Thermal Stress Analysis of Metal Joining Process by Numerical Simulation

Abstract

Due to ever decreasing sizes of components and advanced production technologies the recent trend in PCBs is to arrange more and more components in a small area. One of the greatest problems facing the electronics companies today is a greater number of interconnections between electronic components required. Metal joining is a widely used process for the interconnection of electronic components. The various components and packages mounted on PCB via solder joints are subjected to heating and cooling cycle during the processing. High temperatures fail the sensitive components such as ICs, Chips, etc. and can also fail the structure. PCB would encounter significant deflection (displacement) and stress under operating conditions. This process induced distortions sometimes cause problems such as misalignment during assembling and impose additional costs for their removal. So it is necessary to predict and reduce these problems in order to improve the quality and also the costs involved. In the present study, the joining processes of the soldering of electronic components on the Printed Circuit Board (PCB) are considered for the thermal stress analysis. One of the most important & widely used joining processes is welding in steel construction. Welding deformation & residual stress have negative influence on assembly service performance & accuracy. These are produced in model due to shrinkage of the weld & restrain expansion as a non uniform heating & cooling of a component. However numerical or analytical models for the manufacturing process are too complicated & time consuming. So for the FEA simulation can be used to predict the distortion of the metal during welding process. Here double ellipsoidal geometry is described so that size & shape can be easily changed according to both deep & shallow penetration welding. This heat source model was introduced by Goldak et al (1984) for the simulation of welding process. In order to overcome this problem a Finite Element Model of Printed Circuit Board for the soldering process and Support Bracket Model for the welding process is made and Sequential Thermal Stress analysis is carried out using HYPERMESH and ABAQUS software. Additionally in the welding process, FORTRAN complier is used to solve moving heat source problem. The present work aims to investigate the effects of constraints and sequences on displacement and stress during the soldering & welding process. For the analysis, three different, soldering & welding sequences, and two & three, different constraints are considered for FEA of soldering & welding process respectively. The outcome of thermal analysis is nodal temperature while the output of structural analysis is nodal displacement and stress. This study provides useful guidelines to PCB designers, microelectronics industries and steel manufacturing plant, automobile industries and other manufacturing industries with a profound understanding of the thermal-structural interaction of the process during the soldering and welding process.