JPH04111454A - Semiconductor device and resin molding device thereof - Google Patents

Abstract

PURPOSE:To eliminate the need for forming an air vent in the metal mold of a resin molding device and to prevent the generation of a void in a molding resin by a method wherein a plurality of fine through holes penetrating the surface and rear of a heat dissipation plate are perforated in the resin molding part of the plate. CONSTITUTION:Since a resin b injected via a gate 10 advances in the interior of a cavity 11 in such a way as to cover the upper part of a heat dissipation plate 1a, the air, which is pressed by the intrusion of this resin B, in the cavity 11 is expelled in a venting hole 4a in a bottom force 4 through a multitude of through holes 1c in the plate 1a and is exhausted to the outside. Accordingly, the resin B is filled in this cavity 11 while expelling the air to the outside like a conventional case where an air vent is formed and a void can be reliably prevented from being generated in the molding resin. Moreover, as a new resin is used in these holes 1c each time a resin molding work is performed, a cleaning work for removing a sticked resin becomes unnecessary unlike the conventional method where the air vent is formed.

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Application Field] The present invention relates to a semiconductor device such as a power transistor and a resin molding apparatus for resin molding the semiconductor device.

[Conventional technology]

As shown in FIG.
This lead frame l is sandwiched between a lower mold 4 and an upper mold 5 so that the lead frame a is located in the cavity 11. However, since the illustrated semiconductor device is of a type in which the back surface of the heat sink 1a to which the semiconductor pellet 2 is bonded is exposed to the back surface of the molded resin, the heat sink 1a is placed under the bottom surface of the cavity 11. It is in close contact with the mold 4. Then, when the mold 4.5 is heated and the resin tablet A is loaded into the pot 6 and pressed by the plunger 7, the heated and pressurized and fluidized resin passes through the runner 9 and enters the cavity 10 from the gate 10. Injected. Then, the injected resin covers the heat sink la of the lead frame 1, and is cured in the cavity 11 by heat from the molds 4 and 5, thereby performing resin molding.

Here, when injecting the resin into the cavity 11 as described above, it is necessary to release the air inside the cavity 11 to the outside. For this reason, conventionally, as shown in FIG. 6, an air vent is provided between the lower mold 4 and the upper mold 5 to communicate with the outside! 2, and the air vent 12 is placed at a position where the leads 1b of the lead frame 1 are sandwiched between the lower mold 4 and the upper mold 5, so that air can be evacuated from here when the resin is injected. I was trying to make it come out. The air vent 12 is made by polishing the lower mold 4 or the upper mold 5.
It is an extremely narrow air passage with grooves having a depth of approximately 100 μm. However, during resin molding, some of the resin that fills the cavity will also enter the air pen (12), and if this is left as is, the air will be removed during the next resin molding. The road will be blocked. When the air cannot escape from the air vent 12 in this way, the air that is compressed within the cavity 11 and has no place to escape becomes bubbles in the hardened mold resin and remains, creating voids. If such voids are exposed on the surface of the molding resin, they will cause a poor appearance of the semiconductor device, and if they occur inside, they will reduce moisture resistance and thermal conductivity, leading to a shortened lifespan. Therefore, in the past, the surface of the air vent 12 portion of the mold 4.5 was formed into a matte finish so that an air layer was formed between the resin that had entered the air vent 12 and the hardened resin. By making the resin easy to peel off and by applying surface treatment to the leads 1b of the lead frame 1 so that the resin can be easily absorbed,
When taking out the lead frame l molded with resin, the resin inside the air vent 12 can be peeled off together with the mold resin.

[Problem to be solved by the invention]

However, even with such resin molded '#R tatami mats, as the resin molding work is repeated, resin will gradually adhere to the inside of the air vent 12, and eventually this resin will become stuck and block the air vent) 12. . For this reason, in the past, even when measures were taken to prevent resin from adhering to the inside of the air vent 12 as described above, if the resin molding work was repeated several times, the operator would use a brush to remove the inside of the air vent 12. It was necessary to perform cleaning work to scrape off the resin stuck inside and remove it with air blow.

For this reason, conventionally, when molding a semiconductor device with resin, cleaning the air vent 12 becomes a hassle and reduces work efficiency.Furthermore, if the cleaning work is insufficient, the semiconductor device may have an appearance defect. Problems have arisen in that moisture resistance and thermal conductivity are reduced.

