JP2001077280A - Lead frame and semiconductor device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To improve the reliability of a semiconductor device by preventing the island of a lead frame from being warped and to provide a lead frame and a semiconductor device which can prevent drop in quality and short- circuiting caused by break of a suspension lead. SOLUTION: A lead frame includes an island 11 for mounting a semiconductor chip, a plurality of leads 12 connected electrically to a semiconductor chip mounted on the island 11, and a frame 13 connecting the leads 12. The island 11 is independent of the frame 13 and is supported by a resin tape 16, in a state where it is connected to the frame 13. A semiconductor device is fabricated by cutting the resin tape 16 after the semiconductor chip is mounted on the island 11. Even if changes in the temperature caused accompanying resin forming is applied to the island 11 and the resin tape 16, since the thermal expansion/ contraction coefficient of the resin tape 16 is close to that of sealing resin as compared with a metal, stresses generated between the resin tape 16 and the sealing resin can be kept extremely small, thereby preventing the island 11 from being warped.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a lead frame used for a semiconductor device and a resin-sealed semiconductor device using the lead frame.

[0002]

2. Description of the Related Art As one of package structures of a semiconductor device, a semiconductor chip is mounted on a lead frame obtained by processing a metal plate material, and the semiconductor chip and the lead frame are electrically connected and then sealed with a resin. A package structure has been proposed. Therefore, the lead frame used for this type of package structure has an island for mounting the semiconductor chip, and a lead portion serving as an external lead that is electrically connected to the electrode of the semiconductor chip and is integrally formed by the frame portion. In advance, there is a manufacturing method in which the semiconductor chip is mounted on the lead frame, the semiconductor chip and the lead are electrically connected, and after sealing with resin, the island is separated from the lead by cutting and removing the frame. Has been adopted.

FIG. 5 shows an example of such a lead frame. The lead frame 110 is formed by etching or punching a metal plate, and has a rectangular island 111 and a number of lead portions 112 arranged around the island 111. The lead portion 112 is formed as a part of a frame portion 113 and is connected by a tie bar 114 functioning as a stopper for a sealing resin.
Reference numeral 11 is connected to a frame 115 of the frame 112 by a suspension lead 116. The hanging lead 116
Are arranged between the lead portions 112, particularly at the four corners of the island 111 so as not to interfere with a large number of lead portions 112, thereby connecting and supporting the island 111 to the frame portion 113. The suspension lead 116 has a semiconductor chip mounted thereon as described above,
After resin sealing, the tie bar 114 and the frame 115
It goes without saying that it is cut at the same time.

[0004]

In such a conventional lead frame 110, the semiconductor chip is mounted on the island 111 while being supported by the suspension leads 116 at the four corners of the island 111. Since the wire bonding between the semiconductor chip and the lead portion and the semiconductor chip and the lead portion are sealed with resin, the package after resin sealing tends to have the largest warp on the diagonal line of the island 111. That is, after the resin is sealed in the lead frame 110, stress is generated in each part of the lead frame due to a difference between a coefficient of thermal expansion and a contraction rate of the metal constituting the lead frame and the resin. This stress is also applied to the island 111, but since the island 111 is connected to the frame portion 12 by the suspension leads 116 at the four corners, the suspension leads 116
There is a difference in stress between the part where
This stress causes the island 111 to warp.
In particular, in the island 111, the largest warp occurs on the diagonal line connecting the suspension leads 116, and this warp causes a crack or chip in the semiconductor chip mounted on the island 111, or the semiconductor chip floats from the island, and as a result, The fixed state of the semiconductor chip becomes unstable, and the reliability of the semiconductor device deteriorates, such as the breaking of the bonding wire connecting the semiconductor chip and the lead. Also,
When the suspending lead 116 is cut after resin sealing, since the suspending lead 116 is made of metal, cutting burrs or cutting debris are generated on the cut surface of the suspending lead 116 exposed on the outer surface of the sealing resin, and the cutting burrs cause semiconductor In addition to deteriorating the quality of the device, cutting waste may cause an electrical short circuit accident.

