Online postwelding shift compensation in butterfly laser module packages based on welding spot distance

Postwelding shift (PWS) is the dominant barrier to having high packaging yields. Previous investigation revealed that the PWS in butterfly laser diode module packaging could be mitigated by properly choosing weld process parameters such as welding sequence, clip design, pulse shape, and so on. We study the effect of the distance between the front (first) and the rear (second) welding spots numerically by the finite element method with a more realistic physics-based laser welding model. A novel PWS online measurement system based on the ultra-high-precision laser displacement meter is established to experimentally validate the effect of welding spot distance. Results from both methods are compared. Finally, we show that the influence of welding spot distance can be used to compensate PWS to some extent, if a proper welding spot distance is employed.