Microstructure and properties of electronic packaging box with high silicon aluminum-base alloy by semi-solid thixoforming

The electronic packaging box with high silicon aluminum-base alloy was prepared by semi-solid thixoforming technique. The flow characteristic of the Si phase was analyzed. The microstructures of different parts of the box were observed by optical microscopy and scanning electron microscopy, and the thermophysical and mechanical properties of the box were tested. The results show that there exists the segregation phenomenon between the primary Si phase and the liquid phase during thixoforming, the liquid phase flows from the box, and the primary Si phase accumulates at the bottom of the box. The volume fraction of primary Si phase decreases gradually from the bottom to the walls. Accordingly, the thermal conductivities of bottom center and walls are 107.6 and 131.5 W/(m·K), the coefficients of thermal expansion (CTE) are 7.9×10−6 and 10.6×10−6 K−1, respectively. The flexural strength increases slightly from 167 to 180 MPa. The microstructures and properties of the box show gradient distribution overall.