JPH0864746A - Lead frame, semiconductor device, and manufacture of semiconductor device - Google Patents

Abstract

PURPOSE: To improve the reflow crack resistivity of an LSI package, and to provide the technique with which a lead frame can be standardized. CONSTITUTION: The die-pad provided on the conventional lead frame is disused, retaining leads 3, which are rectilinearly extended to the center of mounting position of a semiconductor pellet 1, are provided, a thermoplastic resin adhesion layer is formed in advance on the upper surface of the retaining leads, and a semiconductor pellet 1 is fixed to the retaining leads 3 through the above- mentioned adhesion layer. Accordingly, by the disuse of the die-pad and by the fixing of the semiconductor pellet using the retaining leads, the adhesion area of the backside of the semiconductor pellet and sealing resin can be increased, and the resistivity of reflow crack can be improved. By the formation of the adhesion layer in conformity with the largest semiconductor pellet, the lead frame can be suitable for the semiconductor pellets of various sizes, and this contributes to the standardization of lead frames.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a lead frame, a semiconductor device, and a method for manufacturing a semiconductor device, and is a technique particularly effective when applied to the improvement of reflow crack resistance of an LSI package and the standardization of the lead frame.

[0002]

2. Description of the Related Art A semiconductor pellet, which has been completed by a wafer process and separated by dicing, is connected to external terminals and sealed in a sealing body to form a product. For connection with external terminals, a method is generally used in which a die pad (tab) on which a semiconductor pellet is mounted and a lead frame which is electrically connected to the semiconductor pellet and serves as an external electrode are integrated by a frame. The lead frame is made of a thin metal plate of 42 alloy, copper or the like and is formed by stamping or etching. The sealing body is easy to manufacture and low in cost. Therefore, epoxy resin or silicon resin is used. A resin mold using a resin as a sealing resin is often used.

However, since these resins have weak adhesion to the metal used for the lead frame and have a large difference in expansion coefficient from the metal, a gap is generated between the die pad and the sealing resin due to temperature change. Sometimes.

Since the sealing resin itself absorbs water, moisture in the atmosphere is absorbed inside the sealing resin, and dew condensation occurs in the gap between the die pad and the sealing resin to form moisture absorption water, which may accumulate inside. Especially TSOP (Thin Small Outline Package)
Type, TQFP (Thin Quad Flat Package) type, and other thin semiconductor devices, the sealing resin of the package is also thin, and water easily enters.

In a semiconductor device in which moisture invades and absorbs moisture, when the semiconductor device is heated in a reflow step of mounting on a mounting board such as a printed circuit board, the invading hygroscopic water vaporizes and expands to increase the internal pressure of the package. However, interface peeling that causes peeling between the sealing resin and the die pad, or this peeling may expand the moisture, that is, package cracks in which the sealing resin cracks due to expansion by water vapor pressure may damage the semiconductor device. is there.

[0006] In order to prevent such damage, measures such as improving the adhesiveness between the die pad and the sealing resin have been taken, but this is not a sufficient solution yet.

Conventionally, as a measure for preventing the peeling of the interface between the resin and the die pad, a slit is provided in the die pad, and the back surface of the semiconductor pellet is brought into close contact with the resin by the slit to disperse the internal stress generated at the interface (JP-A-2- 8
No. 3961) or a method for improving the adhesive force between the resin and the die pad by performing dimple processing on the back surface of the die pad (JP-A-55-160449).

[0008] Further, a method of bringing the back surface of the semiconductor pellet into close contact with the resin by forming the die pad with a small tab structure smaller than the size of the semiconductor pellet (Japanese Patent Application No. 4-7).
No. 1116) is also considered. FIG. 11 shows an example of a lead frame having a small tab structure, and FIG. 12 is a sectional view showing a state after resin sealing, which corresponds to a position along line aa in FIG. The small tab 11 is formed smaller than the semiconductor pellet 12 to be mounted. Small tab 11
The four sides are fixed to the frame 14 by suspension leads 13. The semiconductor pellet 12 is fixed by an adhesive layer 15 formed on the small tab 11. In the figure, 16 is a sealing resin.

