The Effect of Temperature on Tin Whisker Growth under Mechanical Stress

Abstract

The whisker phenomenon has caused the reliability issues which induce short circuit in the electronic manufacturing industries. The research is conducted to study on the formation of pure tin whisker under the control of stress and temperature with the application of mechanical indentation and the formation of whisker can be classified into distinct shape accordingly. The specified ranges of stress and surrounding temperature are set up accordingly to promote the whisker mechanism of pure tin whisker. The pure tin whisker formed is examined in term of morphology characterization via Optical Microscope and Scanning Electron Microscope to analyze on the effect of stress and temperature on the growth morphology of pure tin whisker. This report outlines the research in progress on the development of the pure tin whisker formation.

Atomic layer deposition (ALD) for environmental protection and whisker mitigation of electronic assemblies

“…An overall consensus on factors playing a fundamental role in whisker growth has been reached: (i) in-plane compressive stresses, caused by volumetric expansion following the Sn-Cu intermetallic growth, providing the driving force for whiskers to grow [9], (ii) rapid grain boundary self-diffusion from the tin electroplate interior to the growing whisker [10], and (iii) a surface oxide layer which limits surface vacancy sources, thus preventing diffusion and corresponding stress relief via diffusional processes [11]. In addition, several other factors have shown to influence whisker growth such as morphology and crystallographic structure of the intermetallic compound [12], mismatch in the coefficients of thermal expansion (CTE) causing stress during thermal cycling [13], elevated temperatures and high humidity conditions leading to corrosion [14], and applied external mechanical stress [15]. It is also here important to recall that morphologies and physical properties of the Sn layers such as thickness, grain size, and crystallographic structure [13], as well as other factors such as current load [16,17] and electrostatic forces [18], also contribute to whisker formation.…”

Atomic Layer Deposition (ALD) to Mitigate Tin Whisker Growth and Corrosion Issues on Printed Circuit Board Assemblies

“…7,8 Elevated temperatures and high humidity conditions that result in corrosion are also a potential additional mechanism for stress formation in a tin layer 9,10 , as are directly applied external mechanical loads. [11][12][13][14] There are, however, many factors that may influence the growth of whiskers, including the physical characteristics of the Sn layers (e.g. thickness, 7,15 grain size and crystallographic structure), and despite an increased understanding of the processes that give rise to whisker growth the phenomenon is still not fully understood.…”