JP2667901B2 - Method for manufacturing semiconductor device - Google Patents

Description

Description: BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a lead frame, a method of manufacturing the same, and a semiconductor device using the same. It is about effective technology.

[Conventional technology]

With the increase in the functions of various electronic devices such as computers, the number of pins in a package for encapsulating a semiconductor pellet on which an integrated circuit such as a microcomputer or a gate array is formed is rapidly increasing. QF, a type of surface mount type package, is suitable for high pin count
P (quad flat package) has been receiving a lot of attention, and those with leads of 200 pins or more are being put to practical use.

It is expected that ultra-high pin counts of 300-400 pins or more will be required for future QFPs.

In general, resin-encapsulated packages such as the QFP described above bond semiconductor pellets to the tabs (die pads) of the lead frame with silver paste or the like, and connect the bonding pads of the pellets to the inner leads of the lead frame with wires such as gold. Then, the package is subjected to transfer molding, and then the outer lead portion extending to the outside of the package is formed into a predetermined shape. Therefore, in order to promote the increase in the number of pins of the resin-encapsulated package, it is indispensable to advance the fine processing technology of the lead frame.

As a processing technology of a lead frame, a pressing method and an etching method are conventionally known.Etching method has many processing steps as compared with the pressing method, but it is easy to process a fine pattern. The press method is applied to lead frames with 140 pins or less, and the etching method is applied to lead frames for multi-pin packages with more than 140 pins. The technique for increasing the number of pins of the QFP is described in detail in, for example, "Nikkei Electronics", pages 141 to 154, issued by Nikkei BP on December 12, 1988.

[Problems to be solved by the invention]

The present inventor has found that there are the following problems in the conventional lead frame processing technology, which hinders the promotion of multi-pin packages.

That is, in the above-described etching method, a predetermined resist pattern is formed on both surfaces of a thin plate (a hoop material) made of a conductive material such as copper, and then the thin plate is immersed in an etching solution so that the resist pattern is not applied. A desired lead pattern is formed by a so-called wet etching method of dissolving and removing a conductive material at a location. However, in the wet etching method, since etching generally proceeds isotropically, the side surface of the pattern is likely to be partially over-etched, and as a result, there is a disadvantage that the cross-sectional shape of the obtained lead varies. When a lead having a varied cross-sectional shape is formed, the lead also bends in the direction of the adjacent lead, so that a defect that adjacent leads are short-circuited occurs. Also, if the leads are bent in the direction of the adjacent leads, the heights of the leads will also be uneven, so that when the package is mounted on the substrate, poor connection between the electrode pads of the substrate and the leads will occur.

Further, in the frame portion of the lead frame, a guide hole serving as a guide when positioning the lead frame in the mold during normal molding is formed, but the guide hole formed by the etching method has an inner diameter of the inner diameter for the reason described above. Dimensions are easy to vary. Therefore, when the lead frame is positioned in the mold, a positional deviation occurs, which causes a reduction in the molding yield of the package.

As described above, the etching method has an advantage that a fine pattern can be easily processed as compared with the press method, but has a disadvantage that the cross-sectional shape of the pattern is easily varied.

On the other hand, in the pressing method, since the cross-sectional shape of the pattern is stable, the problems such as the bending of the lead during the above-described forming and the displacement during positioning in the mold are unlikely to occur. However, the press method is inferior in the processing accuracy of a fine pattern as compared with the etching method, and thus has a problem that the dimensional accuracy of the inner lead portion where the pattern width and pitch are the narrowest is remarkably reduced. However, it is difficult to manufacture a lead frame for a multi-pin package with high yield.

The present invention has been made in view of the above-mentioned problems, and an object of the present invention is to provide a technology capable of promoting a multi-pin package.

The above and other objects and novel features of the present invention are as follows.
It will be apparent from the description of this specification and the accompanying drawings.

[Means for solving the problem]

The outline of a typical invention among the inventions disclosed in the present application will be briefly described as follows.

