By Takahiko Kato, Carol A. Handwerker, Jasbir Bath
Discusses the expansion mechanisms of tin whiskers and the powerful mitigation suggestions essential to decrease whisker progress risks
This e-book covers key tin whisker issues, starting from primary technological know-how to sensible mitigation ideas. The textual content starts with a overview of the attribute homes of neighborhood microstructures round whisker and hillock grains to spot why those specific grains and destinations develop into predisposed to forming whiskers and hillocks. The ebook discusses the fundamental houses of tin-based alloy finishes and the consequences of assorted alloying components on whisker formation, with a spotlight on capability mechanisms for whisker suppression or enhancement for every aspect. Tin whisker danger mitigation ideas for every tier of the availability chain for top reliability digital platforms also are described.
- Discusses whisker formation components together with floor grain geometry, crystallographic orientation-dependent floor grain boundary constitution, and the localization of elastic strain/strain strength density distribution
- Examines how whiskers and hillocks evolve in time via real-time reviews of whisker progress with the scanning electron microscope/focused ion beaming milling (SEM/FIB)
- Covers characterization tools of tin and tin-based alloy finishes corresponding to transmission electron microscopy (TEM), scanning electron microscopy (SEM), and electron backscatter diffraction (EBSD)
- Reviews theories of mechanically-induced tin whiskers with case reviews utilizing natural tin and different lead-free finishes proven to judge the pressure-induced tin whiskers
Mitigating Tin Whisker dangers: concept and perform is meant for the wider digital packaging and production neighborhood together with: production engineers, packaging improvement engineers, in addition to engineers and researchers in excessive reliability industries.
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Additional info for Mitigating tin whisker risks: theory and practice
UNDERSTANDING THE MECHANISMS BEHIND IMC-INDUCED STRESS 27 sample was monitored continuously to obtain the whisker density, and other samples were selectively etched after different intervals to measure the stress and IMC volume. Several important features of the whisker formation process can be recognized in these data. The first is that the IMC starts to grow immediately and continues to grow over the entire period of the measurement. The volume increases with a form that becomes parabolic over long times, suggesting that the growth rate becomes limited by diffusion across the IMC layer at the interface .
The whisker density is measured in real time using an optical technique that monitors the scattering of light from the surface . By using oblique illumination in an optical microscope, we can highlight and count surface features over a large area (1 mm × 1 mm) that are too small to resolve directly. 3 was made on a series of samples that were grown at the same time under the same conditions to maintain sample uniformity. 3 Influence of Sn layer thickness/grain size on IMC growth, stress, and whisker density.
The combined results from simulation and experiment verify that grains with high ESEDs are potential whisker formation sites. Extending this to the overall microstructure and to the films, we have identified whisker-resistant textures (low ESEDs) under different stress-generating mechanisms: a strong (100) fiber texture film for a compressive stress induced only by IMC formation and a strong (001) fiber texture film for a compressive stress induced during thermal cycling. 3 SUMMARY AND RECOMMENDATIONS In this chapter, we examined the characteristic properties of the microstructure around whisker and hillock grains with the aim to further identify why these particular shallow surface grains and locations became predisposed to forming whiskers and hillocks.