From the conclusion:
"In summary, a methodology has been developed to incorporate DIC technique with SEM images for mapping the local strain fields during whisker growth. By processing SEM images taken in consecutive time intervals over the area of interest on Sn-Cu finishes, the local strain evolution due to whisker growth can be obtained. This methodology provides an alternative way for exploring the complicated process of whisker growth through the page 9 of 13 morphology changes. From the DIC results, it is proposed that strain or stress gradient, instead of an overall compressive stress field is the key for whisker growth. Results from SEM and DIC analysis also indicate that the whisker growth is a continuously dynamic process, during which the subsequent whisker is triggered by the redistribution of strain or stress field after local strain relaxation. The findings have advanced the understanding of whisker growth mechanisms and may provide insight for developing whisker mitigation technology for lead-free solder alloys."
Oh Europe. Yes, let's ban the use of minuscule amounts of lead so that people will have to replace entire devices when they fail.
As a mechanical engineer I used to work in an electronics factory. there is still a lot of soldering done by hand. not to mention that the operators of the automated soldering machines. during this soldering process there is a considerable amount of fumes, even though you're using blowers and filters, that the workers are exposed to. Lead is known to be hazardous for long exposes. So I guess keeping the manufacture-workers safety is as important as the end user's one.