TY - GEN
T1 - Spalling suppression by Sn-3.5Ag incorporated with Cu particles
AU - Liu, C. Y.
AU - Wang, S. J.
N1 - Publisher Copyright:
© 2002 IEEE.
PY - 2002
Y1 - 2002
N2 - Spalling phenomenon is one of the current urgent reliability issues for the Pb-free solder implementation in flip chip technology. Essentially, spalling was caused by high interfacial energy between intermetallic compound and Cr, which dewetted the layer compound into a spherical compound. In this paper, we report that spalling of Ni thin UBM (Under Bump Metallization) can be prevented during the soldering reaction, if a Cu reservoir is introduced into the structure of C4 (Controlled Collapse Chip Connections) solder joints. Once molten Sn-3.5Ag solder was saturated with Cu atoms, Cu precipitated out as a layer of Cu-Sn compound on Ni thin UBM. Cu-Sn compound layer served as a reaction barrier to retard the consumption of Ni thin UBM. So, spalling is retarded. After prolonged reflowing, Ni thin UBM was converted to ternary Cu-Sn-Ni compounds. Remarkably, we found that Cu-Sn-Ni compound still resided on the Cr surface without spalling. Unlike interfaces of Cu-Sn compound/Cr or Ni-Sn compound/Cr, the interface of Cu-Sn-Ni compound/Cr is very stable and has a low interfacial energy. Hence, spalling effect on Ni thin UBM is prevented.
AB - Spalling phenomenon is one of the current urgent reliability issues for the Pb-free solder implementation in flip chip technology. Essentially, spalling was caused by high interfacial energy between intermetallic compound and Cr, which dewetted the layer compound into a spherical compound. In this paper, we report that spalling of Ni thin UBM (Under Bump Metallization) can be prevented during the soldering reaction, if a Cu reservoir is introduced into the structure of C4 (Controlled Collapse Chip Connections) solder joints. Once molten Sn-3.5Ag solder was saturated with Cu atoms, Cu precipitated out as a layer of Cu-Sn compound on Ni thin UBM. Cu-Sn compound layer served as a reaction barrier to retard the consumption of Ni thin UBM. So, spalling is retarded. After prolonged reflowing, Ni thin UBM was converted to ternary Cu-Sn-Ni compounds. Remarkably, we found that Cu-Sn-Ni compound still resided on the Cr surface without spalling. Unlike interfaces of Cu-Sn compound/Cr or Ni-Sn compound/Cr, the interface of Cu-Sn-Ni compound/Cr is very stable and has a low interfacial energy. Hence, spalling effect on Ni thin UBM is prevented.
UR - http://www.scopus.com/inward/record.url?scp=84966621683&partnerID=8YFLogxK
U2 - 10.1109/EMAP.2002.1188866
DO - 10.1109/EMAP.2002.1188866
M3 - 會議論文篇章
AN - SCOPUS:84966621683
T3 - Proceedings of the 4th International Symposium on Electronic Materials and Packaging, EMAP 2002
SP - 366
EP - 371
BT - Proceedings of the 4th International Symposium on Electronic Materials and Packaging, EMAP 2002
PB - Institute of Electrical and Electronics Engineers Inc.
T2 - 4th International Symposium on Electronic Materials and Packaging, EMAP 2002
Y2 - 4 December 2002 through 6 December 2002
ER -