Stress Induced in Ceramics-Conductor of Mcm

The glass/alumina composite ceramics makes it possible to cofire the circuit board with low-resistivity conductor metals such as copper. The fired copper wiring have high reliability that is unchanged after 1000 cycles of thermal shock test, however, the thermal expansion coefficient of copper is much higher than that of the glass/alumina [1]. The difference of thermal expansion is larger than that of alumina and molybdenum, tungsten in the conventional multilayer circuit boards. The cofired copper wiring, lines and vias, have tensile strength of about 100 MPa, half of bulk copper, and ductile fracture characteristics. The ductility and high tensile strength make the wiring able to withstand stress due to large thermal expansion mismatch at the conductor-ceramic interface. The residual stress of thermal expansion mismatch on fracture of conductors was studied.