High-lead solder ball characteristics in BGA package

摘要

For high performance packages in mainframe systems such as networking switch, telecommunication equipments, higher reliability is always required. Using high-lead solder ball is an effective way to enhance the solder joint performance in board level. The elongation property of high-lead alloy SnlO/Pb90 is 10 times greater than eutectic Sn/Pb alloy. The high-lead ball has higher melting temperature, it can maintain the stand off (gap) between the package and PCB when eutectic solder paste melted at 220℃ . In this study, the performances of high-lead solder SnlO/Pb90 and eutectic Sn63/Pb37 are compared. A series of experiments are performed to characterize the high-lead solder ball solder joint performance. The ball shear test parameters also affect high-lead solder ball strength, such as ram height and shear speed. Lower ram height and higher speed increases the ball shear strength value. Effect of different ball pad openings, solder paste volume and reflow profile for ball placement, is also discussed in this paper. The ratio of ball pad opening diameter to solder ball diameter is related to ball shear force. When the ratio is 0.83, the ball shear is better than other value. The most important factor to ball shear strength is the solder paste amount. However, the refiow condition (the time period over 183℃ ) isn't the significant factor to affect the ball shear strength.