"Tempea, Ioan" wrote:

> Fellow technetters,
>
> we are presently fighting with some ultra low-end TH only PCBs. During
> waving they blister a lot. We tried many things like hotter-colder
> preheating, hotter-colder solder temp, faster-slower speed. No result.
>
> Are there any other tricks to try, or we send them back to the fab?
>
> Thanks, Ioan

Probably there was some problem at the chemical wet PTH process when
processing the PCB such as not long enough in the Metex cleaner which
causes separation under thermal stress. I don't think there is anything
you can do. Correct me if I am wrong!!!!

Francis