JPH1012797A - Lead frame, resin-encapsulated semiconductor device using the lead frame, and method of manufacturing the same - Google Patents

Abstract

(57) [Problem] In the case of a structure in which the area of a die pad is smaller than the area of a semiconductor chip mounted on the die pad, peeling of the back surface of the die pad from the sealing resin and package cracking occur when mounting the semiconductor package. SOLUTION: An area of a die pad 3 is smaller than an area of a semiconductor chip 1 mounted on the die pad 3, and the semiconductor chip mounting of the die pad 3 is performed in a lead frame 13 in which the die pad 3 is held by a plurality of suspension leads 5. A groove-shaped recess 4 is provided so as to surround the center of the surface.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

TECHNICAL FIELD The present invention relates to a lead frame,
The present invention relates to a resin-encapsulated semiconductor device using the lead frame and a method of manufacturing the same, and more particularly to a lead frame smaller than a semiconductor chip size on which a die pad is mounted, a resin-encapsulated semiconductor device using the lead frame and a method of manufacturing the same. is there.

[0002]

2. Description of the Related Art As shown in FIG. 12, a semiconductor package of a surface mount type, for example, a QFP (Quad Flat) is used.
t L-Leaded Package), SOP (S
mall Outline L-Leaded Pac
semiconductor packages such as kage), reflow, VPS
(Vapor Phase Soldering) or the like is generally implemented by an overall heating method. At this time, there is a risk that peeling or cracking may occur at the interface between the die pad 23 and the sealing resin 24 due to the vaporization and expansion of the moisture contained inside the package. When this peeling or crack occurs, defective mounting such as deterioration of moisture resistance or swelling of the sealing resin, and cutting of the wire 25 connecting the semiconductor chip 21 and the inner lead have occurred.

[0003] For this reason, various techniques for improving the resistance to peeling and cracking have conventionally been implemented. For example, dimple processing is performed on the back surface of the die pad to improve the adhesion at the interface between the die pad portion and the sealing resin, the die pad is divided, and the stress generated by vaporization and expansion of water is dispersed, and the polyimide resin is formed on the back surface of the die pad. Is applied to prevent water contained in the package from aggregating on the back surface of the die pad.

Further, there is a method of reducing stress by reducing the area of a die pad as described in JP-A-58-66346 and JP-A-63-204753. As shown in FIG. By using a structure in which the semiconductor chip size is larger than the die pad size (hereinafter, referred to as “small die pad structure”), the area of the die pad having poor adhesion to the sealing resin is reduced, and the bonding with the sealing resin is further improved. Silicon with excellent performance (backside of semiconductor chip)
And the contact area between the sealing resin and
Various structures have been proposed.

On the other hand, the problems with the small die pad structure include the protrusion of the adhesive, insufficient strength of the suspension leads, and insufficient adhesive strength between the die pad and the semiconductor chip. FIG. 12 is a cross-sectional view of a conventional surface mount type semiconductor package, and FIG. 13 is a plan view of a lead frame used for a conventional semiconductor package having a small die pad structure.
Denotes an adhesive, 26 denotes a suspension lead, 27 denotes a semiconductor chip mounting area, and 28 denotes a lead frame.

[0006]

It is desirable that the adhesive is uniformly applied to the entire die pad from the viewpoint of package crack resistance. However, in the lead frame having the structure shown in FIG. It was difficult to properly control the amount of the agent to be applied, and the adhesive protruded from the die pad 23. Silver paste is generally used as an adhesive between the semiconductor chip and the die pad 23. If the amount of the adhesive applied is insufficient, air bubbles may be generated between the die pad 23 and the semiconductor chip, and the air bubbles may cause a package crack. Cause
In a normal die pad structure product, a large amount of adhesive was applied to prevent air bubbles from being generated. The agent adheres to the back surface of the semiconductor chip via the stage for die bonding. When the back surface of the semiconductor chip is contaminated in this way, the adhesiveness between the back surface of the semiconductor chip and the sealing resin is deteriorated, which causes a package crack.

