Printed circuit board and heat sink arrangement

• US 5,646,826 A
• Filed: 02/15/1996
• Issued: 07/08/1997
• Est. Priority Date: 01/26/1995
• Status: Expired due to Fees

• Current Assignee: Nortel Networks Limited (Nortel Networks Corporation)
• Original Assignee: Northern Telecom Limited (Nortel Networks Corporation)
• Inventors: Katchmar, Roman
• Primary Examiner(s): Thompson, Gregory D.
• Application Number:
  US08/601,671
• Time in Patent Office: 509 Days
• Field of Search: 165/80.2, 165/80.3, 165/185, 174/16.3, 174/252, 174/259, 257/706, 257/707, 257/712, 257/713, 257/717-719, 257/722, 257/726, 257/727, 361/688, 361/704-722, 361/767, 361/773
• US Class Current: 361/704
• CPC Class Codes: H01L 2023/405 heatsink to package
• CPC Class Codes: H01L 2023/4056 heatsink to additional heatsink
• CPC Class Codes: H01L 2023/4062 heatsink to or through board or cabinet
• CPC Class Codes: H01L 2023/4068 Heatconductors between device and heatsink, e.g. compliant heat-spreaders, heat-conducting bands
• CPC Class Codes: H01L 23/4006 with bolts or screws
• CPC Class Codes: H01L 23/433 Auxiliary members in containers characterised by their shape, e.g. pistons
• CPC Class Codes: H01L 2924/00 Indexing scheme for arrangements or methods for connecting or disconnecting semiconductor or solid-state bodies as covered by H01L24/00
• CPC Class Codes: H01L 2924/0002 Not covered by any one of groups H01L24/00, H01L24/00 and H01L2224/00
• CPC Class Codes: H05K 1/0203 Cooling of mounted components H05K1/0272 takes precedence
• CPC Class Codes: H05K 2201/0209 Inorganic, non-metallic particles
• CPC Class Codes: H05K 2201/066 Heatsink mounted on the surface of the PCB heatsink inserted in the PCB H05K2201/10416
• CPC Class Codes: H05K 2201/0949 Pad close to a hole, not surrounding the hole if used for surface mounting H05K1/114
• CPC Class Codes: H05K 2201/0959 Plated through-holes or plated blind vias filled with insulating material
• CPC Class Codes: H05K 2201/0969 Apertured conductors
• CPC Class Codes: H05K 2201/10689 Leaded Integrated Circuit [IC] package, e.g. dual-in-line [DIL]
• CPC Class Codes: H05K 2201/10734 Ball grid array [BGA]; Bump grid array
• CPC Class Codes: H05K 2203/0126 Dispenser, e.g. for solder paste, for supplying conductive paste for screen printing or for filling holes
• CPC Class Codes: H05K 3/4069 for via connections in organic insulating substrates
• CPC Class Codes: H05K 7/20463 Filling compound, e.g. potted resin
• CPC Class Codes: H05K 7/20509 Multiple-component heat spreaders; Multi-component heat-conducting support plates; Multi-component non-closed heat-conducting structures

Abstract

Making a heat sink and printed circuit board assembly by providing a heat exchange element on the heat sink which lies in heat exchange contact with the heat sink and passes therethrough. After locating the board and heat sink in relative positions apart and with the heat exchange element aligned with an electronic component on the board, a settable thermally conductive compound is injected through a hole in the heat exchange element to bond it to the electrical component. The heat sink is detachable from the heat exchange element to expose the side of the board carrying the components so that maintenance or repair may be performed. Subsequently the heat sink is returned into its position in the assembly.

Claims

1. A method of making a printed circuit board and heat sink structure assembly comprising:

providing a structure comprising a printed circuit board and an electronic component mounted upon a first side of the printed circuit board;

providing a heat sink structure with a hole defined through the heat sink structure;

relatively disposing the printed circuit board structure and the heat sink structure with a first side of the heat sink structure facing and spaced from the printed circuit board structure and with the hole having its axis extending in the direction generally towards the electronic component and creating a heat conductive path from the heat sink structure to the printed board structure by causing a flowable settable thermally conductive material to flow through the hole to occupy and remain in a spatial region between and in heat conductive contact with the heat sink structure and the printed circuit board structure and in alignment with the electronic component.

