|
Vol.43, No.9, 602 ~ 609, 2005
|
| Title |
| Long Term Reliabilities of Sn-8 wt%Zn-3 wt%Bi Solder and Zn-Phase Change |
| 조선연 Sun Yun Cho , 이영우 Young Woo Lee , 김규석 Kyoo Seok Kim , 정재필 Jae Pil Jung , 문영준 Young Jun Moon , 이지원 Ji Won Lee , 한현주 Hyun Joo Han , 김미진 Mi Jin Kim |
|
|
|
| Abstract |
| In order to evaluate long term reliabilities of Sn-8 wt%Zn-3 wt%Bi (hereafter, Sn-8Zn-3Bi) solder, thermal shock (TS) test and high temperature humidity (HTH) test were applied to the solder joint. TS test was carried out up to 1,000 cycles between -40℃ to 80℃, and HTH was performed at 80℃ up to 1,000 hrs with relative humidity of 85%. The PCB (printed Circuit Board) pads for bonding substrates were finished by OSP (Organic Solderability Preservative), Sn and Ni/Au. A QFP (Quad Flat Package) was used for a bonding specimen with its lead of Cu being plated by Sn-3 wt%Bi. The joint strength of the QFP lead soldered on the pad was estimated by pull test, and Zn-phase behavior in solder joint was also examined. As experimental results, the pull strengths of Sn-8Zn-3Bi joints as soldered state were about 16 N with irrespective of pads coatings. However, the strength after TS test of 1,000 cycles decreased to around 14 N. Meanwhile, the pull strengths after HTH test to 1,000 hrs drastically deceased to around 6 N with irrespective of the pads coatings. The reason of drastic decrease of the pull strength after HTH test was proved to be a crack that was observed along the zinc oxide-phase in solder. The initial Zn-phase of acicular shape in the Sn-8Zn-3Bi solder changed to a line-upped branch type after HTH test of 1,000 hr. |
|
|
| Key Words |
| Sn-8 wt%Zn-3 wt%Bi, Lead free solder, Zn-phase, Joint strength, High temperature humidity test |
|
|
 |
|
