Sophia

- Structure
The solder will change its structure during operation: The lead phases are getting coarser, the tin domains don't change much ( I know Werner, we don't fully agree in this ). However, this will also occur at ambient temperature so I wouldn't care about that.
- Properties
The creep properties of solder are temperature dependent. This means at high temperature the material deforms easier. In this respect one could speak of weakening. This might be a problem if your board is in vertical position and you have heavy components soldered in SMT. But I would consider this rather hypothetical.
- Intermetallics
Yes they grow. However, the problem of rupture occurs with temperature cycles that are fast enough to bring enough shear stress in the intermetallics to break them.

Best regards

Guenter 



Guenter Grossmann
Swiss Federal Institute for Materials Testing and Research EMPA
Centre for Reliability
8600 Duebendorf
Switzerland

Phone: xx41 1 823 4279
Fax :      xx41 1823 4054
mail:     [log in to unmask]

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