Browse Prior Art Database

Chip Cooling and Thermal Contacting

IP.com Disclosure Number: IPCOM000028033D
Original Publication Date: 2004-Apr-21
Included in the Prior Art Database: 2004-Apr-21
Document File: 2 page(s) / 65K

Publishing Venue

IBM

Abstract

The disclosed idea relates to a protective layer of boron nitride (BN) between a Si surface and a liquid metal, e.g. Ga or Ga-alloys, for chip cooling.

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Chip Cooling and Thermal Contacting

With increasing power density of new generation CPUs the cooling capacity of conventional cooling devices has become a very important issue. For instance for laptop CPU cooling fan-heatsink devices are reaching their limits and new generation cooling devices will use water as a coolant. This later approach promises higher cooling power but water has a relatively low thermal conductivity. Liquid Ga is of interest because of its low melting point (302.75 K) and its much higher thermal conductivity. Its thermal capacitance compares well with that of water (1.8 vs 4.2 -3MJmK-1). The new generation of cooling devices requires a sizable reduction of thermal resistance at contact interfaces and of the realization of devices with significantly higher cooling capacity at low acoustic noise levels. Using Ga and its alloys might allow one to reach this goal. The problem with using liquid metals is that they are extremely corrosive and can diffuse into Si or make eutectic alloys if in direct contact with metallic surfaces.

A protective ceramic coating on silicon or other pertinent materials, e. g. metals, is proposed in order to allow one to use Ga and its alloys for the following applications:

I. A thermal-contact material between a cooling device to a CPU chip. Substitute for thermal-contact paste or solder.

II. Cooling liquid in a cooling device.

This proposal deals with the application of gallium and its alloys for thermal contacting as well as cooling liquid for high power chip cooling purposes where it is desirable to have good direct thermal contact to the Si surfaces of a CPU. Ga and its alloys are of interest for this application because of their low melting points [Tm(Ga)=
302.91 K]. Using these metals in a cooling device would allow excellent thermal contact. As a coolant liquids they would have clear advantages compared to water because of their higher thermal conductivity. One problem in usin...