Korean Journal of Materials Research, Vol.12, No.9, 750-760, September, 2002
Ni/Au 및 OSP로 Finish 처리한 PCB 위에 스크린 프린트 방법으로 형성한 Sn-37Pb, Sn-3.5Ag 및 Sn-3.8Ag-0.7Cu 솔더 범프 계면 반응에 관한 연구
Studies on the Interfacial Reaction of Screen-Printed Sn-37Pb, Sn-3.5Ag and Sn-3.8Ag-0.7Cu Solder Bumps on Ni/Au and OSP finished PCB
E-mail:
In this study, three solders, Sn-37Pb, Sn-3.5Ag, and Sn-3.8Ag-0.7Cu were screen printed on both electroless Ni/Au and OSP metal finished micro-via PCBs (Printed Circuit Boards). The interfacial reaction between PCB metal pad finish materials and solder materials, and its effects on the solder bump joint mechanical reliability were investigated. The lead free solders formed a large amount of intermetallic compounds (IMC) than Sn-37Pb on both electroless Ni/Au and OSP (Organic Solderabilty Preservatives) finished PCBs during solder reflows because of the higher Sn content and higher reflow temperature. For OSP finish, scallop-like Cu 6 / Sn 5 and planar Cu 3 Sn intermetallic compounds (IMC) were formed, and fracture occurred 100% within the solder regardless of reflow numbers and solder materials. Bump shear strength of lead free solders showed higher value than that of Sn-37Pb solder, because lead free solders are usually harder than eutectic Sn-37Pb solder. For Ni/Au finish, polygonal shaped Ni 3 Sn 4 IMC and P-rich Ni layer were formed, and a brittle fracture at the Ni-Sn IMC layer or the interface between Ni-Sn intermetallic and P-rich Ni layer was observed after several reflows. Therefore, bump shear strength values of the Ni/Au finish are relatively lower than those of OSP finish. Especially, spalled IMCs at Sn-3.5Ag interface was observed after several reflow times. And, for the Sn-3.8Ag-0.7Cu solder case, the ternary Sn-Ni-Cu IMCs were observed. As a result, it was found that OSP finished PCB was a better choice for solders on PCB in terms of flip chip mechanical reliability.
- Lau JH, Flip Chip Technologies, p. 123, McGraw-Hill, New York, (1996) (1996)
- Chen CJ, Lin KL, IEEE Transactions on Components and Packaging Technologies, 24(4), 691 (2001)
- Jang SY, Paik KW, IEEE Transactions on Electronic Packaging Manufacturing, 24(4), 269 (2001)
- Lau JH, Chang C, Lee SWR, IEEE Transactions on Components and Packaging Technologies, 24(2), 285 (2001)
- Sawada Y, Yamaguchi A, Oka S, Fujioka H, IEEE Transactions on Components and Packaging Technologies, 25(1), 73 (2002)
- Nah JW, Paik KW, Kim WH, Hur KR, in Proceedings of the 3rd International Symposium on Electronic Materials and Packaging (Jeju island, Korea, November 2001), ed, Lee SB, Paik KW (The Institute of Electrical and Electronics Engineers, USA, 2001) p. 115 (2001)
- Carano M, Printed Circuit Fabrication, 21(2), 134 (1998)
- Platt S, Brantingham J, Printed Circuit Fabrication, 21(2), 42 (1998)
- Abtew M, Selvaduray G, Mat. Sci. Eng., 27, 95 (2000)
- Nah JW, Paik KW, IEEE Transactions on Components and Packaging Technologies, 25(1), 32 (2002)
- Carano M, Printed Circuit Fabrication, 20(7), 28 (1997)
- Massalski TB, Binary Alloy Phase Diagram, 2nd ed., p, 1481, American Society of Metals, USA (1986) (1986)
- Jang JW, Kim PG, Tu KN, Ferar DR, Thompson P, J. App. Phys., 85(2), 8456 (1999)
- Kang SK, et al., in Proceedings of 51st Electronic Components and Technology Conference (Orlando, Florida, May 2001) Ed. P. Slota, Jr. (The Institute of Electrical and Electronics Engineers, USA, 2001) p.448 (2001)
- Jang JW, Ferar DR, Lee TY, Tu KN, J. Appl. Phys., 88(11), 6359 (2000)
- Kang SK, et al., in Proceedings of 49th Electronic Components and Technology Conference (San Diego, CA, June 1999). ed. Swager C(The Institute of Electrical and Electronics Engineers, USA, 1999) p.283 (1999)