Microstructural characterisation of spray formed Si–30Al for thermal management applications.pdf

Scripta Materialia 55 (2006) 111–114 Microstructural characterisation of spray formed Si–30Al for thermal management applications S.C. Hogg,a,* A. Lambourne,a A. Ogilvyb and P.S. Granta aDepartment of Materials, University of Oxford, Parks Road, Oxford, Oxfordshire OX1 3PH, UK bSandvik-Osprey Metals Ltd., Millands, Neath SA11 1NJ, UK Received 8 December 2005; revised 3 February 2006; accepted 12 February 2006 Available online 14 April 2006 This paper presents a study of the microstructure of a spray formed Si–30 wt.%Al alloy used in electronic packaging applica- tions. The microstructure consisted of 5 lm equiaxed primary Si grains and a coarse grained Al-rich phase with occasional regions of 10 lm equiaxed Al-rich grains interpenetrating the Si network with no evidence of a lamellar Al–Si eutectic. This unusual micro- structure arose because of the particular solidification conditions during and immediately after the spray forming process and the large alloy freezing range. 2006 Acta Materialia Inc. Published by Elsevier Ltd. All rights reserved. Keywords: Spray forming; Spray casting; Si–Al; Thermal management; Electron backscattering diffraction (EBSD) The increasing power and density of modern avionic integrity found in conventionally cast Al-high Si alloys, and satellite electronics demands efficient heat dissipa- spray forming [7] has been developed for the manufac- tion to prevent the premature failure of semiconductor ture of bulk Si–Al alloys with Si concentrations up to devices [1]. Failure rates inc