The principal, and I suspect the ONLY, reason for using Hydrobromic Acid
(HBr) in a HASL is to solubilize Hydrazine.

Hydrazine Hydrobromide is quite soluble, the Hydrochloride is not.

Hydrazine is the best HASL activator known (at least to this vendor), and
gives good fluxing, even on boards that have sat around too long.

Further, the toxicity of Hydrazine Hydrobromide is "officially" unknown, so
it does not have to be listed on the MSDS, or at least that is clearly the
interpretation of many vendors.  So, the only thing you need to put on the
MSDS is the HBr,

And, of course, the actual toxicity of Hydrazine Hydrobromide is formidable...
A scarey thought.  It is probably as carcinogenic as straight Hydrazine.

Rudy Sedlak
RD Chemical Company

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