JP3251436B2 - Lead frame, semiconductor device, and method of manufacturing semiconductor device - Google Patents

Abstract

PURPOSE: To prevent generation of voids due to chip shift at the time of resin injection and generation of chip cracks at the time of reflow in a resin sealed semiconductor device. CONSTITUTION: Each of the island parts 3 is fixed at the corner part of a chip. Thereby the chip can be stably held at the center of a cavity when a force in the up-and-down direction is applied by the flow of resin at the time of molding. The rear of the chip except the corner parts of the chip is made to practically stick to the resin on the whole surface.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a resin-sealed semiconductor device, and more particularly to a surface-mounted resin-sealed semiconductor device such as a QFP, which prevents package cracks during reflow soldering and voids during resin injection. The present invention also relates to a lead frame capable of obtaining a suitable resin-encapsulated semiconductor device, a semiconductor device using the same, and a method of manufacturing the same.

[0002]

2. Description of the Related Art Semiconductor chips (hereinafter referred to as chips)
Is mounted on a tab provided at the center of the lead frame, and the chip and the lead are electrically connected by wire bonding and then sealed with a resin. In particular, a surface mount type resin seal such as QFP is used. In semiconductor devices that are not fixed,
There is a problem of package cracks generated during the reflow soldering process.

[0003] This is a phenomenon in which an internal stress caused by a high temperature in a reflow soldering process causes peeling at an interface between a resin having low adhesiveness and a tab, and a steam pressure acts on the interface.

[0004] As a method of preventing this peeling, a through hole is provided in the tab by utilizing the fact that resin has higher adhesiveness to the chip (silicon) than the tab (metal). Packaging Technology (Bottom) "(Nikkei BP, 1993), page 126.

[0005]

However, with the recent increase in the occupancy of the chip in the resin of the semiconductor device and the reduction in the thickness of the package, it is difficult to sufficiently prevent the occurrence of package cracks by the above-mentioned method. It is becoming. Therefore, the present inventor has proposed a lead frame having a so-called small tab structure in which the outer dimensions of the tab for mounting the chip are made smaller than the outer dimensions of the chip, and the center of the chip is supported by the small tab. No. is proposed.

In the lead frame having the small tab structure, the outer dimensions of the tab are reduced, and the central portion of the chip is adhered to the small tab, thereby increasing the contact area between the resin and the back surface of the chip at the peripheral portion of the chip. Then, by improving the adhesion, it is intended to prevent interfacial peeling and suppress package cracks.

However, in this structure, the chip adheres to the tab of the lead frame only at the center thereof. Therefore, if a vertical force is applied to the chip due to resin flow during resin injection in the molding process, the tab suspension lead. Is easy to bend upward. Then, the chip is displaced from the center of the mold, and the flow rate of the molten resin is different between the upper side and the lower side of the chip, so that there is a disadvantage that voids are easily generated. This is a problem particularly in a so-called thin package having a package thickness of 2 mm or less.

In order to fix the chip to the tab at the center of the chip, the tab needs to have a certain area from the viewpoint of adhesive strength. In this method, the package crack described above is completely prevented. I can't say that.

An object of the present invention is to prevent the occurrence of voids due to chip displacement during resin injection, and
An object of the present invention is to provide a technique capable of preventing a package crack during reflow.

[0010]

Means for Solving the Problems In order to achieve the above object, the outline of the invention disclosed in the present application will be briefly described as follows.

That is, a rectangular frame, a plurality of support leads extending from each of a plurality of islands for fixing a quadrangular semiconductor chip toward a corner of the frame, and the plurality of islands are combined. A connecting portion to be held on a plane, and a plurality of leads extending from the frame portion between the plurality of support lead portions, wherein each of the plurality of island portions has a four corners of the semiconductor chip; Among them, the distance from the center of the semiconductor chip and the distance from the corner of the semiconductor chip at the corner closest to the resin injection gate provided at one corner of the frame and the corner opposite thereto are 4: 1. A semiconductor device and a method of manufacturing the semiconductor device, wherein the semiconductor chip is fixed at a position or outside thereof.