[0009]

However, in recent years, L
In the SI package, since the area ratio of the semiconductor pellets in the resin body increases and the ratio of the sealing resin to the semiconductor pellets is lower than that of the conventional one, that is, it is extremely thin, the above-mentioned slits and dimples are formed. Methods are becoming difficult to prevent package cracks.

Further, although the above-mentioned small tab structure is an effective method for preventing package cracks, other problems have occurred.

The problem is that since the die pad area is small, the adhesive strength between the pellet and the die pad before pellet adhesion curing is low, and the pellet shifts and the pellet peels off during frame transportation after the pellet adhesion and before the curing step. Further, since the adhesive portion of the semiconductor pellet 12 is only the portion of the small tab 11, that is, the central portion of the semiconductor pellet 12, the suspension lead 1
3 becomes long, the suspension leads 13 are deformed during molding, and tab floating tends to occur as shown in FIG. Furthermore,
Not only in the small tab structure, but in the conventional pelletizing process, there are many control items such as paste storage, paste application amount, wetted area, etc., and it is difficult to stabilize the quality.

An object of the present invention is to provide a technique capable of improving the reflow crack resistance of an LSI package, reducing defects in the assembly process, and simplifying the process.

Further, in recent years, the manufacturing form of LSI has been diversified in demand and is being produced in small quantities of a wide variety of products. As the variety of products increases, many types of lead frames must be prepared, and the management thereof is complicated. Yes, costs are also increasing. Another object of the present invention is to provide a technique capable of realizing a lead frame applicable to various different semiconductor devices, that is, a standardization of the lead frame.

[0014]

Of the inventions disclosed in the present application, a representative one will be briefly described below.
It is as follows.

The die pad provided on the conventional lead frame is abolished, and a support lead extending linearly is provided at the center of the semiconductor pellet mounting position, and an adhesive layer made of a thermoplastic resin is previously formed on the upper surface of the support lead. And the semiconductor pellet is fixed to the support lead via this adhesive layer.

[0016]

According to the above-mentioned means, the die pad is eliminated and the semiconductor pellet is fixed by the support lead, so that the bonding area between the back surface of the semiconductor pellet and the sealing resin is enlarged as compared with the conventional slit structure and the small tab structure. It is possible to improve reflow crack resistance.

Further, by forming an adhesive layer in accordance with the maximum semiconductor pellet, semiconductor pellets of various sizes can be accommodated, which contributes to standardization of the lead frame and adheres the lead frame up to the end of the pellet. As compared with the small tab structure, the floating of pellets during resin sealing is eliminated.

Further, by using a thermoplastic resin for the adhesive layer, the curing process and the curing device required when the thermosetting resin is used are unnecessary, and the process and the work space can be shortened, and the thermoplastic property is improved. Since the resin has a high viscosity even in the high temperature melting state during pelletization, pellet displacement and pellet peeling during frame transfer are eliminated.
Even if the pellet shifts or peels off, the position of the semiconductor pellet can be corrected in the heated state, so that the generation of defective products can be prevented.

The structure of the present invention will be described below together with embodiments.

In all the drawings for explaining the embodiments, parts having the same functions are designated by the same reference numerals, and the repeated description thereof will be omitted.

[0021]

【Example】

(Embodiment 1) FIG. 1 shows an embodiment Q of the present invention.
FIG. 2 is a plan view showing a partially cut-away state of the FP (Quad Flat Package) type semiconductor device before cutting the frame.
3 is a vertical sectional view taken along the line aa, and FIG. 3 is a vertical sectional view taken along the line bb.

In the figure, 1 is a semiconductor pellet, 2 is a lead to be an external terminal, 3 is a support lead for fixing the semiconductor pellet, and 4 is a sealing resin which is a sealing body using a resin.