Further, the back surface of the semiconductor chip exposed at the time of wire bonding is fixed to a bonding device,
Wire bonding is performed, but if an adhesive adheres to the back surface of the semiconductor chip, unevenness occurs on the back surface, and good bonding cannot be performed. In some cases, partial pressure is applied to the semiconductor chip, and chipping or cracking of the chip occurs. When the adhesive is present on the back surface of the semiconductor chip, workability is poor.

When the die pad is formed in a linear shape or a through hole is formed near the center of the die pad as disclosed in JP-A-2-73660 and JP-A-6-61397, the adhesive is applied to the semiconductor chip. It is difficult to perform die bonding without protruding to the back surface. If an attempt is made to bond only at the center of the die pad so that the adhesive does not protrude, the bonding area is reduced, and the bonding strength between the semiconductor chip and the die pad is reduced.

Therefore, it is desired to apply the adhesive to the entire surface of the die pad. However, since the silver paste as the adhesive has high hygroscopicity and is expensive, it is desirable to apply the adhesive as thinly and uniformly as possible.

On the other hand, the die pad is made as small as possible,
If the exposed area on the back surface of the semiconductor chip is increased to improve the adhesiveness with the sealing resin, the length of the suspension lead becomes longer and the mechanical strength is reduced. This trend is
In particular, it becomes more remarkable as the chip size increases. Further, the lead frame is made thinner, and the strength of the suspension lead is further reduced. Specifically, the thickness of the lead frame is 0.1 mm.
1-0.3mm, hanging lead width 0.4-0.6mm
It is about. And the lead frame thickness is 0.15mm
Below this level, deformation will occur at the time of molding unless measures are taken for reinforcement.

For this reason, as described in Japanese Patent Application Laid-Open No. 2-84700, there is a method of reinforcing the suspension lead with an insulating member. However, when heat is applied by wire bonding or the like, the thermal expansion of the insulating member and the lead frame material occurs. Deformation occurs due to the difference in coefficients, which is not preferable. Further, the number of steps for attaching the insulating member increases, and the cost increases.

The present invention provides means for preventing peeling of a back surface of a die pad from a sealing resin and package cracking which occur during mounting of a semiconductor package by using a die pad smaller in size than a semiconductor chip. It is an object of the present invention to provide means for preventing molding defects from occurring during resin sealing even when a semiconductor chip having a plurality of sizes is mounted on a die pad portion using a die pad having a smaller size.

[0013]

According to the lead frame of the present invention, the area of the die pad is smaller than the area of the semiconductor chip mounted on the die pad, and the die pad is held by a plurality of suspension leads. In the lead frame, a concave portion is provided on the semiconductor chip mounting surface of the die pad so as to surround a central portion of the mounting surface.

According to a second aspect of the present invention, there is provided a lead frame according to the present invention, wherein the area of the die pad is smaller than the area of the semiconductor chip mounted on the die pad, and the die pad is held by a plurality of suspension leads.
A side surface of the die pad is inclined outwardly from the semiconductor chip mounting surface in a direction opposite to the mounting surface.

Further, the lead frame according to claim 3 is
The area of the die pad is smaller than the area of the semiconductor chip mounted on the die pad, and in a lead frame in which the die pad is held by a plurality of suspension leads, the plurality of suspension leads are connected with the same material as the suspension leads,
It is characterized by being integrated.

Further, the lead frame according to claim 4 is
3. The lead frame according to claim 1, wherein the plurality of suspension leads are connected to and integrated with the same material as the suspension leads. 4.

According to a fifth aspect of the present invention, there is provided a resin-encapsulated semiconductor device, wherein a semiconductor chip is mounted on a die pad of a lead frame according to the first, second, third or fourth aspect. It is characterized in that the entire semiconductor chip is sealed with resin.

According to a sixth aspect of the present invention, in the resin-encapsulated semiconductor device, the semiconductor chip and the surfaces of the plurality of suspension leads and the semiconductor chip that are in contact with the die pad are fixed with an adhesive. Claim 5
It is a resin-sealed semiconductor device as described in the above.

