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I.

INTRODUCTION

THE demand for advanced thermal management materials with higher thermal conductivity (TC) and lower coefficients of thermal expansion (CTE) for maximizing heat dissipation, minimizing thermal stress, and warping of electronic packages is critical to the continuing miniaturization, increased functionality, and integration of electronic components. The breakdown in the integrity of materials typically used for cooling structures leads to the catastrophic failure of devices associated with immediate total loss of electronic function and package integrity.[1,2] This attributes to deterioration in semiconductor behavior, performance, fracture, delamination, melting, vaporization, and combustion of the packaging materials.[3] The development of materials capable of handling improved power density, reliability, and efficiency of existing semiconductors, such as Si, SiC, and GaAs, and also new semiconductors, such as GaN, capable of operation at higher temperatures is imperative to cater to a broad range of future space, defense, and telecom applications.[4–6]

T.S. KAVITHAA is with the Sensors and Vision Technology Division, Central Manufacturing Technology Institute (CMTI), Bangalore, 560022, India. Contact e-mail: [email protected] L. RANGARAJ is with the Materials Science Division, CSIR - National Aerospace Laboratories (CSIR-NAL), Bangalore, 560017, India. S.S. AVADHANI is with the Chemical Laboratory, Central Manufacturing Technology Institute (CMTI), Bangalore, 560022, India. Manuscript submitted June 14, 2018.

METALLURGICAL AND MATERIALS TRANSACTIONS A

Traditionally, heat dissipation in electronic devices is via passive strategies wherein high TC metals, such as copper (Cu), aluminum (Al), or silver (Ag), are employed as heat sinks or heat spreaders together with a thermal interface material (TIM) or thermal stress-compensating material.[7] This resulted in an increase in thermal resistance necessitating significant design compromises. Invar and Kovar alloys with integrated circuits and substrate compatible CTE possess high densities and limited thermal conductivities.[8] Moreover, maximum thermal dissipation requires direct attachment of the device to a substrate or package.[3] Materials, such as Cu-W and Cu-Mo, offer both CTE compatibility and high TC. However, high material density and cost make them inappropriate choices for weight-sensitive devices.[9] Al/SiCp metal matrix composites (MMCs) have manifested as an efficient thermal management material with a unique set of material properties suitable for high-performance advanced thermal management packaging designs. However, with the exponential increase in heat flux of the electronic system Al/SiCp with TC of 190 W/m K, approximately half of that of Cu will not be able to provide the required thermal management performance.[10] Cu and its alloys with a TC around 396 W/m K and a CTE ~ 17 ppm/C are attractive candidate materials particularly useful for space and fusion reactor applications wherein a stringent requirement of high stiffness together