SUMMARY OF THE INVENTION An object of the present invention is to improve the reliability of a semiconductor device by preventing the occurrence of warpage in an island, and to prevent a decrease in quality or a short circuit accident due to cutting of a suspension lead, and a lead frame. A semiconductor device is provided.

[0006]

SUMMARY OF THE INVENTION The present invention provides an island for mounting a semiconductor chip, a plurality of leads electrically connected to the semiconductor chip mounted on the island, and a frame connecting the leads. The island is formed separately from the frame portion and supported in a state of being connected to the frame portion by a resin tape made of resin. The resin tape is bonded to the island and the frame, respectively, and the island is suspended at a position between the plurality of leads by the resin tape. The island is formed in a rectangular planar shape, the resin tape is formed in an X-shaped planar shape, and the resin tape is attached in a state of being extended along a diagonal of the island. In addition, it is preferable that the extended end portions are attached to the frame portion.

Further, in the semiconductor device of the present invention, a semiconductor chip is mounted on the island of the lead frame of the present invention, and the semiconductor chip and the lead portion are electrically connected by a bonding wire. The bonding wire is sealed with a sealing resin, and the resin tape exposed from the sealing resin is cut and removed. Here, the resin tape is attached along one surface of the island, and the semiconductor chip is mounted on a surface opposite to the resin tape. Further, the resin tape is made of a resin having a value close to that of the sealing resin in thermal expansion coefficient and contraction rate.

According to the present invention, the semiconductor chip is mounted in a state where the island is supported on the frame portion of the lead frame by the resin tape, and the semiconductor chip is sealed with a sealing resin, and then the frame portion is cut and separated. By configuring the semiconductor device, even if a temperature change accompanying resin molding is applied to the island or the resin tape between the resin sealing and the cutting of the frame portion, the resin tape is more sealed than the metal material. Since the thermal expansion coefficient and the contraction rate are close to those of the resin for stopping, the stress generated between the resin for sealing and the resin for sealing is extremely small. Therefore, warping of the island hardly occurs, cracking or chipping of the semiconductor chip mounted on the island can be prevented, and disconnection of the bonding wire connecting the semiconductor chip and the lead can be prevented.

Japanese Patent Application Laid-Open No. Hei 7-212258 describes a technique in which a tape such as a resin is adhered to a part of a lead frame to increase the strength of the lead frame. This is a technique for preventing bending and deformation at the same time, and is not a technique for supporting islands with a resin tape as in the present invention. In Japanese Patent Application Laid-Open No. 7-66347, a fixing tape is adhered to a part of the suspension lead of the island. This fixing tape is a technique for preventing the flow of the resin during resin sealing. This is not a technique of supporting islands with a resin tape as in the present invention.

[0010]

Next, embodiments of the present invention will be described with reference to the drawings. 1A and 1B are a plan view of a lead frame according to an embodiment of the present invention and an enlarged cross-sectional view taken along the line AA. The lead frame 10 is formed by etching or punching a metal plate. Lead frame 1
A rectangular, here square, island 11 is formed in the central part of 0. A large number of leads 12 are radially arranged around the island 11. The plurality of leads 12 are connected by a tie bar 14 as a part of a frame 13 and further connected to a frame 15. The island 11 is supported on the frame 13 by an X-shaped resin tape 16 made of a resin, whereby the island 11 is suspended between the plurality of leads 12. Have been. That is, the resin tape 16 extends along the diagonal line of the island 11 and is bonded to one surface of the island 11, and the four tips of the resin tape 16 are bonded to the frame 15 of the frame 13. Have been. As a result, the resin tape 16 is stretched between the lead portions 12 while being supported by the frame 15 at each end, and the resin tape 16 is supported in a suspended state at the intermediate portion of the stretched state. I have.

