JPH0328510Y2 - - Google Patents

Description

[Detailed Description of the Invention] [Technical Field] The present invention relates to an insulator-sealed semiconductor device having a shape and structure suitable for a high-voltage semiconductor device.

"Prior Art" Figures 1 to 5 show an example of a conventional resin-molded power transistor.
The figure shows the state without the molded resin body, Figure 3~
FIG. 5 shows a molded resin body. Figures 1 and 3 are plan views, Figures 2 and 4 are cross-sectional views taken along line A-A in Figures 1 and 3, and Figure 5 is a plan view.
The figure is a front view corresponding to FIG. 3. In FIGS. 1 and 2, the outer shape of the molded resin body is shown by broken lines.

A transistor chip 1 whose back surface serves as a collector electrode is fixed on a heat sink 2, and an external lead 3 serving as a collector lead extends from the heat sink 2. External leads 4 and 5 arranged in parallel with the external lead 3 are a base lead and an emitter lead, respectively, and are connected to the base electrode or emitter electrode on the surface of the transistor chip 1 by internal lead wires 6 and 7, respectively. . The transistor chip 1 is molded (sealed) with a resin body 8, and external leads 3, 4, and 5 are led out from the resin body 8 in parallel on one plane.

The external leads 3, 4, and 5 have wide portions 3a, 4a, and 5a on the side leading out from the resin body 8, and narrow portions 3b, 4b, and 5b on the tip side thereof. The wide portions 3a, 4a, and 5a are for reinforcing the external lead so that it is not easily deformed in the vicinity of the lead-out portion from the resin body 8 even if an external force is applied to the external lead. Wide parts 3a, 4a, 5a
is a shape in which the narrow portions 3b, 4b, 5b extend to both sides of the resin body 8. The narrow portions 3b, 4b, and 5b are portions that are essentially used as connection terminals to the outside, and are made considerably narrower to provide flexibility necessary for lead wires. Portions of the external leads 4 and 5 adjacent to the heat sink 2 serve as terminal portions 4c and 5c for connecting the internal lead wires 6 and 7.

A hole 9 is formed in the heat sink 2, and a mounting hole 10 is formed in a part of the resin body 8 so as to pass through the hole 9. Mounting holes 10 necessary for screwing the power transistor to an external heat sink, etc.
For example, a diameter of 3.1 mm is required.
For this purpose, a resin body 8 formed around the hole 9 is required.
The hole 9 must be formed to have a diameter of 4.1 mm or more so that a has a thickness strong enough to withstand tightening with screws. in this case,
In order to form the holes 9 by mechanical punching as is normally done, the heat sink 2 is required to have considerable strength in the portion where the holes 9 are to be formed. That is,
When the thickness of the heat sink 2 is 0.4 to 1.0 mm, the length from the center of the hole 9 to the upper end of the heat sink 2 (H in FIG. 1) must be 4 mm or more. Also, at the end of the heat sink 2,
Remaining part 1 of the heat sink connection part that was necessary to keep a large number of heat sinks 2 in parallel and integrated during the manufacturing process
1 and 12 are formed as part of the heat sink 2 and protrude from the resin body 8.

By the way, when a high-voltage transistor chip 1 is used, the shortest distance connecting two points to which high voltage is applied along the surface of the resin body 8, the so-called creepage distance, becomes a problem. That is, if the creepage distance is short, when the resin body 8 is used under adverse conditions, a breakdown voltage failure occurs due to the surface of the resin body 8 serving as a current path. Therefore, for products with a withstand voltage of 400V or more, the creepage distance should be set to 2.
It is desirable to take at least mm.

However, in the conventional structure described above, even when the power transistor is screwed to the external heat sink through an insulating sheet on the bottom of the heat sink 2, the power transistor is inserted into the mounting hole 10 on the surface of the resin body 8a around the hole 9. A dielectric strength failure is likely to occur between the external heat sink and the heat sink 2, that is, between the external heat sink and the collector of the power transistor. This problem can be solved by making the resin body 8a thicker and increasing the creepage distance of this part, but this requires increasing the diameter of the hole 9, which increases H in Fig. 1 accordingly. The planar size of the resin body 8 becomes large.

