JPS6219063B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a semiconductor device in which a semiconductor element portion above a heat sink is surrounded by an outer container, and the inside is filled with resin and sealed.

In recent years, electronic devices have rapidly become smaller and lighter, and the basis for this is the miniaturization of semiconductor devices. Among these, thyristors were previously used as medium-capacity power semiconductor devices, but transistors are becoming larger in current capacity, and they are becoming more popular due to their advantages such as simplification of peripheral circuits and short switching times. It has come to replace thyristors. Furthermore, transistors are increasingly being used in the field of so-called power modules, in which a plurality of power elements are combined into a single package.

The features of such a power module are its light weight and low price, and for this purpose, it is of a resin-sealed type. A power module incorporates a plurality of semiconductor chips, and the semiconductor chips themselves become larger as the current capacity increases, so the external dimensions are considerably larger than conventional resin-sealed semiconductor devices. For example, a recently developed device for inverter control of electric motors has 13 chips built into the package, and its external dimensions are 100 mm long, 100 mm wide, and 100 mm wide.
A model with a height of 30 mm has been put into practical use. For this reason, resin sealing of the power module requires a structure different from the conventional one. Among these, the biggest problem is that as the external size increases, the volume of the resin filled in the container increases, and the temperature rise due to heat generation of the semiconductor chip causes the sealing resin to expand and contract when the temperature drops. The resulting strain is applied to the chip and aluminum wire, causing chip cracking and aluminum wire breakage.

In order to prevent this, recently, the interior is sealed with a lower layer of gel-like soft resin to surround the chip and aluminum wire parts, and after this upper layer is filled, it is sealed with a hardened high-strength sealing resin. Increasingly, devices have a double resin-sealed structure that holds the external terminals pulled out and mechanically protects the module.

A conventional semiconductor device of this type has a sectional view shown in FIG. The figure shows an example in which two sets of elements are incorporated into one package. 1 is a heat sink,
A pair of insulating substrates 2 are fixed to the upper surface. A collector electrode 3, an emitter electrode 4 or 5, and a base electrode 6 are bonded onto these insulating substrates 2, respectively. Among these electrodes, a common-pole external terminal 3a from one collector electrode 3 and a collector-pole external terminal 3c from the other collector electrode 3 are each connected by soldering and drawn upward. Furthermore, an external terminal 4a of the emitter electrode is bent upward from one emitter electrode 4. Transistor chips 7 are bonded on both collector electrodes 3, and aluminum wires 8
It is wire bonded. Reference numeral 9 denotes a connecting piece for connecting two sets of elements, and is joined across the collector electrode 3 on one side and the emitter electrode 5 on the other side. 10 is a plurality of signal terminals pulled out upward;
The electrodes are connected by respective connection lines 11 from corresponding electrodes. Reference numeral 12 denotes an outer container made of an insulating material such as a synthetic resin molded product, which is adhered to the heat sink 1 along its periphery and surrounds each electrode section and chip section, and is open at the top. Reference numeral 13 denotes a lower gel-like sealing resin (for example, silicone gel) filled in the outer container 14 to an intermediate height, and 14 an upper-layer sealant filled in the upper part of the gel-like sealing resin 13, hardened, and molded. The inside is sealed with a sealing resin (for example, epoxy resin), and the external terminals 3a, 3c, 4a and each signal terminal 10 are mechanically held. 15 is made of an insulating material such as a synthetic resin molded product, and the outer container 12
With the lid fitted on the top of the
c, 4a are pulled out upward and their upper ends are bent horizontally, and each signal terminal 10 is pulled out upward.

In the conventional device described above, two types of resin sealing are used: each chip 7 part and aluminum wire 8 part are surrounded by a gel-like sealing resin filled to protect them, and then sealed with a sealing resin filled and cured. It has a stop structure. Therefore, when the temperature of the device rises, the gel-like sealing resin 13 in the lower layer expands, and a force acts to push up the cured sealing resin 14 in the direction of arrow P, as shown in FIG. In particular, the gel-like sealing resin 13 has a linear expansion coefficient of 4 to
Since it is 7×10 ^-4 , which is larger than that of ordinary mold-cured sealing resin (on the order of 10 ^-5 ), a considerably large force will act on it. As a result, the external terminals 3a, 3 fixed with the hardened sealing resin 14
c and 4a directly receive the pulling force. Therefore, under usage conditions such as a heat cycle, a tensile force is periodically and repeatedly applied to the soldered portion 16 at the lower end of the external terminal, causing repeated fatigue and eventually leading to a disconnection state. For example, if the cross-sectional area of the soldering part 16 shown in Fig. 2 is 3 mm ² , -40°C to +125°C.
If we add a heat cycle where one cycle is
A disconnection accident like the one above occurs after 50 cycles.

