Howard
Thanks for reminding us about the potential danger of using nPB as a
cleaning solvent. I was not aware of the issue of the OSHA/NIOSH Hazard
Alert on nPB July 31, 2013. I recommend every user or potential user of
nPB to download the document and carefully read it. It may be found at:
https://www.osha.gov/Publications/OSHA_3676.pdf
Note that nPB-containing solvents are commercialised under many names
and users of any solvents, adhesives, coatings etc. should carefully
read the MSDS and, if they see any of the synonyms nPB, NPB, n-propyl
bromide, 1-bromopropane, n-propyl, n-C3H7Br, Brompropan, Propylbromid,
1-Brompropan, Bromopropane, bromo propane, 1-bromo-propan or propyl
bromide, then be aware. This substance is potentially dangerous,
especially if used from spray cans, or for hand-defluxing. In addition,
it is ozone-depleting and should have been entered as a Controlled
Substance under the Montreal Protocol (the fact that it wasn't was
because of a loophole generated by its short atmospheric residence time,
but it certainly is as bad as some controlled CFCs and HCFCs in tropical
and sub-tropical climates, much less so in temperate climates.)
My advice, which remains unchanged over more than a decade, is to avoid
using nPB wherever possible, for both environmental and H&S reasons. My
experience is such that it is impossible to avoid drag-out when used on
electronic assemblies and rework, even days after cleaning, may release
vapours, especially where there are un-impregnated wound inductors or
capacitors.
Right, to answer your question: the best solution is to use a no-clean
flux and not to clean, provided you can qualify the process. By "applied
topically", I presume you mean hand-cleaning. With any solvent, this
probably means that all you are doing is to spread the residues over a
greater area, so that they are cosmetically invisible (and possibly more
dangerous). Frankly, this is not cleaning, as I define it.
You suggest 3M's Novec 71-DA. This consists of 2 isomers of HFEs (low
toxicity, high global warming potential),
trans-dichloroethylene(medium-high toxicity, little vapour environmental
effect), in roughly equal parts, with a smidgeon of ethyl alcohol
(hic!). It may be slightly less effective than nPB blends for defluxing
and it is more expensive. It will require operator exposure control
because of the high trans-DCE content (I personally think the 200 ppm
PEL is set too high and I would consider a 100 ppm limit for the
azeotrope would be safer, as measured with activated carbon methods, but
I'm always suspicious of halogenated solvents, which have always had a
track record of decreasing PELs.)
Hope this helps!
Brian
On 11.09.2013 20:26, Watson, Howard A wrote:
> Technetters,
>
> In January, Brian Ellis raised some excellent points about the hazards of using nPB, or 1-Bromopropane. With the release of the OSHA/NIOSH Hazard Alert on nPB July 31, 2013, the pressure is on to stop using this stuff. We use the trade name Ensolv. While we slowly convert to aqueous batch cleaning, our need for spot cleaning on the bench will remain, as we are more like an R&D shop. We are using rosin core solder and RMA flux applied topically. The techs love Ensolv, and it does work great. Does anyone have a recommendation for a replacement of Ensolv? I have seen the specs of 3M Novec engineered fluid, maybe 71DA is a good choice?
>
> Thanks in advance for your advice.
>
> Howard A. Watson
>
>
>
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