Low Stressed Multilayer Structure for Reliable Glass-Ceramic Brazing
Original Publication Date: 1985-Aug-01
Included in the Prior Art Database: 2005-Feb-19
The use of thick Au (gold) coatings on Cu (copper) I/O pads on glass- ceramic substrates will effectively lower the stress in the glass- ceramic at the metal pad interface. The low yield strength layer tends to relax some of the stress generated by pin brazing. There is some improvement in pull strength and failure mode resulting from this approach. The loss of pull strength after brazing pins to the glass-ceramic substrate was found to be due to the formation of brittle cracks at the pad edge which propagated into the substrate. The cause of ceramic cracking can be traced back to the high residual stress induced at the pad edges resulting from the differential thermal mismatch between the Cu pad and the substrate.