According to a seventh aspect of the present invention, in the method of manufacturing a resin-encapsulated semiconductor device, the semiconductor chip is mounted on the die pad, and then an adhesive is applied to the suspension leads by a transfer method using a stamp. 7. The method for manufacturing a resin-encapsulated semiconductor device according to claim 6, further comprising a step of fixing the chip and the suspension lead.

Further, in the method of manufacturing a resin-encapsulated semiconductor device according to claim 8, an adhesive is applied to the die pad and the suspension lead by a transfer method using a stamp, and then the semiconductor chip is mounted on the die pad. 7. The method of manufacturing a resin-encapsulated semiconductor device according to claim 6, further comprising a step of bonding the suspension pad and the semiconductor chip at the same time as bonding the die pad and the semiconductor chip.

[0021]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, the present invention will be described in detail based on embodiments.

FIG. 1 is a cross-sectional view of a resin-encapsulated semiconductor device according to an embodiment of the present invention. FIG. 2A shows a resin-encapsulated semiconductor device shown in FIG. FIG. 2B is a plan view of a lead frame used for the resin-sealed semiconductor device shown in FIG. 1 in which grooves are formed by punching, and FIG. 3A is a second view of the present invention. FIG. 3B is a cross-sectional view taken along a line AA in FIG. 3A, and FIG. 4 is a cross-sectional view of a resin-sealed semiconductor device according to a third embodiment of the present invention. FIG. 5 and FIG. 5 are plan views of a lead frame according to a fourth embodiment of the present invention. FIG. 6A shows a state where a semiconductor chip is mounted on a die pad according to a fifth embodiment of the present invention from the rear side of the die pad. FIG. 6B is a side view of FIG.
Is a view showing a part of a manufacturing process of a semiconductor device according to a sixth embodiment of the present invention, FIG. 8 is a plan view of a lead frame according to a seventh embodiment of the present invention, and FIGS. Plan view of the lead frame when the number of
FIG. 11 is a plan view of a lead frame according to the eighth embodiment of the present invention.

1 to 11, 1 is a semiconductor chip, 2 is a first adhesive, 3, 3a and 3b are die pads,
Is a groove-shaped concave portion, 4a is a concave portion, 5 and 5a are hanging leads, 6 is a bar portion, 7 is a second adhesive, 8 is a wire, 9 is a sealing resin,
Reference numeral 10 denotes an inner lead, 11 denotes an outer lead, 12 denotes a semiconductor chip mounting area, and 13 denotes a lead frame.

The present invention is characterized in that, as shown in FIG. 1, a groove-shaped concave portion 4 is formed so as to surround a central portion inside a semiconductor chip mounting surface of a die pad 3a. Even when the first adhesive 2 is applied to the entire die pad 3 a, the first adhesive 2 can be trapped in the groove 4 by the groove-shaped concave portion 4. It can be applied more than the amount required for adhesion to 3a. Therefore, when the first adhesive 2 is applied to the entire surface of the semiconductor chip mounting surface of the die pad 3a, the amount of application can be easily controlled. The groove-shaped concave portion 4 is chemically etched so as to surround the center portion of the semiconductor chip mounting surface of the die pad 3a as shown in FIG. 2A, or mechanically etched as shown in FIG. Pressed to form. The size of the groove-shaped recess 4 is, for example, 100 μm in width and 80 μm in depth, and is formed 100 μm inside from the outer edge of the die pad.

As shown in FIGS. 3A and 3B,
The plurality of recesses 4a may be formed so as to surround the central portion of the die pad. However, as shown in FIG.

