Thermal interface pad utilizing low melting metal with retention matrix

• US 20030187116A1
• Filed: 10/24/2002
• Published: 10/02/2003
• Est. Priority Date: 04/05/2000
• Status: Active Grant

• Current Assignee: Henkel IP & Holding GmbH (Henkel AG & Co KGaA)
• Original Assignee: Berquist Company The (Henkel AG & Co KGaA)
• Inventors: Jewram, Radesh, Misra, Sanjay, Elahee, G M Fazley
• Granted Patent: US 6,984,685 B2
• Time in Patent Office: Days
• US Class Current: 524/404
• 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 23/3736 Metallic materials H01L23/3732, H01L23/3733, H01L23/3735, H01L23/3737, H01L23/3738 take precedence
• CPC Class Codes: H01L 23/3737 Organic materials with or without a thermoconductive filler
• 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: H01L 2924/3011 Impedance
• CPC Class Codes: Y10T 428/24149 Honeycomb-like
• CPC Class Codes: Y10T 428/24157 Filled honeycomb cells [e.g., solid substance in cavities, etc.]
• CPC Class Codes: Y10T 428/24165 Hexagonally shaped cavities
• CPC Class Codes: Y10T 428/24273 including aperture
• CPC Class Codes: Y10T 428/24298 Noncircular aperture [e.g., slit, diamond, rectangular, etc.]
• CPC Class Codes: Y10T 428/24322 Composite web or sheet
• CPC Class Codes: Y10T 428/24331 including nonapertured component

Abstract

A stabilized thermally conductive mechanical compliant laminate pad to be interposed between opposed surfaces of a generating semi-conductor device and a heat sink, with the laminate pad comprising upper and lower laminae on opposed surfaces of a central stabilizing apertured grid. The laminae are subjected to a compressive force at an elevated temperature until portions of the laminae extend through the apertures to form a continuum. The laminae comprise a polymer matrix having a quantity of a low melting indium or gallium alloy and a thermally conductive particulate dispersed there through, with the polymer matrix being a hot wax or melt resin. With the upper and lower laminae positioned on opposed surfaces of a central stabilizing apertured grid a compressive load is applied to force portions of said laminae to pass through apertures in the mesh grid to form a continuum.

Claims

1. In a stabilized thermally conductive mechanically compliant laminate pad for interposing between opposed surfaces of a heat generating semiconductor device and a heat sink wherein the stabilized thermally conductive mechanically compliant laminate comprises upper and lower laminae on opposed surfaces of a central stabilizing apertured grid and with portions of said laminae extending through apertures in said mesh grid to form a continuum, said stabilized thermally conductive laminate being characterized in that:

(a) said upper and lower laminae comprise a mixture of;

(1) a polymer matrix;

(2) a quantity of low melting indium or gallium containing alloy having a melt point at about 120°

C. disbursed within said polymer matrix;

(3) a thermally conductive particulate solid disbursed within said polymer matrix;

(b) said stabilizing open mesh grid comprising a grid body with an array of generally reticulated apertures formed therein, and with the structure and said grid forming between about 10% and 90% of the area of said mesh grid, balance apertures;

(c) each of said reticulated apertures having a cross-sectional dimension greater than about 0.5 mil;

d) said polymer matrix selected from the group consisting of hot melt waxes of paraffin and silicone, elastomers of acrylic, silicone, urethane, and flexible epoxy'"'"'s, and rigid resins consisting of silicone, urethane, epoxy and phenolic polymers with each polymer matrix having a melting point ranging from between about 40°

C. and 120°

C.;

2. The stabilizing thermally conductive mechanically compliant laminate pad of claim 1 wherein said polymer matrix is cross linked prior to being interposed between surfaces of heat generating semi-conductor device and a heat sink.

3. The stabilizing thermally conductive mechanically compliant laminate pad of claim 1 wherein said polymer matrix is mountingly interposed between opposed surfaces of a heat generating semi-conductor device and a heat sink while in the B-stage of cure, and thereafter subjected to a cross-linking operation.

4. The stabilizing thermally conductive mechanically compliant laminate pad of claim 1 wherein said alloy has a melt point between about 30°

C. and 90°

C.;

5. The stabilizing thermally conductive mechanically compliant laminate pad of claim 1 wherein said thermally conductive particulate is selected from the group consisting of boron nitride, alumina, and graphite.

6. The method of preparing thermally conductive mechanically compliant pads comprising the steps of:

(a) preparing a mixture of;

(1) a low melting metal selected from the group consisting of gallium and indium alloys, and being in the liquid state at temperatures below 120°

C.; and

(2) a thermally conductive particulate solid selected from the group consisting of boron nitride, aluminum nitride, and alumina;

(b) mechanically blending said mixture to cause the surfaces of said particulate to become wetted with said liquid alloy to form a homogeneous thermally conductive paste wherein said liquid alloy encapsulates individual of said particles comprising said particulate;

(c) combining said thermally conductive paste with a quantity of a flowable plastic resin material selected from the group consisting of a silicone wax having a siloxane backbone with pendent alkyl chains, and soft silicone polymers consisting of a reactive elastomer to form a thermally conductive mass, with said thermally conductive mass comprising from between about 10% and 90% by volume of metal coated particulate, balance flowable plastic resin blend;

(d) applying said thermally conductive mass to opposed surfaces of a mesh grid having an array of reticulated apertures to form a multi-layer preform grid of between about 10% and 90% open; and

(e) subjecting said preform to pressure sufficient to cause said oppositely disposed coatings to pass through said reticulated apertures to merge and form a continuum.