That is, the method of manufacturing a semiconductor device of the present invention includes a step of punching a guide hole by pressing a predetermined portion of a hoop material, and a step of punching the hoop material punched by the guide hole using the guide hole to form a mold line. A step of punching a pattern of an outer region by a press, and etching a region inside the mold line in a state where the pattern is positioned by using the guide holes to reduce a thickness of the inner region to a plate outside the mold line. A step of forming a pattern of an inner lead portion in an area inside the mold line by etching while positioning using the guide hole, and suspending a tip, a tab, and a tab of the inner lead portion. Bonding an insulating film to the back surface of the lead to fix them, and a semiconductor pellet on the surface of the tab. Electrically connecting the bonding pad of the semiconductor pellet and the inner lead portion, and molding a package in a region inside the mold line while being positioned using the guide hole. And

Further, in the method of manufacturing a semiconductor device according to the present invention, after first punching out the guide hole, the inner region of the mold line is etched to make the inner region thinner than the outer region, and then formed thinner. The pattern of the inner lead portion is formed by etching in the inside region thus formed. Next, the pattern in the region outside the mold line is punched by a press.

[Action]

In the present invention, first, after the guide hole is punched by a press, the hoop material is etched using the guide hole or patterned by the press, so that the dimensional accuracy formed by the press is improved. Using high guide holes, resist mask alignment,
Positioning to the press die can be performed with high accuracy.
Further, the accuracy in positioning the lead frame on the mold is improved. As a result, the lead width and lead pitch of the inner lead portion can be narrowed. Further, by supporting the tips of the inner lead portions and the tab suspension leads with the insulating film, it is possible to prevent them from being deformed.

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

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

A rectangular insulating film 4 which is slightly larger than the tab 2 is joined to the back surface of the tab 2 with an adhesive or the like. A number of leads 5 are arranged around the tab 2 so as to surround the tab 2, and a rectangular frame-shaped dam 6 is provided in the middle of the lead 5.
Are formed. Between the dam 6 and the four corners of the tub 2,
A tab suspension lead 7 for supporting the tab 2 is provided.

The lead 5 is referred to as an inner lead portion 5a on the inner side of the mold line M shown in the figure, and an outer lead portion 5b on the outer side thereof.
It is called. The mold line M indicates a boundary between a region sealed inside the package and a region exposed to the outside.

The tip of the inner lead portion 5a and the tab suspension lead 7
It is joined to the insulating film 4 by an adhesive,
The inner lead portion 5a and the tab suspension lead 7 are prevented from being deformed. On the other hand, the outer lead portion 5b
The tip of the is integrally connected to the frame portions 8a and 8b of the lead frame 1.

In the lead frame 1 of the present embodiment, the outside of the mold line M has a plate thickness of, for example, 150 μm, and each part such as the outer lead part 5b, the dam 6, a part of the tab suspension lead 7, and the frame parts 8a and 8b , All of which are simultaneously patterned by pressing. On the other hand, the thickness of the inside of the mold line M is smaller than that of the outside, for example, 70 to 80 μm, and the inner lead portion 5a, the tab 2, and a part of the tab suspension lead 7 are all simultaneously patterned by etching. .

The lead frame 1 is formed by integrally forming a plurality of unit frames formed in one direction with a unit frame formed by the above-described units in one direction. A guide hole 9 serving as a guide for positioning the lead frame 1 in the mold at the time of molding is formed by pressing.

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

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

Next, as shown in FIG. 2 (b), the mold line M
The entire area inside is etched to a thickness of 70-80μ.
m. At this time, the resist mask is aligned using the guide hole 9. Guide hole 9 formed by press
Since the dimensional accuracy is higher than that of the guide hole formed by etching, by using this guide hole 9, mask alignment can be performed with high accuracy.

Subsequently, as shown in FIG. 2 (c), the region inside the mold line M is etched again to form an inner lead portion.
5a, the tab 2, and the tab suspension lead 7 are simultaneously patterned. Also at this time, the resist mask is aligned using the guide holes 9.

When a desired pattern is formed by etching the hoop material 10, the processing accuracy of the pattern is restricted by the thickness of the hoop material 10, and in general, a finer pattern can be formed with a smaller thickness.

In the present embodiment, since the entire area inside the mold line M is etched in advance and its thickness is reduced to 70 to 80 μm, for example, a fine inner lead having a lead width of about 0.1 mm and a lead pitch of about 0.15 mm The portion 5a can be formed with high accuracy.