"Objective and Features of the Invention" An object of the present invention is to eliminate the above-mentioned conventional drawbacks and provide an insulator-sealed semiconductor device that can provide a large creepage distance with an external heat sink.

The present invention is an insulator-sealed semiconductor device characterized by the shape of a heat sink and the shape of a molded insulator, as will be described below with reference to embodiments.

Embodiment FIGS. 6 to 10 show a resin-molded power transistor according to an embodiment of the present invention, and correspond to the conventional structures shown in FIGS. 1 to 5, respectively. Therefore, the same parts are given the same reference numerals and their explanations will be omitted. In addition, since all the cross sections including the conventional example have substantially the same location, they are expressed as a cross section along the line A-A in a common manner.

The heat sink 2 is divided into two parts, a thick part 2a and a thin part 2b. A transistor chip 1 is installed in the thick portion 2a.
is fixed. A U-shaped recess 13 is formed in the thin portion 2b. There is a recess 1 in the thin part 2b.
3 has a bent part midway between the bottom and top of the heat sink, and the portion from this bent part to the remaining parts 11 and 12 of the heat sink connecting part is offset upward on the transistor chip 1 side of the thick part 2a of the heat sink. It is being Lead wires 3, 4, formed of a thin plate-like member similar to the thin part of the heat sink.
5 is similarly deviated. A resin body 8 with a thickness of 1 mm is placed on the bottom side of the thick part 2a of the heat sink.
It is formed into a thin plate shape with a diameter of 0.5mm or less (for example, 0.5mm),
This structure eliminates the need to place an insulating sheet on this part when attaching this power transistor to an external heat sink. As a result, the external lead wire 3,
The outer surface of this power transistor is entirely covered with the resin body 8 except for the remaining portions 11 and 12 of the heat sink connecting portions 4 and 5 protruding from the resin body 8.

A mounting hole 10 is formed at the position of the recess 13 of the heat sink so that the recess 13 is penetrated by a part of the resin body 8.
is formed. The mounting hole 10 has a structure in which it is not necessary to fit an external insulating bushing and then tighten it with a screw. Further, in order to reinforce the mounting hole 10, the mounting hole 10 is completely accommodated in the recess 13 when viewed in plan view in FIGS. 6 and 8.

Regarding the external lead 3 located at the center, the wide portion 3a extends to both sides of the portion where the narrow portion 3b extends to the resin body 8. Regarding the external lead 4 located on the upper side, the wide part 4a protrudes only above the part extending the narrow part 4b to the resin body 8 (the side opposite to the side facing the external lead 3), and the external lead 4 The lower surface extends linearly from the resin body 8 to the tip. Therefore, the external lead 4 can be regarded as a linear external lead. The external lead 5 located on the lower side is the same as the external lead 4, except for the difference in top and bottom.

Note that, as shown in the plan view of FIG. 11 corresponding to FIG. 8, the wide parts 3a, 4a, and 5a of the external leads remain as a result of cutting the parts that connected the external leads together during the manufacturing stage. Residual portions 14 of lead connections are often seen. However, the lower surface of the external lead 4 and the upper surface of the external lead 5 remain linear from the resin body 8 to the tip, and the external leads 4 and 5 can be regarded as linear external leads. There is no difference.

Between external leads 3 and 4 and external leads 3 and 5
In between, there is a stepped portion 1 due to a change in the shape of the resin body 8.
5 and 16 are provided. The stepped portions 15 and 16 are formed by providing a recess 17 in the resin body 8, and the external lead 3 is led out from the bottom of the recess 17. The external leads 4 and 5 are led out from both sides of the recess 17, which are relatively convex with respect to the bottom surface of the recess 17. Various methods can be considered for providing the stepped portions 15 and 16, such as turning the recessed portion 17 into a convex portion, but there is a method in which the recessed portion 17 is formed without affecting the external dimensions and strength of the resin body 8. is the most practical.

