Heat sink attachment

Abstract: To restrain detachment of heat sinks from printed circuit boards (PCBs) or the components mounted on such boards, a body is attached to the board and extends above the tops of the heat sinks. Above each heat sink, three sides of a rectangle are cut from the body, leaving one side uncut. The tongue thus formed is curved downwards to form a spring which bears against the top of the heat sink to protect the heat sink from disengagement. The body is formed with vertical ends or legs having outward bent feet which are secured to the PCB by screws or other fasteners or are fit through slots in the PCB. A slanted tongue may also be cut from the body to engage an upper corner of a heat sink to restrain the heat sink from lateral movement relative to the PCB.

Description: BACKGROUND OF THE INVENTION 1. Field of the Invention This invention relates to a new and improved heat sink attachment to prevent heat sinks from being detached from PCBs or components mounted on PCBs when subjected to vibration or shock. 2. Description of Related Art Heat sinks applied to heat generating components mounted on printed circuit boards and the like are well known in the electronics industry. When subjected to shock or vibration, the heat sinks are sometimes dislodged or thermal contact is diminished. The present invention provides an attachment which spring biases the components into firm contact with the underlying components or PCBs. WO96/29850 discloses a clip for preventing a heat sink for a CPU from coming away from a PCB. The clip is fastened diagonally across a heat sink, and includes fixing claws to hold the heat sink from above. SUMMARY OF THE INVENTION : Particular and preferred aspects of the invention are set out in the accompanying independent and dependent claims. Features of the dependent claims may be combined with those of the independent claims as appropriate and in combinations other than those explicitly set out in the claims. It is desirable to secure ASIC (application specific integrated circuit) heat sinks on a PCB from a thermal and mechanical rigidity standpoint. During transportation and handling, shock, and vibration may dislodge such heat sinks. The present invention provides an inexpensive means to spring bias multiple heat sinks to hold them in place. A body, preferably of metal, is supported by legs attached to the PCB board so that it extends above the tops of multiple heat sinks attached to the board. In a location above each heat sink, three sides of a rectangle are cut into the body, leaving one side uncut so that a tongue extends outward from the uncut side. The tongue is curved downwardly so that it acts as a spring. When the body is mounted on the board, springs bear against the tops of each heat sink, thereby protecting the heat sinks from disengagement from the board or from the components which underlie the heat sinks. To suspend the body in position, vertical legs are formed at opposed ends and each leg terminates in an outward bent foot which is secured to the PCB by screws or other fasteners or fit through slots in the PCB. In some instances the PCB may be installed so that it is vertical or some other steep angle to the horizontal. In such cases slanted tongues are struck from the body to engage a comer of the heat sink to restrain it from moving relative to the board. BRIEF DESCRIPTION OF THE DRAWINGS : The accompanying drawings, which are incorporated in and form a part of this specification, illustrate embodiments of the invention and, together with the description serve to explain the principles of the invention. Fig. 1 is a schematic top plan view of the present invention. Fig. 2 is an end elevational view as viewed from the bottom of Fig. 1. Fig. 3 is a vertical sectional view taken substantially along the line 3--3 of Fig. 2. Fig. 3A is a view similar to Fig. 3 of a modification. DESCRIPTION OF THE PREFERRED EMBODIMENTS Reference will now be made in detail to the preferred embodiments of the invention, examples of which are illustrated in the accompanying drawings. While the invention will be described in conjunction with the preferred embodiments, it will be understood that they are not intended to limit the invention to those embodiments. On the contrary, the invention is intended to cover alternatives, modifications and equivalents, which may be included within the spirit and scope of the invention as defined by the appended claims. Printed circuit board (PCB) 11 is shown partially in Fig. 1. Heat generating electronic components (not shown) are mounted on board 11 at various locations. Typical heat sinks 12 and 13 are placed in intimate thermal contact with the components and dissipate the heat generated thereby to the surrounding atmosphere. Shock and/or vibration during transportation and handling may cause the heat sinks 12 or 13 to become dislodged or the heat transfer capabilities thereof to be reduced by reason of the fact that the heat sinks are not firmly attached to the components. The number, size and location of such heat sinks is subject to wide variation. As shown in Figs. 1 and 2, two different sizes of heat sinks, respectively 12 and 13, are disclosed and these are positioned in various patterns. It will be understood that the number, relative size and positioning of such heat sinks 12 and 13 is subject to wide variation. The attachment which is the subject of the present application comprises a body 16 preferably formed of a metal which is quite springy. Side edges 17 are preferably sloped downwardly-outwardly. At either end of body 16 are downwardly extending legs 18 and the outer ends of the legs are bent outwardly in feet 19. As shown in Fig. 1 there are two feet 19 at the top and one foot 19 at the bottom but it will be understood that this arrangement is subject to modification. Feet 19 are apertured in screw holes 22. Screws 21 or other fasteners may be used to hold down one or more of the feet 19 by attachment of the screws to the PCB 11 or other means. Above each heat sink 12 or 13 a three-sided cut 23 is stamped or otherwise formed in body 16 leaving the fourth side 26 uncut so that a tongue 24 extends outwardly from side 26 as defined by the three-sided cut 23. The tongue 24 is formed curved downwardly as a spring which bears against the top of each heat sink 12 or 13 and thus prevents it from being dislodged. Where the PCB is to be installed vertically or at a steep angle to the horizontal, tongues 36 may be formed in body 16 by forming three-sided cuts in the body and bending the material between the cuts downward at an angle. Tongues 36 are positioned to engage the upper comers of the heat sinks 12 or 13 to restrain sliding movement of the heat sinks relative to PCB 11. In the modification of Figs. 1-3, the fastemers 21 are applied, two at one end and one at the other. A modification is shown in Fig. 3A wherein a slot is formed in the PCB 11a. Foot 32 attached to the bottom of leg 18a is inserted through the slot 31 and screw 21a is used to fasten the foot 19a at the opposite end of the body 16a to the PCB 11a. In other respects the modification of Fig. 3A resembles that of the preceding modification in the same reference numerals followed by the subscript a are used to designate corresponding parts. The foregoing descriptions of specific embodiments of the present invention have been presented for purposes of illustration and description. They are not intended to be exhaustive or to limit the invention to the precise forms disclosed, and obviously many modifications and variations are possible in light of the above teaching. The embodiments were chosen and described in order to best explain the principles of the invention and its practical application, to thereby enable others skilled in the art to best utilize the invention and various embodiments with various modifications as are suited to the particular use contemplated.

