Homebrew PCBs

On 26 Dec 2016 13:31:09 -0800, you wrote:

>1) Doing doublesided is not easy.

Double sided is easy enough, but the accuracy of the top vs bottom is
critical.

in EAGLE (which I use), you have to mirror and often rotate the board.
The idea is that the top and bottom when printed go over the same spot
on the paper going through the printer. Seems to be better that way.

I have 0.020 (or so) board, single sided, FR4.

I print the top and bottom separately.

I also have an upside down drill press which allows very precise hole
placement.  For the alignment holes (use 3, not 4), this is absolutely
critical.

I use stiff pins when placing top and bottom together, along with
holes that are a very small amount smaller than the pins.  The
accuracy of the alignment is (guess...) critical.

I use 1 hour cure epoxy (hard to find now), even the 5 minute stuff
takes 24 hours to cure completely.

I place the top over the bottom, having first covered the entire
copper surface with masking tape.  It keeps the epoxy fingerprints
off... (don't ask).

Once the boards are sandwiched together, I tape them along the edges
to maintain alignment, then I remove the pins.

the boards are allowed to cure between two ceramic/marble floor tiles,
which are pretty flat, heavy, and cheap.

24 hours later, remove tape, drill, and you should get pretty accurate
holes.  I use a #78 drill for vias, and 0.023 (I think) for the via
pads.  Naturally, with this method, I never place a via underneath a
chip or any component.  

I then lace the board top and bottom together with #26 solid wire,
solder both sides, then cut.

a result is reliable boards with 10/10 spacing, double sided, but
without plated through holes.

Works well enough, but is a lot of steps.

Harvey


>2) The toner costs more than the printer
>3) You only get a sample toner cartridge in the printer
>4) There are no chip counter  hacks on the market for this printer when refilling toner.
>5) I've been considering hacking the chip to allow perpetual Toner  refills, but I need a printer first.
>Ancel