JPH0432538B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION Field of the Invention The present invention relates to a method for manufacturing resin-sealed semiconductor devices such as power transistors and diodes.

BACKGROUND ART In a conventional general resin-sealed power transistor, a resin layer is not formed on the back surface of a heat dissipation support plate to which a transistor chip is fixed. Therefore, when installing this power transistor on an external heat radiator, an insulator with relatively good thermal conductivity is used between the back surface of the heat radiating support plate and the external heat radiator in order to electrically insulate between them. A mica thin plate or the like had to be interposed, making the installation work of the power transistor complicated.

In order to solve the above-mentioned drawbacks, a thin sealing resin layer (several hundred μm thick) is also formed on the back side of the heat dissipation support plate, as disclosed in, for example, Japanese Patent Application Laid-Open No. 147260/1983. However, a structure has been proposed that eliminates the need for mica thin plates and the like. FIGS. 11 and 12 show the conventional transistor and its manufacturing method as described above. 11 and 12, 1 is a heat dissipation support plate, 2 is a lead, 3 is a power transistor chip, 4 is a resin for chip protection,
5 is a sealing resin body, 6 is an upper mold, 7 is a lower mold,
8 is an injection hole for press-fitting the sealing resin into the cavity 9 formed by clamping the upper mold 6 and the lower mold 7, 10 is a mounting hole, and 11 and 12 are lead frames. This is a connecting part for configuring. In addition, in FIG. 12, the connecting portions 11 and 12 are finally cut off.

Problems to be solved by the invention By the way, the support plate 1 on which the chip 3 is attached
The resin coating portion 5a on one main surface side of the support plate 1 is necessarily formed thickly to protect the chip 3.
The resin coating portion 5b on the other main surface side is formed thin in order to improve the heat dissipation effect. For this reason, when resin is injected from the injection hole 8 by, for example, a transfer molding method, the resin does not flow smoothly into the lower side of the support plate 1, and there is a risk that an unfilled portion or a portion with low dielectric strength may be formed. Although the explanation has been given using a power transistor as an example, similar problems occur in other semiconductor devices such as diodes.

SUMMARY OF THE INVENTION Therefore, an object of the present invention is to provide a method for manufacturing a resin-sealed semiconductor device, which allows a thin resin coating to be satisfactorily formed on the surface of a heat dissipation support plate opposite to the chip mounting surface.

Means for Solving the Problems The present invention for achieving the above object includes a metal support plate formed to have a heat dissipation function and having a notch or hole near one end, and a metal support plate having a notch or hole near one end. a semiconductor chip mounted on one main surface of the
a resin coating part on one main surface side of the support plate, comprising a lead electrically connected to the chip, and an insulating resin coating covering a part of the support plate, the chip, and the leads; The resin coating is formed so that the resin coating is thicker than the resin coating on the other main surface side, and the resin coating is formed so that a mounting notch or hole is formed in the notch or hole. In the method for manufacturing a resin-sealed semiconductor device, the resin coating portion on the one main surface side is formed in a thick main coating portion that covers the chip and in a region on one end side of the support plate, and One end region covering portion formed thinner than the covering portion (for example, the covering portion 42 in FIG. 3 or FIG. 13)
and a thin covering portion formed thinner than the one end side area covering portion and disposed adjacent to the one end side area covering portion, and a thin covering portion for forming the thin covering portion. Using a mold for resin sealing, the protruding portion is provided so as to suppress the progress of the sealing resin injected from the injection hole arranged near one end of the support plate, and the resin sealing is performed from the injection hole. The present invention relates to a method for manufacturing a resin-sealed semiconductor device, characterized in that the resin coating is molded by injecting the sealing resin into a molding space of a mold.

Effects According to the present invention, the flow of the sealing resin injected from the injection hole arranged near one end of the support plate flows through the mold corresponding to the one end side region covering portion on one main surface side of the support plate. It is suppressed both by the protrusion and by the protrusion corresponding to the thin coating. Therefore,
It becomes possible to maintain a good injection balance in the sealing resin on one main surface side and the other main surface side of the support plate, and a good resin coating can be obtained.

