David:  No-clean residue is SUPPOSED to be hard to remove, this means it is unreactive, and thus will not corrode the part....

When you mix it with water soluble flux (which usually contain small amounts of strong acid), you reactivate the organic acids in the residues, and they can be quite corrosive, and unlike the water soluble flux acids, they do not vaporize during soldering, and this organic acid combined with the acid in the water soluble flux can work together to corrode.

Hope this helps.

Rudy Sedlak
RD Chemical Company

David Tremmel <[log in to unmask]> wrote:
Technetters,

I have received some microBGAs which I have to reball and they have a
no-clean flux residue which is difficult to remove. Also, when it comes in
contact with our water-soluble flux it creates an acid which is not very
'friendly' to the part.

Would any of the chemical gurus care to edify one of the uneducated ones why
no-clean flux, when dried and allowed to set for a couple of months is so
difficult to completely remove and what possible acids or chemicals are
created when it is combined with water-soluble flux (type ORM1)?

As always, I appreciate the responses I receive.

David Tremmel
Technical Manager
BT Mexico

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