Lead‐free PCB assembly and effects of process conditions on the profile and reliability of solder joints

Abstract

PurposeTo study the effects of design and assembly process conditions on lead‐free solder joints for an area array component.Design/methodology/approachExperiments using SnAgCu solder for assembling plastic ball grid array components on printed circuit boards (PCBs) were carried out to investigate the reliability of the solder joints made under various conditions. The process variables studied include solder pad diameters, solder paste volume and reflow peak temperatures.FindingsThe average joint diameter increased with the peak reflow temperature, stencil thickness and pad diameter. The average joint height decreased with the increasing peak reflow temperature and pad diameter. However, increased stencil thickness would lead to increased solder paste volume and therefore increases both joint diameter and height. The assembled boards were subjected to a temperature cycling test (−40 to +125°C) for 5,700 cycles and no failures of the daisy chained resistance loops were found, indicating that the thermal fatigue resistance of the SnAgCu solder joints was good.Originality/valueThe findings provide greater confidence to implement a lead‐free soldering process without compromising reliability. Reliable lead free soldering can be made over a wide process window allowing flexibility in design and manufacturing.