JPH05114680A - Manufacture of lead frame - Google Patents

Abstract

PURPOSE:To form a precise pattern with high accuracy by forming a thin wall- thickness section containing no residual stress in at least an area which becomes the leading edge section of inner leads by etching and the remaining area by pressing. CONSTITUTION:After the area of a belt-like material other than areas for forming the leading edges of inner leads 12 and another areas for forming die pads 11 is coated with a resist pattern by a photolithographical method, a thin wall-thickness section R1 is formed by etching the belt-like material by using the resist pattern as a mask. Then, after forming another resist pattern by using the metallic wire material, the leading edge sections of the inner leads 12 and die pads 11 are formed by etching. In addition, the remaining area is patterned by loading the metallic wire material in a metallic mold equipped with trimming dies for part of the lead 12, a damper 13, part of an outer lead 14, etc., and performing press working. Therefore, a high accuracy lead frame which is less in process stress, such as torsion, etc., can be obtained without side etching.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a lead frame manufacturing method, and more particularly to a high density lead frame manufacturing method.

[0002]

2. Description of the Related Art Lead frames for semiconductor devices such as ICs and LSIs are 0.25 mm or 0.15 mm in size by either a photo etching method or a press working method.
After performing shape processing by removing unnecessary portions of the metal strip having the plate thickness of, a plating step of plating a predetermined portion,
It is formed through a fixing process of attaching a tape and fixing the inner leads to each other.

By the way, as the chip area increases and the number of lead pins increases as the semiconductor device becomes higher in density, higher in integration, and thinner, the package is the same as the conventional package or the package is made smaller and thinner. There is a tendency.

Therefore, the inner reel is formed within the same area.
As the number of the leads increases, the width of the inner leads and the space between the inner leads adjacent to each other naturally decrease. For this reason, extremely high processing accuracy of the lead frame has been demanded, and deformation of the inner lead due to deterioration of strength and inner lead due to the deformation.
A problem such as a short circuit between terminals is a problem.

Therefore, the present inventors have proposed a method of forming a lead frame by first forming the inner lead by an etching method and forming the outer lead by a press working method (Japanese Patent Publication No. 3-6663). Publication).

However, even if the inner lead is formed by etching, the lead width is narrow with respect to the plate thickness, so the lead cross section becomes rectangular, and the lead is twisted due to the contact of the capillary during wire bonding, or the lead is twisted. Problems such as displacement of the position remained.

In addition, with the recent demand for thinner packages, the thickness of the material used for the lead frame is becoming thinner. However, as the outer leads become thinner, bending of the leads after mounting becomes a serious problem. Is becoming

[0008]

As described above, with the high integration of semiconductor devices, the lead interval and the lead width are becoming smaller, and the improvement of processing accuracy has been a serious problem.

Therefore, it is necessary to reduce the plate thickness of the entire lead frame. However, if the entire lead frame is made thin, the strength of the entire lead frame is reduced, and the lead frame is deformed and damaged during transportation, handling, and positioning, which causes a decrease in reliability and yield of the semiconductor device.

Further, there is an increasing demand for thinner packages, and the thickness of the die pad region has become a problem as well as the problem of resin adhesion accompanying the thinner resin thickness.

The present invention has been made in view of the above circumstances, and an object thereof is to provide a lead frame which is easy to manufacture and has high reliability.

[0012]

In the present invention, therefore, a thin region is formed by etching away a predetermined region of a metal strip to a predetermined thickness, and at least an inner lead tip region is formed in the thin region. As described above, at least the tip region of the inner lead is processed by etching, and the outer lead and the like are processed by the pressing method.

Desirably, a pad for mounting a semiconductor chip is also included in the thin portion.

Further, a region of the inner lead extending in parallel with the outer lead is formed by press working.

[0015]

According to the above structure, at least the region which becomes the tip of the inner lead is formed with a thin portion having no residual stress by etching, and the shape is processed by etching, while the remaining region is processed by pressing. Therefore, while the outer frame is thick and strong, the region such as the inner lead portion where the dimensional accuracy is severe is processed from the thin portion, and it is possible to form a highly precise fine pattern.

Further, by making the pad for mounting the semiconductor chip thin, it becomes possible to further reduce the thickness of the package.

Furthermore, a plurality of recesses may be formed on the back surface of the pad by etching. By doing so, the adhesiveness with the resin is improved and the package is removed even if the resin thickness is small. It is possible to prevent peeling and obtain a highly reliable product.

Further, among the inner leads, the region extending in parallel with the outer leads, which is a region having a relatively large lead interval, is formed by pressing while leaving the wall thickness as it is, so that one having higher mechanical strength can be obtained. be able to.

