Lee,
I agree that using two boards is pretty easy, but I'm enjoying thechallenge! The way I am now doing it (experimental):
1 - Print a "centerline" on the carrier with a cross line nearthe top.
2 - Mark the approximate center of the pcb, making a pencil mark at thetop (leading) edge of the board and the bottom edge.
3 - Use a box cutter to carefully cut a very thin groove through the topand bottom of the pcb, being careful that the cut is as perpendicular tothe plane of the board as possible. This marks the center and is visiblefrom both top and bottom surfaces of the board.
4 - Align the board on the carrier with the top "cut" at thecross on the carrier and the bottom cut on the centerline. Tape it inplace, top and bottom.
5 - When you draw up the board, make a couple of alignment fiducials onthe same place on both top and bottom.
6 - Print the top.
7 - Acetone vapor fix the top.
8 - Drill through the fiducial marks with a very small drill.
9 - Remount the board on the carrier, carefully aligning the"cuts" as in step 4.
10 - Print the bottom side (reverse!).
11 - Check to see if the bottom side fiducials are properly aligned overthe holes. If not, just wipe the toner off with a paper towel, make anyadjustments necessary in the print dialog to get the location better,then loop to step 10. DO NOT remove the pcb from the carrier to do this.The whole "run" takes just a few seconds.
12 - Once the alignment is true fix the bottom in acetone vapor.
13 - Etch!
Of course, everything depends on the printer being able to print the inthe same place every time. I took a pcb and ran it through the printer 5times, printing only a single dot. All the dots were within about .020 ofeach other, with most being on top of each other.
Mark
At 02:14 PM 8/26/2014, you wrote:
Hi Mark,
First of all I want to say thanks to You and Stefan for pioneering workfor DIY prototypes.
I love your processes, development, and sharing of knowledge.
For multilayer boards, I've always been an advocate of printingsingle-sided thin
PCBs and layering them up as needed. On Ebay you can get the material in5mil, 8mil and 10mil
and if only double sided material, you can use the extra side asplanes and isolate route or etch them
in an extra step. If my stackup is to thin, say for only 2 sides, I foundbare FR4 that I use as a base
to bind the sides to for stiffness.
Alignment fudicials or targets are used for each pattern. Then afteretching, I drill fine holes
through which I insert sewing needles or music wire to align during thestackup.
I was using 3M spray adhesive, but it can be unforgiving of misalignment.Someone mentioned a slower thin epoxy solution and that made sense forme. You just have to remove any epoxy 'extrusions' that occur from theholes.
So for me you process is darn near perfect, the added stability youpropose is surely a benefit too.
I hope to get some pictures to share of results as time permits.
Best Regards, and sorry if I came across as pompous in the past, I waskidding.
Lee Studley
R. Lee Studley Senior Hardware / Software Engineer
Innovative Control Systems, Inc.(ICS)
10801 N. 24th Ave. Suite 103
Phoenix, AZ 85029
602-861-6984 Main Line
602-588-9440 FAX
www.icsaero.com