Monitoring of the Effect of Thermal Shock on Crack Growth in Copper Through-Glass Via Substrates

Abstract

This work aims at understanding thermo-mechanically induced cracks in through-glass via (TGV) made in Corning® HPFS® Fused Silica glass substrate, as well as to study the effect of thermal shock on the propagation of cracks. Two types of thermo-mechanically induced cracks were observed; radial cracks formed during heating and circumferential cracks that are formed during cooling. These cracks were initiated as a result of high tensile stresses in the circumferential and radial directions respectively. Thermal shock was found to lead to the growth of radial cracks. After 1000 cycles, catastrophic failures occurred due to the networking of radial cracks from adjacent vias. This suggests that TGV pitch dimension is a critical parameter that needs to be considered in order to limit catastrophic failures. On the other hand, no crack growth was observed for circumferential cracks in the in-plane direction, even after 1000 cycles of thermal shock. These results indicate that the prevention of radial and circumferential crack formation is the most critical step in mitigating risk of failure concerns, thus, the need for optimized crack-free metallized TGV solutions. Through TGV shape re-design, control of Cu metallization thickness as well as the use of lower annealing heating rate, these thermo-mechanically driven cracks were successfully mitigated in a previously reported work.