Silicon is a gray, brittle, tetravalent, chemical element. It makes up 27.8% of the earth’s crust and next to oxygen, it is the most abundant element in nature. Some of the most common materials that contain silicon are quartz, agate, flint, and common beach sand, among others. It is the main component in building materials like cement, brick and glass. Silicon is also the most common material to build semiconductors and microchips with. Ironically, silicon by itself does not conduct electricity very well; however, it can take on dopants precisely in order to control resistivity to an exact specification.
Before a semiconductor can be built, silicon must turn into a wafer. This begins with the growth of a silicon ingot. A single silicon crystal consists of atoms arranged in a three-dimensional periodic pattern that extends throughout the material. A polysilicon crystal is formed by many small single crystals with different orientations, which alone, cannot be used for semiconductor devices.
The high silicon content Si-Al alloy is a typical heat dissipation material that used in the electrical packaging field. A spray forming process is used to produce a 70%Si-Al alloy specimen as a heat dissipation material with a diameter of 76.2 mm (3 inch) and a thickness of 6 mm. Then the rapid solidification Si-Al alloy specimens are hot pressed at 570 ℃ with different pressure ranged from 200 MPa to 700 MPa to increase their density. The physical properties of the experimental alloy specimen are measured. And the microstructures are observed by using optical microscopy and scanning electronic microscopy. The results show that Spray forming is suitable to produce a 70%Si-Al alloy. The size of primary Si phase in the rapid solidification 70%Si-Al alloy is refined only 20~30 mm. The relative density of 70%Si-Al alloy after spray forming is about 90%. With a following hot pressure of 700 MPa, the relative density value can obtain 98%. The typical physical properties such as the thermal conductivity, coe cient of thermal expansion and electrical conductivity of spray formed 70%Si-Al alloy are acceptable as a heat dissipation material for many electronic packaging applications.