JPH02229457A - Lead frame, manufacture thereof and semiconductor device using same - Google Patents

Abstract

PURPOSE:To promote a multipin package by a method wherein a pattern of an inner lead part is formed by etching it and a pattern of an outer lead part is formed by pressing it. CONSTITUTION:Guide holes 9 are stamped, by using a press, at prescribed intervals in peripheral edge parts of a hoop material 10 whose sheet thickness is about 150mum; the whole face of regions at the inside of molding lines M is etched; its sheet thickness is reduced to 70 to 80mum. In succession, the regions at the inside of the molding lines M are etched again; inner lead parts 5a, tabs 2 and tab suspension leads 7 are patterned at the same time. Also during this process, a resist is aligned with a mask by making use of the guide holes 9. Then, a region at the outside of the molding lines M is stamped by using a press; outer lead parts 5b, dams 6, one part of the tab suspension leads 7, frame parts 8a, 8b and the like are patterned at the same time. When the hoop material 10 is positioned to a metal mold of the press, the guide boles 9 are utilized; thereby, a high positioning accuracy can be obtained.

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention relates to a lead frame, a manufacturing method thereof, and a semiconductor device using the lead frame, and is particularly applicable to multi-bin packages for sealing semiconductor pellets. It is about effective techniques.

[Conventional technology]

BACKGROUND ART With the increasing functionality of various electronic devices such as computers, the number of pins in puff cages that seal semiconductor pellets forming integrated circuits such as microcomputers and gate arrays is rapidly increasing. Q, a type of surface mount package, is suitable for multi-bin packaging.
F P (quad flat package) is attracting particular attention, and devices with leads of 200 pins or more are being put into practical use.

Furthermore, it is expected that future QFPs will be required to have a very large number of bins of 300 to 400 pins or more.

Resin-sealed packages, including the above-mentioned QFP, are generally made by bonding a semiconductor pellet to the tab (guid pad part) of a lead frame using silver paste, etc., and then bonding the pellet's bonding butt and the inner lead part of the lead frame using gold or other metal. After making electrical connections with wires, the package is manufactured by transfer molding, followed by forming outer leads extending outside the package into a predetermined shape. Therefore, in order to promote the increase in the number of bottles in resin-sealed packages, it is essential to advance microfabrication technology for lead frames.

Pressing methods and etching methods are conventionally known as lead frame processing techniques.While the etching method requires more processing steps than the pressing method, it is easier to process fine patterns, so for example The pressing method is used for lead frames with 140 pins or less, and the etching method is used for lead frames for packages with more than 140 pins. Regarding the QFP multi-pin technology, for example, published by Nikkei BP, December 12, 1985,
"Nikkei Electronics JP141-P1541 has a detailed explanation.

[Problem to be solved by the invention]

The inventors of the present invention have found that the conventional lead frame processing technology has the following problems, and these problems are an obstacle to increasing the number of bins in packages.

That is, in the above-mentioned etching method, a predetermined resist pattern is formed on both sides of a thin plate (hoop material) made of a conductive material such as copper, and then this thin plate is immersed in an etching solution to remove the resist pattern. A desired lead pattern is formed by a so-called wet etching method that dissolves and removes the conductive material at a location. However, in the wet etching method, since etching generally proceeds isotropically, the side surfaces of the pattern tend to be partially over-etched, resulting in variations in the cross-sectional shape of the resulting leads. Then, when forming leads with varying cross-sectional shapes,
Since the leads also bend in the direction of adjacent leads, a defect occurs in which adjacent leads are short-circuited. Furthermore, if the leads bend in the direction of adjacent leads, the heights of the leads will also be uneven, resulting in poor connection between the electrode pads of the board and the leads when mounting the package on the board.