In the above-described semiconductor device, the chip is fixed to the island at the corner closest to the resin injection gate and at the corner opposite thereto, of the four corners. However, even if a vertical force is generated, the inconvenience that the support lead is bent upward and the chip is displaced from the center of the molded portion does not occur. Therefore, generation of voids can be prevented.

At the same time, the back surface of the chip is adhered to the island only at the corners, and substantially the entire surface is in close contact with the resin except at the corners, so that peeling during reflow is suppressed. As a result, the package crack resistance can be improved.

Further, the provision of the connecting portion allows the island portion to be held substantially on one plane, and the die bonding for bonding the chip and the island portion to be performed reliably in all the island portions. The chip can be stably supported on the lead frame.

[0015]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Embodiments of the present invention will be specifically described below with reference to the drawings.

[First Embodiment] FIG. 1 is a plan view showing the structure of a lead frame used in a resin-sealed semiconductor device according to a first embodiment of the present invention. FIG. 2A is a cross-sectional view for explaining a manufacturing process of the semiconductor device according to the present embodiment, and FIG.
FIG. 3 is a cross-sectional view illustrating a molding step of the semiconductor device of the present example. FIG. 3A is a plan view of the semiconductor device of the present embodiment, and FIG. 3B is a cross-sectional view of the semiconductor device of FIG.

In FIG. 1, a dotted frame 2 'at the center of the lead frame 1 indicates a region where a rectangular chip is mounted.

The island portions 3 of the lead frame 1 are portions for fixing the chip on the lead frame, and are located at four corners of the chip mounting position 2 '. The chip is fixed on the lead frame 1 only by the four island portions 3.

The support lead portion 4 of the lead frame 1 supports the island portion 3 at a predetermined position.
Each support lead 4 extends from each of the islands 3 to each of the four corners of the lead frame 1.

The connecting portion 6 of the lead frame 1 connects the diagonal island portions of the four island portions 3 with each other, and forms a cross shape intersecting at the center of the chip mounting position 2 '. By providing the connecting portion 6, the four island portions 3 are held on one plane. In order to prevent package cracks, it is effective to increase the bonding area between the back surface of the chip and the resin.
It is preferable that the width of the connecting portion 6 is formed thin. In the present embodiment, the width is equal to the width of the support lead portion 4.

The above-mentioned island portion 3, support lead portion 4 and connecting portion 6 are integrally formed diagonally.

A plurality of leads 7 for electrical connection are provided between the support leads 4 and extend from the periphery of the lead frame 1 toward the chip mounting position 2 '. Further, a dam bar 8 for connecting the lead 7 and the support lead portion 4 and preventing the resin from flowing out when the resin is injected in the molding process is provided on the lead frame 1.
Is formed in the shape of a frame at the periphery. In addition, of the lead 7,
The portion outside the dam bar 8 is a portion that is exposed to the outside of the mold portion after resin sealing and serves as an external terminal of the semiconductor device.

The gate portion 14 'indicates the position of the gate into which the resin is injected in the molding process and the direction of the resin injection.

Although not shown, the lead frame has a structure in which a plurality of lead frames 1 each of which is constituted by the above-described components are connected in one direction. Therefore, an outer frame 9 connecting a plurality of lead frames of each unit and an inner frame 10 formed so as to separate the lead frames of each unit from each other are provided at the outermost peripheral portion of the lead frame. The outer frame 9 and the inner frame 10 are integrally formed to form a rectangular frame. Further, a guide hole 11 serving as a guide when positioning the lead frame on the mold is provided in a part of the outer frame 9.

The lead frame 1 has a thickness of 0.1-0.
Using a conductive material such as 42 alloy or copper of about 2 mm, it is molded by means such as punching. For example, one side of the chip to be mounted is 9 mm, and the outer side of the package is 28 m
m, the island part 3 has a width of 0.5 to 1.5 mm and a length of about 2 mm, and the support lead part 4 and the connecting part 6 have a width of 0.2.
It is formed to about 5 mm.