[Means to solve the problem]

In order to solve the above problem, in a semiconductor device in which the back side of a heat sink on which a semiconductor pellet is mounted is exposed and the main part including the semiconductor pellet is molded with resin, the resin molded part of the heat sink has a microscopic structure that penetrates the front and back surfaces. Provided is a semiconductor device characterized by having a plurality of through holes,
In addition, as an apparatus for manufacturing this semiconductor device, a mold cavity facing the above-mentioned through-holes is used to mount the semiconductor pellets and accommodate the semiconductor pellets with the back surface of a heat sink having fine through-holes drilled in the area where the resin mold is to be made. To provide a resin molding device characterized in that a portion thereof is provided with a ventilation hole communicating with the outside.

[For production]

According to the present invention, during resin molding, the area to be resin molded (
The resin injected into the cavity is filled while expelling air from the through holes of the heat sink. [Example] Hereinafter, examples of the present invention will be described in detail with reference to the drawings.

1 to 4 show an embodiment of the present invention, in which FIG. 1 is a perspective view of a semiconductor device, FIG. 2 is a vertical cross-sectional view of the semiconductor device, and FIG. I is a vertical cross-sectional view of the resin molding device, and FIG. 4 is a partially enlarged vertical cross-sectional view of the inside of the cavity in the resin molding device.

Note that the same numbers are added to the structural members having the same functions as those of the conventional example shown in FIGS. 6 and 7.

As shown in FIGS. 1 and 2, the power semiconductor device of this embodiment has a heat sink la connected to a lead frame l.
A semiconductor pellet 2 is bonded on top 1, and a heat sink 1a is attached.
The main part including the semiconductor pellet 2 is molded with a mold tree N3 with the back surface exposed. A large number of fine through holes IC are formed in this heat sink 1a from the top surface to the back surface. The through hole IC is narrowed by the mold resin 3 entering from the upper surface side and hardening inside.

As shown in FIG. 3, the resin molding apparatus for resin molding the semiconductor device is comprised of a lower mold 4 and an upper mold 5. A cylindrical bot 6 is formed in the upper mold 5, into which a plunger 7 is fitted so that it can slide up and down.

Further, a recessed cull 8 is formed at a position corresponding to the bot 6 in the lower mold 4. When the lower mold 4 and the upper mold 5 are overlapped, a plurality of passage-like runners 9 communicating with the bot 6 and the cull 8 are formed between them. Further, between the molds 4.5, a large number of cavities 11 are formed to serve as molds for the mold resin 3 in the semiconductor device, and each cavity 11 is connected to one of the runners 9 via a cage 10. It has become so. A vent hole 4a communicating with the outside is formed in the lower mold 4 constituting the bottom surface of the cavity 11.

The lead frame 1 in the semiconductor device is sandwiched between the lower mold 4 and the upper mold 5 during resin molding, and the heat dissipation plate 1a is positioned within the cavity 11. Further, the second heat dissipating plate 1a is configured such that its back surface is fitted onto the lower mold 4 forming the bottom surface of the cavity 11. Therefore, the ventilation holes 4a formed in the lower mold 4 are narrowed by the back surface of the heat sink 1a, and communicate with the cavity 11 through the numerous through holes C of the heat sink 1a.

In the resin molding apparatus having the above configuration, first, the lower mold 4 and the upper mold 5 are stacked with the lead frame l sandwiched therebetween.

Then, when the molds 4 and 5 are heated and the resin tablet A is loaded into the bot 6 and pressed with the plunger 7, the heated and pressurized resin becomes fi activated and passes through the runner 9. is injected into each cavity. Then, this injected resin fills the cavity 11,
It is cured by heat from the mold 4.5. At this time, game)
As shown in FIG. 4, the resin B injected through the resin B advances through the cavity 11 so as to cover the heat sink la, so that the cavity 1 is compressed by the intrusion of the resin B.
The air in the heat dissipation plate 1a is drawn out through the numerous through holes 1c of the heat sink 1a to the ventilation holes 4a of the lower mold 40 and is discharged to the outside. Therefore, the resin B is filled into the cavity 11 while expelling air to the outside, as in the case where a conventional air vent is formed. However, since this through hole 1c is located at a different position from the conventional air vent provided between the molds 4.5, when the injected resin B reaches the frontage of this through hole 1c, In some cases, it may be necessary to change the shape of the gate 10, the angle of each surface in the cavity 11, etc. so that the resin B is also filled with the resin B. In addition, since the resin B is pressurized for a while even after filling the cavity 11, the through hole 1c
It will also invade. However, when the resin B enters the minute through-holes 1c, it is rapidly heated and hardened by the heat from the molds 4 and 5, so the through-holes 1c immediately cool and even reach the back side of the heat sink 1a. There is almost no possibility that resin B will flow out.

