> > 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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