(A) study on the 3D analysis of micro-scale deformation and the laser speckle measurement in the laser precision joining of small structure

Abstract

In the area of laser welding, numerous studies have been performed in the past decades using either analytical or numerical approaches, or both combined. However, most of the previous studies were process-oriented and modeled differently in conduction and keyhole welding. In this research, new heat source equation was proposed to present various laser welding conditions. This is to address the problem of predicting, by numerical means, the thermo-mechanical behaviors of laser spot welding for mili-structure. Despite numerous studies on laser welding techniques for large joint applications, only limited information is available for micro-scale joints of mili-structure such as optoelectronic applications in which the PWS (Post Weld Shift) in the important issue for package yield. Factors of joint geometry, laser parameters, beam-to-beam energy balance show various degrees of influence of the PWS. A finite element code, ABAQUS is used for the heat transfer analysis with a three-dimensional model. Experimental studies of laser spot welding and ESPI(Electronic Speckle Pattern Interferometry) have also been conducted to validate the numerical models presented. From the results, it is known that the proposed finite element model could estimate weld-shape and displacement of mili-structure precisely when the laser spot-weld is performed. This work has led to an understanding of the effect of laser energy variation and joint design on the PWS and thermal distortion which may provide the design guidelines to produce a reliable laser module with high yield and high performance.