The leads 2 are the inner leads 2a connected to the bonding pads of the semiconductor pellet 1 by the bonding wires 5, and other devices when mounting the semiconductor device.
The outer lead 2b for connecting to the wiring is integrated.

The support leads 3 extend linearly in four directions orthogonal to each other from the center of the mounting position of the semiconductor pellet 1, and penetrate the four corners of the sealing resin 4.

The lead 2 and the support lead 3 are integrated by a frame 6 to form a lead frame 7. The lead frame 7 is formed by molding a thin metal plate, and each lead 2 and support lead 3 before being fixed by resin molding are integrated by a frame 6.

In addition, the lead frame 7 is provided with a dam 8 for preventing the resin from flowing out from the gap formed between the leads 2 in the vicinity of the side surface of the sealing resin 4.

An adhesive layer 9 made of, for example, a polyimide-based thermoplastic resin is applied to the portion of the support lead 3 on which the semiconductor pellet 1 is mounted.

By forming the support lead 3 to have a small width, a required adhesive force can be maintained. In other words, in order to increase the adhesive force between the pellet and the conventional die pad, a method of increasing the collet load (pressing force applied to the pellet) can be considered, but this is difficult because it causes pellet breakage. In the present invention, the adhesion area is reduced by forming the support leads to be thin, but the decrease in the adhesion area increases the pressing force per unit area and increases the adhesive strength of the thermoplastic resin, thus maintaining the required adhesive strength. can do.

The encapsulating resin 4 is integrally molded by resin molding using epoxy or the like, and the fixed semiconductor pellets 1 are accommodated in the support leads 3 and the leads 2 are fixed.

A method of manufacturing the semiconductor device shown in FIG. 1 will be described below.

First, the lead frame 7 is heated by pressing a heated heat block from below the lead frame 7 to melt or soften the thermoplastic resin which is the adhesive layer 9 of the support lead 3.

Next, the semiconductor pellet 1 to be mounted is conveyed to a predetermined position on the support lead 3 and pressure-bonded. afterwards,
For example, by separating the heating heat block from the lead frame 7, the thermoplastic resin is cooled and solidified.

After that, wire bonding is performed without passing through the curing step, and the inner lead 2a and the bonding pad of the semiconductor pellet 1 are electrically connected by the bonding wire 5. The wire bonding is performed at a temperature (for example, about 200 ° C.) lower than the melting point of the thermoplastic resin (about 350 ° C.) in order to prevent remelting of the thermoplastic resin during wire bonding.

The semiconductor device after bonding is housed in a mold of a molding device (not shown), and molten resin is injected into the mold to seal the semiconductor pellet 1 and the inner lead 2a with resin.

After the sealing resin 4 is formed by the resin molding, the lead frame 7 cuts the dam 8 and the frame 6 so that the support lead 3 and each lead 2 become independent, and then the outer lead 2b is fixed. Processed into the shape of.

The thermoplastic resin adhesive layer 9 is formed beyond the mounting position of the semiconductor pellet 1 and near the end of the inner lead 2a. As a result, even if the bonding wire 5 cross-contacts the support lead 3, the resin portion can prevent a short circuit. Further, even if the tip of the inner lead 2a is cut off and a larger semiconductor pellet is mounted, the semiconductor pellet can be sufficiently adhered and fixed.

In this embodiment, since the thermoplastic resin is used as the adhesive layer 9, even when the support lead 3 is warped, the unit area per unit area added when the semiconductor pellet 1 is pressure-bonded as described above. The warp is corrected by the increase of the pressing force to be in a flat state, and since the thermoplastic resin has a high viscosity even in a molten state, the flat state is maintained, so that the tolerance of deformation of the support lead 3 is increased and the lead frame is increased. The production yield of No. 7 is improved. In this embodiment, the width of the supporting lead is set to 0.3, which is substantially the limit of stamping.
mm.

