时效处理对Sn-Bi系无铅焊料的影响研究  

Effect of aging on Sn-Bi lead-free solder

作　　者：李元山[1] 陈振华[2] 雷晓娟[2] 

机构地区：[1]国防科技大学计算机学院,长沙410073 [2]湖南大学材料科学与工程学院,长沙410082

出　　处：《材料科学与工艺》2009年第3期339-342,共4页Materials Science and Technology

摘　　要：为解决Sn-Bi焊料在焊接时容易产生凝固偏析、降低焊点力学性能的问题,采用对焊点进行时效处理的方法来消除Bi的粗化结晶,从而增强焊料的机械性能.研究表明,焊点在125℃时效处理16 h,粗大块状的Bi全部消融,呈颗粒状均匀分布,焊料中的Sn与焊盘上的Cu生成一层厚度约为3μm的Cu6Sn5金属间化合物,使焊点的剪切强度由40 MPa升高到54 MPa.研究还发现,时效处理后的焊点在100℃下长时间放置,微观组织不再发生变化,说明时效处理提高了焊料基体的抗热性能,因此,可以将125℃/16 h的时效处理作为表面贴装生产工艺流程的一道必要工序,使Sn-Bi焊料真正满足实用要求.To solve the problem of solidification segregation formed when Tin-bismuth alloy was soldered, the solder joint of Sn - Bi alloy was treated by aging to eliminate the coarse Bi grains of crystal to improve the me- chanical properties of Sn- Bi alloy. The investigation showed that, when the solder joint was aged at 125 ℃ for 16 hours, bismuth in nubbly shape was melt completely and distributed uniformly in grain shapes. Tin in the solder reacted with copper on PCB pad and formed a layer of intermetallic compound （IMC） of Cu6Sn5 with thickness of about 3 μm. The IMC increased the shear-strength of solder from 40 MPa to 54 MPa. The microstructure of solder joints treated by aging was not changeable any more even they were stored at 100 ℃ for long time. It is indicated that aging treatment can improve the anti-thermal properties of solder joints and make the Sn- Bi alloy meet the practical requirements.

关 键 词：无铅焊料 Sn—Bi合金 Bi的偏析 时效处理 

分 类 号：TG425.1[金属学及工艺—焊接]