Development of a Ceramic-based Composite for Direct Bonded Copper Substrate
Researchers at King Fahd University of Petroleum and Minerals recently published an application paper on Development of a Ceramic-based Composite for Direct Bonded Copper Substrate. A computational approach is presented to design alumina-based composite with tailored properties that could replace commercial alumina used in Direct Bonded Copper (DBC) substrates for applications in power electronic modules. The primary goal for designing such alumina-based composites is to have enhanced thermal conductivity for effective heat dissipation and spreading capabilities together with a coefficient of thermal expansion (CTE) value that is close to the silicon chips in electronic circuits in order to avoid interface layers. At the same time, other functional properties like elastic modulus and electrical conductivity have to be maintained.
A mean-field homogenization and effective medium approximation (EMA) using an in-house code is used for predicting potential optimum thermal and structural properties for DBC substrates by considering the effect of filler type, volume, and size in the alumina matrix.
This study’s strategy incorporates thermal and structural properties of composites as a constraint on the design process. Among various metallic and carbon-based fillers, chromium, silicon carbide and diamond fillers were found suitable candidates that could enhance the thermal and structural performance of the alumina-based substrates. As a validation, alumina-silicon carbide (Al2O3-SiC) composites in line with the designed range of filler size and volume fraction using Spark Plasma Sintering (SPS) process were developed. A C-Therm TCi Thermal Conductivity Analyzer is used to measure the thermal conductivity of developed composites at room temperature. Other thermal and structural properties including CTE, and elastic modulus are also measured to complement the computational design.
The comparison between the predictions and experimentally measured effective thermal conductivity, CTE and elastic modulus of the composites developed using two sources of SiC is shown in Table 1 below.
Experimental and predicted effective thermal conductivity (Keff), effective coefficient of thermal expansion (αeff) and effective elastic modulus (Eeff) values of Al2O3 20% SiC composites. Kmat, αmat, and Ematrepresents the corresponding values pure alumina used as matrix material.
The comparisons of model results with experimental data showed good agreement. Therefore, it can be concluded that the developed computational model is accurate enough in predicting thermal and structural properties of ceramic-matrix composites and it will lead to the further development of a broad range of materials with enhanced thermal and structural performance.
Information source: S.S. Akhtar, et al., Development of a Ceramic-based Composite for Direct Bonded Copper Substrate, Ceramics International (2017)
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