JPH041502B2 - - Google Patents

Description

[Detailed Description of the Invention] [Technical Field of the Invention] The present invention relates to an envelope structure of a semiconductor element for low power use such as a transistor or a thyristor, and in particular has a heat sink and a space between the semiconductor element and the heat sink. This invention relates to an insulated envelope for a medium to low power semiconductor device.

[Technical background of the invention]

A power semiconductor device has a structure in which a support substrate for a semiconductor element also serves as a heat sink in order to facilitate dissipation of heat generated during operation. In order to improve heat conduction, the semiconductor element is not insulated from the supporting substrate.
The support substrate is at the same potential as one electrode of the semiconductor element. FIG. 1 is a longitudinal sectional view of a conventional semiconductor device for explaining this. The outer lead 1 of the lead frame is obtained by press working using a deformed member that is integral with the heat sink 11. There is a step between the outer lead 1 and the heat sink 11, and the heat sink 11 also serves as a support substrate for the semiconductor element 3. The semiconductor element 3 is fixed to the heat sink 11 by soldering 2. 4 is a bonding wire, and 5 is a molding resin. As shown in FIG. 1 of the conventional example, the semiconductor element 3 and the heat sink 11 are bonded with solder and are not insulated. Therefore, the heat sink 11 is at the same potential as one electrode of the semiconductor element 3. When the semiconductor device is put into practical use, the heat dissipation of the heat sink 11 alone is insufficient, and it is usually used by attaching it to another external heat sink or heat sink. Therefore, when the semiconductor device is used as a component of an electronic circuit, the heat sink 11 needs to be insulated from the external mounting plate 7. Actually the first
As shown in the figure, insulation is provided by using an insulating sheet 6 between the mounting plate 7 and the heat sink 11, and an insulating washer 61 between the mounting screws and the heat sink 11. Recently, there are also insulated resin-sealed semiconductor devices in which parts corresponding to the insulating sheet 6 and the insulating washer 61 are made of resin 5, but in both cases, one package per semiconductor element is used, and in the hybrid type, do not have.

[Problems with background technology]

As mentioned above, when mounting a conventional semiconductor device, insulation from the mounting plate 7 is obtained using the insulating sheet 6 and the insulating washer 61. always determines the quality of heat dissipation. Usually, the insulating sheet 6 is made of mica and coated with silicone grease to prevent a decrease in heat dissipation due to uneven adhesion.
Further, the insulating washer 61 is inserted into the mounting hole and secured with a screw, but the tightening torque at this time is also limited so as to maintain insulation. Therefore, considerable care is required for installation, which has the drawback of poor installation workability. Particularly when a plurality of semiconductor devices are used in parallel, this becomes a very difficult task and is a problem.

Next, in the conventional semiconductor device, since the lead frame is integrated with the heat sink 11, a lead frame corresponding to the power consumption of the semiconductor element is required, and copper-based material must be used. Therefore, the semiconductor device is also heavy and expensive. Note that in lead frames such as power ICs, the mounting part of the semiconductor pellet and the heat sink are at the same potential.
Since it is necessary to insulate the inner lead and the heat sink, there is a method of providing insulation by interposing a molded resin. In this case, there is a drawback that the inner leads sag due to the molding pressure during molding, resulting in an electrical short circuit phenomenon.

[Purpose of the invention]

In conventional semiconductor devices, the lead frame and the heat sink are integrated, and the semiconductor element and the heat sink are not electrically insulated, so the above-mentioned problem exists. SUMMARY OF THE INVENTION An object of the present invention is to provide a semiconductor device in which a semiconductor element and a heat sink are insulated and the mounting workability is improved.

