Methods of making printed circuit boards and heat sink structures

• US 5,661,902 A
• Filed: 06/29/1995
• Issued: 09/02/1997
• Est. Priority Date: 10/08/1993
• Status: Expired due to Term

• Current Assignee: Ciena Corporation
• Original Assignee: Northern Telecom Limited (Nortel Networks Corporation)
• Inventors: Katchmar, Roman
• Primary Examiner(s): Vo, Peter
• Assistant Examiner(s): NGUYEN, KHAN
• Application Number:
  US08/496,649
• Time in Patent Office: 796 Days
• Field of Search: 29/840, 29/832, 29/852, 228/179.1, 361/705, 361/719, 174/252, 174/16.3
• US Class Current: 29/840
• CPC Class Codes: H01L 2224/48091 Arched
• CPC Class Codes: H01L 2224/4824 Connecting between the body and an opposite side of the item with respect to the body
• CPC Class Codes: H01L 23/3672 Foil-like cooling fins or heat sinks being part of lead-frames H01L23/49568
• CPC Class Codes: H01L 23/3677 Wire-like or pin-like cooling fins or heat sinks
• CPC Class Codes: H01L 23/3737 Organic materials with or without a thermoconductive filler
• CPC Class Codes: H01L 2924/00014 the subject-matter covered by the group, the symbol of which is combined with the symbol of this group, being disclosed without further technical details
• CPC Class Codes: H05K 1/0206 by printed thermal vias
• 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 2201/09072 Hole or recess under component or special relationship between hole and component
• CPC Class Codes: H05K 2201/0959 Plated through-holes or plated blind vias filled with insulating material
• CPC Class Codes: H05K 2201/10416 Metallic blocks or heatsinks completely inserted in a PCB metallic supports H05K3/0061
• CPC Class Codes: H05K 2201/10689 Leaded Integrated Circuit [IC] package, e.g. dual-in-line [DIL]
• CPC Class Codes: H05K 3/0061 onto a metallic substrate, e.g. a heat sink heat sinks for electric apparatus H05K7/20
• CPC Class Codes: H05K 3/305 Affixing by adhesive
• CPC Class Codes: H05K 3/4069 for via connections in organic insulating substrates
• CPC Class Codes: H05K 3/42 Plated through-holes or plated via connections
• CPC Class Codes: Y10T 29/4913 Assembling to base an electrical component, e.g., capacitor, etc.
• CPC Class Codes: Y10T 29/49144 by metal fusion

Abstract

A method of making a printed circuit board and heat sink structure by initially providing the board with a heat conductive layer oh each of its two sides, the two conductive layers thermally interconnected by heat conductive material extending through holes in the board. An electronic component is mounted spaced apart from the conductive layer on one side of the board and is thermally connected to that layer by a thermally conductive viscous substance injected through a hole from the other side of the board. The viscous material flows in a reverse direction through other holes in the board. A heat sink is then attached by thermally conductive material to the conductive layer on the other side of the board. A method is also included of injecting a thermally conductive curable resin between an electronic component and a printed circuit board with a release agent between the component and the resin. After cooling the resin at sufficiently high temperature for it to be in contact with the release agent, the cured resin cools and shrinks away from the component. Subsequent heating of the resin expands it into heat conductive engagement with the component for quicker release of heat therefrom.

Claims

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

providing a circuitry layer and a plurality of electronic components upon the circuitry layer;

mounting the circuitry layer upon one side of a heat conductive layer means detining a printed circuit board which comprises a heat insulating layer and a first and second heat conductive layers disposed one upon each side thereof and extending across the heat insulating layer and across an area of the printed circuit board between positions in which the heat conductive layer means lies opposite to the plurality of electronic components, the conductive layers interconnected by heat conductive members extending through the heat insulating layer and providing heat conductive means between the electronic components and the first heat conductive layer;

and locating a heat sink on the other side of the heat conductive layer means and in a position spaced from the second heat conductive layer, and connecting the heat sink with the second heat conductive layer by thermally conductive bridge members which extend in localized and spaced positions between the heat sink and the second heat conductive layer.

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

providing a printed circuit board with a heat conductive layer on each side of the board and with heat conductive material extending through holes formed in the board to thermally interconnect the two conductive layers;

mounting an electronic component in spaced relationship from the conductive layer on the one side of the board and with the component having electrical leads connected to electrical terminals on the board;

injecting a thermally conductive viscous substance through a hole in the board from the other side of the board to cause the viscous substance to thermally connect the electrical component and the conductive layer on the one side of the board and cause flow of the viscous substance in a reverse direction into other holes in the board beneath the electronic component;

and then attaching a heat sink with a thermally conductive material to the conductive layer on the other side of the board.

3. A method according to claim 2 comprising providing the two layers as two layers of copper on the two sides of the board and coating surfaces of the holes in the board with the copper to interconnect the two layers.

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

mounting an electronic component upon one side of a printed circuit board and in a position having a facing surface spaced from the board and with electrical leads of the component connected to electrical terminals of the board;

injecting a thermally conductive curable resin between the electronic component and the board, the resin prevented from engaging the surface of the component by the presence of a release agent between the component and resin;

then at a desired temperature, curing the resin to form a thermally conductive mass, the mass contracting away from the component during cooling and being expansible during subsequent heating;

and thermally conducively connecting the cured resin to heat sink.