Next, as shown in FIG. 2 (d), the mold line M
Press out the area outside of the outer lead part 5
b, the dam 6, a part of the tab suspension lead 7, the frame portions 8a, 8b, and the like are simultaneously patterned. When the hoop material 10 is positioned in the press die, high positioning accuracy can be obtained by using the guide holes 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 portion 5b, sufficient processing accuracy can be obtained even by the press method. Further, since the cross-sectional shape of the outer lead portion 5b formed by pressing is stable, there is no possibility that the outer lead portion 5b will bend when the lead 5 is formed 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 an epoxy resin is bonded to the back surface of the tab 2 as shown in FIG. By fixing the tip of the inner lead portion 5a and the tab suspension lead 7 with the insulating film 4, the lead frame 1 shown in FIG. 1 is completed. The insulating film 4 may be adhered to the back surface of the tab 2 when the inner lead portion 5a, the tab 2, and the tab suspension lead 7 are patterned by etching.

Thereafter, the pellet 3 is bonded onto the tab 2 using an adhesive such as a 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 by a wire such as gold. Then, the package is formed by transfer molding. When positioning the lead frame 1 in the mold, high positioning accuracy can be obtained by using the guide holes 9. Subsequently, the outer lead portion 5b is cut from the frame portions 8a and 8b, and finally, the outer lead portion 5b is formed into a predetermined shape, thereby completing a resin-sealed semiconductor device.

An example of a semiconductor device manufactured using the lead frame 1 of this embodiment is shown in FIG.

This semiconductor device is, for example, a QFP.
The package 11 is made of, for example, a resin in which a silicone-modified epoxy resin is filled with a filler such as silica to make the thermal expansion coefficient close to that of silicon.

The pellet 3 is sealed inside the package 11. The pellet 3 is bonded to the upper surface of the central portion of the tub 2 via an adhesive 12 such as a silver paste. Pellets 3
The upper surface thereof forms an integrated circuit formation surface, and an integrated circuit such as a gate array or a microcomputer is formed on the integrated circuit formation surface.

An insulating film 4 is bonded to the back surface of the tab 2 via an adhesive 13 such as an epoxy resin, and the tip of an inner lead portion 5a embedded in the package 11 is fixed to the insulating film 4.

A wire 15 made of gold or aluminum is bonded between the bonding pad 14 arranged 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, in a gull wing shape.

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

(1). Since the region inside the mold line M is patterned by etching that allows easy microfabrication, the inner lead portion 5a with high dimensional accuracy can be obtained. As a result, the lead width and lead pitch of the inner lead portion 5a can be narrowed.

(2). Since the area outside the mold line M was patterned by pressing, the outer lead portion with a stable cross-sectional shape
5b obtained. Accordingly, it is possible to prevent lead bending when forming the outer lead portion 5b, and thus it is possible to avoid a short circuit between the adjacent leads 5,5.

Further, since the height variation of the leads 5 can be prevented, it is possible to avoid a poor connection between the electrode pads of the substrate and the leads 5 when soldering the leads 5 to the substrate.

(3). According to the above (1) and (2), the lead frame 1
Can increase the number of pins.

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

(5). The guide holes 9 having high dimensional accuracy formed by pressing are used to align the resist mask and to position the resist in the press die and the mold die. Therefore, when the guide holes formed by etching are used, Compared with this, mask alignment and positioning with respect to a mold can be performed with higher accuracy, thereby improving the production yield of the lead frame and the molding yield of the package.

(6). Since the inner plate thickness of the mold line M is made thinner than the outer plate thickness, the lead width and lead pitch of the inner lead portion 5a can be reduced.

As described above, the invention made by the inventor has been specifically described based on the embodiments. However, the present invention is not limited to the embodiments, and it can be said that various modifications can be made without departing from the gist of the invention. Not even.

In the above embodiment, after the inside of the mold line M is patterned by etching, the outside of the mold line M is patterned by press. Conversely, after the outside of the mold line M is patterned by press, the mold line M May be patterned by etching.

In the above embodiment, the lead frame was manufactured from one hoop material.For example, only the outside of the mold line M was formed by pressing using a thick hoop material, and a thin hoop material was used. Alternatively, only the inside of the mold line M may be patterned by etching, and then both may be connected to manufacture a lead frame.

In the above embodiment, the entire inside of the mold line M is etched in advance to make the plate thickness smaller than that of the outside of the mold line M. However, only the inside of the mold line M may be thinned by pressing.

