MOUNTING ARRANGEMENT FOR SOLID STATE DEVICES

Abstract: In a mounting arrangement for a solid state device (30), the solid state device (30) is maintained between a thermally conductive support body (20) and a thermally conductive cap member (10) which are urged together by a bolt (14) which passes through an elongated slot (12) in an angled surface (16) of the cap member (10) to engage in a threaded opening (23) in an angled surface (24) in the support body (20). A fastener (44) maintains the support body (20) in contact with a metal chassis (50) serving as a heat sink. The fastener (44) also locates a printed circuit board (40) carrying conductors (48) which connect with conductive leads (36) on the solid state device (30). This mounting arrangement enables highly efficient heat dissipation while maintaining the solid state device (30) in a readily replaceable manner. A plurality of individual solid state devices (30) may be located between the support body (20) and the cap member (10).

Description: MOUNTING ARRANGEMENT FOR SOLID STATE DEVICES Technical Field This invention relates to mounting means for a solid state device, of the kind including a thermally conductive support body adapted to contact a heat sink, wherein said thermally conductive support body includes first and second legs, said first leg being adapted to contact said heat sink and said second leg extending from said first leg and having a flat surface. Background Art Present day solid state devices, for example solid state devices used in power supplies, generate amounts of heat which cannot be adequately transferred to the ambient surroundings without the utilization of a heat sink. It is known to use printed circuit boards to provide a support for the electrical conductors and the associated electrical components such as solid state devices. However, a problem arises in mounting solid state devices so as to connect thermally with a heat sink and simultaneously to connect electrically with conductors on a printed circuit board. Mounting means of the kind specified is known from U.S. Patent No. 4,204,248. In the known means, a solid state device is attached to a support body by a threaded screw which extends through aligned holes in the device and in the support body. An extension of the support body is attached by a threaded screw to a chassis which serves as a heat sink. Leads from the solid state device are soldered to conductors on a printed circuit board which is attached to the chassis by a further threaded screw. Heat generated by the solid state device' is conducted via the support to be dissipated by the chassis serving as a heat sink. However, the amount of heat which can be conducted away from the solid state device is limited. Disclosure of the Invention It is an object of the present invention to provide mounting means of the kind specified having improved heat transfer characteristics. Therefore, according to the present invention, there is provided mounting means of the kind specified, characterized in that said second leg has an angled end portion; in that a thermally conductive cap member is provided having third and fourth legs, said fourth leg having an angled surface adapted to mate with said angled end portion such that said third leg is substantially parallel to said flat surface; and in that urging means are provided adapted to urge said third leg towards said flat surface, whereby said solid state device may be mounted in thermal contact with said support body and said cap member. It will be appreciated that in mounting means according to the invention, thermal contact is made with two surfaces of the solid state device, whereby large heat transfer is achieved. Furthermore, the arrangement of mating angled surfaces provides a strong clamping pressure for firmly maintaining the solid state device in position, while permitting easy removal of a defective device when necessary, without disruption to other mounted devices. The mounting means can be utilized to provide a quick and strong mount for solid state devices in close proximity to a printed circuit board. Brief Description of the Drawings One embodiment of the present invention will now be described by way of example, with reference to the accompanying drawings, in which: Fig. 1 is a perspective view, partially in exploded form, of the preferred embodiment of the invention; and Fig. 2 is an end view of the preferred embodiment of the invention, partly in section. Best Mode for Carrying Out the Invention Referring to Fig. 1, an elongated thermally conductive, support body 20 is shown having a substan¬ tially L-shaped cross section formed by a pair of legs 28 and 22, with leg 22 extending at a right angle from leg 28 and having an angled end portion 24. The legs 22, 28 may be of approximately equal length or, as shown in the drawings, of different lengths. In the preferred embodiment of the invention, the angle of the end portion is approximately 30 degrees. Leg 22 has a first flat surface 25 and leg 28 has a second flat surface 27. Each of a plurality of thermally conductive cap members 10 (shown individually in Fig. 1 as 10A, 10B) has an L-shaped cross section, and one leg thereof is provided with an angled surface 16 that is designed to mate with the angled end portion 24. An elongated opening 12, in each cap member 10, is adapted to receive a fastener, which may be a bolt 14. The bolt 14 contacts a receptacle in the form of a threaded opening 23 in the leg 22 (shown in Fig. 2). Each cap member 10, in the preferred embodiment of the invention, was of a width that permitted two solid state devices 30 to be mounted by the cap member. The solid state devices 30 are shown individually as 30A- 30D in Fig. 1. The cap members 10 may be made wider or narrower in width to permit either more or less solid state devices 30 to be mounted by each cap member. Each solid state device 30, in the preferred embodiment, is comprised of a body section 32, a flat heat transfer plate 34, and electrical conductors (leads) 36. The leads 36 extend from the solid state device to conductors 48 on an associated printed circuit board 40 (shown in Fig. 2). Referring now to Fig. 2, a metallic chassis 50 provides the major heat sink to which the thermally conductive support body 20 is attached. The leg 28 is provided with an opening 26 through which a fastener 44 is inserted and which fastener also passes through an opening 42 in a printed circuit board 40 and an opening 52 in the chassis 50. The leg 22 extends through an opening 46 in the printed circuit board 40. The fastener 44 holds the second flat surface 27 of leg 28 in thermal contact with the chassis body 50, while also holding the printed circuit board 40 in a fixed relationship with respect to the chassis 50 and the support body 20. To assemble, the solid state device 30 is positioned between the leg 18 of cap member 10 and the first flat surface 25 of the leg 22. As the bolt 14 is tightened downwards into the threaded opening 23 of the leg 22, the angled surface 16 slides downwards at an angle which causes the cap member 10 to move in the direction indicated by the direction of arrow B and in the direction indicated by the direction of arrow C. Movement in the B direction causes a force to be transmitted to the solid state device 30, which urges the heat transfer plate 34 into contact with the first flat surface 25 of the leg 22. Once mounted in this sandwiched fashion, the solid state device can transmit heat upwards through the leg 18 and then down through the leg 22 and through heat transfer plate 34 to the leg 22, and hence downward into the chassis 50. The leads 36 are soldered to the corresponding conductors 48 on the circuit board 40 and if necessary, to remove a defective solid state device the leads 36, can be easily de-soldered and the bolt 14 disengaged so that the defective component can be removed and a new component installed. In the preferred embodiment of the invention, the support member 20 and the lap members 10 were formed of aluminum which aluminum was finished black anodized.

