ELECTRONICS MODULE MOUNTING ASSEMBLY

Abstract: An electronics module mounting assembly comprises a rigid heat sink plate (26) for supporting an electronics module, the heat sink plate being formed integrally between two parallel ribs (24, 25), which are received into juxtaposed slots in a mounting rack and clamped therein by means of screw threaded clamps (16, 17) which serve to maintain the ribs in intimate contact with the walls of the slot thereby to facilitate heat transfer from the ribs to the rack by conduction. This construction allows modules such as ceramic tiles carrying electronics components to be stacked in a rack at a high packing density whilst permitting good dissipation in use of the heat generated.

Description: This invention relates to a mounting assembly for electronics modules and more especially it relates to an assembly which facilitates the mounting of modules such as ceramic tiles carrying electronics components in stacked fashion one above the other within a rack. Rack stacking arrangements for electronics components such as printed circuit boards or the like are well known. One of the problems with such arrangements however is that due to the high density of the component packing, heat dissipation may become a problem. In order to minimise this problem, electronics modules are mounted on heat sinks and the heat sinks are supported in a rack such that the heat is conducted away through housing walls which are slotted to define the rack. It has been proposed in US-A-4,345,770 to provide an electronics module mounting assembly comprising a rigid heat sink plate for supporting an electronics module, the heat sink plate being located between two parallel ribs which are in use received into juxtaposed slots in a mounting rack and secured in that position by means of a wedge and anvil arrangement. Such an electronics module mounting assembly can be made simple and inexpensive to fabricate and in use facilitates efficient conduction of heat away from the assembly via the walls of a rack in which the assembly is supported. According to the invention, each rib is formed integrally with the heat sink plate, each rib comprising an elongate channel section adapted at each end to define a ramp, the open sides of each channel section being narrowed thereby to form a neck portion which serves to retain within the channel section an elongate member, which at one end is secured to a first clamp member and which at the other end is screw threaded to receive a nut which is arranged to bear against a second clamp member, such that when the nut is tightenend the clamp members at opposite ends of each channel section are constrained to move toward each other up the ramps, whereby in use the assembly is clamped within opposite slots of a mounting rack by means of the clamp members which serve to maintain the ribs in intimate contact with the walls of the slot and thereby facilitate heat transfer from the ribs to the rack by conduction. The first clamp member may comprise a short bar of circular cross-section secured to the elongate member transversely so that its circular periphery makes contact with the ramp along a line parallel to that axis of the bar which is coaxial with the circular periphery. The second clamp member may comprise a bar of part circular cross-section the circular portion of which is arranged in contact with an adjacent ramp and a flat portion of which is arranged to co-operate with the nut. The heat sink plate and ribs may be constructed of aluminium or an aluminium alloy and formed integrally by means of an extrusion process for example. The nut, the clamp members or the elongate member may be constructed of stainless steel. The mounting assembly may comprise a ceramic tile module secured to and supported by the heat sink plate. One embodiment of the invention will now be described by way of example with reference to the accompanying drawing in which: Figure 1 is a plan view of a ribbed heat sink plate which forms a principal part of an electronics module mounting assembly; Figure 2 is a side view of a part of the heat sink plate and ribs shown in Figure 1; Figure 3 is a sectional view of a rib shown in Figure 1; and, Figure 4 is a perspective view of a mounting assembly for an electronics module. Referring now to Figure 1 a mounting assembly for an electronics module comprises a heat sink plate 1 which is formed integrally between a pair of ribs 2 and 3. an enlarged sectional view of the rib 2 is shown in Figure 3 and it comprises a channel 4 having a narrow neck portion 5, the heat sink plate 1 being arranged to extend orthogonally of the rib intermediate between the narrow neck portion 5 and a clamping surface 6. As shown in Figure 2 each rib is machined to form ramps 7 and 8 at each end of the rib 2 and ramps 9 and 10 at each end of the rib 3. Also as shown in Figure 2, an elongate member or stud 11 which is threaded at each end is located within the channel section of the ribs 2 and 3 and retained therein by means of the narrow neck portion 5 as shown in Figure 3. As shown in Figure 4, first clamp members 12 and 13 are secured at one end of studs 14 and 15 respectively and nuts 16 and 17 are fitted to the other ends of the studs 14 and 15 so as to urge further clamping members 18 and 19 against ramps 20 and 21. Thus as the nuts 16 and 17 are tightened on the studs 14 and 15, the clamping members 18 and 19 tend to advance up the ramps 20 and 21. Similarly the clamping members 12 and 13 are constrained to advance up ramps 22 and 23 at ends of ribs 24 and 25 remote from the nuts 16 and 17. Thus it will be appreciated that when fitted within a rack slot surfaces of the ribs corresponding to the clamping surface 6 will be urged into intimate engagement with one wall of the slot, as the clamps such as members 12, 13, 18 and 19 are urged against the opposing slot wall. In the present example as shown in Figure 4 a heat sink plate 26 formed integrally with the ribs 24 and 25 is used to support a ceramic tile module on which electronics components are mounted. In order to make electrical contact with the electronics components, connector sockets 27 and 28 (shown schematically) are provided. In order to facilitate integral fabrication of the heat sink plate and the ribs by extrusion, the heat sink plate and the ribs are conveniently fabricated from aluminium or an aluminium alloy. The nuts, clamps and studs on the other hand are fabricated from stainless steel. Since the heating plate and the ribs are fabricated as one extrusion they are particularly rigid and little finishing cost is incurred. The clamps 12 and 13 are fabricated from rod material which is inexpensive to provide and the clamps 18 and 19 are fabricated from similar material with minimal machining. It will be appreciated that installation is facilitated since the clamps have no projecting sharp edges. Since the clamps are disposed approximately centrally they have no chance of rotating out of alignment whereby installation would be prevented. By using dissimilar materials for the construction of the clamps and the ramps the occurrence of pressure welded joins is obviated. Various modifications may be made to the arrangements just before described without departing from the scope of the invention as defined in the appended claims and for example nut and clamp arrangements of slightly different shape may be used.

