GB2044528A - Mounting arrangements for high power electronic components - Google Patents

Abstract

A mounting arrangement for high power electronic components consists of a finned heat sink in which the fins run vertically and in which the heat sink is supported by an insulated rod and which is located in a vertically shaped recess formed in the heat sink. One or both ends of the rod are located in open ended slots so that the heat sink on which is mounted a high power electronic component can be withdrawn from a composite assembly without disturbing neighbouring electronic components. <IMAGE>

Description

SPECIFICATION Improvements in or relating to mounting arrangements for high power electronic components.

This invention relates to mounting arrange ments for high power electronic components and is particularly applicable to arrangements in which a high power semiconductor device such as a rectifier or a thyristor is to be mounted in a manner which enables it to be cooled efficiently when it is operating. Even though semiconductor devices can be operated in an efficient manner, nevertheless when they are used to control high power levels they can dissipate a great deal of heat, which must be efficiently dispersed to prevent the semiconductor device over heating. For this reasons, it is customary to hold the semiconductor device in close thermal contact with a heat sink.When a number of high power electronic components are provided in a composite assembly, the mounting arrangement can become very complex and difficulties are often experienced in replacing a particular one of the components if it should fail.

The present invention seeks to provide an improved mounting arrangement for high power electronic components.

According to this invention a mounting arrangement for high power electronic components includes a finned heat sink secured to a vertically disposed electrically insulatin elongate member, the ends of which are rigidly clamped to supports, at least one of said ends being located in an open ended slot formed in the respective support, whereby the heasink can be detached from the supports without the need to move one support relative to the other.

Preferably the finned heat sink is formed of a metallic extrusion in which the individual fins run vertically.

Preferably again the electrical insulating elongate member has a circular cross-section and is located in a vertical channel in the heat sink, the channel being so shaped as to prevent transverse movement of the elongate member relative to the heat sink.

Preferably two or more separate elongate members are provided for the heat sink.

Conveniently the elongate member is in the form of a hollow tube composed of an insulating material which surrounds a metallic tie rod by means of which the heat sink is secured to said supports.

Preferably both ends of each elongate member are located in open ended slots in the supports. When the mounting arrangement is being used in conjunction with a high power semiconductor device, typically the semiconductor device is clamped firmly to the heat sink and preferably it is clamped between a pair of relatively massive heat conducting bodies both of which are finned so as to efficiently cool the semiconductor device and one of said air being constituted by said heat sink which is secured to one or more of said elongate members.

The invention is further described by way of example with reference to the accompanying drawings in which, Figure 1 shows a plan view of a mounting arrangement in accordance with the present invention, Figure 2 shows a side view of the same arrangement and Figure 3 shows a section view through an elongate support member.

Referring to the drawings, the mountig arrangement is used to mount a number of high power semiconductor devices such as thyristors or rectifiers. Devices of this kind can dissipate a great deal of heat in normal operation yet they can be easily and permanently damaged if they are operated at an excessive temperature and consequently it is necessary to mount them so that the heat which they dissipate can be rapidly and efficiently dispersed. Many applications require the presence of a number of semiconductor devices which are to be mounted in a relatively confined space. Even though semiconductor devices are very reliable in operation, it is inevitable that one will fail from time to time and the mounting assembly must be so arranged that a faulty device can be removed and replaced.In the arrangement shown in the drawings, it is possible to remove and replace a particular semiconductor device in a relatively simple manner without the need to disturb the remaining semiconductor device and without the need to dismantle large portions of the mounting assembly which are not specifically concerned with the semiconductor device which has to be replaced.

Referring to the drawings, a semiconductor device in this case a thryistor 1 is clamped between a pair of finned heat sinks 2 and 3 by means of clamping bolts (which are not shown). The two heat sinks 2 and 3 are identical to each other and heat sink 2 is secured to a pair of U shaped channels 4 and 5, which support it via a pair of insulating elongate members in the form of elongate members 6 and 7. These are shown in a section view in Fig. 3 and they consist of an outer cylindrical tube 8 formed of a resin bonded paper material, for example, which in practice is rigid and quite strong. A metal tie rod 9 passed through the tube 8 and is secured at each end of the supports 4 and 5 by means of threaded nuts 10 and 1 1. The tube 8 is so dimensioned that it fits snugly within an elongate vertical channel 12 two of which are formed in each heat sink.The shape and position of the channels 12 can best be seen on heat sink 3 in Fig. 1, the corresponding channels in heat sink 2 which are actually used to support the semiconductor device 1 being obscured by the channel 4.