Claims: An attachment for use with a PCB, wherein in use the attachment fits over a heat sink mounted over a component mounted on the PCB (11) to secure the heat sink (12) against disengagement in the event of shock or vibration, said attachment comprising, a body (16) located above a heat sink, a spring-like tongue (24) struck from said body and comprising a downwardly curved spring located to bear against the top of the heat sink, and a plurality of legs (18, 18a) depending from said body to secure said body to the PCB a fixed distance from the PCB, wherein said body is formed with a three-sided rectangular cut (23), said tongue extending from the fourth side of the rectangle. An attachment according to claim 1 in which there is a plurality of heat sinks mounted on the PCB and said body is formed with a plurality of tongues curved to form a plurality of springs, each said spring being positioned to bear against the top of a heat sink. An attachment according to claim 1 or 2 in which said body is of spring metal. An attachment according to any preceding claim in which each said leg extends vertically down from said body and terminates in a foot (19). An attachment according to claim 4 in which said foot is apertured and which further comprises a fastener (21) through the aperture engaging the PCB slot. An attachment according to claim 4 in which the PCB is formed with a slot aperture and in which at least one said foot extends through said slot. An attachment according to claim 1 which further comprises a downward slanted tongue (36) shaped and positioned to bear against a comer of the heat sink to restrain lateral movement of the heat sink relative to the PCB. A PCB having at least one component with a heat sink mounted thereon, and an attachment of any preceding claim fitted over said heat sink.

Inventors: BARNES RONALD, LE CORNU HERBERT E, MITTY NAGARAJ P, BARNES, RONALD, LE CORNU, HERBERT E., MITTY, NAGARAJ P.
Applicants: SUN MICROSYSTEMS INC, SUN MICROSYSTEMS, INC.
Application year: 1998
Main classification: H05K7
IPC codes: H01L23, H05K7