Microstructure and thermal conductivity of hypereutectic Al-high Si produced by casting and spray deposition
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Fuyang Cao School of Materials Science and Engineering, Harbin Institute of Technology, Harbin 150001, China
Pan Ma School of Materials Engineering, Shanghai University of Engineering Science, Shanghai 201620, China
Sergio Scudino IFW Dresden, Institute for Complex Materials, D-01171 Dresden, Germany
Jürgen Eckertb) Erich Schmid Institute of Materials Science, Austrian Academy of Sciences, Jahnstraße 12, A-8700 Leoben, Austria; and Department Materials Physics, Montanuniversität Leoben, Jahnstraße 12, A-8700 Leoben, Austria
Jianfei Sun School of Materials Science and Engineering, Harbin Institute of Technology, Harbin 150001, China
Gang Wanga) Institute of Materials, Shanghai University, Shanghai 200444, China (Received 20 April 2016; accepted 2 August 2016)
The Al–50Si alloy, as a kind of potential electronic packaging material, is manufactured by different methods, such as casting and spray deposition. The possible influences of the P refiner on the microstructure of the Al–50Si alloy are investigated at different cooling rates. The refinement mechanism of primary Si phase is discussed in view of the P refiner addition, and the variation of the cooling rates. The thermal conductivity (TC), as a key parameter for electronic materials, is measured. The coupled effects of the cooling rate and the addition of the P refiner during the solidification of the Al–50Si alloy on the TC are elucidated based on structural observations. Furthermore, the porosity in the Al–50Si alloy is treated as a second phase influencing the TC.
I. INTRODUCTION
As an important part of microcircuits, the electronic packaging material mainly provides mechanical support for fine-scale electronic circuits, and is treated as a conductive connection medium, which plays a key role for the stability of devices.1–3 Ideal thermal management materials usually possess a low coefficient of thermal expansion (CTE) of 7–9 106 K1, a high thermal conductivity (TC) of .100 W/mK, and a low density of ,3 gcm3, which is of importance especially for transport applications.4,5 It is well known that the densities of Al–Si binary alloys range from 2.3 to 2.7 g/cm3, Contributing Editor: Yang-T. Cheng a) Address all correspondence to this author. e-mail: [email protected] b) This author was an editor of this journal during the review and decision stage. For the JMR policy on review and publication of manuscripts authored by editors, please refer to http://www.mrs. org/jmr-editor-manuscripts/ DOI: 10.1557/jmr.2016.305
depending on the Si content.6 In this binary-alloy system, Al possesses a high TC (238 W/mK at room temperature) and Si exhibits a low CTE (2.6 106/K at room temperature). Therefore, an adjustment of the Si content in Si-rich Al–Si binary alloys (Siwt% $ 50%) to approach a high TC, and a low CTE that can be matched with GaAs alloy or Si is very attractive for thermal management applications.7–10 Previous studies have found that the microstructure of Si-rich Al–Si alloys prepared by conventional casting is mainly composed of a thick, irregular,
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