Laser vacuum welding of aluminium, kovar and Ni-Fe alloys for hermetic incapsulation of electronic components

Laser welding under a vacuum environment for hermetic sealing of miniature electronic components was investigated. It was found that at a pressure of 0.1 mbar or less, laser plasma was almost completely suppressed. This led to an increase in weld penetration of more than double that of laser welding under an argon cover gas environment. The fundamental characteristics of vacuum welding were studied, including the effects of pulse energy and focus position on the aspect ratio of the weld geometry. The optimal conditions of the laser welding process for hermetic sealing of three different material configurations: (i) Al 6061 with Al 4047, (ii) low heat expansion alloy 45 and (iii) coated and uncoated Kovar, were examined. Due to precise energy input, miniature devices with temperature sensitive components can be sealed without part deformation. A major concern with this technique was the contamination of the beam window on the vacuum chamber due to vapor debris from the weld pool. Proper weld strategy was developed to minimize the damage of this window.