Crack Effect on the Equivalent Thermal Conductivity of Porously Sintered Silver
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https://doi.org/10.1007/s11664-020-08325-1 Ó 2020 The Minerals, Metals & Materials Society
Crack Effect on the Equivalent Thermal Conductivity of Porously Sintered Silver FEI QIN,1,2 YUANKUN HU,1 YANWEI DAI ,1,2,3 TONG AN,1,2 PEI CHEN,1,2 YANPENG GONG,1,2 and HUIPING YU1 1.—Institute of Electronics Packaging Technology and Reliability, College of Mechanical Engineering and Applied Electronics Technology, Beijing University of Technology, Beijing 100124, China. 2.—Beijing Key Laboratory of Advanced Manufacturing Technology, Beijing University of Technology, Beijing 100124, China. 3.—e-mail: [email protected]
Characterizations of equivalent thermal conductivity (ETC) of sintered silver is an important topic due to the thermal–mechanical reliability requirements of electronic packaging. In this paper, the effect of various types of cracks on the ETC of sintered silver are discussed. A numerical method to simulate the heat transfer behaviors of porous sintered silver containing the crack effect is presented. The results show that the ETC of sintered silver depends significantly on the crack length, crack orientation, porosity, and pore shape. Theoretical formulae to estimate the ETC of sintered silver are also presented, in which the effects of arbitrary crack depth, arbitrary crack orientation, arbitrary porosity, and arbitrary pore shape factor on ETC are included. It has been found that the influence of the side edge crack on the reduction of the ETC of sintered silver is the most obvious compared with the center crack and the upper edge crack. This study presents a quantitative method to evaluate the crack effect on the ETC of porous sintered silver. Key words: Equivalent thermal conductivity, sintered silver, crack effect, porosity, numerical computation
INTRODUCTION Sintered silver is a very promising alternative material of the die-attach layer which has drawn much attention in recent years due to its excellent performances.1 Evaluations of thermomechanical behaviors for sintered silver under various conditions are the main topics which have been investigated by some researchers and engineers,2–4 as it is the basis of the reliability estimation of sintered silver layers. Due to potential applications of sintered silver as the die-attach layer in power electronics in the next generation, fractures of sintered silver are easily found in experimental works related to thermal mechanical analysis induced by power cycling,5 which could easily lead to the formation of cracks in sintered silver layers. As
(Received March 23, 2020; accepted July 8, 2020)
the die-attach layer is the main heat dissipater, it is crucial to understand the crack effect on the thermal conduction behaviors of sintered silver when cracks appear. Some studies have been presented to show the cracking behaviors of sintered silver under various considerations. Tan et al.6 presented an experimental investigation on the 3D morphology of creep crack growth via an X-ray technique, and they considered that some factors, such as size, shape, and dist
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