JPH0534829B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a semiconductor rectifier device having a heat dissipation effect, which is used, for example, in an alternator for a vehicle.

For example, a semiconductor rectifier that performs full-wave rectification of the voltage generated in a vehicle alternator generates a large amount of heat during practical operation, so it is equipped with a heat dissipation mechanism. FIG. 1 shows the configuration of such a semiconductor rectifier, in which a semiconductor rectifier 13 is connected to an embossed portion 12 formed on a heat dissipation electrode 11 constituting a cooling fin.
are brazed and fixed with solder 14. Here, in the rectifier 13, a semiconductor chip 15 that performs a rectifying operation is connected and fixed to a disk 17 via solder, and a lead wire 18 is also connected and fixed to this semiconductor chip 15 with solder 19, and is inserted into the disk 17. It is configured to be filled with silicone rubber 20 and hermetically sealed.

In such a rectifier, the solder 14 ensures electrical connection between the rectifier 13 and the heat dissipation electrode 11, and protects the rectifier 13 from distortion effects such as deformation of the heat dissipation electrode 11 due to external mechanical impact. It plays an important role in alleviating distortion by preventing it from being applied. Therefore, this solder 1
Control of the thickness of layer 4 is an important issue for improving the reliability of this type of rectifier.

In addition, due to social needs such as resource saving and energy saving, weight reduction of the rectifier is required, and the material of the heat dissipating electrode 11 constituting the cooling fin is being changed to a light metal such as aluminum. However, when such light metal cooling fins are used, they have a large coefficient of thermal expansion and poor mechanical strength compared to materials such as iron and copper. Therefore, in such a rectifier, the effects of thermal strain and mechanical strain applied to the rectifier 13 inevitably become large.

Conventionally known means of controlling the thickness of the solder layer is to control the soldering temperature and amount of solder, but since there are variations in the weight of the rectifier 13, soldering temperature, amount of solder, etc. There is a large variation in the thickness of the solder layer after soldering. Therefore, it is not possible to effectively alleviate the distortion effect of the cooling fins caused by the light metal, and there is a high possibility that the rectifier 13 may be damaged.

This invention was made in view of the above points, and even when the heat dissipation electrodes constituting the cooling fins are made of a light metal material such as aluminum, the bonding state between the heat dissipation electrodes and the semiconductor rectifier cannot be changed. In addition to ensuring sufficient electrical connection, the mechanical connection also prevents thermal distortion and
Avoiding the negative effects of mechanical distortion,
It is an object of the present invention to provide a semiconductor rectifier that can sufficiently improve reliability.

That is, the semiconductor rectifier according to the present invention has the following features:
A solderable metal plate is integrally fixedly bonded to the heat dissipation electrode made of a light metal constituting the cooling fin by metal bonding, and a rectifier is attached to the metal plate by soldering. To attach the metal plate, form a plurality of protrusions facing the rectifier, bring the protrusions into contact with the rectifier, make the solder thickness the same as the height of the protrusions, and apply a solder layer. The thickness is kept constant.

An embodiment of the present invention will be described below with reference to the drawings. FIG. 2 shows its cross-sectional structure, and the heat dissipation electrode 11 constituting the cooling fin is made of a light metal material, such as aluminum. There is a device in which a semiconductor rectifier 13 configured in the same manner as shown in FIG. Metal plate-shaped body 2 made of a metal material that can be soldered to
1 is attached. This metal plate-like body 21 is integrally coupled to the heat-radiating electrode 11 in a solid bonding state, and this integral coupling means is performed, for example, by pressing the metal plate-like body 21 against the heat-dissipating electrode 11. Ultrasonic vibration or high frequency vibration is applied to this plate-shaped body 21. In other words, the oxide film interposed on the bonding surface between the metal plate 21 and the heat dissipating electrode 11 is scattered and the pure metal surface is exposed, so that the bonding pressure causes the bonding surface to have an atomic spacing. As the metal approaches the point of contact, a strong metallic bond is formed at the joint.

Here, the metal plate-like body 21 is made of a metal material having a coefficient of thermal expansion approximately equal to that of the disk 17 constituting the rectifier 13, and having good thermal conductivity and soldering.
For example, it is made of copper.

A plurality of protrusions 22a, 22b, . . . having the same height are formed on this metal plate-like body 21 toward the disk 17 of the rectifier 13. By bringing the tip into contact with the rectifier 13, the rectifier 13 is supported and set in parallel with the metal plate-like body 21. In this case, it is desirable that the number of protrusions 22a, 22b, . . . is at least three or more. The metal plate-like body 21 and the rectifier 13 are integrally connected by solder 14.

That is, in the semiconductor rectifier configured as described above, the thickness of the solder 14 layer supporting the rectifier 13 is uniformly set to be equal to the height of the protrusions 22a, 22b, . This makes it extremely easy to maximize the effects of mechanical strain relaxation, which is the role of the 14 solder layers. Therefore, the occurrence of damage to the rectifier 13, which is important for performance, can be sufficiently minimized, and this is effective for constructing a high-quality semiconductor rectifier device.

Here, the protrusions 22a, 22b, . 11, that is, the heat can be transmitted to the cooling fins, and the temperature of the rectifier 13 can be effectively prevented from increasing by providing a sufficient heat dissipation effect. In this case, the protrusions 22a, 22b, . . . can be formed in a pressure welding process in which the metal plate-like body 21 is integrated with the heat dissipation electrode 11 in a solid bond state, and do not require a special processing process. isn't it.

As described above, according to the present invention, even when the cooling fins are made of a light metal material, the pressure load on the rectifier in the soldering process can be adjusted in advance to compensate for variations in the weight of the rectifier, soldering temperature, amount of solder, etc. By taking this into consideration and determining an appropriate value, the rectifier can be attached to the cooling fin in such a way that the protrusion easily and reliably contacts the rectifier and the solder layer is always equal to the protrusion height. Moreover, it can effectively protect the rectifier from the adverse effects of thermal distortion, mechanical distortion, etc., and is very effective in improving the reliability of this type of rectifier.

In the embodiment, one rectifier 13 is attached to the heat dissipation electrode 11, but it is of course possible to attach a plurality of rectifiers to one heat dissipation electrode 11. .

In the above embodiment, the semiconductor chip is connected and fixed to the disk via solder, and the lead wires are also connected and fixed to the semiconductor chip using solder, and the disk is filled with silicone rubber to seal the chip part. A semiconductor rectifier configured to be hermetically sealed is shown attached. However, this may of course be any semiconductor rectifier as long as it is brazed and fixed with solder.

Furthermore, although the above embodiments are shown with embossed portions formed on the heat dissipation electrodes, it is of course possible to have no embossed portions formed thereon.

[Brief explanation of the drawing]

Figure 1 is a sectional view showing a conventional semiconductor rectifier;
FIG. 2 is a cross-sectional configuration diagram illustrating a semiconductor rectifier according to an embodiment of the present invention. DESCRIPTION OF SYMBOLS 11... Heat dissipation electrode (cooling fin), 12... Embossed part, 13... Semiconductor rectifier, 14... Solder, 15... Semiconductor chip, 21... Metal plate-shaped body, 22a, 22b... Protrusion.

Claims (1)

[Claims] 1. A metal plate-like body that can be soldered to a heat dissipating electrode made of a light metal is integrally fixed and bonded by metal bonding, and a semiconductor rectifier is attached to this metal plate-like body via a solder layer, and the metal plate The shaped body is provided with a plurality of protrusions, and by bringing the protrusions into contact with the semiconductor rectifier, the thickness of the solder layer is kept constant and equal to the height of the protrusions. Semiconductor rectifier device.