Hello all,

Question on pre-tinning of components and wires.  We are in a debate here.

Is it desirable to pre-tin wires and components with a water soluble (high
activity) or an RMA (low activity)?

My position is that water soluble (high activity) is the preffered flux type
over RMA to provide better pre-tin and also ease of cleaning.

Others are arguing that there is significant risk in using the water soluble
due to the corrosive residues, particularly if they are able to wick up the
wire and under the insulation.  They state rosin is to be used for
pre-tinning to mitigate that risk. My issue with this method (aside from the
lower activity level potentially yielding a lower quality pre-tin) is that
our termination process can call for either rosin flux or water soluble
flux, depending on the application or product, and I am concerned that any
rosin residues from the pre-tin (more difficult to remove than water
soluble) could negatively impact the termination solder joint.

Another thing to consider is that we stock pre-cut and pre-tinned wires at
point-of-use, so there could be a significant time-frame between pre-tinning
and termination.   Depending on your view, this could be time for the water
soluble residue to work it's corrosive magic or for RMA residue to nicely
harden.

Thoughts?

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