JPH0529519A - Semiconductor device and manufacture thereof - Google Patents

Abstract

PURPOSE:To prevent cracks of a package generated between the rear of a stage part and the sealing resin by thermal influence at the time of packaging, in a resin seal type semiconductor device. CONSTITUTION:The surfaces of stage support bars 4 on the side opposite to the semiconductor chip mounting side, and the surface of a stage part 2 on the line connecting at least a pair of the stage support bars 4 are subjected to surface treatment like resin tape, silver plating, and acetic acid treatment for decreasing adhesion between sealing resin and the stage support bars 4 or the stage part 2. A recessed part 6 is formed in the sealing resin on the rear of the stage part 2.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a resin-encapsulated semiconductor device and a method for manufacturing the same, and more particularly to a semiconductor device capable of preventing cracks in the encapsulating resin during mounting or the like.

[0002]

2. Description of the Related Art In a resin-encapsulated semiconductor device, moisture is accumulated in a resin package due to the hygroscopicity of the encapsulating resin and the moisture expands due to heating during soldering or the like. It has been pointed out that the sealing resin is cracked. The water accumulated in the resin package is often present at the interface between the lead frame and the sealing resin,
In particular, it has been found that the water accumulated on the back surface of the stage part on which the chip is mounted has a bad influence on the occurrence of cracks.

As a conventional method for removing the adverse effect of the water accumulated in the resin package, the lead frame is subjected to a treatment for improving the adhesiveness with the sealing resin so that the moisture is contained inside. A method is known in which the lead frame and the encapsulation resin are prevented from peeling off while preventing the entry. In addition, in order to prevent water from entering the stage through the stage support bar,
A method is known in which the stage support bar is changed from a linear shape to a bent shape, or the stage support bar is thinned. However, none of the methods can completely eliminate the water accumulated in the resin package.
Therefore, when the water accumulated on the back surface of the stage part expands due to the thermal effect when soldering the semiconductor device to the substrate, etc., it acts to positively escape to the outside from the interface between the stage support bar and the sealing resin. In order to achieve this, a method of reducing the adhesion between the stage support bar and the sealing resin has been proposed (for example, Japanese Patent Laid-Open No. 292849/1990).
(See the official gazette).

[0004]

However, recent semiconductor chips are becoming larger and larger, and the package size is required to be as small and thin as possible. The larger the area occupied, the more the moisture accumulated on the back surface near the center of the stage portion does not escape to the outside, and there is a risk that cracks will occur in the package. In particular, the maximum bending stress that acts on the back surface of the stage during expansion is proportional to the square of the chip length change rate (stage size) and inversely proportional to the square of the mold thickness change rate on the back surface of the stage. It has been known.
Therefore, if the area of the stage is increased to increase the size of the semiconductor chip, and the mold thickness is decreased to reduce the package size, the maximum bending stress acting on the back surface of the stage increases more and more. become.
The present invention has been made in view of the above problems of the conventional technique, and an object of the present invention is to prevent generation of cracks in a package in a resin-sealed semiconductor device.

[0005]

According to the present invention for achieving the above object, at least a surface of a pair of stage support bars opposite to a semiconductor chip mounting side and a stage on a line connecting the pair of stage support bars are provided. The surface of the part is subjected to a surface treatment to reduce the adhesion between the sealing resin and the stage support bar or the stage part, and the predetermined position of the stage part on the line connecting the pair of stage support bars is exposed to the outside. A recess is formed in the sealing resin layer.

Here, it is preferable that the width of the surface treatment applied to the straight surface of the stage portion connecting the pair of stage support bars is not less than the width of the stage support bar.
Further, it is preferable that the surface of the stage portion and the stage support bar on the semiconductor chip mounting side be subjected to a surface treatment that enhances the adhesion between the sealing resin and the stage portion or the stage support bar. Further, the semiconductor device of the present invention has a sealing resin and a stage support on at least the surface of the pair of stage support bars opposite to the semiconductor chip mounting side and the surface of the stage portion on the line connecting the pair of stage support bars. A step of performing a surface treatment to reduce the adhesion to the bar or the stage part, and forming a convex part in contact with the surface of the stage part on the side opposite to the side where the semiconductor chip is mounted in the mold for forming the cavity However, it is preferable that the semiconductor device is manufactured by a method of molding the stage part while vacuum-suctioning the stage part from the tip surface of the convex part.

