Abstract
Highly-aligned flake graphite (FG) reinforced Cu matrix composites with high thermal conductivity and adaptive coefficient of thermal expansion were successfully prepared via the collaborative process of tape-casting and hot-pressing sintering. To overcome the problem of fragile interface, Zr-Cu alloy powder was introduced instead of pure Zr powder to enhance the interfacial strength, ascribed to the physical-chemical bonding at the Cu-FG interface. The results indicate that the synthetic ZrC as interfacial phase affects the properties of FG/Cu composites. The thermal conductivity reaches the maximum value of 608.7 W/m∙K (52% higher than pure Cu) with 0.5 wt % Zr. Surprisingly, the negative coefficient of thermal expansion (CTE) in the Z direction is acquired from −7.61 × 10−6 to −1.1 × 10−6/K with 0 to 2 wt % Zr due to the physical mechanism of strain-engineering of the thermal expansion. Moreover, the CTE in X-Y plane with Zr addition is 8~10 × 10−6/K, meeting the requirements of semiconductor materials. Furthermore, the bending strength of the FG/Cu-2 wt % Zr composite is 42% higher than the FG/Cu composite. Combining excellent thermal conductivity with ultralow thermal expansion make the FG/Cu-Zr composites be a highly promising candidate in the electronic packaging field.
Highlights
The development of microelectronic products towards miniaturization, multi-function and high integration requires that electronic components have greater power density, which inevitably generates high heat
Most of the flake graphite (FG) are stretched in the matrix and are separated from each other by the Cu matrix
The soft FGs are prone to small amount of FGs are stacked and bent as seen in the white dashed area
Summary
The development of microelectronic products towards miniaturization, multi-function and high integration requires that electronic components have greater power density, which inevitably generates high heat. The coatings of metal and carbide on the surface of carbon materials through chemical and physical methods were similar to the layers formed in the matrix alloying, and were commonly used in solid phase sintering and liquid infiltration. Complete continuous thin layers were formed at the Cu-graphite interface, and the filler was firmly connected to the matrix through chemical bonding. The thickness and quality of the thin layers were often uncontrollable, leading to the uncertainties in the performance of the composite On this occasion, it is necessary to improve the interface bonding between the Cu matrix and the FG [27], and need to excavate the potential of inherent high TC of the FG. The effects of Zr on the microstructure, TC, CTE, and mechanical properties of FG/Cu composites were investigated in detail
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