表面封装用无铅软钎料的接头强度及熔点范围的研究

The Surface Mount joint strength and Melting Range of Lead-free Solders

研究了Bi的添加量,对电子表面封装(SMT)用Sn-Ag近共晶无铅软钎料钎焊接头抗拉强度和熔点及熔点范围的影响。随着Bi含量的增加,钎焊接头抗拉强度也随着增加,同时钎料的液固相线温度均降低。当Bi的含量达到5%时,抗拉强度增加快;Bi的添加量大于5%时,抗拉强度上升缓慢。在Bi的含量增加时,熔点温度范围也逐渐变宽,使得凝固时间变长,这对于表面组装中的电子元件与器件的焊接是非常不利的。故在Sn-Ag近共晶无铅软钎料中Bi的添加量,应加以适当的控制。

The effects of the Bi content on the surface mount joint strength soldered with lead-free Sn-Ag near eutectic solder alloys were investigated. With the increase of the Bi content, the solder joint strength rises, but the liquidus temperature and the solidus temperature decrease. The strength increases rapidly when the Bi content is up to 5 percent by weight and the increase rate slows down when the Bi content exceeds 5 percent by weight. What is more, the melting range widens as the Bi content increase, which results in a longer time to solidify. It is unfavorable to solder the electronic components and devices in surface mount. Therefore, the Bi content should be limited to some degree in the research and development of the new Sn-Ag lead-free solders.