It is preferable that the island portion 3 is bonded to the chip at a position where the distance from the center of the chip and the distance from the corner of the chip are about 4: 1 or outside thereof. In other words, since the island portion 3 only needs to be located outside the above approximately 4: 1 position, one lead frame can be used for a plurality of types of chips having different external dimensions. Therefore, since the lead frame can be standardized for each of a plurality of chips having different external dimensions, the manufacturing cost can be reduced, and the semiconductor device can be provided at low cost.

The size of the island portion 3 may be any size as long as it satisfies the adhesive strength required for fixing the chip 2 and the lead frame 1, and the shape may be any shape as long as it is suitable for die-bonding adhesive application. .

Next, a method of manufacturing the semiconductor device of this embodiment shown in FIG. 3 using the above-described lead frame of FIG. 1 will be described. 2A and 2B are cross-sectional views for explaining a manufacturing process, and show cross-sections of the lead frame 1 in FIG. 1 taken along a diagonal line including the gate portion 14 '.

First, the support lead portion 4 of the lead frame 1
Is subjected to downset processing. As shown in FIG. 2A, the downset processing is performed by bending a middle portion of the support lead portion 4 downward by using a press die, so that the position of the island portion 3 viewed from the horizontal direction is higher than that of the lead 7. It is a work to lower. This downset processing is particularly effective when applied to a so-called thin surface mount type package having a resin mold portion having a thickness of 2 mm or less. The specific method of downset processing is described in
This is described in detail in US Pat.

Next, the process proceeds to a die bonding step of mounting the chip 2 on the lead frame 1. First, a die bond adhesive 5 is applied to the island portion 3. As the die bond adhesive 5, an epoxy resin, a polyimide resin, or the like is used. Next, the chip 2 is positioned such that the corners of the chip are located on the island portions 3 to which the die bond adhesive 5 has been applied, and the die bond step is completed by curing the die bond adhesive 5 by heating. In addition, compared with the conventional case where the entire back surface of the chip is bonded on a so-called tab, the bonding is performed only at the island portion 3 having a small area at the corner of the chip, so that the required bonding strength can be obtained with a small amount of die bonding adhesive. And the manufacturing cost can be reduced.

Next, one main surface of the chip 2, that is, a bonding pad provided on the periphery of the surface on which the semiconductor element is formed of the two main surfaces of the chip 2 and the inner end of the lead 7 are connected. Chip 2 is bonded by Au wire 12
And the leads 7 are electrically connected.

Next, the process proceeds to a molding step. As shown in FIG. 2B, the lead frame, which has been completed up to the wire bonding step, is connected to the upper mold 13a and the lower mold 13 of the mold.
Then, a resin 16, for example, an epoxy resin or the like is injected from the gate 14 into the cavity 15 to form a molded portion. The gate 14 is provided on the lower mold 13 b side, that is, at a position below the lead frame 1.
By performing the downset processing on the lead frame 1 as described above, the chip 2 is positioned at the center of the cavity 15, and the thickness of the mold portion on one main surface side of the chip,
The thickness of the mold portion on the other main surface side can be made equal. That is, by equalizing h1 and h2 shown in FIG. 2B, the resin flow speed on the upper surface side and the lower surface side of the chip 2 can be equalized, and the generation of voids can be suppressed. Further, at the corner of chip 2, chip 2
And the island portion 3 are bonded to each other, so that even if a vertical force is applied to the chip 2 due to the flow of the resin 16, the chip 2
Can be stably maintained at the center of the cavity 15, and the above-mentioned voids can be continuously suppressed until the resin injection is completed. When the lead frame 1 is not subjected to the downset processing, the gate 14 is provided on the side having the smaller value among the values corresponding to h1 and h2 shown in FIG. 2B in order to suppress the generation of voids. Is preferred.

Next, unnecessary portions of the lead frame 1, that is, the dam bar 8, the outer frame 9 and the inner frame 10 exposed to the outside of the molded portion are cut and removed by a press, and finally, the leads 7 exposed to the outside of the molded portion are removed. Is molded into a predetermined shape, whereby a resin-sealed semiconductor device as shown in FIGS. 3A and 3B is completed. In FIG. 3A,
In order to clarify the internal structure of the semiconductor device of this embodiment,
The mold portion is indicated only by its outline by a two-dot chain line.

