IGBT Cooling System Using High Thermal Conductive Aluminum Based Composite Containing VGCF-CNT Network

Cooling of Insulated Gate Bipolar Transistors (IGBT) is a huge problem to improve the energy efficiency. To improve the cooling efficiency, a material that has the high thermal conductivity is expected to be employed for the cooling system of IGBT. The authors have fabricated an aluminum based composite material containing a network of vapor grown carbon fiber (VGCF) and carbon nanotube (CNT). The composite has the high thermal conductivity more than three times of pure aluminum. The composite also has the thermal anisotropy caused by VGCF. In this paper, the composite fabricated by authors is employed to a cooling system of IGBT. First, the effect of the thermal conductivity on the thermal efficiency of the cooling system of IGBT is investigated by finite element analyses (FEM). The effect of the thermal anisotropy is, especially, focused on to show the important role of the thermal anisotropy for the cooling system. A method to improve the thermal conductivity of the composite is also shown to decrease the fabrication costs by decreasing in the usage of VGCF. The control of alignments of VGCF is chosen for the method. The alignment is controlled by the contraction flow made by a contraction channel. The experiments show that the contraction flow is effective to control the alignment of VGCF.