In the above-described embodiment, the adhesive layer 9 is formed on the entire area of the support lead 3 for mounting the semiconductor pellet, but as shown in FIG. 4 or 5, the adhesive layer 9 is mounted on the support lead 3 for mounting the semiconductor pellet. It may be partially formed in the region. The adhesive can be effectively used by effectively forming the adhesive layer 9 depending on how the force is applied to the semiconductor pellet 1.

Generally, in selecting a lead frame for a semiconductor device, the main conditions are the size of the semiconductor pellet to be mounted and the number of leads, but in the lead frame 7 of the present invention, as shown in FIG. Since the semiconductor pellet 1 to be mounted has a high degree of freedom, the single lead frame 7 can be applied to many kinds of semiconductor devices. In this case, the adhesive layer 9 may be formed in a small formation area according to the mounted semiconductor pellet 1 as shown in FIG. 6 or may be formed in a wide area as in FIG.

Further, the support leads 3 may extend in two directions as shown in FIG.

(Embodiment 2) FIG. 8 is a plan view showing a lead frame of an SOP (Small Outline Package) type or SOJ (Small Outline J-lead) type semiconductor device according to another embodiment of the present invention. Is.

In the figure, 2 is a lead serving as an external terminal, 3 is a support lead, and 4 is a sealing resin. The support leads 3 extend linearly in four directions across the center of the mounting position of the semiconductor pellet 1 and penetrate the opposite sides of the sealing resin 4.

The lead 2 and the support lead 3 are integrated by a frame 6 to form a lead frame 7.

An adhesive layer 9 made of, for example, a polyimide-based thermoplastic resin is applied to the portion of the support lead 3 on which the semiconductor pellet 1 is mounted.

Further, the arrangement of the support leads 3 of this embodiment is
For example, as shown in FIG. 9, the support leads 3 may be formed by penetrating through the centers of the opposite sides of the sealing body 4 and extending in the long side direction of the semiconductor pellet 1 in only two directions. It is possible to increase the number of leads 2 by utilizing the space of the supporting lead in the short side direction, which becomes unnecessary by forming the leads 2 in two directions.

Furthermore, the arrangement of the support leads 3 of this embodiment is
For example, as shown in FIG. 10, the support leads 3 extend in the long side direction of the semiconductor pellet 1 in only two directions, penetrating through the centers of the opposite sides of the sealing body 4, and the support leads 3 in the short side direction.
Can be formed in the same manner as the semiconductor pellet 1 mounting region.

(Embodiment 3) FIG. 14 is a plan view showing a lead frame of a QFP type semiconductor device according to another embodiment of the present invention, and FIG. 15 shows its ab line. It is a longitudinal cross-sectional view in the completed state corresponding to the position along.

In the figure, 1 is a semiconductor pellet, 2 is a lead to be an external terminal, and 3 is a support lead for fixing the semiconductor pellet. In this embodiment, the rectangular semiconductor pellet 1 is bonded to the support lead 3.

The support leads 3 cross each other from the center of the mounting position of the semiconductor pellet 1 and extend linearly in four directions.

The lead 2 and the support lead 3 are integrated by a frame 6 to form a lead frame 7. The lead frame 7 is formed by molding a thin metal plate, and each lead 2 and support lead 3 before being fixed by resin molding are integrated by a frame 6.

An adhesive layer 9 made of, for example, a polyimide-based thermoplastic resin is applied to the portion of the support lead 3 on which the semiconductor pellet 1 is mounted. The adhesive layer 9 of thermoplastic resin
Is formed beyond the mounting position of the semiconductor pellet 1 to near the end of the inner lead 2a.

