Dave,
Mike McMonagle had good ideas. One suggestion I would like to throw in is
the use of the polyimide stencil from K&J Marketing. It's called the Kepoch
stencil. With your small apertures, this stencil would be great. When laser
cutting stainless, there are still uneven surfaces in the sidewalls of the
apertures, thus creating "sticking" points for the paste to become adhered
to, affecting release. The Kapton material melts as it's cut, creating a
far smoother surface and better release characteristics.
Their contact info is:
KJ Marketing Services
115 Thirtieth Street
Toronto, Ontario
M8W 3C1
Canada
(416)252-1061
(416)253-1687 fax
Jason Gregory
SMT Production Supervisor
LaBarge Tulsa
(918)459-2367
[log in to unmask]
Dave Chapman
<dchapman@CIRCUITS To: [log in to unmask]
ERVICE.COM> cc:
Sent by: TechNet Subject: Re: [TN] stencil
<[log in to unmask]>
09/05/2003 06:41
AM
Please respond to
"TechNet E-Mail
Forum."; Please
respond to Dave
Chapman
Well, we have our first 16 mil fine pitch device, 128 pin QFP. I am worried
about printing shorts on a 6 mil stencil. Everything else on the board is
20
mil or better so 5 mil is not good idea. we normally do a 10% reduction and
round the rectangles for better release. The pad width is .7 mil, I would
be
pushing 6 mil with the reductions, when our normal rule is on 20 mil pitch
do not reduce overall width to less than 9. If I don't reduce the width I'm
sure we will get shorts.
Am I going to have problems if we leave the width alone and only take the
reduction in volume garnered by rounding the rectangles?
Dave C.
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