Structure and kinetics of Sn whisker growth on Pb-free solder finish
Standard Leadframes used in surface mount technology are finished with a layer of eutectic SnPb for passivation and for enhancing solder wetting during reflow. When eutectic SnPb is replaced by Pb-free solder, especially the eutectic SnCu, a large number of Sn whiskers are found on the Pb-free finish. Some of the whiskers are long enough to become shorts between the neighboring legs of the leadframe. How to suppress their growth and how to perform accelerated test of Sn whisker growth are crucial reliability issues in the electronic packaging industry. In this paper, we report the study of spontaneous Sn whisker growth at room temperature on eutectic SnCu and pure Sn finishes. Both compressive stress and surface oxide on Sn are necessary conditions for whisker growth. Structure and stress analyses by using the micro-diffraction in synchrotron radiation are reported. Cross-sectional electron microscopy, with samples prepared by focused ion beam, are included.
- Research Organization:
- Lawrence Berkeley National Lab. (LBNL), Berkeley, CA (United States)
- Sponsoring Organization:
- USDOE Director, Office of Science. Office of Basic Energy Studies (US)
- DOE Contract Number:
- AC03-76SF00098
- OSTI ID:
- 799652
- Report Number(s):
- LBNL-51035; R&D Project: A580ES; B& R KC0204016; TRN: US0206129
- Resource Relation:
- Conference: 52nd Electronic Component and Technology Conference, San Diego, CA (US), 05/28/2002--05/31/2002; Other Information: PBD: 11 Jul 2002
- Country of Publication:
- United States
- Language:
- English
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