Embodiment Next, a resin-sealed transistor and a manufacturing method thereof according to an embodiment of the present invention will be described with reference to FIGS. 1 to 11.

1, 2, and 3 show the completed transistor, FIG. 4 shows the chip attached to the lead frame, FIG. 5 shows the lead frame with resin sealing completed, and FIG. FIG. 6 shows a mold, and FIGS. 7 to 10 show the process of forming a resin coating by transfer molding using the mold.

When forming the transistors shown in FIGS. 1 to 3, first, a semiconductor device assembly called a lead frame shown in FIG. 4 is prepared. In FIG. 4, 21 is a heat dissipation support plate made of a nickel-coated copper plate, 22a, 22b, and 22c are external leads made of the same material, 22a is a base lead, and 22b is an external lead made of the same material.
is the collector lead, and 22c is the emitter lead. A silicon power transistor chip 23 has a base electrode and an emitter electrode formed on its upper surface, and a collector electrode formed on its lower surface.
This chip 23 is fixed to the heat dissipation support plate 21 on the lower surface by solder (not shown). 24
Internal leads a and 24c are made of aluminum wire and are disposed between the base electrode of the chip 23 and the base lead 22a, and between the emitter electrode of the chip 23 and the emitter lead 22c.
25 is a protective layer made of silicone resin for chip protection called juncture coating resin. Reference numeral 26 denotes a connecting portion between the leads called a tie bar. Reference numeral 27 is a connecting portion that commonly connects the lead ends. A U-shaped notch 28 is formed in one end 21a of the heat dissipation support plate 21. In addition,
Instead of the notch 28, holes are often formed in the heat dissipation support plate 21. Although FIG. 4 shows one power transistor in a lead frame, a single lead frame actually contains multiple transistors.

In this embodiment, the lead frame shown in FIG. 4 is provided with a resin coating 37 as shown in FIG. Completes resin-sealed transistor. As is clear from FIGS. 1 to 3, a relatively thick resin coating 37a is provided on one main surface (upper surface) of the support plate 21, and a thin resin coating is provided on the other main surface (lower surface). A portion 37b is provided. The upper resin coating portion 37a is
3. The protective layer 25, the thickest main coating portion 41 that covers the internal leads 24a and 24c, the attachment hole vicinity coating portion 42 that covers the vicinity of the attachment hole 39 provided corresponding to the cutout portion 28, and the main coating described above. A thinner covering portion 43 is provided between the portion 41 and the covering portion 42 near the attachment hole. As a result, a thin coating portion 43 is formed on the surface of the resin coating 37.
A groove 38 is formed corresponding to the groove. In addition, groove 3
8 is not provided on a straight line connecting the mounting hole 39 and the chip 23.

Resin coating 3 shown in FIGS. 1 to 3 and 5
7 is an upper mold 29 and a lower mold 30 shown in FIG.
and are combined as shown in FIGS. 7 and 8, and then formed by injecting resin as shown in FIGS. 9 and 10. In FIGS. 6 to 10, reference numeral 31 denotes an injection hole for press-fitting a sealing resin into a cavity 32 formed by clamping the upper mold 29 and the lower mold 30. 29a is a cylindrical pin protruding from the upper mold 29 to form the mounting hole 39 shown in FIG.
It passes through the notch 28 of 1. Reference numeral 29b denotes a partition-shaped protrusion protruding from the upper mold 29, which forms the groove 38 shown in FIG. Note that the protrusion 29b of the partition plate has a groove 35 in the center thereof to allow the resin to flow. When placing the lead frame shown in FIG. 4 into the molds 29 and 30, the upper mold 29 and the lower mold 30 are brought together and clamped together as shown by arrows 33 and 34 in FIG. At this time, groove 3
At 6a, the lead 22a is held by the groove 36b, and the lead 22c is held by the groove 36c. As a result, as shown in FIGS. 7 and 8, the mold 2
The support plate 21 is placed in the space 32 formed by the parts 9 and 30.
is placed in a floating position. Also, Figures 1 to 3
In order to obtain the resin coating 37 shown in the figure, the arrangement is such that the upper cavity 32a is wide and the lower cavity 32b is narrow. However, according to the present invention, a protrusion 29b is provided near the entrance of the wide space 32a above the chip 23 to suppress the strength of the flow of resin, so that the resin injected from the injection hole 31 flows into the narrow space 32a. It also penetrates into the lower cavity 32b relatively well.

