Since the ban of tin-lead alloys, the formation of Tin whiskers has again become a problem topic.
The whiskers occur seemingly spontaneously. It has not yet succeeded, to reproduce them at any time, since not all the causal mechanisms are known.
According to current knowledge, whiskers arise almost exclusively from the tin layer, which are subject to external or internal compressive stresses. There are also zinc whisker what may be relevant for zinc-plated housing (connectors).
According to current knowledge, whiskers arise almost exclusively from the tin layer, which are subject to external or internal compressive stresses. There are also zinc whisker what may be relevant for zinc-plated housing (connectors).
For press-in technology whiskers are therefore an issue since the tinned press-in contact is pressed into the tin-plated hole. Thus, the tin layers are charged with external pressure and there is a risk of whisker growth.
However, this does not apply to all cases and all contacts.
If contacts already stamped from galvanized strips, the punched edges are blank. Also completely bare contacts are permitted.
If the contact is designed so that it pushes the tin of the hole to the side, then is not a tin between the pressure surfaces. No tin, no whiskers.
The tin on the PCB can still remain a problem. Since PCBs, a nickel layer is not common (as opposed to the contacts), whiskers arise rather from the tin on the PCB when build again compressive stresses.,
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