Claims: CLAIMS 1. Mounting means for a solid state device (30A) including a thermally conductive support body (20) adapted to contact a heat sink (50), wherein said thermally conductive support body (20) includes first (28) and second (22) legs, said first leg (28) being adapted to contact said heat sink (50) and said second leg (22) extending from said first leg (28) and having a flat surface (25), characterized in that said second leg (22) has an angled end portion (24); in that a thermally conductive cap member (10A) is provided having third (18) and fourth legs, said fourth leg having an angled surface (16) adapted to mate with said angled end portion (24) such that said third leg (18) is substantially parallel to said flat surface (25); and in that urging means (14) are provided adapted to urge said third leg (18) towards said flat surface (25), whereby said solid state device (10A) may be mounted in thermal contact with said support body (20) and said cap member (10A). 2. Mounting means according to claim 1, characterized in that said second leg (22) extends from said first leg (28) at substantially a right angle. 3. Mounting means according to claim 1, characterized in that said cap member (10A) has an elongated opening (12) through said fourth leg, in that said second leg (22.) has a fastener receptacle (23) formed therein, and in that said urging means including a fastener (14) which extends through said elongated opening (12) in said fourth leg to engage said fastener receptacle (23) and thereby urge said third leg (18) towards said flat surface (25). 4. Mounting means according to claim 1, characterized in that said first leg (28) has a further flat surface (27) adapted to contact said heat sink (50). 5. Mounting means according to claim 1, characterized in that said heat sink includes a metallic chassis (50); by a printed circuit board (40) having conductors (48) thereon adapted to be connected to electrical leads (36) extending from said solid state device (30A) and having an opening (46) therethrough for allowing said second leg (22) to pass therethrough; and by fastener means (44) adapted to mount said printed circuit board (40) and said support body (20) to said metallic chassis (50) such that said solid state device (30A) is located adjacent said conductors (48). 6. Mounting means according to claim 1, characterized in that a plurality of solid state devices (30A, 30B) are mounted between said support body (20) and said cap member (10A).

Inventors: FAA LELAND MILFORD JR, FAA, LELAND, MILFORD, JR.
Applicants: NCR CO, NCR CORPORATION
Application year: 1987
Main classification: H05K7
IPC codes: H01L23, H05K7