Johan Hektor

Doctoral Student

Research

My research is aimed at understanding the mechanisms causing whisker growth in for example lead-free solders. Whiskers are crystalline grains of e.g. tin, spontaneously growing out of a surface. Although whisker growth was first observed some 60 years ago, little is still known about the underlying mechanisms. The leading hypothesis today is that tin whiskers grow to relax stress in the tin deposit. The stress in the deposit is caused e.g. by the formation of intermetallic compounds in the interface between tin and the underlying substrate.

The modeling part of my research concerns the development of a model able to simulate the formation and growth of intermetallic phases and how this leads to stresses in tin deposits. The mechanical behavior of the tin deposit is simulated using a crystal plasticity model and for the evolution of the intermetallic compound a phase-field approach is taken.

For the experimental part, X-ray diffraction methods are used to quantify the strain field around, growing, tin whiskers in 3D.  

Recent research outputs

Johan Hektor, Marijon, J-B., Matti Ristinmaa, Stephen Hall, Håkan Hallberg, Srinivasan Iyengar, Micha, J-S., Robach, O., Grennerat, F. & Castelnau, O. 2018 Feb 1 In : Scripta Materialia. 144, February 2018, p. 1-4 4 p.

Research output: Contribution to journalArticle

Stefanos Athanasopoulos, Stephen Hall, Pirling, T., Jonas Engqvist & Johan Hektor 2017

Research output: Contribution to conferenceAbstract

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