Making SMD boards - wither paste stencils?
mo at ccr.org
Sun Nov 14 19:46:13 CST 2010
i've been thinking a lot about how one makes
PCBs for home-brew designs using SMDs.
after talking with a number of folks,
the consensus seems to be that making a board
using toner-transfer (plus pen touch-ups)
and etching with ferric chloride will work
when i asked about making stencil for solder
paste, the 2.5 suggestions were: laser cutter,
vinyl cutter (a plotter with a sapphire scalpel
instead of a pen), or (.5) use a syringe and
dot the board manually.
it seems to me that there should be a way to make
a paste stencil that isn't any more complex than
making the board, and the article i referenced
before on the "Ediburgh Etch" for intaglio print-making
may provide the answer. (I almost wrote "solution" but
stopped in time.) the trick is adding some citric acid
to the ferric chloride. it dramatically improves the
using toner-transfer, one ought to be able to image
the stencil on very thin brass shim stock or even
heavy copper foil. paint the back and edges with
a resist and then let the etchant chew all the
way through the metal to make the stencil.
i bring this up to ask if anyone knows of a better
approach before i try this out?
while for small designs one can make a stencil
manually, there is something to be said for
a stencil that is made using the same tape-out
as the board.
however, if people have manually made stencils
(like for the charleston SDR board??), what
techniques seem the best and where is the cross-over
between manual dotting with a paste syringe and
making a stencil?
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