JPH0458181B2 - - Google Patents

Abstract

PURPOSE:To reduce the manufacturing cost of a resin-sealed semiconductor device by forming a remaining part not covered with a semiconductor chip in a resin coating of thermoplastic resin to reduce wasteful resin. CONSTITUTION:First external leads 4a are supported by a mold 16, a support 2 of opposite side to its leading side is supported, thermoset resin of fluidized state is pressed by pressure in the mold to be solidified to form a section 11a covered with the semiconductor chip 7 of a resin coating 11. The remaining section 11a not covered with the chip 7 of the coating 11 is formed by pouring thermoplastic resin in the molding cavity of the same as or another mold from the mold 16. Even if the thermoplastic resin remains in the mold, it is placed in the heating state of the level allowed in resin sealing to be used as next sealing resin, thereby eliminating wasteful resin.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a method for manufacturing a resin-molded transistor or a similar resin-sealed semiconductor device.

[Conventional technology and its problems]

It is known that the back surface of a chip support plate (heat sink) of a resin-molded transistor is coated with resin without being exposed. By the way, when the lead frame is disposed in a cantilevered state in a cavity (molding space) in a mold, the position of the chip support plate changes when resin is injected into the cavity. To prevent this, in addition to supporting the external leads led out from the chip support plate by the mold, attempts have been made to support a part of the support plate or an extension thereof on the side opposite to the leads. . If the chip support plate is supported at a plurality of locations in this way, the chip support plate can be stably positioned within the cavity, but a problem arises in that the portion supported by the mold is not coated with resin.

To solve this problem, we molded the main part, including the semiconductor chip, with the chip support plate supported at multiple locations by a mold that was partially slidable, and then slid part of the mold. Japanese Patent Laid-Open No. 61-2348 discloses a method in which the parts that were not covered in the first molding process are covered in the second molding process by separating the parts from the support plate. According to the above method, the support plate can be coated in such a manner that substantially no exposed portions are formed. However, in the method disclosed in this publication, both the first molding and the second molding are performed using thermosetting epoxy resin. Although thermosetting epoxy resins have excellent performance as sealing resins, they have the drawbacks of being expensive and difficult to handle. In other words, when a fluid thermosetting resin is injected into the cavity through the runner (resin passage) and gate (injection hole) provided in the mold and solidified, the resin remaining in the runner and gate is could no longer be reused and was wasted, which inevitably led to higher material costs. Due to the strict requirement to reduce the cost of semiconductor devices,
The resin remaining on the runner and gate cannot be ignored.

SUMMARY OF THE INVENTION Therefore, an object of the present invention is to provide a method for manufacturing a resin-sealed semiconductor device that can reduce costs.

[Means for solving problems]

To solve the above problems and achieve the above objects, the present invention will be described with reference to the reference numerals in the drawings showing the embodiments. An external lead 4a, second external leads 4b and 4c extending in the same direction as the first external lead 4a, a semiconductor chip 7 fixed to the support plate 2, and a semiconductor chip 7 and the second external lead 4a. The internal leads 8 and 9 connecting the second external leads 4b and 4c, and at least a portion of the first and second external leads 4a, 4b, 4c are exposed. and a resin coating 11 that covers the internal leads 8 and 9 so as not to substantially expose them, wherein the first external lead 4a is supported by a mold 16. At the same time, a part of the support plate 2 on the side opposite to the lead-out side of the first external lead 4a is supported, and the fluidized thermosetting resin is pushed into the mold by applying pressure. to form a portion 11a of the resin coating 11 that covers at least the semiconductor chip 7;
After or before the formation of the remaining portion 11 of the resin coating 11 that does not cover the semiconductor chip 7,
The present invention relates to a method for manufacturing a resin-sealed semiconductor device, characterized in that b is formed by injecting a thermoplastic resin into a molding cavity of the same or different mold 16.

[Effect]

In the present invention, the chip-covered portion 11a of the resin coating 11 is made of thermosetting resin, while the chip-uncovered portion 11b is made of thermoplastic resin.
Therefore, even if the thermoplastic resin remains in the mold when forming the chip non-coated portion 11b, by heating it to a level that is permissible for resin sealing, the next sealing resin can be applied. This makes it possible to use the resin as a resin, and there is no waste of resin. This saves material and eliminates the need to remove resin remaining in the mold.

