What is everyone using to calculate paste stencil artwork?

Hi Robert, are there any particular component types / pad types that are causing the most problems? Some of us in the community should be able to advise. I do recall there are different paste tricks for various different component types. Just let us know which ones are causing the most bother as a starting point. 

Haven't been able to find information on paste tuning.   We have to specify stencil thickness and type of paste.

Previously, I was trained to step back and let each ODM optimize paste stencil design for yield.  0402 or larger devices get a baseball-diamond shaped paste aperture.  I think.  Are they doing this in CAM350/Valor?

Everyone here is new to multi-thousand production runs, so issues tend to flow back to me through all levels of management with crisis-level importance.

Thanks.

Haven't been able to find information on paste tuning.   We have to specify stencil thickness and type of paste.

Previously, I was trained to step back and let each ODM optimize paste stencil design for yield.  0402 or larger devices get a baseball-diamond shaped paste aperture.  I think.  Are they doing this in CAM350/Valor?

Everyone here is new to multi-thousand production runs, so issues tend to flow back to me through all levels of management with crisis-level importance.

Thanks.

Hi Robert,

Might I ask what pad geometry you are using for the small 0402 pads and what surface finish you use for them. I am curious that your ODM has given you some push-back. Usually from my experience it is rare for an ODM to ask the stencil thickness required & the paste you wish to use.
To me that's a bit of a red flag since the MFR is typically totally in the details of how to paste & stuff the board.

Perhaps it could be the boards you are doing are for aerospace, Medical etc or something that requires a certain reliability factor, Not too sure...

Best regards.

Yes agree - very strange for them not to stand over their own assembly process! And quite a red flag...

I worked in pcb design in a high volume ODM for many years and had lots of useful discussions with our own internal manufacturing engineers. The company has multiple subsidiaries around the globe and even these individual assemblers did not fully agree on the same approach to stencils and apertures. The central Europeans would simply trim all pads by approximately 10% for most components, and this paste info was stored for each part in their tool library. There were always 3 x separate paste gerbers produced for each side of every design (a 1:1, b: -10%, c -15% approx) B and C were to account for the different standard stencil thicknesses (100 thou or 150 thou).

The 1:1 stencil gerber was used for the group that would send exact pad size information to their stencil producer. That stencil supplier would then cut the stencil according their expert knowledge of manufacturing. New component types would be discussed before final cut. Anything that didn't work well in production would be fed back to the stencil supplier, who would tweak and store those improvements for the next build. It was a mutually beneficial partnership, you might consider finding a similar stencil partner. 

Are you using any other special components like QFN / DFN with diepads for example?