GB2249875A

GB2249875A - An assembly for printed circuit boards

Info

Publication number: GB2249875A
Application number: GB9124085A
Authority: GB
Inventors: Stafford Malcolm Ellis
Original assignee: GEC Marconi Ltd; Marconi Co Ltd
Current assignee: BAE Systems Electronics Ltd
Priority date: 1990-11-16
Filing date: 1991-11-13
Publication date: 1992-05-20
Anticipated expiration: 2011-11-13
Also published as: GB9024972D0; GB9124085D0; GB2249875B

Abstract

An assembly for mounting printed circuit boards (11), which are interconnected via an electrical backplane (25) includes a housing (23), into which the backplane (25) and boards are insertable via a frontal access aperture (35). The size and shape of the backplane (25) is such that forward portions (39a, 39b) thereof have their free ends juxtaposed the forward wall portions (41a, 41b) of the housing (23) and fastened thereto. To protect the boards from environmental contamination and external electromagnetic radiation, the frontal access aperture (35) has an associated closure member (not shown). To facilitate maintenance, both the boards and the electrical backplane (25) are removable through the access aperture (35) of the housing (23). The upper and lower walls (57a, 57b) of housing (23) are provided with a plurality of liquid cooling channels. <IMAGE>

Description

Environments for Printed Circuit Boards This invention relates to environments for printed circuit boards and for electronic components carried thereby.

In particular, it relates to environments which protect printed circuit boards and electronic components carried thereby from environmental contamination and electromagnetic radiation.

According to the invention, there is provided an environment for a multiplicity of printed circuit boards (PCBs) each carrying, on at least one major surface thereof, electronic components and having, integral therewith, an electrical connector half to which the said devices are connected by way of printed circuit paths of the PCB, being an environment which comprises: a housing having a housing body and a housing closure part, the housing body defining an interior space and having a frontal access aperture closeable by the said closure part; an electrical backplane having electrical connector means defining a multiplicity of electrical connector halves adapted respectively to mate with a corresponding multiplicity of complementary connector halves respectively associated with a corresponding multiplicity of PCBs as aforesaid and having a shape and size such that, said backplane being received in the said interior space, forward portions of the backplane are in juxtaposition with respect to forward wall portions of the housing body; and fastener means releasibly securing the said forward backplane portions and housing body wall portions together, the environment being such that, the housing closure part being displaced so as to reveal the housing body interior and the fastener means being released so as to free the backplane from the housing body, the backplane may be withdrawn forwardly through the access aperture.

Preferably the backplane has an intermediate elongate part and first and second outset horn parts, one at each end of the said elongate part and is dimensioned such that, with the backplane received in said interior space, the horn parts have the free ends thereof in juxtaposition with the housing body forward wall portions; and the said fastener means releasibly secure the said horn part free ends to the housing body forward wall portions.

Suitably the elongate part has the form of a flat slab.

Preferably at least one of two walls being the upper and lower walls of the housing body has a multiplicity of laterally spaced fore and aft extending channels; adapted, when a backplane carrying a multiplicity of PCBs is received in the housing body interior, respectively to receive marginal board portions and clamp mechanism thereon and to serve as a cold wall for the conduction of heat from the board; and the said at least one wall has a passage arrangement therein constituting part of a fluid cooling circuit, the arrangement being such that as coolant fluid circulates in the said circuit, heat conducted from the boards by way of the said cold walls is transferred to the coolant fluid.

Conveniently the housing closure part is hingedly attached to the housing body.

An embodiment of the invention will now be described by way of example with reference to the accompanying drawings, in which: Figure 1 is an exploded diagram of the housing body and electrical backplane of an environment showing a line replaceable module incorporating a PCB for insertion into the housing.

Figure 2 is a plan view of the environment showing broken transverse cross-sections through the housing body of Figure 1.

Figure 3 shows a side elevation of the housing body part with the electrical backplane inserted therein; and Figure 4 shows a part sectioned end elevation of the housing body part of the electrical backplane inserted therein.

