A relative comparison of PWB warpage due to simulated infrared and wave soldering processes

Current trends in the electronic packaging industry are directed at the miniaturization of electronic component size and increasing component density on printed wiring board assemblies (PWBAs). The trend is also towards the manufacture of thin printed wiring boards (PWBs). Developing such technologies creates heightened issues with printed wiring board warpage, which lead to component misregistration during automated component placement and insertion processes. In addition, daily usage may induce PWBA warpage that could lead to further reliability issues such as premature solder joint failures caused by high residual stresses. It is desirable to understand and avoid such problems as redesigns or repairs to reduce excessive warpage is time consuming and costly. Two types of bare, four layer PWB test vehicles were designed and fabricated to replicate simplified versions of typical boards produced by PWB manufacturers. The boards were subjected to simulated infrared and wave soldering reflow processes in a small lab-scale oven integrated with a shadow moire out-of-plane displacement measurement system. The system is capable of on-line measurement of PWB warpage during operational thermal cycling. The highly automated, computer controlled, lab-scale ovens are able to reproduce virtually any given manufacturer's temperature profile. The results presented show the effects that simulated wave and infrared reflow soldering processes have on the warpage of two different PWB designs.