Resolving Thermo-Mechanically Induced Circumferential Crack Formation in Copper Through-Glass Vias

This works aims at eliminating the formation of thermo-mechanically induced circumferential cracks in metallized through-glass via (TGV) substrates, aided by fundamental understanding the root cause for their formation. Circumferential cracks were determined to have formed during the cooling step of annealing treatment due to high tensile radial stresses in the substrate in proximity to metallized TGV. The impact of the thickness of copper (Cu) metallization in TGV on the formation of circumferential cracks was studied after 400 degrees C annealing treatment. It was determined that circumferential crack formation is exponentially dependent on TGV Cu ring thickness and a threshold Cu ring thickness of 12 mu m was determined for the formation of cracks in Cu TGVs achieved in Corning (R) HPFS (R) Fused Silica glass substrate. This means that a crack-free metallized through-glass via (TGV) substrate is achieved when the Cu ring thickness is less than 12 mu m.