〔Example〕

Next, a method for manufacturing a resin-sealed transistor according to an embodiment of the present invention will be explained based on FIGS. 1 to 10. FIG. 1 shows the transistor after resin molding is completed. The transistor shown in FIG. 1 is obtained by sealing the lead frame 1 shown in FIG. 2 with resin. Lead frame 1 has mounting hole 3
A metal heat dissipation support plate 2 having a
the first external lead 4a connected to the support plate 2, the two second external leads 4b, 4c not directly connected to the support plate 2, and the external leads 4a, 4b, 4.
It consists of a strip 5 called a tie bar that interconnects the intermediate portions of the leads 4a, 4c, and a strip 6 that commonly connects the ends of the external leads 4a, 4b, and 4c. A semiconductor chip 7 is fixed to the support plate 2 by solder.
The emitter electrode and base electrode of the semiconductor chip 7 and the external leads 4b, 4c are connected by internal leads 8, 9, respectively, and the semiconductor chip 7 is covered with a protective resin 10. Although not shown, a plurality of support plates 2 are provided on the same lead frame 1.

The resin covering 11 shown in FIG. 1 covers the support plate 2, the semiconductor chip 7, the tips of the external leads 4a, 4b, 4c, and the internal leads 8, 9 so as not to expose them. This resin coating 11 is not made of a single resin, but is made of a thermosetting resin, and includes a first portion 11a that covers the semiconductor chip 7, and a thermoplastic resin, and a tip portion of the support plate 2. and a second portion 11b covering the first portion 11a.

In order to form the resin coating 11, a lead frame 1 to which a semiconductor chip 7 is fixed as shown in FIG.
In addition to preparing the lower mold 12, upper mold 13, first and second slide molds 14, as shown in FIG.
A molding die 16 consisting of 15 is prepared. The lower mold 12 and the upper mold 13 are formed so as to be separable, and one is a fixed mold and the other is a movable mold. The first and second slide molds 14 and 15 are formed to be able to slide vertically in through holes 17 and 18 provided in the lower mold 12 and the upper mold 13, respectively. A first cavity 19 is created by the combination of the lower mold 12 having a recess 19a on the upper surface, the upper mold 13 having a recess 19b on the lower surface, and the first and second slide molds 14 and 15. The upper mold 13 has a cylindrical part 20 for insertion into the mounting hole 3 of the support plate 2. The lower mold 12 includes a runner 21 to which the thermosetting resin is sent, and this runner 21.
It has a hole or gate 22 through which resin is injected into the cavity 19. The runner 21 and the gate 22 are connected to the lower mold 12 and the upper mold 13 so that the thermosetting resin remaining there can be removed.
It is established on the border of

The upper mold 13 has a thermoplastic resin runner 23 or resin passage and a gate 24 or injection hole communicating with the runner 23. In addition, runner 2
A heater 25 for heating the resin is disposed within the housing 3 .

When forming the first portion 11a of the resin coating 11, the first and second slide molds 14 and 15 are used to form a thermoplastic resin gate 24 as shown in FIG.
is closed, but the thermosetting resin gate 22 is not closed. First and second slide molds 1
4 and 15 are the recesses 2 as most clearly seen in FIG.
It has 6,27. A recess 26 in the first slide mold 14 is provided at the center of the upper surface, resulting in a pair of legs 28 and 29.
The recess 27 in the second slide mold 15 is provided at the center of this lower surface, resulting in a pair of legs 30, 31. Note that a step 32 for holding the support plate 2 is provided in the recess 27 of the second slide mold 15.

The attachment of the lead frame 1 to the mold 16 is as follows:
This is done as shown in FIGS. 3 and 4. That is, the support plate 2 is placed inside the cavity 19, and the external lead 4 is placed inside the cavity 19.
a, 4b, and 4c are held between a lower mold 12 and an upper mold 13. Further, as shown in FIG. 4, the tip portion of the support plate 2 is held between the upper surface of the first slide mold 14 and the stepped portion 32 in the recess 27 of the second slide mold 15. As a result, the support plate 2
It is supported by the mold 16 at a total of three locations: a and both sides of the tip of the support plate 2, and is extremely stably positioned within the cavity 19. As a result, it is possible to accurately provide an extremely narrow gap between the support plate 2 and the lower mold 12, and it is possible to form a thin resin there. It is important to form a thin layer of resin on the lower surface of the support plate 2 in order to improve the heat dissipation effect. After the lead frame 1 is placed in the cavity 19, the lower mold 12 and the upper mold 13 are clamped, and the first and second slide molds 14 and 15 are clamped.

