Numerical modelling of solder joint formation

Solder materials are used to provide a connection between electronic compon ents and printed circuit boards (PCBs) using either the reflow or wave sold ering process. As a board assembly passes through a reflow furnace the sold er (initially in the form of solder paste) melts, reflows, then solidifies, and finally deforms between the chip and board. A number of defects may oc cur during this process such as flux entrapment, void formation, and cracki ng of the joint, chip or board, These defects are a serious concern to indu stry, especially with trends towards increasing component miniaturisation a nd smaller pitch sizes. This paper presents a modelling methodology for pre dicting solder joint shape, solidification, and deformation (stress) during the assembly process.