Thermal expansion-adjustable carbon-doped FeCoCrNiMn high-entropy alloys for electronic packaging
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Thermal expansion-adjustable carbon-doped FeCoCrNiMn high-entropy alloys for electronic packaging Jian Peng1,*
1
, Liming Fu1, Yanle Sun1, Ziyong Li1, Xinbo Ji1, and Aidang Shan1,*
School of Materials Science and Engineering, Shanghai Jiao Tong University, 800 Dongchuan Road, Shanghai 200240, People’s Republic of China
Received: 13 July 2020
ABSTRACT
Accepted: 9 September 2020
Application of an electronic packaging material is always limited by its established coefficient of thermal expansivity (CTE) and poor plastic working capacity. Here, we explored that a ductile high-entropy alloy (HEA) could achieve adjustable CTE values via decomposing at 500 °C. The carbon-doped equiatomic FeCoCrNiMn HEAs (0.8, 1.0, and 1.3 at% C) decomposed into B2, L10, M23C6 and σ phases during annealing. The adjustable CTE of the carbondoped HEAs can be ascribed to the relatively low CTE values of the formed B2, L10, M23C6, and σ phases. The CTE value of a single face-centered cubic (FCC)structured FeCoCrNiMn-1.3 at% C HEA is 16.7 9 10–6 °C−1, yet it can be continuously adjusted to 11.3 9 10–6 °C−1 when the FCC matrix is gradually decomposed into the B2, L10, M23C6, and σ phases. Furthermore, the decomposition rate and fractions of the B2, L10, M23C6, and σ phases can be controlled via changing carbon concentration and rolling reduction. More importantly, the CTE range of the 1.3C HEAs meets the requirements of electronic packaging. This work provides a way to design HEAs with desirable CTE for electronic industry via annealing at intermediate temperature.
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1 Introduction Coefficient of thermal expansivity (CTE), the linear or bulk dimensional variations of a material under elevated temperature, is an important thermal physical property for electronic packaging materials [1–3]. The components of a device are expected to have matched CTE in order to avoid device failure caused by
thermally induced stresses. For example, the packaging components with CTE range of 17 9 10–6– 11 9 10–6 °C−1 were required for microwave packaging, backing plates, and opto-electronic housings industries. Scientists and engineers have toiled to fabricate metal matrix composites (MMCs) to match such a CTE range via adding reinforcement particles of low CTE into metal matrix [4–6]. For instance,
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https://doi.org/10.1007/s10854-020-04470-9
J Mater Sci: Mater Electron
27%–50% (weight fraction) of Si were added into Al matrix to fabricate Al-Si MMCs to meet the CTE range of 17 9 10–6–11 9 10–6 °C−1 [7–13]. Unfortunately, these CTE-matched MMCs are hard to deform into desirable components since they contain high fraction of brittle reinforcement particles [9–12]. Thus, we are eager that a packaging material has both desirable CTE and good ductility. Recently, a new series of alloys named high-entropy alloys (HEAs) with outstanding strength and ductility have attracted extensive attention [14]. Interestingly, the
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