Rob:  See below, where I attempt to answer...

Rob Strecker <[log in to unmask]> wrote:
Does this mean that combining different flux chemistries will not contribute to foaming?... Probably not..

Is there enough flux left over on the boards from SMT to be a major contributor to foaming?  ... It would appear you have already answered that question... fluxes contain surfactant-like  components, and surfactants can foam  at  low ppm levels. 

Just to clarify, we are on the low sided of our wash temperature, we are not currently using a defoamer or saponifier, just pure DI water.  
BINGO!  No wonder you are getting foaming!

We have also seen foaming during the first wash load with a fresh water change out.  How important is it to have our wash tank completely clean of all previous wash residues before we refill with fresh water?    REAL IMPORTANT.

Can minimal residues cause major foaming in the next wash?    
You seem to be proving that...

Purchasing a defoamer at this point is not an option, it will be used as a last resort.  We have a run coming up that we will be separating and washing SMT boards pre-wave and washing them again post-wave then washing the last batch after it's been through both processes (worst case) all with fresh water.  What are some of the risks associated with board wash foaming?    Primarily rinse issues...

If some foaming residue is left on the boards what would they look like and what problems could they cause, if any?

You are now asking a question beyond my experience..

Rudy Sedlak
RD Chemical Company


       
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