Hi Darrel,

One of the most important issues in stencil design, especially for fine-pitch applications, is the width of the aperture divided by the thickness of the foil. This value should not be smaller than about 1.7, as this would increase the risk that the solderpaste sticks into the apertures instead of releasing onto the pads.
Another factor to consider is the type of squeegee you're using. Polyurethane squeegees, especially the softer ones, give some "scooping out"  resulting in a thinner deposit than metal blades. 

Daan Terstegge
SMT Centre
Thales Communications
Unclassified mail
Personal Website: http://www.smtinfo.net  


>>> Darrel Therriault <[log in to unmask]> 01/04 2:06 am >>>
TechNet,

What considerations are used for selecting the thickness and aperature
of a solder stencil?  I would guess it has to do with solder volume and
maybe proximity/spacing, but are there other things considered as well?
Are there any "rules of thumb" or guidelines for making this selection
or standards?

All comments and preferences appreciated.

DT





--
Darrel Therriault
VP, Mfg. Operations
INCEP Technologies, Inc
(858)547-9925 223
[log in to unmask] 

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