Stress analysis of spontaneous Sn whisker growth

K. N. Tu, Chih Chen, Albert T. Wu

Research output: Chapter in Book/Report/Conference proceedingChapterpeer-review

18 Scopus citations


Spontaneous Sn whisker growth is a surface relief phenomenon of creep, driven by a compressive stress gradient. No externally applied stress is required for the growth, and the compressive stress is generated within, from the chemical reaction between Sn and Cu to form the intermetallic compound Cu6Sn5 at room temperature. To obtain the compressive stress gradient, a break of the protective oxide on the Sn surface is required because the free surface of the break is stressfree. Thus, spontaneous Sn whisker growth is unique that stress relaxation accompanies stress generation. One of the whisker challenging issues in understanding and in finding effective methods to prevent spontaneous Sn whisker growth is to develop accelerated tests of whisker growth. Use of electromigration on short Sn stripes can facilitate this. The stress distribution around the vicinity and the root of a whisker can be obtained by using the micro-beam X-ray diffraction utilizing synchrotron radiation. A discussion of how to prevent spontaneous Sn whisker growth by blocking both stress generation and stress relaxation is given.

Original languageEnglish
Title of host publicationLead-Free Electronic Solders
Subtitle of host publicationA Special Issue of the Journal of Materials Science: Materials in Electronics
PublisherSpringer US
Number of pages13
ISBN (Print)0387484310, 9780387484310
StatePublished - 2007


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