As shown in FIG. 4, the present invention is characterized in that the edge cross section of the die pad 3b is inclined so as to spread outward from the semiconductor chip mounting surface of the die pad 3b toward the back surface. By forming the edge of the die pad 3b in the above-described shape, even if the first adhesive 2 protrudes from the semiconductor chip mounting surface, it becomes difficult for the first adhesive 2 to protrude from the back surface having a larger area.
The adhesive 2 can be applied more than required for bonding the semiconductor chip 1 and the die pad 3a. Therefore, it is possible to easily control the amount of application of the first adhesive 2 on the entire surface of the semiconductor chip mounting surface. In addition, since the sealing resin 9 bites into the edge of the die pad 3b in a wedge shape, resistance to a package crack is improved. When forming the inclined die pad edge by etching, it can be formed by performing wet etching as isotropic etching from both the front and back surfaces of the die pad 3b to increase the etching on the semiconductor chip mounting surface side. in this case,
The shape of the die pad 3b is inclined outwardly from the semiconductor chip mounting surface of the die pad 3b to a part of the side surface of the die pad opposite to the semiconductor chip mounting surface. Further, in the case of forming by punching, the blade can be formed in a shape as shown in FIG.

The lead frame material is patterned so that the suspension leads 5 are continuously connected and integrated with the bar 6 provided on the die pad side from the tip end of the part to be the inner lead of the lead frame. 5, the suspension leads 5 are reinforced. In order to optimize the installation location according to the package size, semiconductor chip size, etc., the bar portion 6 is installed at a position inside the semiconductor chip mounting region 12 or when a plurality of bar portions 6 are installed between the same suspension leads 5, 5. There is.

As means for reinforcing the suspension lead by substantially shortening the length of the suspension lead 5,
After bonding the semiconductor chip 1 to the die pad 3 as shown in FIG. 6, the suspension leads 5 are attached to the back surface of the semiconductor chip 1 by using an epoxy resin or the like having good adhesion to the sealing resin 6 as the second adhesive 7. It is fixed. The die pad 3 may be fixed simultaneously with the resin as the second adhesive 7.
The second adhesive 7 made of this resin is fixed by potting.

When a silver paste is used as the first adhesive 2 between the die pad 3 and the back surface of the semiconductor chip 1, if the adhesive is transferred by a transfer method using a stamp as shown in FIG. The first adhesive 2 can be thinly and evenly applied simultaneously with the die pad 3 to the thin suspension lead 6 which is difficult to perform, and the first adhesive 2 allows the die pad 3 and the suspension lead to be connected to the back surface of the semiconductor chip 1. Can be glued. Similarly, after bonding the die pad 3 and the semiconductor chip 1, the second adhesive 7 may be transferred to the suspension lead by a stamp method, and the suspension lead 5 and the back surface of the semiconductor chip 1 may be fixed. .

The semiconductor chip 1 can be easily positioned by mounting the semiconductor chip 1 by changing the width of the suspension lead 5a stepwise at predetermined intervals as shown in FIG. It can be mounted in a predetermined place.

Further, in order to suppress deformation of the suspension leads 5, the number of suspension leads 5 is increased, for example, from two to four.
The number may be increased from four (FIG. 9) to six (FIG. 10).

Further, a structure combining the structure of the die pad shown in FIGS. 1 to 4 with the structure of the suspension lead shown in FIGS. 5 to 10, for example, as shown in FIG. It goes without saying that the structure in which the bar portions 6 are formed between the suspension leads 5 and the suspension leads 5 and 5 further improves the effect of preventing package cracks and the like.

[0033]

As described above in detail, by using the present invention, it is possible to apply a stable adhesive to a semiconductor device having a structure in which the size of the die pad is smaller than the size of the semiconductor chip. It can have package crack resistance.

Further, by using the present invention as defined in claims 3 to 8, the suspension leads are reinforced, so that the vertical balance in the package according to the size of the semiconductor chip to be mounted is conventionally reduced by the center of gravity of the semiconductor chip and the die pad. Since the position changed, it was necessary to finely adjust the vertical balance by down-setting when the sealing resin flowed in.However, this is no longer necessary, and the degree of freedom in the size of the semiconductor chip that can be mounted on the lead frame is increased. A cost-effective semiconductor device can be provided.

Further, by using the present invention described in claim 7, the adhesive can be thinly and uniformly applied even to a thin suspension lead to which the application of the adhesive is difficult. According to the present invention, since the semiconductor chip and the die pad are simultaneously bonded, the manufacturing process can be simplified.

