Making SMD boards - wither paste stencils?

Mike O'Dell mo at
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
acceptably well.

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
etching performance.

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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