Homebrew PCBs

Re-did one of my boards that had a section of dense 6/6 traces.
Technically, 6 mil traces on 12.5 mil centers.  The last attempt way
over-etched and cut many of the traces; this time I "bloated" all
edges by 1.25 (i.e. 8.5/4 rules) and the undercutting brought all
the traces down to their expected sizes.  So far, I've found only one
flaw, a 2 mil gap in one of the traces, easily fixed.

Photos: http://www.delorie.com/pcb/lab/

Today's tips:

To laminate the photofilm, I used 240F and an oversized (9" by 6")
PCB.  The board is 4.5" by 5".  I cut a 12" by 6.5" film, peeled the
first cover, laid it sticky side UP on a piece of paper and positioned
the PCB copper *down* on it, leaving 1/2 inch sticking out the top.  I
folded that 1/2" over and pressed it flat (no wrinkles!) on the pcb,
where it stuck.  Flip over and un-stick the film.  Run it through the
laminator, with the paper, stuck edge first of course, holding the
other two corners of the film.  Hold the film AWAY from the board!
Up, back, and out.  The extra 2.5" of film let me hold the film until
the whole PCB went through the rollers.  Run through a second time,
same direction.  Use scissors to cut around the PCB, freeing it from
the paper.  After noting the bubbles, I trimmed the board to the 5x5
section I wanted and saved the rest (I have an aluminum foil pouch I
store them in) for less critical boards.

Note that I was much more careful about ambient light this time; it's
night (dark) and I unscrewed most of the bulbs in the basement,
leaving only indirect light from distant bulbs.  I kept it this way
from when I opened the film tube to when I finished developing.  I
don't know if this made that much of a difference, but I didn't see
any significant film webbing between traces, and no shorts.

Exposure and development were as usual; 6 minutes UV, 10 minutes
develop.  Etch was as usual too, about 5-8 minutes.  For develop and
etch, I used double-sided tape to tape the pcb to a stick so I could
move it around and easily remove it for inspection.  These are SS
boards.

To strip I put it in the stripper until the small traces started
coming up, then laid it flat on some PVC I have.  After a minute or
so, all the film was bubbled off and I just scraped it off (wearing
gloves, of course) and rinsed.  No film in the stripper tank :-)

--- In Homebrew_PCBs@yahoogroups.com, DJ Delorie <dj@...> wrote:
>
> 
> Re-did one of my boards that had a section of dense 6/6 traces.
> Technically, 6 mil traces on 12.5 mil centers.  The last attempt way
> over-etched and cut many of the traces; this time I "bloated" all
> edges by 1.25 (i.e. 8.5/4 rules) and the undercutting brought all
> the traces down to their expected sizes.  So far, I've found only one
> flaw, a 2 mil gap in one of the traces, easily fixed.
> 
> Photos: http://www.delorie.com/pcb/lab/

Bragging aren't you? I just looked at the photos - and you have something to brag about - CONGRATS, good job.

Maybe someday I'll move "up to" photo resist etching.  For now, the GBC laminator and the HP P1006 printer seem to be doing a good job.  The HP P1006 is new, anyone want to buy a "good" Brother 2140 printer?

73 de Ken H>

Lines look good DJ.

Where did you get your aquarium heater? Mine died on me. I went to a pet store and all they had were ones with a bunch of decorations on them. I did not want to take a chance on it not being compatible with my acid bath. I want to find a plain glass one like you have in your picture in Lab Setup section.

"sailingto" <sailingto@...> writes:
> Bragging aren't you?

Yes, and sharing how I got there so others can benefit.

> I just looked at the photos - and you have something to brag about -
> CONGRATS, good job.

Thanks!  I think 6/6 is my limit though.  I need a 4 mil hole to etch
a 6 mil gap reliably, and 3 mil holes leave some shorts.  I could
probably do some 5/5 as needed on a board, though.

> Maybe someday I'll move "up to" photo resist etching.  For now, the
> GBC laminator and the HP P1006 printer seem to be doing a good job.

I still use TT when appropriate.  I think the temperature control on
the laminator is a big help in getting predictable results there, too.
But you do need a UV source and two more chemical tanks, although the
chemicals are cheap.

Oh, this is with the MG Chemicals film, even with Na2CO3 developer
(they "require" K2CO3).

I came to a TT realization last night.  I realized that the outer PCB
layers I use are thin enough to see though - I can laminate on the TT
silk layer and align it by looking through the *pcb*, not by looking
through the *paper*.  Now I think crosshairs on the silk where the
larger holes are would let me see through even thicker pcbs to line up
the silk layer.

"javaguy11111" <javaguy11111@...> writes:
> Where did you get your aquarium heater? Mine died on me. I went to a
> pet store and all they had were ones with a bunch of decorations on
> them. I did not want to take a chance on it not being compatible
> with my acid bath. I want to find a plain glass one like you have in
> your picture in Lab Setup section.

http://webtronics.stores.yahoo.net/lowcosettans.html

Check the solder joints on the heater, though.  Mine were "cold" and
eventually failed, I had to take it apart and re-solder them (works
fine now).