Referring to Figure 1, an environment accomodates a multiplicity of PCBs incorporated in respective ones of a multiplicity of line replaceable modules (LRMs), 11 at median planes therethrough, only one LRM being shown in Figure 1.

Each line replaceable module (LRM) 11 comprises a board, first and second multiplicities of electronic components (not illustrated) carried by the board at major surfaces thereof, and two PCB housing members 15a, 15b, which, with the board, cover and protect the said multiplicities of components against environmental contamination.

Each board has, at one of its major surfaces, a heat conductive pattern, or heat ladder (not illustrated) for conducting heat from electronic components to first and second major heat conductive segments of the pattern, being segments extending transversely of the associated major board surface at opposite marginal board portions 17a, 17b, respectively.

There is mounted connected to each marginal board portion 17a, 17b, at the major surface of the board opposite to that carrying a heat conductive segment, a resilient clamp mechanism 19a, 19b, respectively.

The resilient clamp mechanisms 19a, 19b, are of any suitable form.

As indicated in Figure 1 of the accompanying drawings, the housings 15a, 15b, enclose central areas of the board at each major surface thereof leaving the marginal board portions 17a, 17b carrying the major heat conductive segments on one side and the resilient clamp mechanisms 19a, 19b, on the other unprotected outside opposite boundaries of the said PCB housing members.

The several LRMs 11 each have an electrical connector half 21 to which electronic components, carried by the board within the PCB housing members, are connected by way of printed circuit paths of the PCB.

The environment for several LRMs 11 shown in Figure 1 comprises a housing 23, an electrical backplane 25 and fastener means 27.

The housing 23 shown in Figures 2 and 3 has a housing body part 29 and a housing closure part 31 both of aluminium alloy. The housing body part 29 defines an interior space 33 having a frontal aperture 35 closeable by the closure part 31. The closure part 31 is constituted as a door leaf hingedly connected to the housing body part 29.

The electrical backplane 25 shown in Figure 2 has electrical connector means 37 defining a multiplicity of electrical connector halves adapted respectively to mate with a corresponding multiplicity of complementary connector halves 21 respectively associated with a corresponding multiplicity of PCBs as aforesaid.

The backplane 25 has a shape and size such that, being received in the interior space 33, forward portions 39a, 39b of the backplane 25 are juxtaposed with forward wall portions 41a, 41b, respectively of the housing body part 29 as shown in Figure 1.

The backplane 25 has, more specifically, an elongate intermediate part 43 and the said forward wall portions 39a, 39b thereof are in the form of first and second outset horn parts, one at each end of the said intermediate part 43. With the backplane 25 received in the housing body part interior 33, the horn parts 39a, 39b, have their free ends 45a, 45b juxtaposed as aforesaid with forward wall portions 41a, 41b, of the housing body part 29.

The free ends 45a, 45b, of the horn parts 39a, 39b, have upper and lower flange portions 47a, 47b, respectively, the said flange portions each being pierced by holes.

The fastener means 27 comprises a set of four bolts 51 which, extending through the said holes pierced in the aforesaid flange portions 47a, 47b, engage the forward wall portions 41a, 41b at threaded bores 53 respectively formed therein.

The backplane 25 has dimensions such as, when received, as shown in Figure 2 and 3 within the interior 33 of the housing body part 29, to make a snug fit within the said housing body part 29.

To facilitate the mating of the connector halves 21, the backplane 25 has a locating dowel 69 as shown in Figures 2 and 4 which mates with a complementary female part 71 secured to the rear wall 73 of the housing body part 29.

The arrangement described provides an environment for the LRMs 11 whereby the PCBs may be protected from environmental contamination and from external electromagnetic radiation. The maintenance of the LRMs 11 is facilitated since the backplane 25 is removable, following release of the fastener means 27, by withdrawal of the backplane 25 through the forward access aperture 35 of the housing body part 29.

The LRMs 11 being as hereinbefore described, the housing body part 29 shown in Figures 1 and 3 has a multiplicity of laterally spaced fore and aft extending channels 55 correspondingly located in the upper and lower walls 57a, 57b, of the said body part, the said channels constituting part of the interior space 33.