Claims: An electronics module mounting assembly comprising a rigid heat sink plate (26) for supporting an electronics module, the heat sink plate (26) being located between two parallel ribs (24, 25), which are in use received into juxtaposed slots in a mounting rack, characterised in that each rib (24, 25) is formed integrally with the heat sink plate (26), each rib (24, 25) comprising an elongate channel section (4) adapted at each end to define a ramp (20, 22, 21, 23), the open sides of each channel section being narrowed thereby to form a neck portion (5) which serves to retain within the channel section (24, 25) an elongate member (14,15), which at one end is secured to a first clamp member (12, 13) and which at the other end is screw threaded to receive a nut (16, 17) which is arranged to bear against a second clamp member (18, 19), such that when the nut (16, 17) is tightened the clamp members (12, 18, 13, 19) at opposite ends of each channel section (24, 25) are constrained to move toward each other up the ramps (22, 20, 23, 21), whereby in use the assembly is clamped within opposite slots of the mounting rack by means of the clamp members which serve to maintain the ribs in intimate contact with the walls of the slot and thereby facilitate heat transfer from the ribs to the rack by conduction. An electronics module mounting assembly as claimed in claim 1, in which the first clamp member comprises a short bar of circular cross-section secured to the elongate member transversely so that its circular periphery makes contact with the ramp along a line parallel to that axis of the bar which is coaxial with the circular periphery. An electronics module mounting assembly as claimed in claim 1 or 2, in which the second clamp member comprises a bar of part circular cross-section the circular portion of which is arranged in contact with an adjacent ramp and a flat portion of which is arranged to cooperate with the nut. An electronics module mounting assembly as claimed in any one of claims 1 to 3, in which the heat sink plate and ribs are constructed of aluminium or an aluminium alloy and formed integrally by means of an extrusion process. An electronics module mounting assembly as claimed in any one of claims 1 to 4, in which the nut, the clamp members or the elongate member are constructed of stainless steel. An electronics module mounting assembly as claimed in any one of claims 1 to 5, the assembly comprising a ceramic tile module secured to and being supported by the heat sink plate.

Inventors: HALES, ARTHUR CHARLES GEORGE
Applicants: GEC-MARCONI LIMITED
Application year: 1987
Main classification: H05K7
IPC codes: H05K7