In the semiconductor device of this embodiment, as shown in FIG. 3B, the back surface of the chip is bonded to the island portion only at the corner. Therefore, portions other than the corners of the chip back surface are in close contact with the resin 16 on the chip back surface except for the portion where the thin connecting portion 6 exists. That is, the entire back surface of the chip except for the corners of the chip is substantially in close contact with the resin 16, so that interface separation during reflow can be suppressed and package crack resistance can be improved.

[Embodiment 2] FIG. 4 is a plan view showing a configuration of a lead frame used in a resin-sealed semiconductor device according to Embodiment 2 of the present invention.

The structure of the lead frame 1 is different from that of the first embodiment in that only two islands 3 are provided as shown in FIG. 4, and the other parts are the same as those of the embodiment described in FIG. Same as 1. One of the two island portions is located at the corner of the chip mounting position 2 'closest to the gate portion 14', and the other is located at the corner diagonally opposite thereto. Therefore, there are no island portions in the remaining two corners. Therefore, the cross-shaped connecting portion 6 that intersects at the center of the chip mounting position 2 ′ connects the two island portions and extends to the two corner portions of the frame at the corner where the island portion does not exist. The island portion 3, the support lead portion 4, and the connecting portion 6 are integrally formed diagonally.

Even when the lead frame of this embodiment is used, the semiconductor device of this embodiment can be obtained by the same manufacturing steps as in the first embodiment.

According to the present embodiment, only two island portions 3 are provided. However, since the position is strongly influenced by the force generated by the flow of the resin when the resin is injected, the two island portions 3 are different from those of the first embodiment. Substantially the same void prevention effect can be obtained. Further, the number of island portions is smaller than that of the first embodiment, and the bonding area between the resin and the back surface of the chip is larger, so that a package crack prevention effect superior to that of the first embodiment can be obtained.

Third Embodiment FIG. 5 is a plan view showing a configuration of a lead frame used for a resin-sealed semiconductor device according to a third embodiment of the present invention.

The lead frame 1 of the above two embodiments is
Although the cross-shaped connecting portion 6 is provided, the lead frame 1 of this embodiment has a band-shaped insulating film 17 around the chip mounting position 2 'so as to connect the supporting lead portions 4 to each other. Features. Insulating film 17
By connecting the support leads 4 and also connecting the plurality of leads 7, the leads 7 can also serve to prevent variations in the leads 7.

The insulating film 17 has a width of, for example, 1.5 m.
An acrylic resin-based adhesive is applied to one side of a polyimide resin film having a thickness of about 0.05 m and a thickness of about 0.05 mm.
It is configured to apply about 02 mm.

Even when the lead frame of this embodiment is used, the semiconductor device of this embodiment can be obtained by the same manufacturing steps as in the first embodiment. However, as described above, in order for the insulating film 17 to also serve to prevent the leads 7 from varying, the downset processing is performed on the insulating film 17.
It is necessary to bend the support lead portion 4 downward on the chip side.

According to the present embodiment, since the cross-shaped connecting portion 6 of the first embodiment does not exist, the bonding area between the resin and the back surface of the chip is further increased. Can be obtained.

As described above, the present invention has been specifically described based on the embodiments. However, the present invention is not limited to the above-described embodiments, and it is needless to say that various modifications can be made without departing from the gist of the present invention. Absent.

For example, the shape of the connecting portion 6 is not limited to the embodiment, but has a structure in which the island portion located at the corner of the chip can be held on one plane and the chip can be stably supported. Any structure other than the corners of the chip may be used as long as the back surface of the chip is substantially entirely in contact with the resin. Therefore, for example, in the case of the first embodiment, the connecting portion 6 is not limited to the cross shape, but connects adjacent ones of the four island portions to each other and forms a peripheral portion of the chip mounting position 2 ′. The structure which forms a square frame along may be sufficient.

[0046]

According to the present invention, the occurrence of package cracks during reflow and voids during resin injection is prevented.
A lead frame capable of obtaining a suitable resin-encapsulated semiconductor device, a resin-encapsulated semiconductor device using the same, and a method for manufacturing the same can be provided.

