Influence of processing route on electrical and thermal conductivity of Al/SiC composites with bimodal particle distribution

Abstract

Al/SiC composites with volume fractions of SiC between 0.55 and 0.71 were made from identical tapped and vibrated powder preforms by squeeze casting (SC) and by two different setups for gas pressure infiltration (GPI), one that allows short (1-2 min) liquid metal/ ceramic contact time (fast GPI) and the other that operates with rather long contact time, i.e., 10-15 min, (slow GPI). Increased liquid metal-ceramic contact time is shown to be the key parameter for the resulting thermal and electrical conductivity in the Al/SiC composites for a given preform. While for the squeeze cast samples neither dissolution of the SiC nor formation of Al 4 C 3 was observed, the gas pressure assisted infiltration led inevitably to a reduced electrical and thermal conductivity of the matrix due to partial decomposition of SiC leading to Si in the matrix. Concomitantly, formation of Al 4 C 3 at the interface was observed in both sets of gas pressure infiltrated samples. Longer contact times lead to much higher levels of Si in the matrix and to more Al 4 C 3 formation at the interface. The difference in thermal conductivity between the SC samples and the fast GPI samples could be rationalized by the reduced matrix thermal conductivity only. On the other hand, in order to rationalize the thermal conductivity of the slow GPI a reduction in the metal/ceramic interface thermal conductance due to excessive Al 4 C 3 -formation had to be invoked. The CTE of the composites generally tended to decrease with increasing volume fraction of SiC except for the samples in which a large expansive drift was observed during the CTE measurement by thermal cycles. Such drift was essentially observed in the SC samples with high volume fraction of SiC while it was much smaller for the GPI samples. G. Sinicco-formerly an undergraduate student of É cole Polytechnique Fédérale de Lausanne, EPFL.

SiC as Base of Composite Materials for Thermal Management

“…The differential effective medium (DEM) scheme has been applied with success to model and interpret transport properties in different composite materials (Clyne, 2000b;Molina et al, 2008a;Molina et al, 2008b;Molina et al, 2009;Tavangar et al, 2007;Weber et al, 2010). Its predictive capacity is in many cases considerably superior to other available models in literature (see for example (Tavangar et al, 2007)).…”

“…In (Weber et al, 2010) it is presented a complete study of comparison of the different properties encountered for Al/SiC composites processed by these two fabrication techniques. In this work, bimodal powder mixtures of green quality SiC powders with average sizes of 170 µm and 17 µm, respectively, were used.…”

“…14a resumes the thermal conductivities for both series of composites together with modelling predictions using the DEM scheme. For the slow GPI this parameter has a value which is about the half, most probably due to the abundant reaction product (Al 4 C 3 ) at the interface (Weber et al, 2010). The results of the CTE measurements are collected in Fig.…”

Al/stainless-invar composites with tailored anisotropy for thermal management in light weight electronic packaging

“…As a corollary, the second phase has to contribute significantly to the strength of the composite. Many types of fibre or particulate have been tested for reinforcing an Al-matrix in view of packaging applications: SiC [3][4][5][6][7], Al 2 O 3 [8,9], diamond [10][11][12], graphite flakes [13], fly ash [14], and carbon nanotubes [15,16]. The composites can be processed by squeeze casting or by powder metallurgy provided to control properly the phenomena governing wetting and interfacial reactions with Al.…”

Effect of chromium carbide coating on thermal properties of short graphite fiber/Al composites

“…Among these, aluminum reinforced with SiC or diamond composites for thermal dissipation in electronic packaging have been extensively studied. However, despite their favorable thermal properties, high price and poor machinability of SiC/Al and diamond/Al have obstructed the materials to reach commercialization state [4][5][6][7]. Meanwhile, although the upand-coming carbon nanotube/Al composites can potentially combine remarkable thermal properties and ease of machinability, the reported composites have much lower thermal conductivity (TC) than the one expected due to the difficulties in homogenously dispersing high fraction carbon nanotubes during fabrication [8,9].…”