Research On Laser Diode Packaging Using Laser Welding

the Nd: YAG laser welding technology is being widely used in To-Can style package for laser diode. However, the disadvantage of laser welding is the so-called post-weld-shift (PWS). The end result is a reduction in light coupling efficiency. The shrinkage force generated by the solidification process is so great that no known mechanical structure can counteract the shrinkage from shifting the joint—at least at the micron level. Laser hammering (LH) was developed to minimize PWS. The laser-hammering process is the technique that utilize the solidification shrinkage to regain the optical throughput lost by PWS.In this paper, a three-dimensional brick element model with temperature-varied material properties was built. An Ansys parametric design language (APDL) was used to simulate the temperature distribution, the distribution of the residual stresses, and PWS in process of laser hammering with variant voltage and pulse width. The fields of Von Misses stress distribution and temperature field distribution expand with voltage and pulse width increasing. At the same time, the correcting valuation of laser hammering increases with the increment of pulse and Voltage. The Y direction is the major shift. At the same welding condition, the shift of Y direction is about two times than that of Z direction.If the weld spot size is the same, the welding- parameter both high voltage, short pulse width and low voltage, long pulse width can get the same PWS of LH. But the range of influence of thermal stress by long pulse is larger than by high voltage. High voltage, short pulse is the preferred welding-parameter in the process of welding packaging.The experimental measurements of LH were in reasonable agreement with the numerical calculations of the finite-element method (FEM) analysis. The min PWS of LH in Y direction is 0.1μm, and the range of angle shift is from 0.0005degree to 0.005 degree. Angle shift can reduce in light coupling efficiency. Therefore, the angle shift is an important factor for light coupling efficiency when PWS is corrected by LH for laser diode packaging. When pulse width is long enough to above 2.5ms, the corrected direction of laser hammering is away from the laser head, which may be the reason for weld bath being fatal destroyed.The purpose of this paper is to present a clear choice of welding-parameter of laser hammering induced fiber alignment shift. The research results obtained by this paper will be helpful to correct the PWS with laser hammering technique.