2. A method according to claim 1 comprising:

relatively disposing the printed circuit board structure and the heat sink structure with the first side of the heat sink structure facing the first side of the printed circuit board;

and causing the settable thermally conductive material to flow through the hole to fill the space between the heat sink structure and the electronic component and to heat conductively contact the electronic component.

3. A method according to claim 1 comprising:

relatively disposing the printed circuit board structure and the heat sink structure with the first side of the heat sink structure facing and spaced from a second side of the printed circuit board;

and causing the thermally conductive material to flow through the hole to fill the spatial region between the heat sink structure and the printed circuit board structure and to flow from the spatial region through at least one aperture in the printed circuit board and towards the electronic component.

4. A method according to claim 3 comprising causing the thermally conductive material to flow through the aperture in the printed circuit board and into heat conductive contact with the electronic component.

5. A method according to claim 1 comprising:

relatively disposing the printed circuit board structure and the heat sink structure with the first side of the heat sink structure facing and spaced from a second side of the printed circuit board;

causing a first mass of the thermally conductive material to flow between the first side of the printed circuit board and the electronic component and into heat conductive contact with the electronic component;

and causing a second mass of the thermally conductive material to flow through the hole and between the second side of a printed circuit board and the heat sink structure and into heat conductive contact with the heat sink structure and into heat conductive contact with the first mass.

6. A method according to claim 5 comprising inserting an injection means through the hole in the heat sink structure and into an aperture in the printed circuit board and injecting the first mass of the thermally conductive material between the first side of the printed circuit board and the electronic component;

and subsequently causing the second mass to flow through the hole to occupy the spatial region between the heat sink structure and the second side of the printed circuit board.

7. A method according to claim 1 comprising:

with the printed circuit board structure separate from the heat sink structure, causing a first mass of the thermally conductive material to flow between the first side of the printed circuit board and the electronic component and into heat conductive contact with the electronic component;

and then assembling the printed circuit board and heat sink structures together and subsequently causing a second mass of the thermally conductive material to flow through the hole and between the second side of the printed circuit board and the heat sink structure and into heat conductive contact with the heat sink structure and into heat conductive contact with the first mass.

8. A method according to claim 1 comprising:

providing a plurality of electronic components mounted upon the first side of the printed circuit board;

providing the heat sink structure with a plurality of holes therethrough;

relatively disposing the circuit board structure and the heat sink structure with the holes generally axially directed towards an associated electronic component;

and causing the thermally conductive material to flow through the holes in the heat sink structure to occupy spatial regions between the heat sink structure and the printed circuit board structure and in alignment with the electronic components.

9. A method according to claim 1 wherein the heat sink structure comprises a heat sink and heat sink exchange element thermally conductively mounted upon the heat sink, the heat exchange element spaced from and opposing the printed circuit board structure and facing in a direction towards the electronic component, the method comprising causing the settable thermally conductive material to flow into a spatial region between the printed circuit board structure and the heat exchange element and into heat conductive contact with the heat exchange element, the thermally conductive material having an adhesive property which provides adherence between the printed circuit board structure and the heat exchange element, heat sink release means being provided to enable the heat sink to be removed from the heat exchange element which is adhered to the printed circuit board structure by the thermally conductive material.

10. A method according to claim 7 wherein side walls are provided upon the heat sink structure, the method comprising abutting edge regions of the printed circuit board against engagement surfaces of the side walls to determine the position of the circuit board structure relative to the heat sink structure and determine the distance between the two structures before the thermally conductive material is caused to flow through the holes.

25. An assembly according to claim 10 wherein the heat sink forms one part of a housing for completely enclosing the printed circuit board structure.

