodiment. In the drawing, 1 is a pad for mounting a chip 2, 3 is an inner lead, the tip of which faces the pad 1, and the other end is connected to an outer lead 4. In this embodiment, the inner lead portion 3 is formed in an area thinned by etching before its formation. A tie bar 5 and a support bar 6 support the pad 1. 7 is a side rail.

The lead frame 8 having the above structure is manufactured by using both etching and press working, but the working order is arbitrary and may be carried out first.

First, the outer lead 4 is punched in the thin metal plate 9 with a die by a press. After that, as shown in FIG. 2, a photoresist 11 is provided in a portion other than the formation region of the inner lead 3 portion, and the formation region is thinned by etching to have, for example, 1/2 to 1/3 of the thickness of the thin metal plate 9.
Since the inner lead 3 part is etched in this thinned region, even a multi-pin lead frame having fine leads, for example, about 0.1 mm and more than 100 pins can be accurately formed by the synergistic effect of etching only from one side described later.

Next, photoresist 11-2 is provided on both sides of the thinned portion 10 as shown in FIG. 3, and the photomask pattern 12 of the inner lead portion is brought into contact with one surface of the photoresist 11-2 film. Expose.

Thereafter, the photomask pattern 12 is treated with a developing solution to remove the photoresist 11-2 film other than the exposed region of the one surface, and a resist pattern 13 is formed on the one surface side.

Resist pattern 1 on inner lead 2
Etching is performed by spraying an etching solution on the one side where 3 is formed. By this etching, the underside of the resist pattern 13 is deeply eroded, but the side of the other surface where the photoresist 11-2 film is provided is not eroded, and the cross-sectional state after the etching penetration is as shown in FIG. In addition, the lead width on the photoresist 11-2 film side becomes wider and the width changes in the plate thickness direction. This stabilizes the subsequent wire bonding work, and when packaged with a sealing material such as resin, the degree of adhesion with the lead portion becomes strong.

The resist pattern 13 may be formed by etching not only the entire inner lead 2 but also the tip of the inner lead, for example, a portion which is not parallel to the outer lead 4 and radially faces the pad 1 side.

Alternatively, the resist pattern 13 may be formed from the inner lead 2 portion to the pad 1 and etched to etch the inner lead 2 portion and the pad 1 together.

The portions other than those formed by etching, such as the outer leads 4 and the like, are punched and formed by a press using a die. However, when the tips are formed by etching, the outer leads 4 to the inner leads 2 are pressed. It suffices to form up to a continuous portion in a shape parallel to the section side.

Positioning between etching by etching and formation by pressing is facilitated by using the guide hole 14 formed in the side rail 7 as a reference, and the lead frame 8 is formed by etching and punching by pressing.

Further, the inner lead 2 part forming region or the forming region including the pad 1 part in the thin metal plate 9 is first made thin by etching, and then the outer lead 4 part is formed by pressing, and then the thinning part is formed by photolithography. Even if a resist 11-2 is provided, and a photomask pattern 12 including up to two inner leads or one pad is exposed on one surface of the photoresist 11-2 and exposed to light, a resist pattern 13 is formed and etching is performed. Various advantageous effects can be obtained, and the lead width becomes wider on the plate surface on the photoresist 11-2 side.

In the above-mentioned embodiment, the manufacture of the quad type lead frame is described, but it can be applied to the manufacture of various lead frames such as a dual in-line type.

Further, plating may be applied between the pressing and the etching.

[0027]

According to the present invention, when a lead frame is manufactured by using both pressing and etching, the inner lead portion or the tip of the inner lead is provided with a photoresist film in the thinned region of the metal thin plate to be formed, A resist pattern is formed on one surface of the resist film, and etching is performed only from one surface side. Therefore, even if the lead width and spacing are minute, it is formed with high accuracy, the side of the photoresist plate has no side etching, the inner lead width is wider, and the lead width changes in the plate thickness direction, and the wire bonding property is excellent. Adhesion with the package encapsulant becomes stronger. Further, the outer leads and the like are formed by a press, so that the advantages of high speed and stable workability of the press can be enjoyed.

[Brief description of drawings]

FIG. 1 is a diagram showing a lead frame according to an embodiment of the present invention.

FIG. 2 is a diagram in which the inner lead portion forming region of the metal thin plate in one embodiment of the present invention is made thin.

FIG. 3 is a diagram showing a photoresist and a resist pattern in a part of an inner lead according to an embodiment of the present invention.

FIG. 4 is a diagram showing a cross-sectional shape of a part of an inner lead after etching according to an embodiment of the present invention.

[Explanation of symbols]

 1 Pad 2 Chip 3 Inner Lead 4 Outer Lead 5 Tie Bar 6 Support Bar 7 Side Rail 8 Lead Frame 9 Metal Thin Plate 10 Thinned Area 11 Photoresist 12 Photomask Pattern 13 Resist Pattern 14 Guide Hole

Claims (2)

[Claims] 1. A method of manufacturing a lead frame having at least an outer lead portion and an inner lead portion which is continuous with the outer lead portion and faces the periphery of a pad, wherein the inner lead portion or the inner lead tip portion of a metal plate to be formed. Is thinned, a photoresist film is provided on the thinned portion, and a photomask pattern of the inner lead portion or the tip of the inner lead is formed on one surface of the photoresist film, and the outer lead is etched from the one surface. The method for manufacturing a multi-pin lead frame is characterized in that the parts are formed by pressing. 2. A method of manufacturing a lead frame, which comprises at least an outer lead portion and an inner lead portion which is continuous with the outer lead portion and faces the periphery of a pad, wherein the inner lead portion or the inner lead tip portion of the metal plate to be formed. And thin the pad formation area,
A photoresist film is provided on the thinned portion, and a photomask pattern of the inner lead portion or the inner lead tip portion and the pad portion is formed on one surface of the photoresist film, and the inner lead portion or inner lead tip is etched from the one surface. Part and pad part are etched,
A method for manufacturing a multi-pin lead frame, wherein the outer lead portion is formed by pressing.