USC doctoral student unravels ‘tin whisker’ mystery
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Re: USC doctoral student unravels ‘tin whisker’ mystery
#2Congratulations, now can you actually link to the paper instead of summarizing it in half a sentence as is "caused by high-strain gradient built up inside the device"? This is useless reporting.
Re: USC doctoral student unravels ‘tin whisker’ mystery
#3Congratulations, now can you actually link to the paper instead of summarizing it in half a sentence as is "caused by high-strain gradient built up inside the device"? This is useless reporting.
It is a bit hard to find one that isn't behind a paywall, but here's the actual paper: http://www.osti.gov/bridge/servlets/purl/1013351-BXJitV/1013...
Re: USC doctoral student unravels ‘tin whisker’ mystery
#4I assume whiskers cause a short circuit. Why can't the circuit board be coated with plastic, epoxy, non-conductive paint, or something to prevent the whiskers from causing a short?
Re: USC doctoral student unravels ‘tin whisker’ mystery
#5I assume whiskers cause a short circuit. Why can't the circuit board be coated with plastic, epoxy, non-conductive paint, or something to prevent the whiskers from causing a short?
Conformal coating is often used for protection in harsh environments.
Re: USC doctoral student unravels ‘tin whisker’ mystery
#6I assume whiskers cause a short circuit. Why can't the circuit board be coated with plastic, epoxy, non-conductive paint, or something to prevent the whiskers from causing a short?
Since the growth is caused my material stress, coating the solder with a hard plastic will shift the stress elsewhere, might cause another suite of problems.
Re: USC doctoral student unravels ‘tin whisker’ mystery
#7I assume whiskers cause a short circuit. Why can't the circuit board be coated with plastic, epoxy, non-conductive paint, or something to prevent the whiskers from causing a short?
Conformal coating is often used for protection in harsh environments. http://en.m.wikipedia.org/wiki/Conformal_coating
Tin whiskers can break through conformal coating in some situations and the coating process does not always cover the entire surface evenly leaving thin areas or even entirely uncovered places in which whiskers can still form and escape. http://www.freelists.org/post/tinwhiskers/NASA-experiments-c...
Re: USC doctoral student unravels ‘tin whisker’ mystery
#8 "Historically lead (Pb) has been added to the solders to prevent whisker growth. Due to the harmful effects on human health and environments, it is no
longer a valid solution to prevent whisker growth with lead. With the shift to whisker- prone “Pb-free” solders, controlling whisker growth from low melting point metals has again become technically challenging."
Re: USC doctoral student unravels ‘tin whisker’ mystery
#9This is the University of South Carolina, not Southern California which most people probably associate with “USC”.
Re: USC doctoral student unravels ‘tin whisker’ mystery
#10Congratulations, now can you actually link to the paper instead of summarizing it in half a sentence as is "caused by high-strain gradient built up inside the device"? This is useless reporting.
From my reading it sounds like we've known for sometime that it was due to strain on the board, but the work provides some insight by mapping stresses, and SEM imaging.
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."