DEVELOPMENT OF HIGHLY RELIABLE LEAD FREE SOLDER

本文研究了Sn-3.5%Ag钎料合金铸态的蠕变特性，蠕变温度范围为298 ~ 398 K，蠕变速率范围为1 × 10 ~<-8><-1>（-3）s ~（-1）<-2>s ~（-1）<-1>。结果表明，Sn-3.5%Ag二元合金在Ag_3Sn颗粒的弥散强化作用下，表现为幂律蠕变，应力指数（n）约为10。当Cu的质量分数为2%时，Sn-3.5%Ag二元合金在298 K和398 K下的蠕变强度都略有提高;当Bi的质量分数为10%时，合金在室温下通过Ag_3Sn和Bi相的弥散强化和Bi原子的固溶强化的协同作用而得到显著提高，但在398 K的低应力区，由于蠕变过程中铋相的粗化，使其劣化。

Creep characteristics of Sn-3.5%Ag solder alloys in the as-cast state have been investigated in temperature range between 298K and 398K and creep rate range between 1x10^<-8>s^<-1> and 1x10^<-2>s^<-1> with special reference to the effect of third elements. It is found that Sn-3.5%Ag binary alloy shows power-law creep in which stress exponent (n) is about 10 due to the dispersion strengthening effect of Ag_3 Sn particles. The addition of copper up to 2mass% improves the creep strength of Sn-3.5% Ag binary alloy only slightly both at 298K and at 398K.The addition of bismuth up to 10mass% strengthens it considerably at room temperature through the cooperation of dispersion hardening due to Ag_3 Sn and bismuth phases and solution hardening due to solute bismuth atoms, but degrades it in the low stress regime at 398K principally due to the coarsening of bismuth phase during creep.