| High power module is mainly consisted of chip, conductor/insulating substrate baseplate and heat sink. They are connected together, by bonding and thermal interface materials. The heat generated by power chip gets to heat sink through a variety of materials. The interface and packaging thermal resistances are hardly reduced. Ceramic insulating metal substrate could be prepared by directly producing ceramic flim on the surface of heat sink materials. The packaging structure of power module could be great simplified and thermal resistance could be great decreased, if ceramic insulating metal substrate is used as insulated substrate. In this article, multiphase ceramic layer was fabricated by water vapor assisted sinter ing process, and consisted of Al N, α-Al2O3 and mullite. And ceramic insulating metal substrate was obtained. Through water vapor assisted sintering, aluminum nitride hydrolyzated and hydrolysate thermal cracking generated unsteady state alumina. Meanwhile, polycarbonsilane generated amorphous silica by water vapor etching. Unsteady state alumina and amorphous silica could react with each other and generate Al Si O glass, which further crystallized and generated mullite. And α-Al2O3 was generated by redundant unsteady alumina. At last, multiphase ceramic film was fabricated which was consisted of Al N, α-Al2O3 and mullite. The multiphase ceramic film owns excellent comprehensive performance for aluminum nitride phase could improve its thermal conductivity and mullite phase could reduce its dielectric constant and dielectric loss factor. Microstructures of ceramic films and ceramic/metal interfacial reaction behaviors were systemly studied, due to process parameters had great effect on them. Meanwhile, mechanical performance, thermal performance and electrical insulating performance were tested. And one half bridge IGBT module was fabricated based on ceramic insulated substrate. In this paper, the main results are summarized as follows:Perfect multiphase ceramic layer was fabricated on the surface of W80Cu20/Cr by water vapor assisted sintering, which was mainly composed of Al N, α-Al2O3 and mullite. The water vapor content of sintering atmosphere condition had great effect on the microstructures of ceramic layer. When the water vapor content of sintering atmosphere was low, particle gaps of ceramic layer was very wide. But as the water vapor content of sintering atmosphere increased, particle gaps of ceramic layer became tight. There was obviously interfacial reaction between ceramic and Cr metal layer, whose thickness was about 2μm. There was obviously O and Cr elements diffusion at the interfacial reaction layer where Cr-O-Al compound may be generated, which could improve adhesion strength for ceramic layer. There were κ-Al2O3 and Al1.98Cr0.02O3 phases at the interfacial reaction layer between ceramic and Cr metal. κ-Al2O3 is unstable phase and owns high chemical reaction activity. Meanwhile, it is easy to react with Cr2O3 and generate Al1.98Cr0.02O3, realizing element diffusion reaction between ceramic and Cr metal. Nano-elastic modulus and nano-hardness of ceramic layer were 265±3GPa and 21±1GPa, respectively.With sintering temperature increasing, the thermal conductivities of multiphase ceramic layers firstly rised and then declined. The thermal conductivity of specimen fired at 1060 oC holding one hour was highest, and the value was 41.2 W(m·K)-1. Electrical insulating property is one main performance for ceramic insulating metal substrate. With test voltages increasing, insulation resistances of ceramic layers began declined. When the test voltage was 600 V, insulation resistance was 4.85×1012 Ω. With increasing of test temeratures, insulation resistance obtained at the same test voltage also declined. When the test voltage was 600 V, the insulation resistances obtained at rome temperature, 100 oC, 150 oC and 200 oC were 4.85×1012Ω、1.97×1011Ω、2.56×1010Ω and 2.74×109Ω, respectively. With test temperature increasing, DC breakdown voltages also declined, and the value reduced from 3100 V at room temperature to 1890 V at 200 oC. AC(50Hz) breakdown voltages were lower than DC breakdown voltages. The relative dielectric constants were 2.39, 2.12 and 2.00, corresponding to different test frequency of 10 KHz, 100 KHz and 1MHz, respectively. Meanwhile, with test frequency increasing, the relative dielectric constant declined. Under the test frenquency of 10 KHz and 100 KHz, dielectric loss factor firstly rised and then declined, as test temperature rised. The maximum dielectric loss factors were 0.62 and 0.60, respectively.In this article, multiphase ceramic insulating metal substrate was used as insulating substrate for power module. Meanwhile, a half bridge IGBT power module was packaged and test. The thermal resistance from chip to W80Cu20 substrate was 0.8 W/K, and this value was reduced by 20%, relativing to another half bridge module based on alumina DBC substrate. Well, the power module based on multiphase ceramic insulating metal substrate has better heat dissipation. And multiphase ceramic insulating metal substrate is expected to be widely used in the field of power modules. |
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