[0007]

In the present invention thus constituted, when the water accumulated on the back surface of the stage section expands due to heating when soldering the semiconductor device to a substrate or the like, the water near the center of the stage section is sealed. It is discharged to the outside from the recess formed in the resin stopping layer. On the other hand, the water around the stage part is discharged to the outside from the interface between the surface-treated part of the stage part and the sealing resin, passing through the interface between the stage support bar and the sealing resin. . That is, a concave portion for directly discharging water is formed in the center of the stage portion, and in the periphery of the stage portion, a part of the stage portion and the sealing resin, and a stage support bar and the sealing resin are formed. Since the passages that reduce the adhesion between them and facilitate the removal of water are positively provided, even if the surface area of the stage part is large and the package is thin, the water accumulated on the back surface of the stage part It will come out through the recess and the discharge passage.

At this time, if the width of the surface treatment applied to the straight surface of the stage portion connecting the pair of stage support bars is equal to or larger than the width of the stage support bar, the water accumulated on the stage portion due to the capillary phenomenon or the like will be removed. It is sucked toward the support bar, and the effect of discharging moisture to the outside is further enhanced. In addition, if the surface of the stage part and stage support bar on the semiconductor chip mounting side is subjected to a surface treatment that enhances the adhesion between the sealing resin and the stage part or stage support bar, Since the adhesiveness with the stage part or the stage support bar is enhanced, the moisture absorbed by the sealing resin is accumulated only on the back surface side of the stage part, which allows the moisture of the entire semiconductor device to be discharged to the outside. .

In manufacturing such a semiconductor device according to the present invention, a convex portion is formed in a mold forming a cavity for molding, the central portion being in contact with the surface center of the stage portion on the side opposite to the semiconductor chip mounting side. If the stage part is molded by vacuum suction from the tip end surface of the convex part, the stage part can be accurately positioned at the same time when the concave part is formed in the sealing resin layer. Moreover, it is convenient because resin burr or the like is less likely to occur in this portion.

[0010]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described below with reference to the drawings. 1 is a plan view showing a lead frame according to an embodiment of the present invention, and FIG. 2 is a longitudinal sectional view of a semiconductor device according to the embodiment, which is a sectional view corresponding to line AA in FIG. Three
FIG. 4 is an enlarged plan view of the vicinity of a stage portion showing another embodiment of the present invention, and FIG. 4 is a sectional view taken along the line BB of FIG. This is a type of semiconductor device that is held by a bar.
Further, FIG. 7 is a cross-sectional view showing a molding step in manufacturing the semiconductor device of the present invention.

As shown in FIG. 1, in the lead frame 1 according to this embodiment, two (die-bonding) stage portions 2 for mounting semiconductor chips are provided on two rail portions 3 located on both sides of the lead frame 1. Stage support bar 4
Are held through. Around the stage portion 2, a plurality of inner leads 5 that are wire-bonded to the semiconductor chip die-bonded to the stage portion 2 are provided. After this wire bonding, resin sealing (packaging) is performed. Then, after cutting the periphery of the lead frame 1, the inner lead 5 is bent.

In this embodiment, as shown in FIG.
The surface of the stage support bar 4 on the side opposite to the semiconductor chip mounting side of the stage portion 2 of the lead frame 1 and the straight surface of the stage portion 2 connecting the pair of stage support bars 4 and 4 are covered with a sealing resin. Stage support bar 4
Alternatively, a surface treatment is performed to reduce the adhesion with the stage unit 2. As this surface treatment, it is preferable to attach a resin tape made of a resin having low adhesiveness to the resin forming the sealing resin, or to apply silver plating. The film thickness is preferably 3 μm or more. In the present invention, the sealing resin and the stage support bar 4 or the stage portion 2 are used.
There is no particular limitation on the method of lowering the adhesiveness with, and a method of subjecting the stage portion 2 and the stage support bar 4 to gloss polishing such as acetic acid treatment to chemically smooth these surfaces is also applied. be able to. In addition, the surface treatment of the stage unit 2 and the stage support bar 4
It is not always necessary to use the same surface treatment method.

