Copper/titanium dioxide thick film and application for through-hole

The mechanism of strip-off and the characteristics of conductor materials are investigated. Roughness and other features that affect the adhesion are investigated by SEM and EPMA in order to elucidate why the conventional copper thick film will not form a reliable conductor on a laser-drilled through-hole. A copper paste to which a large amount of titanium dioxide powder is added is studied. Titanium dioxide reduces the shrinkage of the conductor in firing and makes the thermal expansion coefficient close to that of the substrate. Adhesion to the substrate, resistance, and conductor condition on the hole are evaluated. The microstructure and crystalline phase of the copper/titanium-dioxide fired thick film are analyzed to clarify the adhesion mechanism. It is found that compound forms between the titanium dioxide and the alumina, which increases the adhesion.<<ETX>>