回流焊峰值温度对混装BGA焊点的影响研究

针对当前大量使用有铅焊料焊接无铅BGA的实际现状,通过调控有铅制程回流曲线的峰值温度,研究其对混装BGA焊点坍塌高度、空洞率及微观组织的影响。结果表明,峰值温度从210℃提升至225℃,无铅BGA焊球能够全部充分坍塌且高度保持一致;峰值温度为210℃时,混合焊点内的空洞率最低,随着峰值温度的升高,空洞尺寸和空洞率均有所增加;峰值温度为215℃时的微观组织最细小且尺寸分布最均匀,继续提升峰值温度,微观组织尺寸会随之增大。因此使用有铅焊料焊接无铅BGA的最佳峰值温度为215℃,与有铅制程保持一致。

Effect of peak temperature on BGA mixed solder joint during reflow process

Given the present situation of lead-free BGA welding with SnPb solder in large quantities,the peak temperatures of the reflow curve in the traditional SnPb assembly process were adjusted to investigate their effect on the collapse height,void and microstructure of BGA mixed solder joint.The results show that the lead-free BGA solder balls can fully collapse and maintain the same heights when the peak temperature increases from 210℃to 225℃.When the peak temperature is 210℃,the cavity rate in the mixed solder joint is the lowest.However,the cavity rates and size are both increased as the peak temperature increases.When the peak temperature is 215℃,the microstructure is smallest,and the size distribution is the most uniform.If the peak temperature continues to rise,the microstructure will increase accordingly.Therefore,the optimal peak temperature for lead-free BGA welding with SnPb is 215℃,which is consistent with that in the SnPb assembly process.