The resin is injected into the cavity 32 by softening it in a thermosetting epoxy resin pot and pressurizing it into the molds 29 and 30 based on a known transfer molding method.
Inject inside. As a result, liquid resin is injected from the injection hole 31 shown in FIG. 7, and the entire cavity 32 is filled with the resin. Since the molds 29 and 30 are heated to a temperature that thermosets the resin (approximately 150°C to 200°C), the filled resin is thermosetted within a short time (several minutes), and as shown in Figs. A resin coated body 37 shown in FIG. 10 is obtained. Note that, in order to completely heat cure the lead frame, after the lead frame is taken out from the molds 29 and 30, heat treatment is performed for a longer time.

In forming the resin coating 37 by the transfer molding method as described above, if the liquid resin is injected under pressure in the direction indicated by the arrow 40 in FIGS. 6, 7, and 9, a relatively wide area can be formed. The resin tends to be easily filled into the upper space 32a. However, in this embodiment, the protrusion 29b is provided so as to cross the resin injection direction indicated by the arrow 40.
The flow of the resin is suppressed, and as a result, the flow of the resin in the narrow space 32b below the support plate 21 is relatively strengthened. As a result, the balance between the sealing flow in the upper cavity 32a and the lower cavity 32b is improved, and the unfilled state of the lower cavity 32b, which was conventionally present, is almost no longer observed. That is, the lower space 32
The problem of poor insulation of the thin resin coating portion 37b formed on the portion b can be solved.

By arranging the protrusion 29b of the upper mold 29 in the form of a partition perpendicular to the main flow direction of the sealing resin (direction of arrow 40), the flow of the resin is effectively suppressed. The optimum value differs depending on the number of molds, the size of the package, etc.

Note that since the pin 29a is located in the main flow direction of the sealing resin when viewed from the injection hole 31, the pin 29a also acts to suppress the flow of the sealing resin. Therefore, the sealing resin may not be filled in the area on the extension of the line connecting the injection hole 31 and the pin 29a and on the opposite side of the injection hole 31 of the pin 29a. However, in this embodiment, as is most obvious from FIG. 6, the flow of the sealing resin divided by the pin 29a is suppressed again by the protrusion 29b. The sealing resin easily wraps around the area, and unfilling is reliably prevented. Furthermore, in this embodiment, a groove 35 is provided on an extension of the straight line connecting the arrow 40 and the pin 29a, and this groove 35 reduces the effect of the protrusion 29b.
Since it works to offset the effect of suppressing the flow of the sealing resin by the pin 9a, it is possible to reliably prevent the area opposite the pin 29a from being unfilled.

Further, since the attachment hole vicinity covering portion 42 covering the region on the one end side of the support plate 21 is formed thinner than the main covering portion 41, it is different from the portion of the upper mold 29 where the attachment hole vicinity covering portion 42 is provided. The gap with the support plate 21 becomes narrower, and the flow of the resin is also suppressed here. Therefore, the resin injected from the injection hole 31 arranged near one end of the support plate 21 is suppressed by both the mold part for forming the thin attachment hole vicinity covering part 43 and the protruding part 29b. , it is possible to satisfactorily adjust the balance of resin flow between one main surface side and the other main surface side.

By the way, when mounting the transistor shown in FIGS. 1 to 3, the lower resin coating 37b is usually placed against a mounting plate that has an external heat dissipation function, and a mounting member such as a screw or bolt is inserted through the mounting hole 39. This is done by fixing it to the mounting plate. During such installation, if the head or nut of a screw or bolt strongly presses the vicinity of the mounting hole 39,
The area near the mounting hole 39 cannot be made too thin because cracks will occur. Therefore, in this embodiment, the covering portion 42 near the mounting hole 39 is formed to a thickness that does not hinder the mounting, and the groove 39 according to the present invention
The thin covering portion 43 in is formed thinner than the covering portion 42 near the attachment hole 39.

