Fabrication of through glass via (TGV) substrates using a pulse width modulated (PWM) vacuum suction system for molten solder filling

In this study, we present a method for filling molten solder into through-glass via (TGV) substrates using a pulse width modulated (PWM) vacuum suction system. The TGV substrates were fabricated using micro-electro-mechanical systems (MEMS) techniques, incorporating anodic bonding and glass reflow processes. The vacuum suction system comprises a vacuum chuck, pressure sensor, pulse control circuit, and solenoid valve. The solenoid valve modulates the vacuum level of the chuck by opening and closing. The switching frequency was set to 1 Hz with a 20% duty cycle. TGVs were fabricated in the glass substrates with diameters of 150 μm and thicknesses of 350 μm. The vacuum filling yield was approximately 30% at 40 kPa and exceeded 98% at 80 kPa vacuum level. X-ray imaging confirmed void-free filling results. The individual via resistance of the tin-filled TGVs was measured at 69.8±38.5 mΩ using the four-probe method.