[Brief description of the drawings]

FIG. 1 is a sectional view of a resin-sealed semiconductor device according to a first embodiment of the present invention.

2A is a plan view of a lead frame used in the resin-sealed semiconductor device shown in FIG. 1 in which a groove is formed by etching, and FIG. 2B is a view in which the groove is formed by punching; FIG. FIG. 3 is a plan view of a lead frame used for the resin-sealed semiconductor device shown in FIG.

FIG. 3A is a plan view of a lead frame according to a second embodiment of the present invention, and FIG. 3B is a sectional view taken along line AA of FIG.

FIG. 4 is a sectional view of a resin-sealed semiconductor device according to a third embodiment of the present invention.

FIG. 5 is a plan view of a lead frame according to a fourth embodiment of the present invention.

FIG. 6A is a diagram showing a state in which a semiconductor chip is mounted on a die pad according to a fifth embodiment of the present invention;
FIG. 6B is a sectional view taken along line BB of FIG.

FIG. 7 is a manufacturing process diagram of a resin-sealed semiconductor device according to a sixth embodiment of the present invention.

FIG. 8 is a plan view of a lead frame according to a seventh embodiment of the present invention.

FIG. 9 is a plan view of a lead frame when the number of hanging leads is increased from two to four in the related art.

FIG. 10 is a plan view of a lead frame when the number of hanging leads is increased from four to six in the related art.

FIG. 11 is a plan view of a lead frame according to an eighth embodiment of the present invention.

FIG. 12 is a sectional view of a conventional surface mount type semiconductor package.

FIG. 13 is a manufacturing process diagram of a plan view of a lead frame used for a conventional semiconductor package having a small die pad structure.

[Explanation of symbols]

 Reference Signs List 1 semiconductor chip 2 first adhesive 3, 3a, 3b die pad 4 groove-shaped recess 4a recess 5, 5a hanging lead 6 bar portion 7 second adhesive 8 wire 9 sealing resin 10 inner lead 11 outer lead 12 semiconductor chip mounting area 13 Lead frame

Claims (8)

[Claims] 1. A lead frame in which an area of a die pad is smaller than an area of a semiconductor chip mounted on the die pad, and the die pad is held by a plurality of suspension leads. A lead frame surrounding a central portion of the lead frame. 2. A lead frame in which an area of a die pad is smaller than an area of a semiconductor chip mounted on the die pad, and wherein the die pad is held by a plurality of suspension leads, wherein a side surface of the die pad is separated from the semiconductor chip mounting surface. A lead frame which is inclined outward in a direction opposite to the mounting surface. 3. A lead frame in which an area of a die pad is smaller than an area of a semiconductor chip mounted on the die pad, and the die pad is held by a plurality of suspension leads, wherein the plurality of suspension leads are the same as the suspension leads. A lead frame characterized by being connected by a material and being integrated. 4. The lead frame according to claim 1, wherein the plurality of suspension leads are connected to and integrated with the suspension leads using the same material. 5. A semiconductor chip is mounted on the die pad of the lead frame according to claim 1, 2, 3, or 4, and at least the entire die pad and the semiconductor chip are resin-sealed. Resin-encapsulated semiconductor device. 6. The semiconductor chip is fixed to a surface of the semiconductor chip in contact with the plurality of suspension leads and a die pad of the semiconductor chip with an adhesive.
The resin-encapsulated semiconductor device according to claim 5. 7. A step of mounting the semiconductor chip on the die pad, applying an adhesive to the suspension lead by a transfer method using a stamp, and fixing the semiconductor chip and the suspension lead. Claim 6
The manufacturing method of the resin-sealed semiconductor device according to the above. 8. An adhesive is applied to the die pad and the suspension lead by a transfer method using a stamp. Then, the semiconductor chip is mounted on the die pad, and the die pad and the semiconductor chip are bonded to each other. The method for manufacturing a resin-encapsulated semiconductor device according to claim 6, further comprising a step of bonding the semiconductor chip to the semiconductor chip.