The Structure and Kinetics of Tin-Whisker Formation and Growth on High Tin Content Finishes

Author(s):  
W Choi ◽  
George Galyon ◽  
King-Ning Tu ◽  
T Lee
2008 ◽  
Author(s):  
Tadahiro Shibutani ◽  
Qiang Yu ◽  
Masaki Shiratori

Author(s):  
Jin Liang ◽  
Xiaodong Li ◽  
Zhi-Hui Xu ◽  
Dongkai Shangguan

Tin whisker formation has been a serious concern for application of pure Tin as a Pb-free component lead finish. It has been long believed that residual stress is the root cause of whisker formation. A fundamental question is if stress produced by other than the plating processing and post-plating metallurgical reactions can induce whisker formation. In this study, micro indents were made on pure Tin plated component leads to induce stress for studying stress induced whisker formation. Nano-indentation was performed to measure hardness and elastic modulus of the Tin coating layer where whiskers initiate. Scanning electron microscopy (SEM) was used to study indentation deformation mechanisms and to monitor the nucleation and growth of whiskers in-situ. In additions, finite element analysis was carried out to theoretically calculate the stress/strain distribution around the indentations. Experimental and theoretical calculation results show that whiskers form at a certain stress level. This suggests that there might exit a critical stress threshold that governs the whisker formation. It is believed that establishment of a quantitative relationship between stress level and whisker formation/growth could lead to a breakthrough in risk and reliability assessment with pure Tin application in the electronic industry and in safeguard for smooth Pb-free transition.


2009 ◽  
Vol 12 (1) ◽  
pp. 53-61 ◽  
Author(s):  
Tadahiro Shibutani ◽  
Takuma Yamashita ◽  
Yu Qiang ◽  
Masaki Shiratori

Author(s):  
Noor Zaimah Mohd Mokhtar ◽  
Mohd Arif Anuar Mohd Salleh ◽  
Aimi Noorliyana Hashim

Author(s):  
Nausha Asrar

Abstract While considerable amount of researches and investigations have been made on lead-free solder joint reliability, limited number of literatures are available on the effect of gold content on lead-free solder joint performance. The challenges of lead-free solder/gold metallization interdiffusion during high temperature application/test are: gold embrittlement, intermetallics growth, void formation, and tin-whisker formation. Tin whiskers causing system failures in earth and space-based applications have been reported. This paper illustrates a few case histories of such challenges. The results confirmed that the synergistic effects of void formation, intermetallic compounds formation due to the thick gold plating, and coefficient of thermal expansion mismatch between organic and ceramic substrates resulted in brittle fracture of the solder joint. The tin whisker formation was attributed to the compressive stress in the tin solder material, which was caused by diffusion of the end-cap metallization, formation of intermetallics, and thermal cycling of the soldered components.


Author(s):  
Jocelyn P. Siplon ◽  
Gary J. Ewell ◽  
Eric Frasco ◽  
Tom Gibson ◽  
Jay A. Brusse

Abstract This paper discusses the issues of tin whisker growth on discrete electronic components. It presents both a critical analysis of existing published documents on tin whisker nucleation and growth and a summary of very recent experiments that provide further understanding of the potential means of whisker formation mitigation. Many of the proposed techniques for reducing the likelihood of whisker formation are inadequate, including control of the immediate underplating material, use of conformal coating, regulating the thickness of the tin coating, use of matte tin electroplating, and annealing or fusing of the tin layer. They likely reduce the incidence of nucleation or growth but do not provide guaranteed protection from lack of whisker formation. The first report of tin whiskers on electronic components dates back to 1946 [16]. Since that time whisker-related problems have been reported consistently. Today the concern is for the of increased number of whisker-related problems due to circuit geometry reductions, lower application voltages and the probability of more suppliers (rapidly) introducing pure tin plated alternatives to comply with pending Pb-free legislation.


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