Michael

Prewash to drain? Not all components of some W/S masks are disposable to drain. Above
all, check BOD5 and COD5 with your water treatment authority.

Brian

"Barmuta, Mike" wrote:

> Just a little clarification on the term "peelable" soldermask.
>
> The peelables are not just latex based. They also include vinyl, silicone
> and urethane based chemistries.
> Although I personally am not a big fan of peelable masks they are not all
> the same in their ionic properties and flux absorption characteristics. So
> we need to be careful in not painting them all with the same broad brush.
>
> The Lackwerke Peters SD 2954 that Mickey Weiner spoke of is a vinyl based
> compound and behaves differently than the latex masks.
>
> If it was me I would choose an unfilled water soluble mask if a high
> dissolution rate coupled with a decent inline aqueous cleaner that had a
> prewash to drain.
>
> Just my 2 cents.
>
> regards
>
> Michael Barmuta
>
> Staff Engineer
>
> Fluke Corp.
>
> Everett WA
>
> 425-356-6076
>
> -----Original Message-----
> From: Douglas Pauls [mailto:[log in to unmask]]
> Sent: Wednesday, August 23, 2000 6:06 AM
> To: [log in to unmask]
> Subject: Re: [TN] Peelable SolderMask
>
> In a message dated 08/23/2000 12:47:47 AM US Eastern Standard Time,
> [log in to unmask] writes:
>
> >  I am not aware of any contamination issues-  Always glad to learn
>
> Yes, but I hope you don't have to learn the *hard* way!
>
> My colleague, Dave Morrow, will be publishing an article in PC Fab on a case
> study we did involving peelable latex mask.  Or at least he will once I stop
> redlining his drafts...............
>
> The one in the study, while not named, is a very popular one.  The
> fabricator
> would put it on the panels at the request of the assembler.  In the state it
> was delivered to the assembler, the mask material itself had roughly 2
> micrograms per square inch of chloride and about 3 micrograms/in2 of
> sulfate,
> when measured by ion chromatography.  As soon as it had been exposed to the
> assemblers process, a no-clean RMA, it had chloride levels in the 185-200
> microgram/in2 range.  The mask either chemically broke down after thermal
> exposure or it absorbed flux, or both.  The surface of the assembly UNDER
> the
> mask went from about 1-2 micrograms per square inch to about 35 micrograms
> per square inch.  We recommend a maximum of 4.5.  The result was corrosion
> found during temperature cycling.
>
> A point I would like to make is that people don't pay much attention to
> materials that are not part of the final assembly.  Why worry about the
> latex
> mask?  I'm just going to throw it away anyway.  Well, they can have
> detrimental effects.  The same thing applies to other "temporary" materials
> like water soluble solder mask, water soluble temporary spacers, water
> soluble tapes, etc.  Just keep in mind that every material has an effect,
> and
> every material has to go somewhere.
>
> Doug Pauls
> Contamination Studies Labs
>
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