Modifications The present invention is not limited to the above-described embodiments, but can be modified in various ways. For example, as shown in FIG. 13, a relatively thick covering part 42 may be provided in a cylindrical shape around the attachment hole 39, and a thin covering part 43 may be provided surrounding this part. At this time, the main covering portion 41 is of course formed thick. Also,
When the attachment hole 39 is located close to the chip 23, a protrusion 29b may be provided between the injection hole 31 and the pin 29 in FIG. In addition, the mounting hole 39
may be a notch (groove or recess). It is also applicable to diodes.

Effects of the Invention As is clear from the above, according to the present invention, the resin coating portion on one main surface side of the support plate has a thick main coating portion that covers the chip, a thinner one end area coating portion, and a thick main coating portion that covers the chip. Furthermore, since the mold is formed to have a thinner covering portion, the balance of resin flow between one main surface side and the other main surface side of the support plate can be maintained.
Adjustment can be made by both the mold part forming the thin one end side area covering part and the protrusion part forming an even thinner covering part, and it is possible to form the entire resin covering body well. I can do it.

[Brief explanation of drawings]

1 is a perspective view showing a transistor according to an embodiment of the present invention, FIG. 2 is a plan view of the transistor shown in FIG. 1, FIG.
The figure is a perspective view showing a lead frame for forming the transistor shown in Fig. 1, Fig. 5 is a perspective view showing the lead frame shown in Fig. 4 with a resin coating provided, and Fig. 6 shows a mold. The perspective view, Figure 7, is the same as that of Figure 2, which shows the lead frame placed in the mold.
Figure 8 is a cross-sectional view of the part corresponding to the line, and Figure 8 is the - of Figure 2 showing the state where the lead frame is placed in the mold.
Cross-sectional views of the portion corresponding to the line, Figures 9 and 10
The figures are cross-sectional views showing the states in which the molds shown in Figs. 7 and 8 are filled with resin, Fig. 11 is a perspective view showing a conventional transistor, and Fig. 12 is a process for forming the transistor shown in Fig. 11. FIG. 13 is a sectional view showing a state in which a lead frame is placed in a mold and filled with resin, and a perspective view showing a modification of the present invention. 21... Heat radiation support plate, 22a, 22b, 22c
...Lead, 23 ...Transistor chip, 24
a, 24b...internal lead, 25...protective layer, 2
8... Notch, 29... Upper mold, 29a... Pin, 29b... Protrusion, 30... Lower mold, 31
... injection hole, 32 ... void, 32a ... upper space, 32b ... lower space, 37 ... resin coating,
37a... One resin coated part, 37b... Other resin coated part, 38... Groove, 39... Mounting hole, 41
... Main covering part, 42... Covering part near the mounting hole,
43...thin covering part.

Claims (1)

[Scope of Claims] 1. A metal support plate formed to have a heat dissipation function and having a notch or hole near one end, and a semiconductor chip mounted on one main surface of the support plate. , a lead electrically connected to the chip, and an insulating resin coating covering a portion of the support plate, the chip, and the lead, and a resin on one main surface side of the support plate. The resin coating is formed such that the coating portion is thicker than the resin coating portion on the other main surface side, and the resin coating is formed such that a mounting notch or hole is formed in the notch or hole. In the method for manufacturing a resin-sealed semiconductor device, the resin coating portion on the one main surface side is formed on a thick main coating portion that covers the chip and a region on one end side of the support plate, and The main covering portion includes a one end region covering portion formed thinner than the main covering portion, and a thin covering portion formed thinner than the one end region covering portion and disposed adjacent to the one end side region covering portion. and a protruding portion for forming the thin covering portion is provided so as to suppress the progress of the sealing resin injected from the injection hole arranged near one end of the support plate. A resin-sealed semiconductor device characterized in that the resin coating is molded by using a sealing mold and injecting the sealing resin into the molding space of the resin-sealing mold from the injection hole. Production method.