Corresponding opposed channels 55 receive respectively the exposed marginal board portions 17a, 17b, of individual ones of the several LRMs 11. The major heat conductive segment on one marginal surface portion of each marginal board portion is adjacent to the surface 59 of one of the opposed walls defining the relevant channel 55. The opposed walls serve as 'cold walls' for the conduction of heat from each board. The clamp mechanism affixed to the other marginal surface portion of the marginal board portion operates in any suitable way; for example, the lateral expansion of the clamp mechanism 19a, 19b can cause the major heat conductive segment to be forced into intimate heat conductive contact with the wall surface 59.

The upper and lower walls 57a-, 57b, of the housing body part 29 are of hollow construction, there being a multiplicity of interior passages 61, half A of the latter passages communicating at one end with an inlet manifold 63a, half B with an outlet manifold 63b as shown in Figure 2. At the other end, both half A and half B of the passages 61 communicate with a common manifold 65.

The passages 61 and manifolds 63a, 63b and 65 and a bleed valve 64 constitute elements of a liquid coolant cooling circuit.

The inlet and outlet manifolds 63a, 63b have conduits 67a, 67b, respectively, connected thereto. Cooled liquid flows in the circuit from a refrigeration unit (not shown) by way of the inlet conduit 67a, the inlet manifold 65a, the passages 61, half A, the common manifold 65, the passages 61 half B, the outlet manifold 63b and the outlet conduit 67b back to the refrigeration unit. In the process, heat abstracted from the electronic components mounted on the PCBs of the line replaceable modules 11 is conducted by way of the heat conductive patterns of the several PCBs, from the major heat conductive segments at the opposite margins of the boards, thence to the walls defining one of the opposed surfaces 59 of each of the channels 55. The heat thereby transferred to the upper and lower walls 57a, 57b, of the housing body part 29 is transferred to liquid coolant flowing in the coolant circuit, finally to be dissipated at a location remote from the environment of the PCBs.

Claims

1. An environment for a multiplicity of printed circuit boards (PCBs) each carrying, on at least one major surface thereof, electronic components and having, integral therewith, an electrical connector half to which the said devices are connected by way of printed circuit paths of the PCB, being an environment which comprises: a housing having a housing body and a housing closure part, the housing body defining an interior space and having a frontal access aperture closeable by the said closure part; an electrical backplane having electrical connector means defining a multiplicity of electrical connector halves adapted respectively to mate with a corresponding multiplicity of complementary connector halves respectively associated with a corresponding multiplicity of PCBs as aforesaid and having a shape and size such that, said backplane being received in the said interior space, forward portions of the backplane are in juxtaposition with respect to forward wall portions of the housing body; and fastener means releasibly securing the said forward backplane portions and housing body wall portions together, the environment being such that, the housing closure part being displaced so as to reveal the housing body interior and the fastener means being released so as to free the backplane from the housing body, the backplane may be withdrawn forwardly through the access aperture.

2. An environment as claimed in Claim 1 wherein the backplane has an intermediate elongate part and first and second outset horn parts, one at each end of the said elongate part and is dimensioned such that, with the backplane received in said interior space, the horn parts have the free ends thereof in juxtaposition with the housing body forward wall portions; and the said fastener means releasibly secure the said horn part free ends to the housing body forward wall portions.

3. An environment as claimed in Claim 2 wherein said elongate part has the form of a flat slab.

4. An environment as claimed in any preceding claim wherein at least one of two walls, being the upper and lower walls of the housing body, has a multiplicity of laterally spaced fore and aft extending channels and is adapted, when a backplane carrying a multiplicity of PCBs is received in the housing body interior, respectively to receive marginal board portions and clamp mechanism thereon and to serve as a cold wall for the conduction of heat from the board; and the said at least one wall has a passage arrangement therein constituting part of a fluid cooling circuit, the arrangement being such that as coolant fluid circulates in the said circuit, heat conducted from the boards by way of the said cold walls is transferred to the coolant fluid.

5. An environment as claimed in any preceding claim wherein said housing closure part is hingedly attached to said housing body.

6. An environment as hereinbefore described and illustrated in the accompanying drawings.