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We have developed a new alumina multi-layer ceramic substrate material, whose properties of low resistance conductor and excellent mechanical and thermal characteristics, providing a new and unique substrate solution for automotive ECU applications. Unique to this material is the circuit conductor which is made from a composite material of tungsten and copper, providing low electric resistance and high thermal diffusivity. This material system (AO600) utilizes a low-temperature, co-fireable alumina with a low resistance metal conductor composite. Electric current path is made by copper in the composite to effectively reduce the resistance. Thick film on the alumina substrates surface is also effective for the resistance reduction. Using this material system, substrates with miniaturized design, high strength and high thermal diffusivity have been realized. We have also tested reliability by temperature cycle tests between -40 and 150 degrees centigrade.

A new process for a highly reliable ceramic substrate with electric circuit has been developed for power devices of automotive applications. The circuit conductor has high conductivity to accept a current of 10 to 200 Amperes, and has strong joining strength to ceramic substrates. The conductor is made of sintered copper powders with several kinds of diameters to get a porous structure, for reducing Young's modulus and thermal stress between the circuit conductor and ceramic substrate. Sintering shrinkage of the circuit conductor has been restrained, and joining strength to the ceramic substrates kept strong by an anchor effect. The copper circuit conductor realized electric resistivity of 2.3×10-6 ohm-cm, and coefficient of thermal conductivity, 290 W/mK. We have also confirmed superior reliabilities in the joining strength and conductivity by thermal cycling tests.