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Date: | Tue, 2 Jan 1996 19:47:24 GMT |
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> > All,
> > Does anyone have any data on the relationship between solder balls (no
> > clean flux w/ N2) and various solder masks?
> > Some of our lines run OK and some do not for the same mask. The hard
> > part to understand is that a mask will run poorly on one line and OK on
> > another. My feeling is that the mask is statistically significant, but
> > not necessarily the major contributor. All DOE have shown no sweet spot,
> > but of course going to aqueous or eliminating N2 have shown positive
> > results.
> > The other variable that has completely eliminated solder balls is to
> > shorten leads to ~.080". This went over poorly with the connector
> > people.
> > Any help would be appreciated.
> > Steve Joy
> > [log in to unmask]
> >
> >
Steve,
We use no clean technology and had problems early on with solder balls adhering
to the solder mask. The company that supplied our soldering equipment did do a
lot of work evaluating different fluxes and solder mask finishes. They are
Blundell Production Equipment Ltd at Coventry in England; Paul Blundell is the
MD and their telephone number is UK 1203 473003.
The solder mask surface is important and a smooth high gloss finish will enable
solder balls to attach more readily than a micro matt surface. Unfortunately
most solder masks today are applied by curtain coat and have a very smooth
surface. The solder ball is stuck to the surface of the mask by a small residue
of flux.
The main emphasis is therefore in finding a flux which will give the least
solder balling. The soldering parameters such as pre-heat temperature, solder
temperature, and speed through the wave are also important.
We use Apple House NC213 no clean flux on a Coates Imagecure XV501TSM solder
mask applied by curtain coat and have no problems.
Hope this assists you,
Paul Gould
Teknacron Circuits Ltd
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