By forming the support lead 3 to have a small width, a required adhesive force can be maintained. In other words, in order to increase the adhesive force between the pellet and the conventional die pad, a method of increasing the collet load (pressing force applied to the pellet) can be considered, but this is difficult because it causes pellet breakage. In the present invention, the adhesion area is reduced by forming the support leads to be thin, but the decrease in the adhesion area increases the pressing force per unit area and increases the adhesive strength of the thermoplastic resin, thus maintaining the required adhesive strength. can do.

In this embodiment, since the semiconductor pellet 1 has a rectangular shape, part of the bonding wire 5 connecting the bonding pad on the semiconductor pellet 1 and the inner lead 2a extends so as to cross the support lead 3. However, even if the bonding wire 5 cross-contacts with the support lead 3 as shown in FIG. 15, the support lead 3 is covered with the resin portion of the adhesive layer 9, so that the support lead 3 and the bonding wire 5 are short-circuited. Can be prevented.

As described above, the inventions made by the present inventor are
Although the present invention has been specifically described based on the above-mentioned embodiments, the present invention is not limited to the above-mentioned embodiments, and it goes without saying that various modifications can be made without departing from the scope of the invention.

[0055]

The effects obtained by the typical ones of the inventions disclosed in the present application will be briefly described as follows.

(1) According to the present invention, the die pad is eliminated and the semiconductor pellets are fixed by the support leads, so that the bonding area between the back surface of the semiconductor pellet and the sealing resin is enlarged as compared with the conventional slit structure and the small tab structure. Therefore, there is an effect that the reflow crack resistance is improved.

(2) According to the present invention, by forming an adhesive layer in accordance with the maximum semiconductor pellet, semiconductor pellets of various sizes can be dealt with, which contributes to standardization of the lead frame. is there.

(3) According to the present invention, by forming the adhesive layer of the thermoplastic resin in accordance with the largest semiconductor pellet, it is possible to adhere to the lead frame up to the end of the pellet. As a result, there is an effect that pellet floating during resin sealing is eliminated.

(4) According to the present invention, by using the thermoplastic resin for the adhesive layer, the curing process and the curing device required when the thermosetting resin is used are unnecessary, which shortens the process and reduces the working space. There is an effect that reduction is possible.

(5) According to the present invention, since the thermoplastic resin is used for the adhesive layer, the viscosity of the thermoplastic resin is high even in the high temperature molten state during pelletizing, so that the pellet shifts and the pellet peels off during frame transportation. There is an effect of disappearing.

(6) According to the present invention, by using a thermoplastic resin for the adhesive layer, the position of the semiconductor pellets can be corrected in the heated state even if pellet misalignment or pellet peeling occurs. The effect is that it can be prevented.

[Brief description of drawings]

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

FIG. 2 is a vertical sectional view showing a semiconductor device according to an embodiment of the present invention.

FIG. 3 is a vertical sectional view showing a semiconductor device according to an embodiment of the present invention.

FIG. 4 is a plan view showing a lead frame which is a modification of the embodiment of the present invention.

FIG. 5 is a plan view showing a lead frame which is a modification of the embodiment of the present invention.

FIG. 6 is a plan view showing a lead frame which is a modification of the embodiment of the present invention.

FIG. 7 is a plan view showing a lead frame which is a modification of the embodiment of the present invention.

FIG. 8 is a plan view showing a lead frame which is another embodiment of the present invention.

FIG. 9 is a plan view showing a lead frame which is a modified example of another embodiment of the present invention.

FIG. 10 is a plan view showing a lead frame which is a modified example of another embodiment of the present invention.

FIG. 11 is a plan view showing a conventional lead frame having a small tab structure.

FIG. 12 is a vertical cross-sectional view showing a conventional semiconductor device having a small tab structure.

FIG. 13 is a vertical cross-sectional view showing a conventional semiconductor device having a small tab structure.

FIG. 14 is a plan view showing a lead frame which is another embodiment of the present invention.

FIG. 15 is a vertical sectional view showing a semiconductor device according to another embodiment of the present invention.

