Impact of processing conditions and solder materials on surface mount assembly defects

The conversion to lead-free solder alloys and increasing dynamic warpage due to the coefficient of thermal expansion (CTE) mismatch and thinner microelectronic packaging technology has resulted in a significant increase in the risk of solder joint defects for ball grid array (BGA) components. This paper will review head-and-pillow (HnP) defects observed after surface mount assembly with specific focus on fine-pitch BGA technology on motherboards. The mechanisms related to various aspects of design and materials characteristics that affect the creation of these defects within the solder joints will be discussed. Finally, potential material solutions for eliminating these defects will be reviewed.