Wave Soldering of Surface Mount Components

In facing the upcoming surge of ‘surface mount technology’, many manufacturers of printed circuit boards have taken steps to convert some portions of their boards to this new process. However, as the availability of surface mount components is still limited, many have taken to mixing the lead‐inserted standard dual‐in‐line packages (DIPs) with the surface mounted devices (SMDs). Furthermore, to take advantage of using both sides of the board, surface‐mounted components are generally adhered to the bottom side of the board while the top side is reserved for the conventional lead‐inserted packages. If processed through a wave solder machine, the semiconductor components are now subjected to extra thermal stresses (now that the components are totally immersed into the molten solder). A discussion of the effect of wave soldering on the reliability of plastic semiconductor packages follows. This is intended to highlight the limitations which should be understood in the use of wave soldering of surface mounted components.