A user prospective:
 For Years now we are specifying Peters SD 2954 .
 Its a blue peelable which stands more than 3 heat cycles.
 Our main application is covering the connectors area on boards with double
 sided SMT. The bottom side is wave soldered, where the connectors are
press-fit type
  and the area has to be kept clean of solder from penetrating the press fit
holes.
 I am not aware of any contamination issues-  Always glad to learn.
  Occasionally we do have problems which can be contributed to the PWB
manufacturer
  ( we always blame them) over-curing the stuff .It then becomes brittle and
leaves
  solder mask "plugs" in the holes.
  On the other hand we have manufacturer who mastered the process and
supplied us
  with boards without any problem .

 Michael Weiner
Tel  (972-3) 9262937
Fax  (972-3) 9261803
mailto:[log in to unmask]



> Doug
>
> I second every word you say. Some of them make large contributions to a
> reduction of
> reliability.
>
> I've also tested some water-soluble ones, with results from total removal
> to poor
> removal and no detriment to reliability to total disaster. However, the
> removal process
> takes much longer than flux removal, in most cases, and is usually
> insufficient in
> conveyorised machines running under usual conditions.
>
> Brian
>
> Douglas Pauls wrote:
>
> > In a message dated 08/21/2000 1:41:53 PM US Eastern Standard Time,
> > [log in to unmask] writes:
> >
> > > Any manufacturers in here have experience with peelable mask?
> >
> > Sure.  Both good and bad............
> >
> > >  Only the good points are ever discussed in the sales brochures.
> >
> > I'm shocked.
> >
> > >  I'm looking for the evil
> > >  side. It seems to go against everything I've ever tried to accomplish
> with
> > a
> > >  solder mask and it makes me a little nuts to think a customer wants
> to undo
> > >  what we try so hard to do! I'm afraid next they'll want removable
> > >  traces.....Any thoughts or comments appreciated.
> >
> > We have done a number of failure analysis in which the latex peelable
> mask
> > was the source of detrimental halide residues.  A couple have been
> published
> > in Circuits Assembly and one upcoming one in PC Fab.  I think they are
> on our
> > web site (Library section of www.residues.com).
> >
> > We found that the latex masks leave high levels of chloride and sulfate
> on
> > the surface of the boards.  The organic residues can inhibit soldering
> and
> > the halide residues cause leakage and corrosion.  Not a good idea to use
> > these in a no-clean application.  The mask itself can (depending on the
> mask)
> > absorb the flux it comes into contact with.  The vendors say this is not
> a
> > problem because you throw away the mask later.  Unfortunately, the
> residues
> > remain on the board surface.  In other cases, we have found that the
> reaction
> > mechanism leaves by-products on surrounding surfaces.  As one other
> > contributor pointed out, the masks may be ammonia based.  If you can
> smell
> > the reaction byproducts, then it is depositing on other surfaces as
> well.
> >
> > I have played around with SIR testing on the latex masks and don't get
> very
> > good response from either the material or the residues left by the
> material.
> >
> > Doug Pauls
> > CSL
> >
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