Last week I received the Circuit Bridge silkscreen kit.  With great anticipation, I ripped into the packaging and proceeded to read absolutely no directions.  Ok, I read some.  The kit was $20 and came with a contact frame for exposing the mesh, instructions, a paint squeegee,  and two small pieces of high resolution material, already pre-sensitized. 

In the picture to the right, you can see the contact frame and the circuit design that I used to expose the mesh.  You might be observing that I was crazy enough to use regular paper instead of a transparency.  You are correct!  Even more surprising...it worked! 

Exposing the mesh was a simple matter of layering the paper, ink side down, on top of the mesh inside the magnetic contact frame.  Once the art was arranged properly, I placed it under a standard fluorescent lamp for five minutes.  Once I finished ruining that piece of mesh, I tried again.  This time for 25 minutes.  Much better results.  Once I removed the mesh from the frame, I put it in water and let it soak for about 15 minutes.  The light hardens the mesh wherever it strikes, so the material that has not been exposed washes out in water.

The mesh on the left is the first one.  You can see that the entire area covered by the paper was underexposed.  You can also see how find the traces are.  The traces were very solid.  The smudge in the upper left corner is because the material was underexposed.

On my next trial, results were much better.  The high resolution mesh worked out almost perfectly, and washed very well.  This photo shows the mesh continuing to be exposed after it was developed in the tap water.

The photo below shows the original artwork I used, plus a sample mesh that came with the kit.  Once the mesh is dry, it's time to apply the paint.  Holding the mesh to the circuit board, I used the squeegee to glob paint around on the mesh.  The results were lackluster.

The problem I ran into was twofold.  First, getting the paint to stick to the metal in a way that was thick enough to resist etching was difficult at best.  Second, keeping the mesh steady while moving the paint around was also a problem.  My conclusion is that either I need a better way to apply the paint, or I should just stick to using the mask for labeling boards (typical silk screen printing).  If a board could be made using this process, it could likely be made very well, easily, and most importantly, with a high level of repeatability!

Update 10/1/2007

Yeah, it didn't take me long to post an update.  I got a bright idear while writing this up.  I was able to use a permanent marker to get pretty good results.  While I'm not so crazy about using a marker regularly, using very thin paint might work out just as well.  It would probably be best to use a fixture for holding the mesh down as well.

On a side note, the low resolution mesh works really well for making PCBs, but you would have a difficult time getting the resolution necessary for surface mount parts.

Gary