[Summary of the invention]

FIG. 2 shows an example of a semiconductor device according to the present invention, which corresponds to the conventional example shown in FIG. Note that the same parts will be denoted by the same reference numerals in the subsequent figures. An insulating substrate is used, in which a copper foil is attached to an aluminum plate or a copper plate using an insulating adhesive 12, such as an epoxy insulator, and the copper foil has an area 13 for mounting at least one semiconductor element. The pattern is formed by etching. After that, an insulating heat sink 1 having a desired external shape is formed by press working.
1' is obtained. On the other hand, using copper-based or iron-based materials,
A lead frame provided with a chip mount land 16 for mounting at least one semiconductor element is formed by etching or pressing, and bent so that the outer lead 1 of the lead frame and the chip mount land 16 have a step. Next, the chip mount land 16 is bonded to the area 13 by soldering 2' so that the area 13 of the copper foil surface of the heat sink and the chip mount land 16 of the lead frame overlap, and the insulated lead frame with the heat sink is attached. obtain. The semiconductor element 3 is fixed to the chip mount land 16 of this lead frame by soldering 2 or the like. Furthermore, bonding wire 4
The bonding pads on the semiconductor element and the bonding pads on the lead frame are connected using a wire. By sealing the resin 5 by molding or the like, an insulated semiconductor device with a resin-sealed heat sink is obtained. As shown in FIG. 2, the heat sink 11' is insulated from the semiconductor element 3 by an insulating layer 12.
The insulating sheet 6 and insulating washer 61 are not required for mounting the mounting plate 7. As described above, the present invention is characterized by the combination structure of a heat sink having a copper foil surface and a lead frame with an insulating film having high thermal conductivity interposed on the heat sink.

[Embodiments of the invention]

FIG. 3 shows an external view of a Darlington transistor array semiconductor element device as an embodiment of the present invention. Figure a is a plan view, and figure b is a front view. FIG. 4 is a diagram of the internal structure of the semiconductor element device, and is shown with the molding resin removed for the purpose of explanation. FIG. 5 shows an electrical wiring diagram of the semiconductor device.
FIG. 6 shows an insulated heat sink with a pattern formed thereon. Figure a is a plan view, figure b is a right side view, figure c is a sectional view taken along line A-A', figure d is a front view, and figure e is a bottom view. Figure 7 is a layout diagram of the heat sink, Figure 8
The figure shows a lead frame, and figure a is a plan view of a series on which four Darlington transistor elements can be mounted. Figure b is a partial sectional view taken along line B-B'. The manufacturing process of the insulated heat sink shown in FIG. 6 is as follows. As a base material, for example, a HITT plate (trade name of Denka Co., Ltd.), which is a 2 mm thick aluminum plate with copper foil (35 μm) pasted using an insulating adhesive having high thermal conductivity, is used. FIG. 7 is a layout diagram of the heat sink. As shown in the figure, a resist pattern of area 13 for mounting a semiconductor element is placed on the copper foil side of the HITT plate, and area 13 is left by etching. Remove other copper foil and insulating layer 1
Expose 2. Next, two guide holes 15 are made for each heat sink to form the external shape of the heat sink and the mounting holes 8 by pressing. After that, it is cut into strips by shearing process, and the outer shape is cut by press process. Furthermore, in order to improve the adhesion between the heat sink and the molded resin and ensure moisture resistance, both or one side of the outer periphery of the heat sink 11' is crushed to form a crushed portion 14.

Next, the lead frame is made of a copper-based material, such as a 0.5 mm thick copper plate made of KFC (product name of Kobe Steel).
As shown in Figure a, it is etched into a shape that allows four elements to be mounted. Figure 8b is B- of Figure 8a.
FIG. 3 is an enlarged view of a stepped portion in a cross section taken along line B'. As shown in the figure, the chip mount land surface is lower than the lead surface.
The lead is bent to lower it by 0.55 mm, and at the same time, a V-groove is formed by press work on the semiconductor element mounting surface of the lead to ensure moisture resistance. Next, the chip mount land 16 is bonded to the area 13 using soldering 2' so that the area 13 of the insulated heat sink (see FIGS. 2 and 6) overlaps the chip mount land 16 of the lead frame. .
The melting point of the solder 2' is preferably 220 to 230°C. Darlington transistor elements 3 are mounted at four locations on the chip mount lands 16 of the lead frame, and diodes 9 are mounted at two locations on the diode mounting pads by soldering 2, respectively. The melting point of solder 2 is lower than that of solder 2', and the sn:pb is 63:37 (183).
°C is fine. Next, the bonding pads on the pellet of the semiconductor element 3 and the diode 9 are electrically connected to the bonding pads on the lead frame using gold wire bonding wire 4, thereby obtaining the electronic circuit shown in FIG. In order to protect the pellet pad and bonding wires, encap resin (RTV silicone rubber) was used to cover the area around the semiconductor element and diode, and then transfer molding was performed with mold resin (epoxy type) as shown in Figure 1. An insulated semiconductor device with a resin-sealed heat sink having a Darlington transistor array as shown in FIG.