Furthermore, a guide hole is usually formed in the frame of the lead frame to serve as a guide when positioning the lead frame in the mold during molding, but the guide hole formed by etching has a smaller inner diameter for the reasons mentioned above. Dimensions tend to vary. Therefore, when positioning the lead frame in the mold, misalignment occurs, which causes a reduction in the molding yield of the package.

In this way, the etching method has the advantage that it is easier to process fine patterns than the pressing method, but on the other hand,
It has the disadvantage that the cross-sectional shape of the pattern tends to vary.

On the other hand, in the press method, since the cross-sectional shape of the pattern is stable, problems such as lead bending during forming and positional deviation during positioning in a mold are unlikely to occur. However, the pressing method has a problem in that the processing accuracy of fine patterns is inferior to the etching method, and the dimensional accuracy of the inner lead part, which is the narrowest part of the pattern width and pitch, deteriorates significantly. ,
It is difficult to manufacture lead frames for multi-pin packages with good yield.

The present invention has been made in view of the above-mentioned problems, and its purpose is to provide a technology that can promote the increase in the number of bins in packages.

The above and other objects and novel features of the present invention will become apparent from the description of this specification and the accompanying drawings.

[Means to solve the problem]

A brief overview of typical inventions disclosed in this application is as follows.

That is, the invention according to claim 1 is a lead frame including an inner lead portion patterned by etching and an outer lead portion patterned by pressing.

The invention according to claim 2 is the lead frame according to claim 1, in which an insulating film supporting the inner lead portion is bonded to the back surface of the tab.

The invention according to claim 3 provides that when manufacturing the lead frame according to claim 1 or 2, a guide hole is first formed in a predetermined location of the hoop material by pressing, and then a region to be sealed inside the package is etched. This is a method for manufacturing a lead frame in which a pattern is formed and a pattern is formed in an area exposed to the outside of a puff cage by pressing.

According to a fourth aspect of the present invention, in the lead frame manufacturing method according to the third aspect, the thickness of the region sealed inside the package is made thinner than the thickness of other regions.

The invention according to claim 5 is a semiconductor device in which a semiconductor pellet bonded to the tab of the lead frame according to claim 1 or 2 is sealed in a package.

[Effect]

According to the invention described in claim 1, a lead frame for a multi-bin package is obtained in which the lead width and lead pitch of the inner lead portion are narrowed and the cross-sectional shape of the outer lead portion is stable.

According to the second aspect of the invention, by supporting the tips of the inner lead portions and the tab suspension leads with the insulating film, deformation thereof can be prevented.

According to the third aspect of the invention, when manufacturing a lead frame by patterning the hoop material by etching and pressing, the guide hole formed by pressing with high dimensional accuracy is used to align the resist mask and press metal. Positioning to the mold can be performed with high precision. Furthermore, the accuracy when positioning the lead frame in the mold is also improved.

According to the invention described in claim 4, the thickness of the region sealed inside the package is made thinner than the thickness of the region exposed to the outside of the package, making microfabrication easier. Narrowing of the lead width and lead pitch of the lead portion is promoted.

〔Example〕

FIG. 1 is a plan view of a lead frame according to an embodiment of the present invention, FIGS. 2(a) to (e) are plan views of a hoop material showing a method of manufacturing this lead frame, and FIG. FIG. 2 is a cross-sectional view of a semiconductor device manufactured using this lead frame.

As shown in FIG. 1, a rectangular tab (die pad portion) 2 is formed in the center of the lead frame 1 of this embodiment made of a conductive material such as copper. A semiconductor pellet 3 on which an integrated circuit such as a gate array or the like is formed is mounted.

A rectangular insulating film 4, which is one size larger than the tab 2, is bonded to the back surface of the tab 2 with an adhesive or the like. A large number of leads 5 are arranged around the tab 2 so as to surround the tab 2, and a square frame-shaped dam 6 is formed in the middle of the leads 5. Tab suspension leads 7 for supporting the tab 2 are installed between the dam 6 and the four corners of the tab 2.