In particular, in this embodiment, as shown in FIG. 1, the width a of the surface treatment applied to the surface of the stage portion 2 which is a straight line connecting the two stage support bars 44 is set to be not less than the width b of the stage support bars. There is. This is the stage section 2
This is intended to further enhance the effect of discharging the water to the outside by sucking the water collected in the direction of the stage support bar 4 by the capillary phenomenon. It should be noted that the present invention is not limited to the embodiment shown in FIG. 1, and the width a of the surface treatment applied to the surface of the stage portion 2 which is a straight line connecting the two stage support bars 4 and 4 is the stage support. It can also be set equal to the bar width b.

On the other hand, in order to enhance the adhesion between the sealing resin and the stage portion 2 or the stage support bar 4 on the surface of the stage portion 2 and the stage support bar 4 on the semiconductor chip mounting side of the lead frame 1 according to this embodiment. In addition, surface treatment such as blasting is applied. This is because the adhesiveness between the sealing resin on the semiconductor chip mounting side and the stage unit 2 or the stage support bar 4 is enhanced, and all the moisture absorbed by the sealing resin is collected only on the back surface side of the stage unit 2. This is because the whole water is discharged to the outside. The surface treatment is not limited to the blast treatment, and a method of eliminating silver plating (silver plating-less) may be adopted. Further, in the semiconductor device of the present embodiment, as shown in FIGS. 1 and 2, the sealing resin layer 7 corresponding to the center of the straight stage portion 2 connecting the two stage support bars 4 and 4 is formed. The recess 6 is formed. The recess 6 is formed so that the back surface of the stage 2 is exposed to the sealing resin layer 7 including the semiconductor chip 8 and the stage 2 of the lead frame 1 when the semiconductor device is molded. May be circular as shown in FIG. 1 or rectangular as shown in FIGS. 3 and 4, but the inner diameter of the recess 6 is a straight line connecting the two stage support bars 4, 4. It is preferable that the width is a or more.

In the semiconductor device according to this embodiment having such a structure, when the water accumulated on the back surface of the stage portion 2 expands due to heating or the like when soldering the semiconductor device to a substrate, etc. Moisture in the vicinity is discharged to the outside from the recess 6 formed in the encapsulating resin layer 7 corresponding to the center of the stage portion 2, while water around the stage portion 2 is subjected to the surface treatment of the stage portion 2. From the interface between the portion and the sealing resin, it passes through the interface between the stage support bar 4 and the sealing resin and is discharged to the outside. That is,
A concave portion 6 for directly discharging water is formed in the center of the stage portion 2. Further, in the periphery of the stage portion 2, a part of the stage portion 2 and a sealing resin, and a stage support bar 4 and a sealing resin are sealed. Since a passage for reducing the adhesion with the resin and for facilitating the escape of water is positively provided, even if the surface area of the stage portion 2 is large and the package is thin, it is accumulated on the back surface of the stage portion 2. The moisture will escape to the outside through the recess 6 and the discharge passage.

At this time, since the width a of the surface treatment applied to the surface of the stage portion 2 which is a straight line connecting the pair of stage support bars 4 and 4 is not less than the width b of the stage support bar, the stage portion 2 is affected by the capillary phenomenon. The accumulated water is sucked toward the stage support bar 4, and the effect of discharging the water to the outside is further enhanced. Further, in the present embodiment, the surface of the stage portion 2 and the stage support bar 4 on the semiconductor chip mounting side is subjected to a surface treatment for enhancing the adhesion between the sealing resin and the stage portion 2 or the stage support bar 4. Therefore, the adhesiveness between the sealing resin on the semiconductor chip mounting side and the stage portion 2 or the stage support bar 4 is increased, whereby the moisture absorbed by the sealing resin is accumulated only on the back surface side of the stage portion 2. Moisture in the entire semiconductor device can be discharged to the outside.