A procedure for manufacturing the lead frame 10 shown in FIG. 1 will be described. First, as shown in FIG. 2A, a metal plate is punched to form an island 11 and a lead portion 12. At this time, the island 11 is separated from the lead portion 12 and is formed as a separate component. As described above, each of the lead portions 12 is formed by a tie bar 14 in which a plurality of lead portions 12 are radially arranged and extending in a direction orthogonal to the tie bar 14 and a frame portion 13 including a rectangular frame 15. Be linked. On the other hand, FIG.
As shown in (b), an X-shaped resin tape 16 is formed. The material of the resin tape 16 has good adhesion to a sealing resin forming a package of a semiconductor device described later,
In addition, a resin having a heat expansion coefficient and a contraction rate close to each other and having heat resistance that can withstand heat during resin sealing, for example, a polyimide resin is used. Here, the diagonal length of the resin tape 16 is formed to be substantially equal to the diagonal interval of the frame 15. Then, the island 11, the lead portion 12, and the frame portion 13 are placed on a fixed rock or the like so as to be at predetermined positions, and for example, temporarily fixed to a lower surface side with a temporary fixing tape or the like, Island 11
By attaching the island 11 and the frame portion 13 with the resin tape 16 from the upper surface side of the frame portion 13 and integrally connecting the island 11 and the frame portion 13 and then removing the temporary fixing tape, the lead frame 10 shown in FIG. Manufactured. Note that the resin tape 16 may be a long tape having a continuous X-shape, which may be cut after being attached to the lead frame 10.

To assemble a semiconductor device using such a lead frame 10, as shown in FIG. 3A, the lead frame 10 is placed with the resin tape 16 on the lower side, that is, Is placed on an assembly stage (not shown) in the absence of
1, a semiconductor chip 21 is mounted. For this mounting, a conductive adhesive, a low melting point brazing material, or the like can be used. Next, the electrodes of the mounted semiconductor chip 21 and the lead portions 12 of the lead frame 10 are connected by bonding wires 22 and are electrically connected to each other. Figure 3
As shown in (b), the lead frame 10 is connected to the resin molding die 4.
1, the island 11, the semiconductor chip 2
1, a region including the bonding wire 22 and the lead portion 12 inside the tie bar 14 is sealed with a resin 23 for sealing.
And sealing. Then, as shown in FIG. 3 (c), the frame 15 and the tie bar 14 of the frame 13 exposed from the sealing resin 23 and the resin tape 16 are cut by a press machine (not shown), and simultaneously the frame is cut. The outer end regions of the many lead portions 12 separated from the portion 12, that is, the external connection terminals 12a are bent in the thickness direction. Thereby, as shown in FIG. 4, a resin-sealed semiconductor device 20 in which a large number of external connection terminals 12a protrude from the four surroundings of the sealing resin is completed.

Since the resin tape 16 is cut off from the frame 13 at the same time as the cutting and bending of the frame 13, the function of supporting the island 11 with respect to the frame 13 is lost. Since the resin tape 16, the island 11, the semiconductor chip 21, and the like are integrally sealed in the sealing resin 23, no problem occurs. Further, during the period from the resin sealing step to the step of cutting the frame portion 13 and the resin tape 16, a temperature change accompanying the resin molding is applied to the island 11, the resin tape 16, and the like. Since the resin 23 is made of a resin having a similar thermal expansion coefficient and contraction rate to the resin 23, the stress generated between the resin 23 and the sealing resin 23 is extremely small. For this reason, warpage hardly occurs in the island 11, cracking or chipping in the semiconductor chip 21 mounted on the island 11 can be prevented, and the bonding wire 22 electrically connecting the semiconductor chip 21 and the lead portion 12 can be prevented. Disconnection can be prevented.
Further, when the resin tape 16 is cut after the resin sealing, the resin tape 16 is integrated with the sealing resin 23, so that no cutting burrs or cutting debris are generated at the cutting portion, and the quality of the semiconductor device is reduced. There is no occurrence of electrical short-circuit accidents.

