Equivalent thermal conductivity of a composite structure considering heat spreading on neighboring layers

Abstract

A novel method for the equivalent thermal conductivities (K <inf xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">eq</inf> ) extraction of a composite structure is proposed and analyzed by theoretical calculation and experimental results. It is found that K <inf xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">eq</inf> should be extracted considering neighboring layers owing to the involvement of spreading resistance on neighboring layers. Simulation results show that the K <inf xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">eq</inf> is affected by thermal properties of adjacent layers and this phenomenon is successfully explained by introducing spreading thermal resistance formed on neighboring layers. For quantitative understanding of heat spreading effect, the measurement mimicking hot spot was carried out and it is found that the calculated spreading resistance curves fit very well with the experimental ones. In addition, the K <inf xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">eq</inf> calculation method for a composite structure with larger number of particulates is proposed for practical applications. From the comparison between simulated and calculated results it is elucidated that spreading resistance plays an important role in this heat transfer. The novel method proposed in this paper could be used to generate simplified thermal models for the replacement of detailed structures containing particulates, such as, bumps, via, and patterns.