Making SMD boards - wither paste stencils?

[Nan and Sandy Sanders]

Mike, I have  done a lot of surface mount at both home and work, both 
board house and toner-transfer. Almost all has been using a syringe ( 
or sometimes a tooth pick). Of course most of the time the syringe 
was hooked up to something like this http://www.zeph.com/zt-5100.htm 
. Some where around 0603 or smaller it does not work as well as with 
larger sizes. With fine pitch quad flat packs I just flood the pins 
with solder and clean up with solder wick.
      Sandy
      WB5MMB


At 08:46 PM 11/14/2010, Mike O'Dell wrote:
>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?
>
>         -mo
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