THE ORIGIN AND PREVENTION OF POST REFLOW DEFECTS IN SURFACE-MOUNT ASSEMBLY

This paper addresses the origins of post solder reflow defects. In par ticular, an inter-relationship between solder bridges, insufficient an d no solder (opens) is established. Simple response contours are also constructed to determine the optimal combination of key screen printin g parameters to give optimum solder paste thickness (i.e. at the nomin al value) and minimize solder bridge variability. Also a self-aligning mechanism using vibration that can be incorporated in to a reflow ove n is also evaluated to address position-related soldering defects.