The inside of the lead 5 shown in the figure is called an inner lead part 5a, and the outside thereof is called an outer lead part 5.
It is called b. This mold line M indicates the boundary between the area sealed inside the package and the area exposed to the outside.

The tip of the inner lead portion 5a and the tab suspension lead 7 are
It is bonded to the insulating film 4 with an adhesive, and thereby,
Deformation of the inner lead Iffl5a and the tab hanging lead 7 is prevented.

On the other hand, the tips of the outer lead portions 5b are integrally connected to the frame portions 3a and 3b of the lead frame 1.

The lead frame 1 of this embodiment has a plate thickness of, for example, 150 μm on the outside of the mold line M, and includes an outer lead portion 5b, a dam 6, a part of the tab suspension lead 7, a frame portion 3a,
All parts such as 3b are patterned at the same time by pressing.

On the other hand, the thickness of the inside of the mold line M is, for example, 7.
The inner lead part 5a is thinner than the outside at 0 to 80 μm.
The s-tub 2 and a portion of the tab suspension lead 7 are all patterned at the same time by etching.

The lead frame 1 is formed by integrally forming a plurality of unit frames constituted by the above-mentioned parts in one direction, for example, seven series, and the lead frame 1 is formed with gold at a predetermined location of the frame part 8a during molding. A guide hole 9 is formed by a press to serve as a guide when positioning the mold.

Next, an example of a method for manufacturing the lead frame 1 described above will be explained.

First, as shown in FIG. 2(a), a hoop material 10 made of a thin copper plate with a thickness of about 150 μm is prepared, and guide holes 9 are formed at predetermined intervals on the periphery of the hoop material 10 by pressing. Punch out.

Next, as shown in FIG. 2(b), the entire area inside the mold line M is etched to a thickness of 70 to 80 mm.
Let it be μm. At this time, mask alignment of the resist is performed using the guide hole 9. Since the guide hole 9 formed by pressing has higher dimensional accuracy than the guide hole formed by etching, mask alignment can be performed with high precision by using this guide hole 9.

Next, as shown in FIG. 2(C), the mold line M
The inner lead part 5 is etched again.
a, the tab 2 and the tab hanging lead 7 are patterned at the same time. At this time as well, the guide hole 9 is used to perform mask alignment of the resist.

When etching the hoop material 10 to form a desired pattern, the processing accuracy of the pattern is limited by the thickness of the hoop material 10, and generally, the thinner the board thickness, the more accurately a fine pattern can be formed.

In this example, the area inside the mold line M is etched on the entire surface in advance to reduce the plate thickness to 70 to 80 μm, so that, for example, the lead radius is about 0.1 M and the lead pitch is about 0.1 M. The fine inner lead portion 5a of 15 ms can be formed with high accuracy.

Next, as shown in FIG. 2 (6), the area outside the mold line M is punched out using a press to form the outer lead portion 5b.
, the dam 6, a part of the tab suspension lead 7, and the frame parts 8a and 8b are patterned at the same time. When positioning the hoop material 10 in a press mold, high positioning accuracy can be obtained by utilizing the guide hole 9.

Since the lead width and lead pitch of the outer lead portion 5b are wider than the lead width and lead pitch of the inner lead IIS 5b, sufficient processing accuracy can be obtained even with the pressing method. Further, since the outer lead portion 5b patterned by pressing has a stable cross-sectional shape, there is no risk of lead bending of the outer lead portion 5b when forming the lead 5 after molding.

Subsequently, after plating the inner lead portion 5a with silver (Ag) or the like, an insulating film 4 made of an insulating material such as epoxy resin is adhered to the back surface of the tab 2, as shown in FIG. By fixing the tip of the inner lead part 5a and the tab suspension lead 7 with this insulating film 4,
The lead frame 1 shown in FIG. 1 is completed. Nahu,
This insulating film 4 includes an inner lead portion 5a and a tab 2.
, the tab suspension lead 7 may be bonded to the back surface of the tab 2 at the stage where the pattern is formed by etching.