On the other hand, when molding such a semiconductor device, as shown in FIG. 7, the semiconductor chip 8 is mounted on one surface of the stage portion 2 of the lead frame 1 (die bonding), and the semiconductor chip 8 and the inner leads are connected. After 5 and 5 are wire-bonded, this is placed at a predetermined position of molds 9a and 9b forming a cavity for molding. The surface of the stage support bars 4 and 4 and a part of the surface of the stage portion 2 are subjected to a surface treatment for reducing the adhesiveness. The lower mold 9b of the mold is provided with a convex portion 10 corresponding to the concave portion 6 to be formed in the sealing resin layer 7, and suction for vacuum suction of the stage portion 2 from the tip surface of the convex portion 10 is formed. A hole 11 is provided. Then, when the lead frame 1 for which wire bonding has been completed is installed in the mold, molten resin is injected from the injection port 12 while performing suction molding of the stage portion 2 by a vacuum suction device (not shown) to perform molding. According to such a manufacturing method, the stage portion 2 can be accurately positioned at the same time when the recess 6 is formed in the sealing resin layer 7.

Next, as another embodiment of the present invention, a lead frame in which the stage portion is held by four stage support bars 4 will be described. FIG. 5 is a plan view showing a lead frame according to another embodiment of the present invention, and FIG. 6 is an enlarged plan view of the vicinity of a stage portion showing still another embodiment of the present invention. In the lead frame 1 according to the present embodiment,
Rail parts 3 on which semiconductor chip mounting (die bonding) stages 2 are located on both sides of the lead frame 1.
3 is held via four stage support bars 4. Around the stage portion 2, a plurality of inner leads 5 that are wire-bonded to the semiconductor chip die-bonded to the stage portion 2 are provided. After this wire bonding, resin sealing (packaging) is performed. Then, after cutting the periphery of the lead frame 1, the inner lead 5 is bent. In this semiconductor device, the inner lead 5 is a semiconductor chip
It is a type that is located on all sides.

In this embodiment, as shown in FIG.
On the surface of the stage support bar 4 on the side opposite to the semiconductor chip mounting side of the stage portion 2 of the lead frame 1 and on the surface of the linear stage portion 2 connecting these two pairs of stage support bars 4, the sealing resin and the stage are provided. A surface treatment is performed to reduce the adhesion with the support bar 4 or the stage unit 2. As the surface treatment, the above-mentioned resin tape, silver plating, acetic acid treatment or the like can be applied.
Further, the surface treatments of the stage unit 2 and the stage support bar 4 do not have to be unified. Particularly in this embodiment,
As shown in FIG. 5, the widths a and c of the surface treatment applied to the surfaces of the two straight stage portions 2 connecting the two pairs of stage support bars 4 are set to be equal to or larger than the widths b and d of the corresponding stage support bars. There is. This is intended to suck the water accumulated in the stage portion 2 toward the stage support bar 4 due to a capillary phenomenon or the like to further enhance the effect of discharging the water to the outside. The present invention is shown in FIG.
However, the present invention is not limited to the embodiment shown in FIG. 2 and includes two linear stage portions 2 that connect two pairs of stage support bars 4.
It is also possible to set the widths a and c of the surface treatment applied to the surface of the same as the widths b and d of the stage support bar.

In the semiconductor device of this embodiment,
As shown in FIGS. 5 and 2, the recess 6 is formed in the sealing resin layer 7 corresponding to the center of the straight stage portion 2 connecting the four stage support bars 4. The recess 6 is formed so that the back surface of the stage 2 is exposed to the sealing resin layer 7 including the semiconductor chip 8 and the stage 2 of the lead frame 1 when the semiconductor device is molded. May have a circular shape as shown in FIG. 5 or a cross shape as shown in FIGS. 6 and 4.
It is preferable that the inner diameter of the recess 6 is set to be equal to or larger than the width a of the straight line connecting the two stage support bars 4 and 4.

