Numerical modeling of wave soldering in PCB

摘要

Manufacturing of electronic boards (commonly referred asPCB) is a highly automated process that requires an accuratecontrol of the various processing variables. Amongst thesoldering processes, wave soldering is one of the most oftenused. In this, the various electronic components are provisionallyinserted onto the PCB, and a low velocity jet of melted solder isdirected to the moving board. Due to capillarity effects the solderadheres to the component/board interface and the process iscompleted. This methodology is most often used for smallcomponents. The adjusting of the operating parameters (soldernozzle orientation and velocity) is often carried out on a trial anderror basis resulting in a time consuming process that is at oddswith the increasing demand for smaller production series that theelectronics industry is faced with.In addition the number of defects (mostly from missingcomponents that are washed away by the impacting jet) is morelikely to occur when thinner substrates are used in the PCBmanufacturing.The present paper describes the application of aComputational Fluid Dynamics model to describe the interactionof the solder jet with the PCB and the integrated circuits. Themodel includes the conservation equations for mass, momentumand energy in a transient time frame. The jet and surroundingambient atmosphere are modeled as two separate fluids and theinterface is tracked by a VOF model. By adjusting thecomputational mesh refinement the interface is captured withaccuracy. The drag forces occurring in the various componentsare computed from the pressure data field. The model allows the optimization of the wave operating parameters as a function ofthe component type of and its layout in the PCB.