| With the integration,miniaturization and growth in power density of electronic components,the demand for efficient heat dissipation continues to increase,and the design and fabrication of advanced electronic packaging materials are of great practical importance.Al-high Si alloys are widely used as electronic packaging materials in aerospace and other fields because of their low density,matching thermal expansion and high thermal conductivity.However,the coefficient of thermal expansion of the widely used Al-50Si alloy is 11.0×10-6·K-1,which is difficult to meet the application requirements of high power density electronic components;increasing the Si content can reduce the coefficient of thermal expansion,but it also has the problem of poor processing and sealing performance.Al-high Si functionally graded materials（FGMs）combine the advantages of low Si content alloys for easy processing and sealing,and high Si content alloys for low thermal expansion coefficient,which can meet the comprehensive requirements of material properties and process performance for high power packaging.This paper aims to obtain new electronic packaging materials with good performance through the design and fabrication of Al-high Si alloys with gradient structures,combined with the microstructure and macroscopic properties.The main research contents are as follows:（1）Study on the relationship between the microstructure and macroscopic properties of Al-high Si alloys and Si content.The microstructure of the spray-deposited Al-x Si（x=22–70）alloys is fine and dense,and the Si phase is uniformly distributed in the Al matrix and gradually forms a network-like structure with the increase of Si content.With the increase of Si content,the tensile strength and flexural strength of the alloys first increase and then decrease,first increased and then decreased,with the highest tensile strength（274 MPa）for the Al-50Si alloy and the highest flexural strength（313 MPa）for the Al-42Si alloy;the thermal conductivity and thermal expansion coefficient gradually decrease.（2）Structural design and finite element analysis of Al-high Si FGMs.The introduction of the transition layer has an obvious effect on the thermal stress mitigation of the FGMs,and the maximum equivalent stresses of the optimal structures of three-layer FGMs are more than 44%lower than those of two-layer FGMs,and the stress change trend remains the same when changing temperature conditions.The shell structures with higher thermal conductivity of the joining layer have lower maximum temperatures under the same thermal generation rate.（3）Study on the preparation and the microstructure and properties of Al-high Si FGMs.The interfacial bonding of the Al-high Si FGMs is fine,and the interlayer bond strength of the FGMs decreases as the difference in Si content between adjacent layers increases,with the lowest bond strength（83 MPa）for the 22/70 FGM.The flexural strength of the two-layer FGMs is lower than that of the three-layer FGMs,and the flexural strength of the specimen in the H-L direction is higher than that in the L-H direction by more than 77%.Compared with the two-layer FGMs,the three-layer FGMs significantly improve the thermal expansion matching while maintaining good thermal conductivity(>130 W·m-1·K-1).（4）Study on the thermal shock resistance of Al-high Si FGMs.During thermal cycling,continuous cracks are produced at the interfaces of the two-layer FGMs,while only fine cracks are formed at the interfaces with high Si content of the three-layer FGMs.The comparative analysis reveals that the cracks are more frequent near the interfaces of the layers with large differences in Si content.36 figures,17 tables,135 references... |
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