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Long term evolution of microstructure and stress around tin whiskers investigated using scanning Laue microdiffraction

Hektor, Johan LU ; Micha, Jean Sébastien; Hall, Stephen A. LU ; Iyengar, Srinivasan LU and Ristinmaa, Matti LU (2019) In Acta Materialia 168. p.210-221
Abstract

Scanning Laue microdiffraction was used to study the evolution of the microstructure and the stress field around two tin whiskers during ageing for up to 21 months. In the heterogeneous stress fields obtained, localised ridges of high compressive stress leading to the root of the whiskers were found. Due to the evolution of the intermetallic compound in the interface between the copper substrate and the tin coating, the stress field was also evolving with time. The temporal evolution of the stress field indicates that the regions supplying material to the whisker root is changing with time, highlighting that whisker growth is a highly dynamical process. During the experimental campaign, a new surface feature appeared in a grain boundary... (More)

Scanning Laue microdiffraction was used to study the evolution of the microstructure and the stress field around two tin whiskers during ageing for up to 21 months. In the heterogeneous stress fields obtained, localised ridges of high compressive stress leading to the root of the whiskers were found. Due to the evolution of the intermetallic compound in the interface between the copper substrate and the tin coating, the stress field was also evolving with time. The temporal evolution of the stress field indicates that the regions supplying material to the whisker root is changing with time, highlighting that whisker growth is a highly dynamical process. During the experimental campaign, a new surface feature appeared in a grain boundary within the scanned area of the sample. The new feature had a twinning relationship with one of the neighbouring grains, a similar twin relation was also seen for one of the two larger whiskers. It is suggested that tin atoms diffuse out from the ridges of high compressive stress to the nearby, less compressed grain boundaries along which diffusion towards the root of the whisker occurs. The observations made from the Laue diffraction measurements also suggest that whiskers form in regions where the gradient in hydrostatic stress is large and that they grow to relax compressive stresses.

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author
organization
publishing date
type
Contribution to journal
publication status
published
subject
keywords
Lead-free solder, Tin whiskers, X-ray diffraction
in
Acta Materialia
volume
168
pages
12 pages
publisher
Elsevier
external identifiers
  • scopus:85061967609
ISSN
1359-6454
DOI
10.1016/j.actamat.2019.02.021
language
English
LU publication?
yes
id
5f87381d-b787-4776-877b-82dd2e77f256
date added to LUP
2019-03-05 14:20:57
date last changed
2019-03-27 04:39:50
@article{5f87381d-b787-4776-877b-82dd2e77f256,
  abstract     = {<p>Scanning Laue microdiffraction was used to study the evolution of the microstructure and the stress field around two tin whiskers during ageing for up to 21 months. In the heterogeneous stress fields obtained, localised ridges of high compressive stress leading to the root of the whiskers were found. Due to the evolution of the intermetallic compound in the interface between the copper substrate and the tin coating, the stress field was also evolving with time. The temporal evolution of the stress field indicates that the regions supplying material to the whisker root is changing with time, highlighting that whisker growth is a highly dynamical process. During the experimental campaign, a new surface feature appeared in a grain boundary within the scanned area of the sample. The new feature had a twinning relationship with one of the neighbouring grains, a similar twin relation was also seen for one of the two larger whiskers. It is suggested that tin atoms diffuse out from the ridges of high compressive stress to the nearby, less compressed grain boundaries along which diffusion towards the root of the whisker occurs. The observations made from the Laue diffraction measurements also suggest that whiskers form in regions where the gradient in hydrostatic stress is large and that they grow to relax compressive stresses.</p>},
  author       = {Hektor, Johan and Micha, Jean Sébastien and Hall, Stephen A. and Iyengar, Srinivasan and Ristinmaa, Matti},
  issn         = {1359-6454},
  keyword      = {Lead-free solder,Tin whiskers,X-ray diffraction},
  language     = {eng},
  pages        = {210--221},
  publisher    = {Elsevier},
  series       = {Acta Materialia},
  title        = {Long term evolution of microstructure and stress around tin whiskers investigated using scanning Laue microdiffraction},
  url          = {http://dx.doi.org/10.1016/j.actamat.2019.02.021},
  volume       = {168},
  year         = {2019},
}