[Explanation of symbols]

1, 12 ... Semiconductor pellet, 2 ... Lead, 2a ... Inner lead, 2b ... Outer lead, 3 ... Support lead,
4, 15 ... Sealing resin (sealing body), 5 ... Bonding wire, 6, 14 ... Frame, 7 ... Lead frame, 8 ... Dam, 9 ... Adhesive layer, 11 ... Small tab, 13 ... Suspension lead.

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Kunihiro Tsubozaki 5-20-1, Josuihoncho, Kodaira-shi, Tokyo Inside the Semiconductor Division, Hitachi, Ltd. (72) Inventor Hiroshi Ono Kamisuimoto-cho, Kodaira-shi, Tokyo 5-22-1 Hitachi Microcomputer System Co., Ltd. (72) Inventor Asao Matsuzawa 5-22-1 Kamisuihoncho, Kodaira-shi, Tokyo In-house Hitachi Microcomputer System (72) Takafumi Nishida Kodaira, Tokyo 5-22-1, Josuihoncho, Ichi-shi Hitachi Microcomputer System Co., Ltd.

Claims (16)

[Claims] 1. A lead frame in which a lead, which is electrically connected to a mounted semiconductor pellet and serves as an external terminal, is integrated by a frame, a support lead extending linearly is provided in the center of a semiconductor pellet mounting position, and an adhesive layer is provided. A lead frame, characterized in that the semiconductor pellets are fixed on the supporting leads via. 2. The lead frame according to claim 1, wherein a thermoplastic resin adhesive is used for the adhesive layer. 3. The support lead is provided with an adhesive layer, and the formation area thereof is equal to or larger than the maximum semiconductor pellet size mountable on the lead frame.
Alternatively, the lead frame according to claim 2. 4. The lead frame according to claim 1, wherein the adhesive layer is formed partially and at a plurality of locations within the semiconductor pellet mounting range. 5. The lead according to claim 1, wherein the supporting lead extends linearly in four directions orthogonal to each other from the center of the semiconductor pellet mounting position. flame. 6. The lead frame according to claim 1, wherein the support lead extends linearly across the center of the semiconductor pellet mounting position. 7. The lead frame used in a resin-sealed semiconductor device, according to claim 1.
The lead frame according to any one of 1. 8. A semiconductor device in which a semiconductor pellet and a lead serving as an external terminal are electrically connected to each other and sealed in a sealing body. In a semiconductor device, a linearly extending support lead is provided on the semiconductor pellet through an adhesive layer. A semiconductor device characterized by being fixed to a central lower surface. 9. The semiconductor device according to claim 8, wherein the adhesive layer is a thermoplastic resin adhesive. 10. The semiconductor device according to claim 8, wherein the adhesive layer is formed on the support lead in a range equal to or larger than the size of the semiconductor pellet. 11. The semiconductor device according to claim 8, wherein the adhesive layer is formed partially and at a plurality of locations. 12. The semiconductor device according to claim 8, wherein the support lead extends linearly in four directions orthogonal to each other from the center of the semiconductor pellet. .. 13. The semiconductor device according to claim 8, wherein the support lead extends linearly across the center of the semiconductor pellet. 14. The semiconductor device according to claim 8, wherein a resin is used for the sealing body. 15. A method of manufacturing a semiconductor device, in which a semiconductor pellet is adhered and fixed to a lead frame, the semiconductor pellet and an inner lead of the lead are electrically connected, and sealed by a sealing body, in the center of the semiconductor pellet mounting position. Provided with a linearly extending support lead, using a lead frame for fixing the semiconductor pellets to this support lead via an adhesive layer of a thermoplastic resin, under a heating atmosphere, a step of softening the thermoplastic resin, And a step of pressing the semiconductor pellets to the softened thermoplastic resin and fixing the semiconductor pellets to the support leads. 16. The method of manufacturing a semiconductor device according to claim 15, wherein the sealing body is formed by resin molding.