TY - GEN
T1 - Sagging phenomenon of micro-solder joints fabricated by laser reflow process
AU - Liu, Wei
AU - Wang, Chunqing
AU - Tian, Yanhong
AU - Kong, Lingchao
PY - 2007
Y1 - 2007
N2 - Au surface finish is very common used as a protection layer on pad. In the traditional reflow process, Au will be dissolved into solder, and AuSn 4 Intermetallic Components (IMCs) will form. However, for the solder joints fabricated by laser soldering, the morphology and distribution of the AuSn, IMC are quite different from that in solder joints fabricated by traditional reflow methods. This paper reports a 'sagging phenomenon' that has been observed from a study in the right-angled solder interconnections fabricated by laser reflow process. The solder was Sn-3.5Ag-0.7Cu and Sn-2.OAg-0.75Cu-3Bi alloys (120μm in diameter). On the laser reflowed solder joint, sink steps were found near the interface of solder and the edge of pad, which was made up of Cu plated with 3μm thickness of Au, and this phenomenon was called as sagging. However, no sagging phenomenon was observed at the interface of solder and the edge of another pad finished with 0.01μmTa/0.1μmNi/ 4.0μmAu, the material beneath the pad was thick Al2O3. In addition, Sn-Pb eutectic solder was also introduced in this study as a comparison, the sagging phenomenon in Sn-Pb eutectic solder joint was not as seriously as that in the two kinds of lead-free solder. The study results indicate that sagging phenomenon happened after the laser reflow process is related to the following factors: different cooling speed at the interfaces of solder and the pads, the Melting temperature difference between solder and IMCs, shrinkage of solder when it solidifies, and wetting performance of solder on solidified IMCs.
AB - Au surface finish is very common used as a protection layer on pad. In the traditional reflow process, Au will be dissolved into solder, and AuSn 4 Intermetallic Components (IMCs) will form. However, for the solder joints fabricated by laser soldering, the morphology and distribution of the AuSn, IMC are quite different from that in solder joints fabricated by traditional reflow methods. This paper reports a 'sagging phenomenon' that has been observed from a study in the right-angled solder interconnections fabricated by laser reflow process. The solder was Sn-3.5Ag-0.7Cu and Sn-2.OAg-0.75Cu-3Bi alloys (120μm in diameter). On the laser reflowed solder joint, sink steps were found near the interface of solder and the edge of pad, which was made up of Cu plated with 3μm thickness of Au, and this phenomenon was called as sagging. However, no sagging phenomenon was observed at the interface of solder and the edge of another pad finished with 0.01μmTa/0.1μmNi/ 4.0μmAu, the material beneath the pad was thick Al2O3. In addition, Sn-Pb eutectic solder was also introduced in this study as a comparison, the sagging phenomenon in Sn-Pb eutectic solder joint was not as seriously as that in the two kinds of lead-free solder. The study results indicate that sagging phenomenon happened after the laser reflow process is related to the following factors: different cooling speed at the interfaces of solder and the pads, the Melting temperature difference between solder and IMCs, shrinkage of solder when it solidifies, and wetting performance of solder on solidified IMCs.
UR - https://www.scopus.com/pages/publications/50249188762
U2 - 10.1109/ICEPT.2007.4441450
DO - 10.1109/ICEPT.2007.4441450
M3 - 会议稿件
AN - SCOPUS:50249188762
SN - 1424413923
SN - 9781424413928
T3 - Proceedings of the Electronic Packaging Technology Conference, EPTC
BT - Proceedings of the 2007 8th International Conference on Electronic Packaging Technology, ICEPT
T2 - 2007 8th International Conference on Electronic Packaging Technology, ICEPT
Y2 - 14 August 2007 through 17 August 2007
ER -