In this embodiment, a HITT plate (trade name of Denka Corporation) was used, but it is also possible to use an aluminum insulating substrate manufactured by other manufacturers, or a copper-based material instead of the aluminum plate. In addition, in this embodiment, four semiconductor elements and two diodes are combined into one
Although the present invention is mounted in one package, a structure that fulfills the purpose of the present invention can be obtained even with a single semiconductor element or a single diode. In addition, the pattern on the insulated copper foil substrate is an area 13 that overlaps with the chip mount land 16 of the lead frame in this embodiment, but there are other copper foil patterns on the copper foil substrate, and other semiconductor elements are placed on the pattern. There is no problem even if it is installed.

〔Effect of the invention〕

In the insulated semiconductor device with a resin-sealed heat sink according to the present invention, the semiconductor element and the heat sink are insulated from each other, so there is no need for an insulating sheet or an insulating washer that is always used in conventional semiconductor devices when mounting it on a mounting plate. becomes. In addition, when installing the semiconductor device, conventional methods require careful attention to tightening torque and damage to insulators, resulting in poor installation workability, but the semiconductor device of the present invention is easy to install, and workability has been greatly improved. be done. Furthermore, in conventional semiconductor devices, the lead frame and heat sink are integrated, but in the semiconductor device of the present invention, the lead frame and heat sink are made separately and then bonded together. The base material of the heat sink can be selected according to the power consumption, and there is a degree of freedom in the combination of the heat sink and lead frame.

In addition, in the case of a circuit configuration in which a plurality of semiconductor elements are used side by side, a semiconductor device using the heat sink of the present invention utilizes the copper foil pattern of the heat sink.
The degree of integration of semiconductor elements can be increased, and as a result, the semiconductor device with the circuit configuration can be made smaller. In semiconductor devices that use a heat sink without an insulating layer,
The part where the semiconductor element is mounted and the heat sink have the same potential, and there is a drawback that the inner leads hang down during molding and come into contact with the heat sink, causing an electrical short circuit, but there is no such concern with the semiconductor device of the present invention. .

[Brief explanation of drawings]

FIG. 1 is a longitudinal sectional view of a conventional semiconductor device, FIG. 2 is a longitudinal sectional view of a semiconductor device of the present invention, and FIGS. Figures 4a and b are plan and side views showing the internal structure of the array in Figure 3 with the resin removed, Figure 5 is an electrical wiring diagram of the array in Figure 3, and Figures 6 a to e are the Fig. 7 shows a plan view, side view, sectional view taken along the line A-A', front view, and bottom view of the heat sink of the array; Figure 3: A plan view of each lead frame used in the array, B-
It is a partial sectional view taken along the line B'. 1...Outer lead (lead frame), 2,
2'...Soldering, 3...Semiconductor element, 5...Mold resin, 6...Insulating sheet, 8...Mounting hole, 11, 11'
...heat sink, 12...insulating layer, 13...area, 14...
Crushed part, 16...Chip mount land.

Claims (1)

[Scope of Claims] 1 (a) An insulating substrate formed by interposing an insulator between an aluminum plate or a copper plate and a copper foil is used, and the copper foil has an area for mounting at least one semiconductor element. (b) a copper-based or iron-based lead frame provided with a chip mount land for mounting at least one semiconductor element; (c) a copper foil of the heat sink; (d) using an insulated lead frame with a heat sink formed by bonding a chip mount land of the lead frame so that the chip mount land of the lead frame overlaps with the chip mount land of the lead frame; (d) mounting a semiconductor element on the chip mount land of the lead frame; An insulated semiconductor device with a resin-sealed heat sink, characterized by being bonded and resin-sealed.