Lee,
I agree that using two boards is pretty easy, but I'm enjoying the challenge! The way I am now doing it (experimental):
1 - Print a "centerline" on the carrier with a cross line near the top.
2 - Mark the approximate center of the pcb, making a pencil mark at the top (leading) edge of the board and the bottom edge.
3 - Use a box cutter to carefully cut a very thin groove through the top and bottom of the pcb, being careful that the cut is as perpendicular to the plane of the board as possible. This marks the center and is visible from both top and bottom surfaces of the board.
4 - Align the board on the carrier with the top "cut" at the cross on the carrier and the bottom cut on the centerline. Tape it in place, top and bottom.
5 - When you draw up the board, make a couple of alignment fiducials on the 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 over the holes. If not, just wipe the toner off with a paper towel, make any adjustments 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 in the same place every time. I took a pcb and ran it through the printer 5 times, printing only a single dot. All the dots were within about .020 of each other, with most being on top of each other.
Mark
At 02:14 PM 8/26/2014, you wrote:
I agree that using two boards is pretty easy, but I'm enjoying the challenge! The way I am now doing it (experimental):
1 - Print a "centerline" on the carrier with a cross line near the top.
2 - Mark the approximate center of the pcb, making a pencil mark at the top (leading) edge of the board and the bottom edge.
3 - Use a box cutter to carefully cut a very thin groove through the top and bottom of the pcb, being careful that the cut is as perpendicular to the plane of the board as possible. This marks the center and is visible from both top and bottom surfaces of the board.
4 - Align the board on the carrier with the top "cut" at the cross on the carrier and the bottom cut on the centerline. Tape it in place, top and bottom.
5 - When you draw up the board, make a couple of alignment fiducials on the 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 over the holes. If not, just wipe the toner off with a paper towel, make any adjustments 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 in the same place every time. I took a pcb and ran it through the printer 5 times, printing only a single dot. All the dots were within about .020 of each 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 work for DIY prototypes.
I love your processes, development, and sharing of knowledge.
For multilayer boards, I've always been an advocate of printing single-sided thin
PCBs and layering them up as needed. On Ebay you can get the material in 5mil, 8mil and 10mil
and if only double sided material, you can use the extra side as planes and isolate route or etch them
in an extra step. If my stackup is to thin, say for only 2 sides, I found bare FR4 that I use as a base
to bind the sides to for stiffness.
Alignment fudicials or targets are used for each pattern. Then after etching, I drill fine holes
through which I insert sewing needles or music wire to align during the stackup.
I was using 3M spray adhesive, but it can be unforgiving of misalignment. Someone mentioned a slower thin epoxy solution and that made sense for me. You just have to remove any epoxy 'extrusions' that occur from the holes.
So for me you process is darn near perfect, the added stability you propose 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 was kidding.
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