Low melting point thermal interface material

Author

Webb, Ralph L. ; Gwinn, Joshua P.

Author_Institution

Pennsylvania State Univ., University Park, PA, USA

fYear

2002

fDate

2002

Firstpage

671

Lastpage

676

Abstract

A high performance thermal interface material has been developed that consists of a 25 μm coating of low-melting-temperature alloy (LMTA) tinned on each side of a 50 μm copper substrate. The alloy has a melting point below the maximum CPU operating temperature. Steady-state tests per ASTM D-5470 show 0.058 K-cm²/W at 138 kPa contact pressure. Contact pressures as small as 34 kPa are permissible. Thermal cycling tests (1000 cycles) show negligible performance degradation, if the temperature is cycled less than 12 K above the melting point. Thermal cycling 20 K above the melting point results in degradation due to formation of a low thermal conductivity intermetallic alloy at the LMTA-copper interface. Removal and replacement of the LMTA results in negligible increase in interface resistance. Manufacturing methods are discussed, and a concept for the application of LMTA to the CPU-heatsink interface is presented. The LMTA alloy offers performance competitive with the best thermal grease, without the "messy" disadvantages of thermal grease.

Keywords

heat sinks; melting point; thermal resistance; ASTM D-5470 test; CPU-heatsink interface; Cu; LMTA-copper interface; contact pressure; copper substrate; intermetallic compound formation; low-melting-temperature alloy coating; manufacturing method; melting point; thermal conductivity; thermal cycling; thermal interface material; thermal resistance; Central Processing Unit; Conducting materials; Contact resistance; Copper; Materials testing; Resistance heating; Surface resistance; Temperature; Thermal conductivity; Thermal resistance;

fLanguage

English

Publisher

ieee

Conference_Titel

Thermal and Thermomechanical Phenomena in Electronic Systems, 2002. ITHERM 2002. The Eighth Intersociety Conference on

ISSN

1089-9870

Print_ISBN

0-7803-7152-6

Type

conf

DOI

10.1109/ITHERM.2002.1012519

Filename

1012519