Here, the thin portion is approximately 1 / thick of the thick portion of the outer frame or the like.
It is desirable to process so as to have a wall thickness of about 2.

Since the starting material is thin when etching the shape of the inner lead tip or the like, it is possible to form a highly accurate pattern with less undercut.

[0021]

Embodiments of the present invention will now be described in detail with reference to the drawings.

The lead frame formed by the method of the embodiment of the present invention has a die pad as shown in FIG. 1 (a) which is a plan view, FIG. 1 (b) is its sectional view and FIG. 2 is a partial perspective view. The tip regions R1 of the inner leads 11 and the inner leads 12 are thinned to about ½ of the thickness of the outer regions such as side bars and then processed by etching, while the inner leads have relatively large lead intervals (R2). The region extending in parallel with the outer lead, the outer lead, the side bar, and the like are characterized in that they are formed by press working as they are.

That is, the die pad 11 and the inner lead tip region R1 radially arranged around the die pad 11 and the outer region R2 in which the inner lead parallel region, the dam bar 13, the outer lead 14, the side bars 15 and 16 are formed. It consists of If necessary, a polyimide tape may be attached to the back surface.

Next, a method for manufacturing this lead frame will be described.

First, a region of the strip material excluding the inner lead 12 tip forming region and the die pad 11 forming region is covered with a resist pattern by photolithography.

Then, using this resist pattern as a mask, etching is performed to a depth of about 1/2 to form a thin region R1.

A resist pattern is formed using the metal strip in which the thin region is formed in this manner, and etching is performed using the resist pattern as a mask to shape the tips of the inner leads 12 and the die pad 11.

Then, the inner lead 12, a part of the dam bar 13, the outer lead 14 and the like are attached to a die equipped with a punching die, and press working is performed to pattern the remaining region.

Subsequently, if necessary, a polyimide tape for fixing the inner leads is attached to the entire back surface, and after the plating process, the lead frame is shaped.

In the lead frame thus formed, the starting material for the etching process for processing the fine shape of the inner lead tip portion is thin, so that there is no side etching and there is high precision. It is possible to obtain a lead frame with less processing stress such as twisting, and thus it is possible to obtain a lead frame with less deformation even after a heating process in a subsequent process.

Furthermore, the lead spacing is maintained well,
The bondability can be improved.

Further, since the pad for mounting the semiconductor chip is also thin, the thickness of the package can be further reduced.

Although this lead frame is completed as a semiconductor element through steps such as mounting of element chips, wire bonding, and resin sealing, it is thin and extremely reliable.

In the above embodiment, only the inner lead tip and the die pad are made thin, but as shown in FIGS. 3A and 3B, the inner lead tip forming region R is formed.
Only 3 may be thinned by half etching to form a plurality of recesses H on the back surface of the die pad. By doing so, the adhesiveness with the resin is improved, and even if the resin thickness is small, it is possible to prevent the package from coming off or peeling and obtain a highly reliable package.

[0035]

As described above, according to the present invention, a thin portion having no residual stress is formed by etching in at least a region which will be the tip of the inner lead, and the shape is processed by etching, while the remaining region is pressed. Since the shape is processed by processing, the outer frame is thick and strong, while the area such as the inner lead part where the dimensional accuracy is severe is processed from the thin part, forming a highly precise fine pattern. Is possible.

[Brief description of drawings]

FIG. 1 is a diagram showing a lead frame formed by the method of the first embodiment of the present invention.

FIG. 2 is a perspective view of a main part of the lead frame.

FIG. 3 is a diagram showing a lead frame formed by the method of the second embodiment of the present invention.

[Explanation of symbols]

 11 Die Pad 12 Inner Lead 13 Dam Bar 14 Outer Lead 15 Side Bar 16 Side Bar H Recess

Claims (3)

[Claims] 1. A method of manufacturing a lead frame, comprising: a die pad for mounting a semiconductor chip; inner leads arranged at a predetermined distance from the pads; and outer leads connected to the inner leads. A thinning step of thinning a region of the metal strip including at least an inner lead tip forming region by etching, and forming at least a part of the inner lead by etching the metal strip through a resist pattern; And a second shape processing step of forming the remaining region by pressing. 2. The method of manufacturing a lead frame according to claim 1, wherein the thinning step is a step of thinning the die pad to include a die pad forming region. 3. The method of manufacturing a lead frame according to claim 1, wherein the second shape processing step includes a step of pressing a region of the inner lead extending in parallel with the outer lead. ..