Heat conductive substrate mounted in PC board for transferring heat from IC to heat sink

• US 5,825,625 A
• Filed: 10/09/1996
• Issued: 10/20/1998
• Est. Priority Date: 05/20/1996
• Status: Expired due to Term

• Current Assignee: Samsung Electronics Co. Ltd.
• Original Assignee: Hewlett-Packard Company (HP Inc.)
• Inventors: Lang, Tracy A., Smith, Mark A., Esterberg, Dennis R., Rubens, Paul A.
• Primary Examiner(s): Tolin, Gerald P.
• Application Number:
  US08/728,394
• Time in Patent Office: 741 Days
• Field of Search: 165/80.3, 165/185, 174/16.3, 174/252, 257/706, 257/707, 257/709, 257/711-713, 257/717, 257/720, 257/726, 257/727, 361/704-712, 361/717-719, 361/722, 361/761, 361/764, 361/789, 361/792, 361/795
• US Class Current: 361/719
• 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 23/3677 Wire-like or pin-like cooling fins or heat sinks
• CPC Class Codes: H01L 23/4006 with bolts or screws
• CPC Class Codes: H01L 24/50 Tape automated bonding [TAB] connectors, i.e. film carriers; Manufacturing methods related thereto thin flexible metallic tape with or without a film carrier H01L23/49572, flexible insulating substrates H01L23/4985, H01L23/5387
• CPC Class Codes: H01L 24/86 using tape automated bonding [TAB]
• 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 2924/07802 not being an ohmic electrical conductor
• CPC Class Codes: H01L 2924/14 Integrated circuits
• CPC Class Codes: H05K 1/0204 using means for thermal conduction connection in the thickness direction of the substrate H05K1/0207 takes precedence
• CPC Class Codes: H05K 2201/09054 Raised area or protrusion of metal substrate
• CPC Class Codes: H05K 2201/10409 Screws
• CPC Class Codes: H05K 2201/10416 Metallic blocks or heatsinks completely inserted in a PCB
• CPC Class Codes: H05K 2201/10681 Tape Carrier Package [TCP]; Flexible sheet connector
• CPC Class Codes: H05K 2203/0191 Using tape or non-metallic foil in a process, e.g. during filling of a hole with conductive paste

Abstract

A heat conductive substrate is mounted within a through-opening of a printed circuit board. An integrated circuit then is mounted to one side of the heat conductive substrate, while a heat sink is fixed in thermal contact to the other side of the substrate. There is no direct thermal contact between the IC and the PC board. The substrate is mounted to an undersurface of the PC board and concentrically spaced from the PC board within the opening. An air gap occurs between the substrate and the PC board within the opening to substantially reduce heat conductivity into the PC board.

Claims

1. An apparatus for conducting heat away from an integrated circuit, the integrated circuit defining a underlying surface area and an overlying surface area, the apparatus comprising:

a PC board defining a through-opening over a thickness of the PC board, the PC board having a first surface and a second surface;

a heat conductive substrate, a first portion of which is mounted within the through-opening, a second portion of which is mounted with a quantity of solder to the first surface of the PC board adjacent to the through-opening to define a contact area extending outward from the through-opening for a first length, said first length being less than the PC board thickness to minimize thermal communication between the heat conductive substrate and the PC board, the heat conductive substrate having a first surface with an area at least as large as the integrated circuit underlying area, wherein the first surface of the heat conductive substrate is co-planar with the second surface of the PC board;

a first heat sink removably mounted into thermal contact with the substrate;

a second heat sink having a plurality of legs, the second heat sink positioned on an opposing side of the PC board than the first heat sink and the second heat sink mounted to the overlying surface area of the integrated circuit;

a plurality of mounting screws, the first heat sink attached to the second heat sink with the plurality of mounting screws extending through the PC board into the plurality of legs of the second heat sink; and

wherein the integrated circuit is fixed into thermal contact with the heat conductive substrate first surface at the integrated circuit'"'"'s underlying surface area.

2. The apparatus of claim 1, in which the PC board comprises a top surface, a bottom surface and an intermediary layer, and in which the substrate is concentrically spaced apart from the PC board intermediary layer.

3. The apparatus of claim 1, in which the contact area occurs along the entire perimeter of the through-opening.

4. An apparatus for conducting heat away from an integrated circuit, the integrated circuit having an underlying surface area and an overlying surface area, the apparatus comprising:

a PC board defining a through-opening of a first area;

a heat conductive substrate, a portion of which is positioned within the through-opening, the heat conducting substrate having a first surface with an area less than the first area and at least as large as the integrated circuit underlying area, wherein the integrated circuit is fixed into thermal contact with the heat conductive substrate first surface at the underlying surface area, and wherein the heat conductive substrate has a second surface opposite the first surface with an area less than the first area, wherein the substrate is spaced apart from the PC board by a thermally insulating adhesive.

5. The apparatus of claim 4, further comprising a first heat sink removably mounted to the substrate.

6. The apparatus of claim 5, in which the first heat sink is removably mounted into thermal contact with the substrate without forming direct thermal contact between the heat sink and the PC board.

7. The apparatus of claim 6, further comprising a second heat sink positioned on an opposing side of the PC board than the first heat sink, the second heat sink mounted to the overlying surface area of the integrated circuit and attached to the first heat sink.