ODP: Newbie PCB question

[Luc Van Den Bosch]

Seems like nobody is using photo-sensitive PCB ?
This is how I do it (for years now) with great success.
No problems with tracks between DIP-leads and works
for double sided PCB's as well (if carefully positioned).

1. Design PCB layout with CAD software and print tracks in 1:1 twice on a
slide with a laser printer, or print on paper and photocopy on a slide twice.
2. Cut slide and position the two prints over eachother (to make the tracks
darker than with a single print).
3. Cut photosensitive PCB to required size and peel off the black cover on
the copper-side
4. Sandwich the photosensitive copper-side of the PCB to the slide (be
carefull not to mirror the tracks) and keep in place with a glassplate and
some heavy stuff, or whatever.
5. Apply UV-light for X minutes (time has to be determined first and only
once, by making a series of small "test-pcb's" with different exposure
times before starting the real work)
6. Develop photosensitive PCB, until exposed photosensitive film is
dissolved. 
7. Rinse PCB with water.
8. Etch & rinse.
9. Remove Photosensitive film with thinner (must be removed for easy
soldering afterwards).
10. Drill (easy because of the pad-holes etched in the copper)
11. Solder.
12. Protect copper-tracks against corrosion with plastic-spray or whatever.


>anyway here's my story of making homebrew pcbs:
>1. Design PCB layout with some CAD software, or on paper
>2. Print "drill guide" or "pad master" in 1:1, where only small dots are
>printed
>(on paper) and, of course, both layers in appropriate scale.
>3. Stick the paper to PCB with transparent adhesive tape
>4. Drill through the paper - the drill comes in more steady than without
>paper
>(doesn't slip) 0.6mm for vias, 0.8-1mm for components
>5. Cut sharpy hole edges with a knife
>6. Use carbid (?) paper to make the copper shine
>7. Wash it depending on your choice (I use soap + water)
>8. Put the board on clean styrofoam, so you can rotate the foam, not board.
>(bottom side doesn't get scratched)
>9. Paint the artwork. I use old automobile anti-rust tar paint desolved in a
>solvent
>(the one that does not react with polystyrene). As painting tool I use this
>device
>used by draftsmen (?). It is small pipe (0.5mm inner diameter) with wire
>inside.
>For thinner tracks I use smaller bit - 0.3mm. Works perfectly for SSOP
>packages
>(0.65mm lead pitch). With this you can freely use all kinds of rulers, so
>tracks
>are straight and look pro-like.
>8. Turn the board upside down, and paint the artwork on the other side
>(holes
>are your guides). Don't forget to print bottom layer in mirror version.
>This tar-paint dries fast, so no need to extra drying, unless you put thick
>layer
>of it.
>9. Etch it in ferrum chloride, or nitro acid. Not too strong, but decent
>amount of
>bubbles coming out during etching process doesn't hurt painted traces.
>10. Wash off the paint with nitro solvent
>11a. Make vias. Put 0.6mm copper wire in via hole, and cut it, so it sticks
>out of
>each side for about 0.5-1mm. Take a hammer and smash it! this way you get
>almost invisible vias. After that you must solder all vias from both sides
>for
>protection.
>11b. Make vias - another way. Put small pieces of thin wire into via holes,
>bend it
>from both sides, and siply solder.
>12. Fluxing (optional). Disolve rosin in alcohol, and paint the board with
>it.
>I pour some of alcohol in rosin can, and stir till it leaves visible marks
>on paper.
>12a. Dry the flux in an oven 100-150 deg C for 20 minutes
>13. Voila!
>
>Final remarks:
>I had never problem with side-etching phenomenon, so I don't paint tracks
>wider
>and dont drill the board after etching
>For large areas I use bits of adhesive tape and paint it around.Less work,
>good results.
>This tar-paint is the best stuff I've ever seen. No permanent markers or
>anything
>works better. Even layers so thin that copper shines through are safe.
>
>But now, I use this method only when I want PCB quick. Usually I send
>design file to PCB shop, and get boards 2 weeks later.
>
>hope this is at least a little help to anyone
>

>Roman
>