After that, the pellet 3 is bonded onto the tab 2 using a bonding agent such as silver paste, and then the bonding pad of the pellet 3 and the inner lead portion 5a of the lead frame 1 are electrically connected with a wire made of gold or the like. After that, the package is formed using transfer molding. When positioning the lead frame l in the mold, high positioning accuracy can be obtained by utilizing the guide hole 9. Subsequently, the outer lead portion 5b is cut from the frames ffls8a, 8b, and finally the outer lead portion 5b is formed into a predetermined shape, thereby completing the resin-sealed semiconductor device.

FIG. 3 shows an example of a semiconductor device manufactured using the lead frame 1 of this example.

This semiconductor device is, for example, a QFP, and in the figure,
The package 11 is made of, for example, a silicone-modified epoxy resin filled with a filler such as silica so that its coefficient of thermal expansion approaches that of silicon.

A pellet 3 is sealed inside the package 11. This pellet 3 is bonded to the upper surface of the central portion of the tab 2 via an adhesive 12 such as silver paste. The upper surface of the pellet 3 forms an integrated circuit forming surface, and an integrated circuit such as a Kate array or a microcomputer is formed on this integrated circuit forming surface.

An insulating film 4 is bonded to the back surface of the tab 2 via an adhesive l3 such as epoxy resin, and the tip of an inner lead portion 5a embedded in the package l1 is fixed to this insulating film 4.

A wire 15 made of gold or aluminum is bonded between a bonding pad 14 disposed along the outer periphery of the pellet 3 and the inner lead portion 5a.

The outer lead portion 5b extending outward from the side surface of the package 11 is bent, for example, into a gull wing shape.

According to this embodiment as described above, the following effects can be obtained.

(1). Since the area inside the mold line M is patterned by etching, which is easy to microfabricate, inner lead portions 5a with high dimensional accuracy can be obtained. Thereby, the lead width and lead pitch of the inner lead portion 5a can be narrowed.

(2). Since the area outside the mold line M is patterned by pressing, an outer lead portion 5b having a stable cross-sectional shape can be obtained. This makes it possible to prevent the leads from bending when forming the outer lead portion 5b, thereby avoiding short circuits between the adjacent IJ + leads 5, 5.

Furthermore, since variations in the height of the leads 5 can be prevented, when the leads 5 are soldered to the board, poor connection between the electrode pads of the board and the leads 5 can be avoided.

(3). According to (l) and (2) above, lead frame 1
The number of pins can be increased.

(4). Since the tip of the inner lead portion 5a and the tab suspension lead 7 are fixed with the insulating film 4, deformation of the inner lead portion 5a and the tab suspension lead 7 can be prevented. Thereby, it is possible to avoid a decrease in the molding yield of the package due to, for example, a short circuit between the inner lead portions 5a or deformation of the tab 2 due to resin flow during molding.

(5). Since the guide hole 9 formed by pressing with high dimensional accuracy is used to align the resist mask and position it to the press die and mold die, it is possible to use the guide hole 9 formed by etching. In comparison, mask alignment and positioning to the mold can be performed with high precision, thereby improving lead frame manufacturing yields and package molding yields.

(6). Since the plate thickness inside the mold line M is made thinner than the plate thickness outside the mold line M, it is possible to promote narrowing of the lead width and lead pitch of the inner lead Iffl5a.

As above, the invention made by the present inventor has been specifically explained based on Examples, but it should be noted that the present invention is not limited to the Examples and can be modified in various ways without departing from the gist thereof. Not even.

In the above example, the inside of the mold line M was patterned by etching, and then the outside of the mold line M was patterned by a press, but conversely, after the outside of the mold line M was patterned by a press, the mold was patterned. The inside of the line M may be patterned by etching.