The ends of the-tie rods 9 are located in open ended slots 13 formed in the channels 4 and 5. By slackening the nuts 10 and 11 on both tie rods 9, the assembly consisting of the two finned heat sinks 2 and 3 with the semiconductor device 1 clamped between them can be withdrawn in the direction of the arrow A shown on Fig. 1.

The drawings illustrate a composite assembly in which a number of semiconductor devices are mounted in a single unit side by side and one above the other, although only one mounting sub-assembly is shown in detail.

The other mounting sub-assemblies are referenced generally as 14 and 15 on Fig. 1 and parts of two further sub-assemblies 20 and 21 are indicated on Fig. 2. Electrical connections between adjacent semiconductor devices can be provided by electrically conductive bus bars 16 and 17 and, of course, it will be necessary to remove some of these before any particular semiconductor devices can be removed from the composite assembly, but this is a relatively minor matter, since as shown, all securing screws are accessible from the front of the composite assembly. Conductors 28 and 29 are fixed to heat sinks 2 and 3 as shown, and these are shaped so that they can be left in- position on the heat sinks when subassembly is withdrawn. These conductors can be made in accordance with our co-pending patent application No 7909032.

Fig. 2 shows that when two or more semiconductor devices are mounted vertically one above the other, the channel 5 is used to support both the lower end of one tie rod 8 and the upper end of another tie rod which supports a pair of heat sinks and semiconductor devices which form the sub-assembly 20.

The lower end of this mounting sub-assembly is supported by a further U shaped channel which is not shown.

It will be seen that the fins of the finned heat sinks 2 and 3 run vertically and this enables them to be efficiently cooled by air which flows over them due to convection heating thereby making forced air cooling unncessary except possible for very high power devices. Additionally, the use of the insulating tubes 8 to support the heat sinks enables a high degree of electrical insulation to be provided between the channels 4 and 5 on the one hand the heat sinks 2 and 3 on the other. A washer 20 which is shaped so as to provide a long tracking path and thereby reduce the likelihood of flash over is positioned over the upper and lower ends of each tube 8. The washer 20 is a close fit on the enter surface of the tube 8 to prevent the presence of an internal tracking path. The channels 12 are formed as an integral part of the extruded heat fins, which are usually formed of aluminium and therefore it is unnecessary to subject the heat fins to any additional machining operation to enable them to be mounted on the channels 4 and 5.

If desired ancillary components such as fuses can conveniently be mounted using the front mounting bus bar arrangements. In the drawings, fuses 23, 24, 25 and 26 are shown and these are mounted on small plates 27, which are secured to a heat fin 2 by means of the front conductors 28.

Claims (8)

1. A mounting arrangement for high power electronic components including a finned heat sink secured to a vertically disposed electrically insulating elongate member, the ends of which are rigidly clamped ot supports, at least one of said ends being located in an open ended slot formed in the respective support, whereby the heat sink can be detached from the supports without the need to move one support relative to the other.

2. An arrangement as claimed in claim 1 and wherein the finned heat sink is formed of a metallic extrusion in which the individual fins run vertically.

3. An arrangement as claimed in claim 1 or 2 and wherein the electrical insulating elongate member has a circular cross-section and is located in a vertical channel in the heat sink, the channel being so shaped as to prevent transverse movement of the elongate member relative to the heat sink.

4. An arrangement as claimed in any of the preceding claims and wherein two or re separate elongate members are provided for the heat sink.

5. An arrangement as claimed in any of the preceding claims and wherein the elongate member is in the form of a hollow tube composed of an insulating material which surrounds a metallic tie rod by means of which the heat sink is secured to said supports.

6. An arrangement as claimed-in any of the preceding claims and wherein both ends of each elongate member are located in open ended slots in the supports.

7. An arrangement as claimed in any of the preceding claims and wherein a high power semiconductor device is clamped between a pair of relatively massive heat conducting bodies both of which are finned so as to efficiently cool the semiconductor device, and one of said pair being constituted by said heat sink which is secured to one or more of said elongate members.

8. A mounting arrangement for high power electronic components substantially as illustrated in and described with reference to the accompanying drawings.