Further, according to the present invention, the island portion located at the corner of the chip is held on one plane and the chip is stably supported, and the resin-encapsulated semiconductor device using the lead frame. And its manufacturing method can be provided.

[Brief description of the drawings]

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

FIG. 2A is a cross-sectional view for explaining a manufacturing step of the semiconductor device according to one embodiment of the present invention; FIG. 4B is a cross-sectional view illustrating a molding step of the semiconductor device according to the embodiment of the present invention.

FIG. 3A is a plan view of a semiconductor device according to an embodiment of the present invention. FIG. 2B is a cross-sectional view of the semiconductor device according to one embodiment of the present invention.

FIG. 4 is a plan view of a lead frame according to another embodiment of the present invention.

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

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 ... Lead frame, 2 ... Semiconductor chip, 2 '... Semiconductor chip mounting position, 3 ... Island part, 4 ... Support lead part, 5 ... Die bond adhesive, 6 ... Connecting part, 7 ... Lead,
8 dam bar, 9 outer frame, 10 inner frame, 11 guide hole, 12 bonding wire, 13a upper mold, 13b lower mold, 14 gate
14 ': gate portion, 15: cavity, 16: resin, 17: insulating film

──────────────────────────────────────────────────続 き Continuing on the front page (72) Inventor Takao Yoshimura 145 Nakajima, Nanae-cho, Kameda-gun, Hokkaido Inside Nippon Hokkai Semiconductor Co., Ltd. (56) References JP-A-6-216303 (JP, A) JP-A-6-132442 (JP, A) (58) Fields investigated (Int. Cl. ⁷ , DB name) H01L 23/50

Claims (7)

(57) [Claims] A square semiconductor chip having a semiconductor element and a bonding pad formed on one main surface; a plurality of island portions for fixing the semiconductor chip on another main surface; and a plurality of island portions. A plurality of support leads extending outward, a connecting part for holding the plurality of islands on one plane, and one end between the plurality of support leads near the semiconductor chip. A plurality of leads, the other ends of which extend outward, wires that electrically connect one end of the leads and the bonding pad, and at least the semiconductor chip;
One end of the lead, the wire, the island portion, the support lead portion and a sealing portion that seals the connecting portion with a resin, each of the plurality of island portions, the four corners of the semiconductor chip Of these, the corners closest to the resin injection gate and the corners opposite to the resin injection gate have distances from the center of the semiconductor chip.
And the distance from the corner of the semiconductor chip is 4: 1
The semiconductor chip is fixed at such a position or outside thereof, and the other main surface of the semiconductor chip fixes the semiconductor chip.
A semiconductor device, wherein substantially the entire surface is in close contact with the resin except at positions where the resin is formed. 2. The method according to claim 1, wherein the plurality of islands include two islands.
A connection part connecting the two island parts to each other.
Along with two corners of the semiconductor chip.
The land portion, the support lead portion, and the connection portion are integrally formed.
2. The semiconductor device according to claim 1, which is formed diagonally.
13. The semiconductor device according to claim 1. 3. The method according to claim 1, wherein the plurality of islands include four islands.
Each of which is provided with the semiconductor chip.
Fixed at a corner portion, the connecting portion connects the four island portions to each other,
The island portion, the support lead portion, and the connecting portion
2. The semiconductor device according to claim 1 , wherein the semiconductor device is formed integrally . 4. The connecting portion is connected to the four island portions.
Are connected in a cross shape, and the island portion and the support lead
Part and the connecting part are integrally formed diagonally.
4. The semiconductor device according to claim 3, wherein: 5. The width of the connecting part is equal to the width of the supporting lead part.
5. The method according to claim 2, wherein the values are equal.
13. A semiconductor device according to claim 1. 6. A plurality of islands each including four islands.
And each of them includes the semiconductor device chip.
At the four corners, and the connecting portion is made of a strip-shaped insulating film.
Number of support leads so as to connect the support leads to each other
2. The semiconductor device according to claim 1 , wherein the semiconductor device is provided on a part . 7. The connecting portion is connected to the plurality of supporting lead portions.
And connecting the plurality of leads to each other.
7. The semiconductor device according to claim 6 , wherein: