Online measurement and correction of post-weld shift in laser welding packaging for laser diodes

In order to measure and correct post-weld shift (PWS) which is inherent in the laser welding packaging process for laser diodes, a novel method based on strain gauges was proposed to perform online measurement of the welding shift in real time. This method can measure micro-displacement caused by laser welding in two directions with submicrometer accuracy. The direction and magnitude of PWS can be determined from measurement results, and then correction welding is applied to compensate the PWS in prescribed direction. The measurement system was established and experiments of laser welding, PWS measurement, and correction for specially designed laser diode packaging assembly are conducted. Experimental results show that the proposed method is able to measure the PWS accurately in real time, and the coupling light power can be regained to over 90% of the power before welding with laser hammering technique according to measurement results. With advantages of low cost, comparable accuracy, and real-time measurement, the proposed method will be very useful for improving the packaging productivity and performance for widely used transistor outline (TO)-Can style laser diodes.