Abstract
The causes of the surface cracks of the multilayer ceramic substrates has been investigated. As the result, it was confirmed that the surface cracks on the multilayer ceramic substrates have been caused by various stresses generated between the alumina layer and W metallized conductor while they were cofired.
These cracks can be controlled by addition of the flux to the W paste and matching of the firing shrinkage of the alumina to that of the W matallized conductor. The crackless multilayer ceramic substrates are little deteriorated under the forced deteriorating conditions made by high-temperature bias test and high-temperature and high humidity bias test.