When the resin B filled in each cavity 11 as described above is cured by the heat of the molds 4 and 5, it becomes the mold resin 3 in the semiconductor device. Then, the upper mold 5 is lifted and knocked out. The lead frame 1 is taken out using a bin and the tips of the leads lb are cut off to complete the semiconductor device.

As a result, according to this embodiment, the large number of through holes 1c of the heat sink 1a that communicate with the ventilation holes 4a of the lower mold 4 are used instead of the conventional air vents to prevent air in the cavity 11 when resin B is injected. As a result, it is possible to reliably prevent the generation of voids in the mold resin 3 formed within the cono cavity 11. Moreover, this through hole 1c allows new mold resin to be removed each time the resin mold is worked. This eliminates the need for cleaning work to remove stuck-on resin, which is required for conventional air vents.

In addition, in the above embodiment, the resin B that entered the through hole 1c was cured in the middle of this through hole IC, but
Depending on the conditions, this resin B may not be cured in time and a portion may leak out onto the back surface of the heat sink l&. Therefore, when there is such a possibility, as shown in FIG. 5, a recess 1d is provided on the back surface of the heat sink la, and all through holes IC are formed in this recess 1d to prevent leakage. The resin B can be stopped in this recess 1d. Therefore, the resin B will not protrude from the back surface of the heat sink 1a, so the resin B will be used as a lever in the later process.
There is no need to add additional work to remove it.

〔Effect of the invention〕

As is clear from the above description, the present invention allows the air in the cavity to be extracted to the outside through the through hole provided in the heat sink of the lead frame and through the ventilation hole in the lower mold during resin molding. As a result, it is possible to prevent voids from forming in the molding resin, which has the effect of preventing appearance defects in semiconductor devices and deterioration of moisture resistance and thermal conductivity. play. Furthermore, since it is not necessary to form an air vent in the mold of the resin molding device, there is an effect that cleaning work for scraping off the resin that is 1 inch thick from the second air vent ζ is unnecessary.

[Brief explanation of the drawing]

1 to 4 show an embodiment of the present invention, in which FIG. 1 is a perspective view of a semiconductor device, FIG. 2 is a vertical sectional view of the semiconductor device, and FIG. 3 is a resin mold. longitudinal cross-sectional view of the device;
′! Figure s4 is a partially enlarged vertical cross-sectional view of the inside of the cavity in the resin molding device, and Figure 5 is a vertical cross-sectional view of the semiconductor device, and Figures 6 and 7 are views showing another embodiment of the present invention.
The figures show a conventional example, in which FIG. 5 is a longitudinal cross-sectional view of a resin molding device, and FIG. 6 is a partially enlarged vertical cross-sectional view of the inside of a cavity in the resin molding device. l...Lead frame, 1a...Radiation plate, 1c...Through hole, 3...Mold resin, 4...Lower mold, 4a...Vent hole, 11...Cavity. Figure 1 patent application Ningen Nishinippon Electric Co., Ltd. Figure 3 Figure 4 Figure 5

Claims (2)

[Claims] (1) In a semiconductor device in which the back side of a heat sink on which a semiconductor pellet is mounted is exposed and the main part including the semiconductor pellet is molded in resin, a plurality of fine through holes are drilled through the front and back surfaces of the resin molded part of the heat sink. A semiconductor device characterized by: (2) Ventilation holes communicating with the outside in the part facing the through-holes of the mold cavity, which accommodates the semiconductor pellets in close contact with the back side of a heat dissipation plate with fine through-holes drilled in the area where the resin molding is planned. A resin molding device characterized by being provided with.