Integrated circuit subassembly with thermally anisotropic heat transfer element

• US 6,104,090 A
• Filed: 06/15/1998
• Issued: 08/15/2000
• Est. Priority Date: 03/21/1996
• Status: Expired due to Fees

• Current Assignee: Bryte Technologies Incorporated
• Original Assignee: Bryte Technologies Incorporated
• Inventors: Unger, Scott M., Riddle, Guy T.
• Primary Examiner(s): WILLIAMS, ALEXANDER O
• Application Number:
  US09/097,844
• Time in Patent Office: 792 Days
• Field of Search: 257/706, 257/705, 257/712, 257/707, 257/713, 257/677, 257/710, 257/796, 257/729, 257/717, 257/730, 257/720, 257/704, 257/703, 428/195, 428/336, 428/323, 438/122, 438/125
• US Class Current: 257/729
• CPC Class Codes: H01L 2224/48091 Arched
• CPC Class Codes: H01L 2224/48247 connecting the wire to a bond pad of the item
• CPC Class Codes: H01L 23/3733 having a heterogeneous or anisotropic structure, e.g. powder or fibres in a matrix, wire mesh, porous structures H01L23/3732, H01L23/3737 take precedence
• 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: H01L 2924/15311 being a ball array, e.g. BGA
• CPC Class Codes: Y10T 428/24802 Discontinuous or differential coating, impregnation or bond [e.g., artwork, printing, retouched photograph, etc.]
• CPC Class Codes: Y10T 428/25 Web or sheet containing structurally defined element or component and including a second component containing structurally defined particles
• CPC Class Codes: Y10T 428/265 1 mil or less

Abstract

An integrated circuit heat transfer element (6,30) is made by selecting thermally conductive fibers having aspect ratios of length to diameter of more than 1, selecting a resin and combining the fibers and the resin to create a formable resin/fiber compound. The resin/fiber compound is formed into a composite material in part by applying pressure to the formable resin/fiber compound, which aligns the fibers, and when cured creates a thermally anisotropic composite material to maximize heat conduction along the aligned fibers. The thermally anisotropic composite material has a coefficient of thermal expansion (CTE) of less than about 10×10^-6 cm/cm/° C. The composite material has a thermal conductivity in the direction of the carbon fibers of at least 50 W/m° K. The IC device is preferably secured to the heat transfer element using a thermally conductive adhesive.

Claims

1. An integrated circuit subassembly comprising:

an integrated circuit (IC) device having a first CTE;

a heat transfer element, comprising a thermally anisotropic composite material with a second CTE adjacent said IC device; and

said composite material comprising thermally conductive fibers oriented generally perpendicular to said IC device, at least 30% of said fibers having aspect ratios of length to diameter of greater than 1.

2. The subassembly according to claim 1 wherein said second CTE is within 60% of the first CTE.

3. The subassembly according to claim 1 wherein said first and second CTE'"'"'s are about 5-6×

10^-6 cm/cm/°

C.

4. The subassembly according to claim 1 wherein said second CTE is less than about 10×

10^-6 cm/cm/°

C.

5. The subassembly according to claim 1 wherein said heat transfer element comprises a heat slug.

6. The subassembly according to claim 1 wherein said heat transfer element comprises a chip lid.

7. The subassembly according to claim 1 wherein said heat transfer element has a thermal conductivity in a direction generally perpendicular to said IC device of at least 50 W/m°

K.

8. The subassembly according to claim 1 wherein said thermally conductive fibers comprise carbonaceous fibers and said composite material comprises said carbonaceous fibers within a matrix.

9. The subassembly according to claim 8 wherein said matrix is at least 60% carbon by weight.

10. The subassembly according to claim 1 wherein said heat transfer element comprises a thermally conductive layer covering said composite material.

11. The subassembly according to claim 1 further comprising a thermally conductive adhesive securing said IC device to said heat transfer element.

12. The subassembly according to claim 11 wherein said adhesive is a non-elastomeric material.

13. The subassembly according to claim 11 wherein said adhesive is selected from the following group:

cyanate esters, epoxy, silicone, polyimide or bismaleimide.

14. An integrated circuit subassembly comprising:

an integrated circuit (IC) device having a first CTE;

a heat transfer element, comprising a thermally anisotropic composite material with a second CTE adjacent said IC device;

said second CTE being less than about 10×

10^-6 cm/cm/°

C.;

a thermally conductive adhesive securing said IC device to said heat transfer element;

said composite material comprising carbon fibers oriented generally perpendicular to said IC device; and

said heat transfer element having a thermal conductivity in a direction generally perpendicular to said IC device of at least 50 W/m°

K.

15. The subassembly according to claim 14 wherein said composite material comprises said carbon fibers within a matrix which is at least 60% carbon by weight.