How can, formerly harmless small quantities of halides in soldering materials, suddenly pose a risk with the change-over to lead free alloys?

It has everything to do with the formation of dangerously hydroscopic metal salts when using halogens in combination with lead free alloys.
An increased risk on corrosion and migration of metals on electronic circuits have been reported and confirmed.
This is why using absolutely halogen free soldering materials in lead free processes is the only safe way.

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