PULSED ND-YAG LASER-WELDING OF CARDIAC-PACEMAKER BATTERIES WITH REDUCED HEAT INPUT

The effects of Nd:YAG laser beam welding process parameters on the res ulting heat input in 304L stainless steel cardiac pacemaker batteries have been studied. By careful selection of process parameters, the res ults can be used to reduce temperatures near glass-to-metal seals and assure hermeticity in laser beam welding of high reliability component s. Three designed response surface experiments were used to compare we lding performance with lenses of varying focal lengths. The measured p eak temperatures al the glass-to-metal seals varied from 65 degrees to 140 degrees C (149 degrees to 284 degrees F) and depended strongly on the levels of the experimental factors. It was found that welds of eq uivalent size can be made with significantly reduced temperatures. The reduction in battery temperatures has been attributed to an increase in the melting efficiency. This increase is thought to be due primaril y to increased travel speeds, which were facilitated by high peak powe rs and low pulse energies. For longer focal length lenses, weld fusion zone widths were found to be greater even without a corresponding inc rease in the size of the weld. It was also found that increases in las er beam irradiance either by higher peak powers or smaller spot sizes created deeper and larger welds. These gains were attributed to an inc rease in the laser energy transfer efficiency.