In the above-described embodiment, the inner lead portion, the tab and the tab suspension lead are simultaneously patterned by patterning the inside of the mold line M by etching, but only the inner lead portion where the pattern width and pitch are the narrowest is etched. , And other portions (tabs, tab suspension leads, outer lead portions, dams, frame portions, and the like) may be formed by pressing.

〔The invention's effect〕

The effect obtained by the representative one of the inventions disclosed in the present application will be briefly described as follows.

(1). By forming the inner lead portion where the width and pitch of the pattern are the narrowest by etching, and forming the outer lead by pressing, the dimensional accuracy of the inner lead is improved, and the outer lead Since the cross-sectional shape becomes stable, the number of pins of the package can be increased.

(2). By supporting the tip of the inner lead portion and the dove suspension lead with the insulating film bonded to the back surface of the tab, it is possible to prevent their deformation, for example, short-circuiting between the inner lead portions due to resin flow during molding and tabs It is possible to avoid a decrease in the molding yield of the package caused by deformation of the package.

(3). When forming the inner lead part of the lead frame by the etching method and forming the outer lead part by the press method, the guide hole is formed in advance at a predetermined position of the hoop material by pressing, so that the guide hole with high dimensional accuracy is used. Since the resist mask alignment and the positioning with respect to the press die can be performed with high accuracy, the lead frame manufacturing yield is improved. In addition, since the accuracy in positioning the lead frame in the mold is improved, the molding yield of the package is improved.

(4). The thickness of the region sealed inside the package The thickness of the region exposed to the outside of the package is made thinner to facilitate the fine processing of the inner lead portion. Is promoted.

[Brief description of the drawings]

FIG. 1 is a plan view of a lead frame according to an embodiment of the present invention, FIGS. 2 (a) to 2 (e) are plan views of a hoop material showing a method of manufacturing the lead frame, and FIG. It is sectional drawing of the semiconductor device manufactured using this lead frame. 1 ... lead frame, 2 ... tab, 3 ... semiconductor pellet, 4 ... insulating film, 5 ... lead, 5a ... inner lead section, 5b ... outer lead section, 6 ... dam,
7 ... tab suspension lead, 8a, 8b ... frame, 9 ... guide hole, 10 ... hoop material, 11 ... package, 12, 13 ... adhesive, 14 ... bonding pad, 15 ... wire , M ...
... mold line.

 ──────────────────────────────────────────────────続 き Continuation of the front page (72) Inventor Kazu Hasebe 145 Nakajima, Nanae-cho, Kameda-gun, Hokkaido Inside Hitachi Kokusai Semiconductor Co., Ltd. (56) References JP-A-62-114254 (JP, A) JP-A-61 -170053 (JP, A) JP-A-63-148667 (JP, A) JP-A-63-87843 (JP, U)

Claims (2)

(57) [Claims] 1. A step of punching a guide hole at a predetermined position of a hoop material by pressing, and pressing a pattern of an area outside a mold line in a state where the hoop material punched by the guide hole is positioned using the guide hole. A step of punching, and a step of etching a region inside the mold line in a state where the positioning is performed using the guide holes to make a plate thickness of the inside region smaller than a plate thickness of a region outside the mold line. Forming a pattern of an inner lead portion in an area inside the mold line by etching in a state of being positioned using the guide hole, and an insulating film on a tip of the inner lead portion and a back surface of a tab and a tab suspension lead. Bonding the semiconductor pellets to the surface of the tub, Electrically connecting the bonding pad of the pellet and the inner lead portion; and molding a package in a region inside the mold line while being positioned using the guide hole. Semiconductor device manufacturing method. 2. A step of punching a guide hole in a predetermined position of a hoop material by a press, and etching a region inside a mold line while positioning using the guide hole to reduce a plate thickness of the inside region to the mold. A step of making the thickness smaller than the plate thickness of the area outside the line, and forming the pattern of the inner lead portion of the inside area after being formed thinner than the area outside the mold line in a state of being positioned using the guide holes. A step of forming by etching, after etching the pattern of the inner lead portion, pressing the pattern of the area outside the mold line by pressing the hoop material punched out of the guide hole using the guide hole by pressing Punching, and connecting an insulating film to the end of the inner lead portion, the tab, and the back surface of the tab suspension lead. Attaching the semiconductor pellet to the surface of the tab, electrically connecting a bonding pad of the semiconductor pellet to the inner lead portion, and positioning using the guide hole. And a step of molding a package in a region inside the mold line in the above state.