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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.

Alumina substrates have been developed for a flip-chip mount ECU ( Electronic Control Unit ). On this substrate, large sized IC chips as a flip-chip and other electronic components have been mounted. Cu thick film circuit has also been mounted on the other surface. This circuit consists of printed resistors by connecting tungsten metallized layer and Cu thick film through Cu plating. In order to mount the large sized flip-chip IC, the substrate needs strictly precise dimensions. The tolerance of the dimensions are within ± 0.1 % and the warp of the flip-chip area is less than 10 μm per 10 mm.