As described above, according to this embodiment, the following effects can be obtained.

(i) Since the heat sink 2 is not exposed on the inner periphery of the mounting hole 10 or in the vicinity thereof, a breakdown voltage failure due to insufficient creepage distance between the screw inserted into the mounting hole 10 and the heat sink 2 will not occur. .

In this case, the remaining parts 11 and 12 of the heat sink connecting part
The creepage distance between the power transistor and the bottom of the resin body 8 (m in Figure 10) and the creepage distance between the external leads 3, 4, 5 and the bottom of the resin body 8 (n in Figure 10) are the same as those between the power transistor and the external heat sink. This will determine the dielectric strength between. Regarding the creepage distance m,
The remaining parts 11 and 12 of the heat sink connecting part are formed on the thin part 2b of the heat sink, and the remaining parts 11 and 12 of the heat sink connecting part are formed above the transistor chip 1 side with respect to the thick part 2a of the heat sink. Sufficient length is obtained by offsetting it. Regarding creepage distance n, thin external leads 3, 4, 5
A sufficient length is obtained by deviating the remaining portions 11 and 12 of the heat sink connecting portions in the same way as the remaining portions 11 and 12 of the heat sink connecting portion. For example, m and n are set to 2.5 mm.

Therefore, even compared to conventional products in which the resin body 8 is thinly formed on the bottom side of the heat sink 2, it is superior in terms of dielectric strength with respect to an external heat sink.

(ii) By changing the formation location of the mounting hole 10 from the hole 9 of the heat sink plate to the recess 13, H in Fig. 1 was previously required to be 4 mm or more due to processing constraints, but this constraint has been removed. It's gone. Therefore, h in FIG. 6, which corresponds to H, was shortened to, for example, 2.3 mm, but no problem occurred. Therefore, the planar size of the resin body 8 in FIG. 8 can be reduced, and a reduction in size and weight is achieved. Cost reduction is also achieved by reducing the material used for the heat sink 2. In addition, by dividing the heat sink 2 into a thick wall portion 2a and a thin wall portion 2b and forming a recess 13 in the thin wall portion 2b, the effect of weight reduction and cost reduction due to material reduction of the heat sink 2 is further enhanced. It's getting bigger.

Note that the portion of the heat sink 2 corresponding to H in FIG.
Due to its structure, it does not have much heat dissipation effect. Therefore, as in this embodiment, the heat dissipation plate 2 in the portion corresponding to h in FIG. It is reasonable to make adjustments. For this reason, although the thin portion 2b can no longer be called a heat sink, it is considered to be a part of the heat sink 2 for the sake of convenience.

(iii) The creepage distance between the external leads is also important in order to ensure dielectric strength on the surface of the resin body 8 between the external leads. However, the wide part 3 of the external lead
There is a limit to how small the widths of a, 4a, and 5a can be in order to have the effect of reinforcing parts. Furthermore, there is a limit to the distance between the external leads 3, 4, and 5 because it is necessary to design the width of the resin body 8 to be as small as possible in order to meet the demand for miniaturization of semiconductor devices. Moreover, the spacing between external leads often has a standard value as an industry, and there is often no freedom in design. For this reason, especially in small resin-molded power transistors, the creepage distance between the external leads may be insufficient considering the withstand voltage.

Therefore, by changing the overhanging shape of the wide parts 4a and 5a of the external leads to the extent that they can be considered as linear external leads, the creepage distance between the external leads can be increased without compromising the ease of handling that linear external leads have. I'm taking it. Furthermore, the stepped portions 15 and 16 due to the formation of the recessed portion 17 in the resin body 8
Also, the creepage distance between the external leads is large. As an example, the spacing of external leads
2.54mm, the width of the wide part of the external lead is 1.4mm, the width of the narrow part of the external lead is 0.7mm, the stepped part 15,
16 (depth of recess 17) is 0.6 mm, the creepage distance between the external leads is 2.09 mm.
Under the same conditions and with the conventional structure, the creepage distance between external leads is 1.14mm.