11. A printed circuit board and heat sink structure assembly comprising:

a structure of a printed circuit board and an electronic component mounted upon a first side of the printed circuit board;

a heat sink structure with a hole defined through the heat sink structure;

the two structures disposed face-to-face and spaced apart with the hole extending in a direction generally towards the electronic component;

and thermally conductive material that has flowed through the hole to be disposed between the two structures and occupy a spatial region extending across the hole and in heat conductive contact with both structures and in alignment with the electronic component.

12. An assembly according to claim 11 wherein the heat sink structure faces the first side of the printed circuit board and the thermally conductive material is disposed between and in heat conductive contact with the electronic component and with the heat sink structure.

13. An assembly according to claim 11 wherein the heat sink structure faces a second side of the printed circuit board and the thermally conductive material extends through an aperture in the printed circuit board into heat conductive contact with the electronic component.

14. An assembly according to claim 11 wherein the heat sink structure faces the second side of the printed circuit board and the thermally conductive material extends between and is in thermal conductive contact with the second side of the printed circuit board and with the heat sink structure and extends between and is in thermal conductive contact with the electronic component and the first side of the printed circuit board, the heat exchange material on one side of the board being in thermal conductive relationship to the heat exchange material on the other side of the board.

15. An assembly according to claim 14 wherein the heat conductive material extends through at least one aperture in the printed circuit board to interconnect the thermal conductive material on both sides of the board.

16. An assembly according to claim 14 wherein another heat conductive material is located within at least one aperture in the printed circuit board and is in thermal conductive contact with the thermally conductive material on each side of the board.

17. An assembly according to claim 11 wherein the heat sink structure faces the second side of the printed circuit board and the electronic component has terminals attached to terminals of the printed circuit board by a solder ball grid array, and thermally conductive material extends between and is in thermal conductive contact with the heat sink structure and with the second side of the printed circuit board and the thermally conductive material extends into apertures in the printed circuit board and is in heat conductive relationship with the solder ball grid array.

18. An assembly according to claim 11 wherein the heat sink structure comprises a heat sink and heat exchange element extending through the heat sink and facing towards the electronic component and the thermally conductive material has an adhesive property and is disposed between and in heat conductive contact with the printed circuit board structure and the heat exchange element, and the heat exchange element is formed with the hole through which the thermally conductive material has flowed, the heat exchange element being adhered to the printed circuit board structure by the thermally conductive material and mounted upon the heat sink so as to enable the heat sink to be removed from the heat exchange element while the heat exchange element remains carried upon the printed circuit board structure by the thermally conductive material.

19. An assembly according to claim 18 wherein the heat exchange element comprises a wide portion and a narrow portion, the hole extending through the wide and narrow portions, the heat exchange element mounted upon the heat sink with the narrow portion extending through the heat sink and the wide portion on the side of the heat sink facing the printed circuit board structure, the thermally conductive material disposed between the wide portion and the printed circuit board structure.

20. An assembly according to claim 19 wherein a screw-threaded arrangement is provided to mount the heat exchange element to the heat sink and to render the heat sink detachable from the structure.

21. An assembly according to claim 20 wherein the narrow portion of the heat exchange element has an end region remote from the wide portion, and the screw-threaded arrangement comprises a screw-thread on the end region and a nut engageable on the end region on a second side of the heat sink.

22. An assembly according to claim 21 wherein the heat exchange element has a frangible region upon the narrow portion and the heat exchange element is rotatable within the aperture of the heat sink to cause fracture of the heat exchange element with the narrow portion remaining in the aperture and so as to enable detachment of the heat sink.

23. An assembly according to claim 18 wherein the thermally conductive material is frangible and the heat exchange element is rotatable within the aperture of the heat sink to cause fracture of the adhesive between the structure and the wide portion of the heat exchange element so as to allow for detachment of the heat sink together with the heat exchange element from the structure.

24. An assembly according to claim 19 wherein side walls are provided upon the heat sink and the side walls have engagement surfaces for abutting end regions of the printed circuit board when the heat sink is in the position mounted upon the narrow portions.