JPS59115547A - Resin-sealed semiconductor device - Google Patents

Abstract

PURPOSE:To reduce the invasion of moisture into a resin-sealed semiconductor device and to enable to exhaust water content which has once been introduced into the device by forming a plurality of steps on a heat sink plate while positioning a semiconductor element pellet at the periphery of the pellet when mounting the pellet on the plate and molding it with resin and opening a plurality of grooves between the steps, thereby lengthening the water content introducing passage. CONSTITUTION:When a semiconductor pellet 12 is mounted on a heat sink plate 11, steps 13 are respectively formed at the ends of the plate 11 corresponding to the sides of the pellet 12. Then, a plurality of grooves 14 are formed in parallel between adjacent steps 13, and resin 15 is molded on the entire surface which includes the grooves. In this manner, the moving distance of the water content which is invaded via the steps 13 and the grooves 14 is lengthened, and the exhaust of the water content produced in the resin mold 15 can be, on the contrary, readily exhausted out of a semiconductor device. Accordingly, the rate of causing troubles in high humidity atmosphere can decrease, thereby increasing the lifetime of the device.

Description

DETAILED DESCRIPTION OF THE INVENTION [Technical Field of the Invention] The present invention relates to a resin-sealed semiconductor device, and more particularly to a moisture-proof structure for a resin-sealed semiconductor having a heat sink.

[Technical background of the invention and its problems] As a package for semiconductor devices, ceramic R-taskage, resin sealing,
There is a resin-sealed cage, but the resin-sealed cage is widely used because it is suitable for mass production and is inexpensive. However, resin-sealed groove cages have the disadvantage of poor airtightness, and especially in semiconductor devices that have a heat sink, the boundary between the resin and the metal plate that is the heat sink is long, preventing moisture from entering through minute cracks. It's not easy.

FIG. 1 is a partially cutaway perspective view showing the internal structure of a semiconductor device having a heat sink, in which a semiconductor chip 2 is fixed with a mounting material 3 on a heat sink 1 made of metal, and leads 4 and semiconductor pellets are mounted on the heat sink 1. 2 is connected with a wire 5 made of aluminum or the like, and the bottom surface of the heat sink 1 and the protrusion 1a are connected with a resin 6 such as epoxy resin.

All except lead 4 are molded.

Further, FIGS. 2 and 3 show a flat seven cage type semiconductor device having a similar structure, with FIG. 2 being a plan view and FIG. 3 being an AA sectional view thereof.

In addition, in FIGS. 2 and 3, the same parts as in FIG. 1 are given the same reference numerals, except that the lee P having a different shape is changed to 4'.

When a semiconductor device having such a structure is used in a humid environment, moisture enters through the boundary 7 between the heat sink 1 and the molding resin 6, corroding the electrodes and wires 5 on the surface of the semiconductor pellet 2, and causing disconnection. may cause permanent damage.

In order to eliminate such failures, semiconductor devices as shown in FIGS. 4 and 5 have been proposed.

4 and 5 are plan views showing the semiconductor pellets attached on the heat sink 1. In the case of FIG. 4, the semiconductor pellets 2 are placed on the heat sink 1 around the semiconductor pellets 20 in an endless shape. A plurality of protrusions or grooves 8 are provided concentrically surrounding the semiconductor pellet 2 in the case of FIG.
A stepped portion 9 is provided at the end of the heat sink 1 corresponding to the side.

In such a structure, when moisture permeates toward the semiconductor pellet 2, it is blocked by the grooves 8 and the step portions 9, so that the permeation can be delayed and failures are less likely to occur. In addition, the case shown in FIG. 5 has a characteristic that the heat sink and the resin fit well together, and peeling does not easily occur.

However, even with this structure, the heat sink 1 and the mold resin 6
There is no change in the fact that moisture can easily enter from the boundary between the
In a humid environment, failures are likely to occur over a long period of time. In addition, especially in the structure shown in Fig. 4, once the groove 8
On the other hand, the moisture accumulated in the 0 part remains forever, and the problem is that the moisture may have an adverse effect.

[Purpose of the invention]

SUMMARY OF THE INVENTION Accordingly, an object of the present invention is to provide a resin-sealed semiconductor device with a heat sink that prevents moisture from reaching semiconductor pellets and causes fewer failures.

[Summary of the invention]

In order to achieve the above object, in the present invention, a stepped portion is provided at the periphery of the heat sink to which the semiconductor pellet is attached, and a plurality of grooves or protrusions are provided to connect the stepped portions. Since moisture does not accumulate inside the device, there are fewer failures due to moisture intrusion.

[Embodiments of the invention]

Embodiments of the present invention will be described below with reference to the drawings.

6 to 8 are plan views showing some embodiments of the present invention, and show the relationship between the heat sink 11 and the semiconductor plate 12 before resin molding.

In FIG. 6, stepped portions 13 are provided at the ends of the heat sink 11 corresponding to each side of the semiconductor pellet 12, and the depth and width of these stepped portions are each 0.2 mm.
They are connected by a plurality of grooves 14 of about 100 mm.

