Brian, why not? On the one hand bromine compounds integral to the prepreg are bound intrinsically, and on the other hand the sulfur compounds are an integral part of the cured fillers. Neither are capable of outgassing to any great degree, at least not until either reaches their Td as you have pointed out, correct? Neither presents a case of loosely bound ions or catons.
Further, after the initial release from heating during curing, are not the remaining molecules bound (physically)? I am not a chemical engineer, so forgive my ignorance. I'm just asking.

-----Original Message-----
From: TechNet [mailto:[log in to unmask]] On Behalf Of Brian Ellis
Sent: Tuesday, May 07, 2013 11:05 AM
To: [log in to unmask]
Subject: Re: [TN] Solder mask contain low levels of sulfur

I have a rhetorical question.

The bromine compounds in FR4 are bound by covalent bonds into the epoxy structure and are theoretically harmless, at least until they reach decomposition temperature.

Filler materials may have sulfur bound into their molecules either covalently or ionically, but always another relatively small molecule which is not integral in the epoxy structure.

Surely, these two cases cannot be considered as similar???

Brian

On 07.05.2013 15:46, Victor Hernandez wrote:
> Fellow TechNetters:
>
>     We are doing some preliminary investigation of solder mask and have found out that it contains low levels of sulfur.   Not sure what sulfur constituents.   Is This a typical finding of sulfur?
>
> Victor,
>
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