Next, a fluidized thermosetting resin made of, for example, epoxy resin is filled into the cavity 19 through the liner 21 and the gate 22 by applying pressure, and is heated in the mold 16 for several minutes to solidify. That is, the first portion 11a of the resin coating 11 is formed as shown in FIGS. 6 and 7 by a transfer molding method. Note that by heating the mold 16 in advance to the curing temperature of the thermosetting resin (150° C. to 180° C.), the resin injected into the cavity 19 solidifies in 2 to 3 minutes. In this process, the thermoplastic resin gate 24 is closed by the second slide mold 15, so even if thermoplastic resin exists in the runner 23, it does not flow into the cavity 19. Resin coating 1
As is clear from FIGS. 6 and 7, the first portion 11a of the support plate 2 includes most of the support plate 2 except for the tip, the semiconductor chip 7, the protective resin 10, the internal leads 8, 9, the external leads 4a, The tips of 4b and 4c are covered. However, the tip portion 2 of the support plate 2 that was in contact with the first and second slide molds 14 and 15
a is not covered with the first portion 11a of the resin coating 11 and is exposed. Therefore, the exposed tip portion 2a of this support plate 2 is coated with thermoplastic resin in the next step.

In the molding process using thermoplastic resin,
The mold 16 is brought into the state shown in FIGS. 8 and 9.
That is, the first and second slide molds 14 and 15 are slid outward as shown in FIGS. 8 and 9. As a result, the second cavity 3 is placed in the moved portions of the first and second slide molds 14 and 15.
3 is generated, and a resin runner 23 is connected to this second cavity 33 via a thermoplastic resin gate 24. First and second slide molds 14, 1
5 is separated from the support plate 2, the first part 11a made of the thermosetting resin coating is already fixed, so the support plate 2 is connected to the lower mold 12 via the first part 11a. It is stably supported by the upper mold 13.

Next, as shown in FIG. 10, a thermoplastic resin 34 made of, for example, polybutylene terephthalate resin is heated with a heater 25 to make it active, and then pressure is applied to the second cavity 33 from the gate 24. and fill it. Since the temperatures of the lower mold 12 and the upper mold 13 are lower than the softening temperature (solidification temperature) of the thermoplastic resin, the thermoplastic resin injected into the second cavity 33 solidifies, and the second mold of the resin coating 11 This becomes part 11b. That is, in this step, the second portion 11b made of thermoplastic resin is formed by an in-die extension molding method.

Next, the lower mold 12 and the upper mold 13 are unfastened, and the molded body is taken out from the mold 16. FIG. 1 shows a molded body, and the support plate 2, semiconductor chip 7, internal leads 8, 9, and tip portions of external leads 4a, 4b, 4c in the lead frame 1 shown in FIG. 2 are resin-coated bodies. 11. That is, the first portion 11a shown in FIG.
In the state where only the support plate 2 is provided, the tip 2a of the support plate 2
was exposed to some extent, but the exposed tip portion 2a is covered by the second portion 11b. The thermoplastic resin constituting the second portion 11b is inferior to the thermosetting resin in terms of moisture resistance, adhesive strength, etc., but the tip 2a of the support plate 2 is sufficiently far away from the semiconductor chip 7.
Therefore, the electrical characteristics of the resin-sealed transistor are not substantially deteriorated. Note that the cylindrical portion 20 of the upper mold 13 is attached to the resin coating 11.
A corresponding mounting hole 35 is formed, but the support plate 2 is not exposed in this mounting hole 35.

Finally, the strips 5 and 6 of the lead frame 1 shown in FIG.
Obtain b and 4c to complete the transistor.

This embodiment has the following advantages.

(1) Since the second portion 11b of the resin coating 11 is made of thermoplastic resin instead of thermosetting resin, the resin remaining in the runner 23 can be used as the next injection resin without being thrown away. Therefore, materials can be saved. Further, since the resin of the runner 23 can be used continuously, there is no need to remove the remaining resin.

(2) The second slide mold 15 not only contributes to the formation of the second cavity 33 for obtaining the second portion 11b of the resin coating 11, but also controls the injection of the thermoplastic resin 34. Also, the first portion 11a made of thermosetting resin and the second portion 11b made of thermoplastic resin can be formed with a relatively simple structure.