An example of the shape of this groove is shown in the BB enlarged sectional view of FIG.
A groove 14b having a V-shaped cross section and a protrusion 16 at the end as shown in FIG. 9(b), a groove 14c having a trapezoidal cross section as shown in FIG. 9(c), etc. can be used. An example of the shape of the stepped portion 13' is shown in the CC enlarged sectional view of FIG.
A stepped portion 13a1 having a rectangular tip and a thickness change only on the upper surface of the heat sink 11 as shown in FIG.
A stepped portion 13b having a protrusion at the tip and having a thickness change only on the upper surface of the heat dissipating plate 11, and a stepped portion 13c having a thickness change on the upper and lower surfaces of the heat dissipation plate 11, etc. are possible.

Such grooves 14 and step portions 13 can be formed by known methods such as punching and embossing.

FIG. 7 shows almost the same structure as FIG. 6, but the difference is that the stepped portion 13' extends over the entire circumference of the heat sink 11'.

In FIG. 8, a heat sink 1 having a stepped portion 13'' at the end
A groove 14' is provided so as to surround the semiconductor pellet 12 placed near the end surface of the semiconductor pellet 12 on three sides.

These grooves 14, 14' and steps 1311.3'
113'' surrounds the semiconductor pellet 12 so as to be approximately equidistant from the semiconductor pellet 12.

Further, in the embodiments shown in FIGS. 6 to 8, the stepped portion 13
, 1.3', 13'' and the bottom of the groove 14, 14' are approximately at the same height.

After wire bonding from the semiconductor millet 12 to leads (not shown) is completed, resin molding is performed, and this resin mold 15 is indicated by a dashed line.

The steps and grooves described above lengthen the path for moisture entering from the outside to move, and conversely have the ability to guide moisture generated inside the resin molding P to the outside of the device. This is remarkable in the embodiment shown in FIG. 8, and the mall F″L
In the curved portion 15a of No. 5, moisture is most likely to enter groove 1.
4' to the stepped portion 13'' of the heat dissipation plate 11'', and is discharged from the apparatus through the stepped portion 13''.

In addition, the stepped portion 13113'+13'' is the heat sink 11,
ll', 11'' and the molding 1'15.

FIG. 11 is a graph showing how the moisture resistance is improved by applying the present invention, and shows the structure of the conventional example shown in FIGS. 2, 4, and 5, and the structure of the embodiment of the present invention shown in FIG. The results of an investigation of the relationship between the cumulative failure rate and the time the product was made from two types of resin and immersed in water at a temperature of 120° C. and a pressure of 2 kg/~ are shown on Wiiple probability paper. According to this, the life of the product to which the present invention is applied is long with both resin A, which has a weak adhesiveness, and resin B, which has a strong adhesiveness, but the lifespan is dramatically longer with resin B, which has a particularly strong adhesiveness and less peeling of the resin. You can see that it is growing.

In the above embodiments, grooves were used to connect the stepped portions of the heat sink, but the same effect can be obtained even if the grooves are used as projections. Furthermore, the cross-sectional shapes of these grooves or protrusions are not limited to those shown in the embodiments, and can be modified in various ways. Furthermore, the arrangement shape of the grooves or protrusions is not limited to the linear shape as in the embodiments, but may be arcuate or any other shape.

〔Effect of the invention〕

According to the semiconductor device according to the present invention as described above, since the semiconductor pellet is surrounded by the stepped portion provided at the periphery of the heat sink and the plurality of grooves or protrusions connecting the stepped portions, The path of moisture intrusion becomes longer, reducing the amount of moisture intrusion, and the presence of grooves or protrusions also allows moisture that has once entered to be drained outside again, reducing the probability of moisture adhering to the semiconductor pellet, resulting in high humidity. Even in an atmosphere, the failure rate is low and long life can be achieved.

[Brief explanation of the drawing]

FIG. 1 is a partially cutaway perspective view showing the structure of a conventional resin-sealed semiconductor device; FIGS. 2 and 3 are a plan view and a sectional view showing the structure of another conventional resin-sealed semiconductor device; Figures 4 and 5 are plan views showing the structure of a conventional heat sink;
9 to 8 are plan views showing the structure of a heat sink according to an embodiment of the present invention, FIG. 9 is an enlarged sectional view showing the shape of the grooves, and FIG.
FIG. 0 is an enlarged sectional view showing the shape of the stepped portion, and FIG. 11 is a graph comparing the life test results of a resin-sealed semiconductor device to which the present invention is applied and a conventional one. 1.11... Heat sink, 2.12... Semiconductor pellet, 4... Lead, 6, 16... Resin mold, 13
, 13', 13''...Stepped portion, 14, 14
'···groove. Applicant's agent Kiyoshi Inomata

Claims (1)

[Claims] A resin-sealed semiconductor device in which a semiconductor element pellet is attached to a heat sink and resin molded, the device having a stepped portion provided at the periphery of the heat sink, and a plurality of grooves or protrusions connecting the stepped portions. . A resin-sealed semiconductor device in which the semiconductor pellet is surrounded by the stepped portion and the groove or the protrusion.