In the above embodiment, the lead frame was manufactured using a single hoop material, but for example, a thick hoop material may be used to form a pattern only on the outside of the mold line M using a press, and a thin hoop material may be used to form a pattern using a press. It is also possible to form a pattern by etching only the inside of the mold line M, and then connect the two to manufacture a lead frame.

In the embodiment described above, the inside of the mold line M was entirely etched in advance to make the board thinner than the outside of the mold line M, but only the inside of the mold line M may be thinned by pressing.

In the above embodiment, the inside of the mold line M was patterned by etching, and the inner lead part, the tab, and the tab suspension lead were patterned at the same time, but only the inner lead part, where the pattern width and pitch were the narrowest, was etched. to form a pattern, and other parts (tab,
The tab hanging lead, outer lead portion, dam flap, frame portion, etc. may be patterned by pressing.

〔Effect of the invention〕

A brief explanation of the effects obtained by typical inventions disclosed in this application is as follows.

(1). By forming the inner lead part, where the pattern width and pitch are the narrowest, by etching and the outer lead part by pressing, the dimensional accuracy of the inner lead part is improved, and the outer lead part is Since the cross-sectional shape becomes stable, it is possible to increase the number of pins in the package.

(2). By supporting the tip of the inner lead part and the tab suspension lead with an insulating film bonded to the back surface of the tab, it is possible to prevent their deformation, so for example, short circuits between the inner lead parts due to resin flow during molding, or tab suspension leads can be prevented. It is possible to avoid a decrease in the molding yield of the package due to deformation of the package.

(3). When forming the inner lead part of the lead frame by etching and the outer lead part by pressing, guide holes are formed in advance at predetermined locations on the hoop material by pressing, thereby making it possible to utilize guide holes with high dimensional accuracy. As a result, the mask alignment of the resist and the positioning to the press mold can be performed with high precision, thereby improving the manufacturing yield of the lead frame. In addition, the accuracy when positioning the lead frame in the mold is also increased, so
Package molding yield is improved.

(4). By making the plate thickness of the area sealed inside the package thinner than the plate thickness of the area exposed to the outside of the package, microfabrication of the inner lead part becomes easier, so the lead width and lead pitch of the inner lead part can be reduced. The narrowing of the area will be promoted.

[Brief explanation of the drawing]

Fig. 1 is a plan view of a lead frame according to a second embodiment of the present invention; Figs. 12 (a) to (e) are plan views of a hoop material showing a method of manufacturing this lead frame; , is a cross-sectional view of a semiconductor device manufactured using this lead frame. l... Lead frame, 2... Tab, 3... Semiconductor pellet, 4... Insulating film, 5... Lead, 5a... Inner lead part, 5b... Outer lead part, 6 ...Dam, 7...Tab suspension lead, 3a, 3b...Frame part, 9...Guide hole, 10...
・Hoop material, 11...Package, 12.13...
Adhesive, 14... Bonding pad, l5... Wire, M... Mold line. Agent Patent Attorney Daiwa Tsutsui

Claims (1)

[Scope of Claims] 1. A lead frame used for manufacturing a package for sealing a semiconductor pellet, in which an inner lead portion is patterned by etching and an outer lead portion is patterned by pressing. 2. The lead frame according to claim 1, wherein an insulating film supporting the inner lead portion is bonded to the back surface of the tab. 3. The method for manufacturing a lead frame according to claim 1 or 2, wherein after forming the guide hole at a predetermined location of the hoop material by pressing, a region to be sealed inside the package is patterned by etching. A method for manufacturing a lead frame, characterized in that a pattern is formed in an area exposed to the outside of a package by pressing. 4. The thickness of the area sealed inside the package,
4. The method of manufacturing a lead frame according to claim 3, wherein the thickness of the lead frame is made thinner than the thickness of the region exposed to the outside of the package. 5. A semiconductor device using the lead frame according to claim 1 or 2, wherein a semiconductor pellet bonded to the tab of the lead frame is sealed in a package.