Even in this embodiment having the above structure,
The water accumulated in the center of the back surface of the stage portion 2 is directly discharged from the recess 6 to the outside, while the water accumulated around the periphery of the stage portion 2 is an interface between the surface-treated portion of the stage portion 2 and the sealing resin. Therefore, it can be discharged to the outside through the interface between the stage support bar 4 and the sealing resin. The present invention is not limited to the above-mentioned embodiments,
Various modifications can be made without departing from the scope of the present invention.

[0022]

As described above, according to the present invention, the surface of the stage support bar on the side opposite to the semiconductor chip mounting side of the stage section and the straight surface of the stage section connecting the pair of stage support bars are formed. A surface treatment is performed to reduce the adhesion between the sealing resin and the stage support bar or the stage portion, and a concave portion is formed in the sealing resin layer corresponding to substantially the center of the straight stage portion connecting the pair of stage support bars. Therefore, it is possible to efficiently discharge the water accumulated on the back surface of the stage portion to the outside, and it is possible to reliably prevent the crack of the package between the back surface of the stage portion and the sealing resin due to the thermal influence during mounting. it can. In addition, if the width of the surface treatment applied to the straight surface of the stage connecting the pair of stage support bars is equal to or larger than the width of the stage support bar, the effect of discharging moisture to the outside is further enhanced due to the capillary phenomenon. Become.

Further, if the surface of the stage portion and the stage support bar on the semiconductor chip mounting side is subjected to a surface treatment for enhancing the adhesion between the sealing resin and the stage portion or the stage support bar, the sealing resin absorbs moisture. Moisture will be collected only on the back surface side of the stage portion, whereby the moisture of the entire semiconductor device can be discharged to the outside. Further, in manufacturing such a semiconductor device according to the present invention, a convex portion which is in contact with the center of the surface of the stage portion on the side opposite to the semiconductor chip mounting side is formed in the mold forming the molding cavity, and the convex portion is formed. If the stage part is molded by vacuum suction from the front end surface of the part, the stage part can be accurately positioned at the same time when the recess is formed in the sealing resin layer.

[Brief description of drawings]

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

FIG. 2 is a vertical cross-sectional view of the semiconductor device according to the embodiment, which is a cross-sectional view corresponding to line AA of FIG.

FIG. 3 is an enlarged plan view of the vicinity of a stage portion showing another embodiment of the present invention.

4 is a cross-sectional view taken along the line BB of FIG.

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

FIG. 6 is an enlarged plan view in the vicinity of a stage unit showing still another embodiment of the present invention.

FIG. 7 is a cross-sectional view showing a molding step in manufacturing the semiconductor device of the present invention.

[Explanation of symbols]

1 ... Lead frame 2 ... Stage part 3 ... Rail part 4 ... Stage support bar 5 ... Inner lead 6 ... Recessed part 10 ... Convex part

Claims (2)

[Claims] 1. A resin-encapsulated semiconductor device comprising a semiconductor chip mounted on the surface of a stage portion held through at least a pair of stage support bars, and the periphery of the semiconductor chip being molded. A surface treatment for reducing the adhesion between the sealing resin and the stage support bar or the stage part on the surface of the support bar on the side opposite to the semiconductor chip mounting side and the stage part surface on the line connecting the pair of stage support bars. And a recess is formed in the encapsulating resin layer so that a predetermined position of the stage portion on the line connecting the pair of stage support bars is exposed to the outside. 2. A method of manufacturing a resin-encapsulated semiconductor device, comprising: mounting a semiconductor chip on a surface of a stage portion held via at least a pair of stage support bars; and molding the periphery of the semiconductor chip. , The adhesion between the sealing resin and the stage support bar or the stage part is reduced on the surface of the stage support bar on the side opposite to the semiconductor chip mounting side and the stage part surface on the line connecting the pair of stage support bars. In the step of performing the surface treatment, and in the mold for forming the cavity used for the molding, a convex portion that is in contact with the surface of the stage portion opposite to the semiconductor chip mounting side is formed, and from the tip surface of this convex portion A method of manufacturing a semiconductor device, comprising a step of molding while vacuum suctioning the stage portion.