SMT007 Magazine


Issue link:

Contents of this Issue


Page 53 of 115

54 SMT Magazine • January 2017 by Yoshinori Ejiri, Takehisa Sakurai, Yoshinori Arayama, Yoshiaki Tsubomatsu, and Kiyoshi Hasegawa HITACHI CHEMICAL CO. LTD Abstract The influence of Pd film thickness in elec- troless Ni/Pd/Au plating on the solder ball joint reliability after reflow cycles and thermal aging was investigated by conducting a high-speed solder ball shear test. Sn-3.0Ag-0.5Cu (SAC305) was used as the solder ball in this study. On the basis of the solder joint reliability obtained after multiple reflow cycles and thermal aging, the optimum thickness of the Pd film was found to be 0.05–0.2 µm. The covering property of electroless Pd plat- ing film on the electroless Ni plating film was also investigated. We found that an electroless Pd plating film with a thickness of 0.02 µm or more covered the electroless Ni plating film ad- equately, and the solder ball joint reliability in this case was better than that with electroless Ni/Au plating. We consider that the shape of the intermetallic compounds (IMCs) is one of the factors that influence the solder joint reli- ability after multiple reflow cycles. Consequent- ly, we inferred that the high adhesion at the dendrite layers of IMCs/solder interface result- Solder Ball Joint Reliability with Electroless Ni/Pd/Au Plating– Influence of Electroless Pd Plating Film Thickness ed in excellent solder ball joint reliability after the reflow cycles. We consider that the thick- ness of the IMCs is one of the factors that in- fluence the solder joint reliability after thermal aging. In (Cu, Ni, Pd)6Sn5 IMCs that contained trace amounts of Pd, the growth of the IMCs is prevented by Pd, resulting in excellent solder ball joint reliability after thermal aging. Introduction With the widespread use of portable elec- tronic equipment, chip scale packages (CSPs) and ball grid arrays (BGAs) mounted on high- density printed circuit boards (PCBs) have be- come popular as semiconductor package assem- blies. The CSPs and BGAs are connected to the PCBs using solder balls. Such connection meth- ods require smaller connection areas and no metal leads, thus resulting in a lower ability to resist the stress relaxation than in the case of the traditional methods of connecting the leads of thin small outline packages (TSOP) and quad flat packages (QFPs). The connection methods em- ploying solder balls, therefore, involve many problems related to joint reliability. Several stud- ies on the reliability of solder ball joint connec- tions with CSPs and BGAs are now in progress 1-16 . The conventional electrolytic Ni/Au plat- ing is a mature technology that has long been FEATURE

Articles in this issue

Archives of this issue

view archives of SMT007 Magazine - SMT-Jan2017