(3) Since both the gate 22 for the thermosetting resin and the gate 24 for the thermoplastic resin are arranged on the tip side of the support plate 2, the mold 16 can be made smaller. That is, in the mold disclosed in Japanese Patent Application Laid-Open No. 61-2348, the first gate is provided on the external lead side and the second gate is provided on the tip side of the support plate. However, in this embodiment, since the two gates 22 and 24 are arranged on the tip side of the support plate 2, the size is reduced by one gate. The miniaturization of unit molding parts in this way means that when molding a large number of transistors using a common mold, it is possible to simultaneously mold more transistors using a common mold than before. It means that you can.

[Modified example]

The present invention is not limited to the above-described embodiments, but can be modified, for example, as follows.

(1) As shown in FIG. 11, a through hole 36 is provided in the portion 2a of the support plate 2 covered with the second portion 11b made of thermoplastic resin, or a notch 37 is provided as shown in FIG. The adhesive strength between the thermoplastic resin and the support plate 2 may be increased.

(2) Instead of making the thickness of the support plate 2 uniform, the bonding area of the semiconductor chip 7 may be made thicker and the tip area may be made thinner.

(3) A thermoplastic resin runner 34 may be provided in the lower mold 12.

(4) Although both ends of the tip of the support plate 2 are clamped by the first and second slide molds 14 and 15, they may be clamped at one, three or more positions.

(5) Connect the gate 22 to the external lead 4 using thermosetting resin.
It may be moved to the a, 4b, and 4c sides.

(6) It can also be applied to the manufacture of diodes, thyristors, etc.

(7) Slide the lower mold 12 and upper mold 13 into mold 1
The lower mold and the upper mold may be constructed by combining the four molds by dividing the mold into left and right parts at the portions in contact with the molds 4 and 15.

(8) After forming the first portion 11a, it may be removed from the mold and the second portion 11b may be formed using another mold.

〔Effect of the invention〕

As is clear from the above, according to the present invention, since a part of the resin coating is made of thermoplastic resin, less resin is wasted, and manufacturing costs can be reduced.

[Brief explanation of the drawing]

Fig. 1 is a perspective view showing a transistor sealed with resin according to an embodiment of the present invention, Fig. 2 is a perspective view showing a lead frame of the transistor shown in Fig. 1 after a chip is attached, and Fig. 3 is a resin coating. 4 is a cross-sectional view of the mold with a lead frame attached to it to form a mold, FIG. 5 is a cross-sectional view taken along the line -- in FIG. FIG. 6 is a cross-sectional view showing the mold after thermosetting resin is injected into the first cavity, and FIG. 7 is a perspective view of the transistor provided with the first portion of the resin coating. A perspective view showing a part, FIG. 8 is a sectional view showing the mold with the second cavity provided, and FIG.
10 is a sectional view showing a state in which thermoplastic resin is injected into the second cavity,
FIGS. 11 and 12 are plan views showing modified examples of the support plate, respectively. 1...Lead frame, 2...Support plate, 4a,
4b, 4c...External lead, 7...Semiconductor chip, 8, 9...Internal lead, 11...Resin coating, 11a...First part, 11b...Second part, 12...Bottom metal Mold, 13... Upper mold, 14...
First slide mold, 15... Second slide mold, 19... First cavity, 21... Runner, 22... Gate, 23... Runner, 24...
Gate.

Claims (1)

[Scope of Claims] 1. A support plate 2, a first external lead 4a directly connected to the support plate 2, and a second external lead 4b extending in the same direction as the first external lead 4a. , 4c, a semiconductor chip 7 fixed to the support plate 2, and internal leads 8, which connect the semiconductor chip 7 and the second external leads 4b, 4c.
9, and the first and second external leads 4a, 4
A resin-sealed type comprising a resin coating 11 that exposes at least a portion of the semiconductor chip 7 and the internal leads 8 and 9, but covers the support plate 2, the semiconductor chip 7, and the internal leads 8 and 9 so as not to substantially expose them. In the method for manufacturing a semiconductor device, the first external lead 4a is supported by a mold 16, and a part of the support plate 2 on the side opposite to the lead-out side of the first external lead 4a is supported. Pressing a fluidized thermosetting resin into the mold and solidifying it within the mold to form a portion 11a of the resin coating 11 that covers at least the semiconductor chip 7; After or before forming the portion 11a that covers the semiconductor chip 7, the remaining portion 11b of the resin coating 11 that does not cover the semiconductor chip 7 is formed.
A method for manufacturing a resin-sealed semiconductor device, characterized in that: is formed by injecting a thermoplastic resin into a molding cavity of the same or different mold 16.