(iv) The distance between the side surface of the resin body 8 opposite to the side from which the external leads are led out and the bent portion of the heat sink 2 is larger than the distance between the bent portion and the thick wall portion 2a of the heat sink 2. ing. As a result, the bent portion of the heat radiating plate 2 can be separated from the side surface of the resin body 8, and cracks and cracks are prevented from occurring in the resin body 8 near the bent portion when the heat radiating plate connection portion is broken. Therefore, it is possible to provide a highly reliable resin-molded power transistor that does not suffer from characteristic deterioration even after long-term use.

"Effects of the Invention" As described above in the embodiments, according to the present invention, the exposed parts of the heat sink and external leads are substantially Thus, an insulator-sealed semiconductor device can be obtained in which the creepage distance between the exposed portion of the remaining portion of the heat sink connecting portion and the lead-out portion of the external lead and the bottom surface of the resin body is increased. Therefore, the dielectric strength between the insulator-sealed semiconductor device and the external heat sink is increased, and it is possible to provide an insulator-sealed semiconductor device suitable for incorporating a high-voltage semiconductor element. In addition, since the bent portion of the heat sink is spaced apart from the side surface of the insulator, it is possible to create an insulator-sealed semiconductor device with a structure in which cracks or cracks do not easily occur in the insulator near the bent portion when the heat sink connecting portion breaks. Can be provided.

[Brief explanation of the drawing]

1 to 5 show conventional insulator-sealed semiconductor devices. 6 to 11 show an insulator-sealed semiconductor device according to the present invention. In addition, Fig. 1, Fig. 2,
The broken lines in FIGS. 6 and 7 indicate the outer shape of the insulator. 1 is a power transistor chip (semiconductor element),
2 is a heat sink, 2a is a thick part of the heat sink, 2b is a thin part of the heat sink, 3, 4, 5 are external leads, 3a, 4
a, 5a are wide parts of external leads, 3b, 4b, 5
b is the narrow part of the external lead, 4c and 5c are the terminal parts for the internal lead wire of the external lead, 6 and 7 are the internal lead wires, 8 is the resin body (insulator), 9 is the hole 9 in the heat sink,
8a is a resin body formed around the hole 9, 10 is a mounting hole, 11 and 12 are remaining parts of the heat sink connecting part, 1
3 is a concave portion of the heat sink, 14 is a remaining portion of the lead connection portion, 15 and 16 are stepped portions of the resin body, and 17 is a concave portion of the resin body.

Claims (1)

[Scope of utility model registration request] A heat sink having a thick wall portion on one main surface of which a semiconductor element is fixed, and a thin wall portion having a remaining portion of the heat sink connecting portion at its tip, and a plate-like member that is thinner than the thick wall portion of the heat sink. and a plurality of external leads formed from the heat sink, the thin portion of the heat sink having a bent portion such that the tip side including the remaining portion of the heat sink connecting portion is connected to the one of the thick portions of the heat sink. The semiconductor element is sealed with an insulator, and the remaining portion of the heat sink connecting portion is offset above the one main surface of the thick portion of the heat sink. an exposed portion exposed from the insulator at a position where the
The plurality of external leads have a lead-out portion led out from the insulator at a position deviated upward from the one main surface of the thick portion of the heat sink, and the exposed portion of the remaining portion of the heat sink connecting portion and the heat sink and the plurality of external leads are not exposed from the insulator except for the lead-out portions of the plurality of external leads, and the main surface of the thick portion of the heat sink is opposite to the one main surface. The thickness of the insulator formed on the surface is 1 mm or less, and the bent portion of the thin portion of the heat sink and the side surface opposite to the side surface from which the plurality of external leads of the insulator are led out. An insulator-sealed semiconductor device characterized in that a distance between the bent portion of the thin portion of the heat sink and a thick portion of the heat sink is larger than a distance between the bent portion of the thin portion of the heat sink and the thick portion of the heat sink.