The present invention is not limited to the above embodiment. The resin tape has a plane shape such as a cross shape, a cross-girder shape, a Y-shape, a frame shape, etc.
Various shapes can be used as long as the shape can be connected and supported. Further, in the above-described embodiment, an example is shown in which the distal end portion of the resin tape 16 is connected to the frame portion 13, but the resin tape 16 may be connected to a part of the lead portion 12. Further, various types of resin constituting the resin tape 16 can be adopted according to the type of the sealing resin 23.

[0015]

As described above, according to the present invention, since the island of the lead frame is supported on the frame by the resin tape, the semiconductor chip is mounted on the island and sealed with the sealing resin. After that, by cutting and separating the frame part to configure the semiconductor device, even if the temperature change accompanying the resin molding is applied to the island or the resin tape, etc., from the resin sealing to cutting the frame part, Since the tape has a similar thermal expansion coefficient and shrinkage to the sealing resin compared to the metal material, the stress generated between the tape and the sealing resin is extremely small, and therefore, it is possible to generate a biased stress on the island. Disappears. Therefore, warping of the island hardly occurs, cracking or chipping of the semiconductor chip mounted on the island can be prevented, and disconnection of the bonding wire connecting the semiconductor chip and the lead can be prevented. Further, even when the resin tape is cut when the frame portion is cut and the cut portion is exposed from the sealing resin, cutting burrs and cutting debris such as a metal material do not occur. It is possible to prevent the deterioration of the quality due to the above and the occurrence of the electric short circuit accident due to the cutting waste.

[Brief description of the drawings]

FIG. 1 is a plan view and an AA line enlarged cross-sectional view of an embodiment of a lead frame of the present invention.

FIG. 2 is a plan view for explaining a manufacturing process of the lead frame of FIG. 1;

FIG. 3 is a process diagram for explaining a manufacturing process of the semiconductor device according to the present invention.

FIG. 4 is a partially broken perspective view of one embodiment of the semiconductor device according to the present invention.

FIG. 5 is a plan view of an example of a conventional lead frame.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 10 Lead frame 11 Island 12 Lead part 13 Frame part 14 Tie bar 15 Frame frame 16 Resin tape 20 Semiconductor device 21 Semiconductor chip 22 Bonding wire 23 Resin for sealing

Claims (6)

[Claims] 1. A lead frame comprising: an island for mounting a semiconductor chip; a plurality of leads electrically connected to the semiconductor chip mounted on the island; and a frame connecting the leads. The lead frame, wherein the island is formed separately from the frame portion, and is supported by being connected to the frame portion by a resin tape made of resin. 2. The resin tape is adhered to the island and the frame, respectively, and the resin tape suspends the island at a position between the plurality of leads. 2. The lead frame according to 1. 3. The island is formed in a rectangular planar shape, the resin tape is formed in an X-shaped planar shape, and the resin tape is extended along a diagonal of the island. The lead frame according to claim 2, wherein the lead frame is attached to the frame portion at an extended end portion. 4. A semiconductor chip is mounted on the island of the lead frame according to claim 1, and the semiconductor chip and the lead are electrically connected by a bonding wire, and at least the island, the semiconductor chip, and the bonding are provided. A resin-sealed semiconductor device, wherein a wire is sealed with a sealing resin, and the resin tape exposed from the sealing resin is cut and removed. 5. The resin tape according to claim 4, wherein the resin tape is attached along one surface of the island, and the semiconductor chip is mounted on a surface opposite to the resin tape. Semiconductor device. 6. The semiconductor device according to claim 4, wherein the resin tape is made of a resin having a value close to that of the sealing resin in thermal expansion coefficient and contraction rate.