Effects of Heat Treatment on the Microstructure and Whisker Growth Propensity of Matte Tin Finish
2
조회
0
다운로드
1
인용
0
참고문헌
키워드
초록
The effects of heat treatment on matte pure tin-plated Cu leadframes at high temperature and humidity conditions were investigated. After 1800 hrs of storage at 55oC/85% RH, approximately 14.5 μm long striation-shaped whiskers were observed on the surface of the without postbake treatment (WOPB) samples, while no whiskers were found in with postbake treatment (WPB) samples. The preferred orientations of Sn grains in WOPB and WPB sample did not change after the postbake treatment at 125oC for 1 hr. However, both changed from (112) to (321) and (101), respectively,after 1800 hrs of storage at 55oC/85% RH. The tensile stress of 8 MPa generated in as-plated sample was changed to a compression stress of 17 MPa after 2 days in room temperature storage. Due to the grain growth during postbake treatment,the WPB samples have more regular grains than the WOPB samples. In the as-plated sample, 0.32 μm thickness of planar intermetallic compound (IMC) was observed. The IMCs in the WOPB and WPB samples had two distinct layers with large grains of Cu6Sn5 and with small grains of η-Cu6.26Sn5.
Abstract
The effects of heat treatment on matte pure tin-plated Cu leadframes at high temperature and humidity conditions were investigated. After 1800 hrs of storage at 55oC/85% RH, approximately 14.5 μm long striation-shaped whiskers were observed on the surface of the without postbake treatment (WOPB) samples, while no whiskers were found in with postbake treatment (WPB) samples. The preferred orientations of Sn grains in WOPB and WPB sample did not change after the postbake treatment at 125oC for 1 hr. However, both changed from (112) to (321) and (101), respectively,after 1800 hrs of storage at 55oC/85% RH. The tensile stress of 8 MPa generated in as-plated sample was changed to a compression stress of 17 MPa after 2 days in room temperature storage. Due to the grain growth during postbake treatment,the WPB samples have more regular grains than the WOPB samples. In the as-plated sample, 0.32 μm thickness of planar intermetallic compound (IMC) was observed. The IMCs in the WOPB and WPB samples had two distinct layers with large grains of Cu6Sn5 and with small grains of η-Cu6.26Sn5.
참고문헌 (33)
- K. N. Subramanian, "Lead-free electronic solders", pp.281~ (2007), Springer
- 문윤성, "무전해 도금법을 이용한 Sn-Cu 범프 형성에 관한 연구", 마이크로전자 및 패키징학회지, 15(2), pp.17~21 (2008), 한국마이크로전자및패키징학회
- U. Lindborg, "A model for the spontaneous growth of zinc, cadmium and tin whiskers", Acta Metall., 24(2), pp.181~ (1976)
- Chong-Hee Yu, "The Observation of Intermetallic Compound Microstructure Under Sn Whisker in Lead-free Finish", 마이크로전자 및 패키징학회지, 16(2), pp.27~31 (2009), 한국마이크로전자및패키징학회
- B. Z. Lee, "Spontaneous growth mechanism of tin whiskers", Acta Mater., 46(10), pp.3701~ (1998)
- I. Boguslavsky, "Recrystallization principles applied to whisker growth in tin", Proc. IPC, 2003, ~
- W. J. Boettinger, "Whisker and hillock formation on Sn, Sn-Cu and Sn-Pb electrodeposits", Acta Mater., 53(11), pp.5033~ (2005)
- K. N. Tu, "Stress analysis of spontaneous Sn whisker growth", J. Mater. Sci. Mater. Electron., 18(2), pp.269~ (2007)
- C. Xu, "Driving force for the formation of Sn whiskers: Compressive stress-pathways for its generation and remedies for its elimination and minimization", IEEE Trans. Elect. Packag. Manuf., 28(1), pp.31~ (2005)
- M. E. Williams, "Hillock and whisker growth on Sn and SnCu electrodeposits on a substrate not forming interfacial intermetallic compounds", J. Electron. Mater., 36(3), pp.214~ (2007)
- W. Zang, "Effects of lead on tin whisker elimination - efforts toward lead-free and whisker-free electrodeposition of tin", Electrochem. Soc., 153(5), pp.C337~ (2006)
- P. Oberndorff, "Root cause of tin whisker growth", EFSOT Europe (2003)
- Y. Fukuda, "Length distribution analysis for tin whisker growth", IEEE Trans. Electron. Packag. Manuf., 30(4), pp.36~ (2007)
- P. Oberndorff, "Whisker formation on matte Sn influencing of high humidity", Proc. 55th Electron. Compon. Technol. Conf. (ECTC), pp.429~ (2005)
- Y. Fukuda, "The effect of annealin on tin whisker growth", IEEE Trans. Elect. Packag. Manuf., 29(4), pp.252~ (2006)
- P. Oberndorff, "Humidity effects on Sn whisker formation", IEEE Trans. Elect. Packag. Manuf., 29(4), pp.239~ (2006)
- J. H. Lau, "3D large deformation and nonlinear stress analyses of tin whisker initiation and growth on lead-free components", Proc. 52rd Electron. Compon. Technol. Conf. (ECTC), pp.692~ (2003)
- M. Sobiech, "The microstructure and state of stress of Sn thin films after post-plating annealing: An explanation for the suppression of whisker formation?", Proc. 57th Electron. Compon. Technol. Conf. (ECTC), pp.192~ (2007)
- S. Ganesan, "Lead-free electronics", pp.251~ (2006), CALCE EPSC Press
- S. C. Britton, "Spontaneous growth of whiskers on tin coatings: 20 years of observation", Metal Finishing, 52, pp.95~ (1974)
- D. Shangguan, "Lead-free solder interconnect reliability", pp.161~162 (2005), ASM International
- C.S. Barrett, "Structure of metals", pp.204~206 (1966), Pergamon
- J.M. Bennett, "Introduction to surface roughness and scattering", pp.28~ (1989), Optical Society of America
- C. E. Birchenall, "Physical metallurgy", pp.216~217 (1959), McGraw- Hill
- JEDEC, "Current tin whiskers theory and mitigation practices guideline, JP002", J. S. S. T. Association, VA 22201-3834: Electronic Industries Association, ~ (2006)
- K. N. Tu, "Cu", Sn interfacial reactions: thin-film case versus bulk case, 1996, pp.46(2), 217~
- K. N. Tu, "Kinetics of interfacial reaction in bimetallic Cu-Sn thin films", Acta Metall., 30(10), pp.947~ (1982)
- K. N. Tu, "Irreversible processes of spontaneous whisker growth in bimetallic Cu-Sn", Phys.Rev. B., 49(3), pp.2030~ (1994)
- Y. Fujiwara, "Sn deposition onto Cu and alloy layer growth by a contact immersion process", Thin Solid Films, 425(1), pp.121~ (2003)
- J. Y. Song, "Effects of reactive diffusion on stress evolution in Cu-Sn films", Scripta. Mater., 51(2), pp.167~ (2004)
- L. A. Clevenger, "Interdiffusion and phase formation in Cu(Sn) alloy films", J. Appl. Phys., 83(1), pp.90~ (1998)
- P. Vianco, "Solid-state intermetallic compound layer growth between copper and 95.5Sn-3.9Ag- 0.6Cu solder", J. Electron Mater., 33(9), pp.991~ (2004)
- JCPDS, "International Centre for Diffraction Data", ~ (2002)