In this way, conventional semiconductor devices are double-sealed with a lower layer gel-like sealing resin 13 and an upper layer hard sealing resin 14 to protect chips and aluminum wires, but due to temperature rise, external The soldered portion of the terminal repeatedly generated tensile stress, resulting in fatigue failure and low reliability.

This invention provides a relief chamber in a part of the outer container that communicates downward with the gel-like sealing resin in the lower layer to release thermal expansion, so that even if the gel-like sealant expands due to temperature rise, it will not escape to the relief chamber. The purpose of the present invention is to provide a highly reliable semiconductor device by preventing push-up force from acting on the upper layer of cured sealing resin, eliminating disconnection accidents of external terminals, and providing a highly reliable semiconductor device.

FIG. 3 is a cross-sectional view of a semiconductor device according to an embodiment of the present invention.
3c and 4a are the same as those of the conventional device described above.
Reference numeral 21 denotes an outer container made of an insulating material such as a synthetic resin molded product, which is adhered to the upper part of the heat sink 1 along the periphery, encloses each internal component, and is open at the upper part, and has an open lower and upper part in one side. A relief chamber 21a is formed. The relief chamber of this outer container 21 is shown in a perspective view in FIG. A lid 22 is made of an insulating material such as a synthetic resin molded product, and is fitted onto the top of the outer container 21. Each external terminal 3a, 3c, 4a is pulled out and the upper end is bent horizontally. is pulled upwards. Further, the lid 22 is provided with a ventilation hole 22a that communicates with the escape chamber 21a and communicates with the outside air. The upper layer sealing resin 14 is not filled in the escape chamber 21a.

In the apparatus of the above embodiment, even if the lower layer gel-like sealing resin 13 filled in the outer container 21 expands thermally due to a rise in temperature, the volume of the expansion is within the escape chamber 21a of the outer container 12. entered from below, was taken into custody, and then released. Therefore, the push-up force acting on the upper hardened sealing resin 14 becomes extremely small, and accidents of disconnection of external terminals are eliminated.

In the above embodiment, a power module using a transistor chip 7 was explained as a semiconductor device, but the present invention is not limited to this. This can also be applied to other types of semiconductor devices that are double-sealed.

As described above, according to the present invention, an escape chamber that is open at the bottom and open at the top that communicates with the gel-like sealing resin in the lower layer is provided in the outer container, and the escape chamber is provided in the lid fitted on the top of the outer container. Since we have provided a ventilation hole that connects to the chamber and communicates with the outside air, even if the gel-like sealing resin expands due to temperature rise, it will escape into the relief chamber, and the pushing force on the upper layer of cured sealing resin will be extremely small. ,
Disconnection accidents of external terminals are prevented and reliability is improved.

[Brief explanation of the drawing]

FIG. 1 is a sectional view of a conventional semiconductor device, FIG. 2 is an enlarged sectional view showing part of the electrode section and external terminal section of FIG. 1, and FIG. 3 is a sectional view of a semiconductor device according to an embodiment of the present invention. 4 is an enlarged perspective view of the relief chamber of the outer container shown in FIG. 3. In the figure, 1... heat sink, 2... insulating substrate,
3... Collector electrode, 4, 5... Emitter electrode,
3a, 3c, 4a...external electrode, 6...base electrode, 7...transistor chip, 13...lower layer gel-like sealing resin, 14...upper layer hardened sealing resin,
21...Outer container, 21a...Escape chamber, 22...
...Lid, 22a...Vent hole. Note that the same reference numerals in the figures indicate the same or equivalent parts.

Claims (1)

[Claims] 1. An insulating substrate fixed on a heat sink, a plurality of types of electrodes arranged and fixed on this insulating substrate, a semiconductor chip mounted on a predetermined electrode among these electrodes, and a predetermined electrode among the above-mentioned electrodes. It is made of a plurality of external terminals pulled upward from the insulating material and has an open top and a bottom, and an escape chamber is formed inside with a gap from the bottom and an open top. An outer container fixed along the periphery on the heat dissipation plate, and a lower layer gel-like sealing resin filled in the outer container, whose volume increase due to thermal expansion enters the escape chamber from below and escapes. , an upper layer of cured sealing resin filled and cured on the gel-like sealing resin except for the escape chamber in the outer container, and an insulating material, which is fitted into the upper part of the outer container, and each of the external terminals is connected upwardly. A semiconductor device, the semiconductor device having a lid that is pulled out from the top and has a ventilation hole that communicates from the relief chamber to the outside.