Electronics Forum / CAD / February 2006

Simplest and cheapest way is copper clad board, ferric chloride,
acetone, metal polish and a permanent, black felt pen.
1. Thoroughly clean the copper cladding with wadding metal polish and
buff-up to high shine.
2. Draw out the tracks where you want them with the felt pen.
3. Allow the ink to dry thoroughly in a warm atmosphere.
4. Heat the ferric chloride solution in a shallow plastic tray  to
around 50'C.
5. Drop the board into the solution and agitate until unwanted areas
of copper are dissolved.
6. Remove, wash in warm water, dry.
7. Wash off the black marker traces with acetone  and repeat step 1
wrt to the metal polish.
8. After soldering in components, lacquer the board (optional).

I think I've etched one board, ever.  After that experience I just use
breadboards from vector or rat-shack, or I dead-bug things on an
unetched copper groundplane.  If I feel a need for an "etched" board I
slice islands out of the copper with an x-acto knife and surface-mount
through-hole components onto the pads (think of dead bugging with pads).

If I really needed accuracy I'd make the circuit on Eagle and send it
out to http://www.pcbexpress.com or another fast-turn house.  If you
want to be trapped by proprietary software you could use
http://www.expresspcb.com.  Both of these latter methods, incidentally,
work extremely well if you are being paid by the hour -- they can do it
much cheaper than you can unless you're getting starvation wages.

The ARRL Handbook covers all of these methods.

Buy a batch of double-sided, plated-through boards from AP Circuits or
one of the other cheapie board houses.

John

Wow, that's pretty bad.

When I tried the iron-on method, I had to go back and
fix up a couple of traces but nowhere near 20-30% of em.

Indeed, direct positive PCB's are preferable.  But even then you really
do have to check each and every trace because it's a tricky process.

For the past 5 years I've been using www.expresspcb.com for all my
stuff and had 100% success for single and double-sided stuff.
Single-sided, double-sided, ridiculously high lead pitch surface mount
stuff, I ain't ever gonna go back to etching this stuff myself.

Tim.

You should be able to do *much* better using the iron on method,
per the following url:
http://www.fullnet.com/u/tomg/gooteepc.htm

Ed

I've been using Pulsar film, available from Digikey (182-1003-ND and
182-1021-ND) to do a dozen or so boards so far, including some
fine-pitch SMT designs, though all single-sided.

The process is fairly straightforward, but has taken me a lot of
experimentation and frustration to get it right.  As a result I'm going
to write up what I've learned one of these days soon, so others don't
have to figure the same stuff out the hard way.  Here's the quick
version, off the top of my head, with as much detail as I can in this
format:

0) Design your board carefully, according to a number of rules that I
still need to codify.  Some easy ones: use copper pours wherever
possible to remove less copper; make sure you set your trace/gap numbers
to a comfortable level, I haven't gone below 10mil/10mil yet though I
easily could; set the pad annulus to 15+mil so you have some drilling
slop; don't let the copper pour or other traces get too close to the
*inside* of any SMT chip pads, you can't wick that stuff away.

1) *Laser* print the *positive* artwork onto the transfer paper, cut to
size and taped (Avery laser label bits) to a piece of backing paper
(both to feed into the laser, and for positioning).

2) Thoroughly rough up (Scotchbrite pad / steel wool) every sq. mm of
the board, then wash very carefully, possibly using acetone as the last
step (to remove oils *and* copper dust).  Do not touch the copper after
this step.

3) Laminate/iron the artwork to the board.  Pulsar resells a GBC
laminator that has both high heat and pressure, and will accept up to
0.03125" boards (not 0.0625", big deal, IMO) for ~$50.

4) Dump the board paper-side up onto the *surface* of a bowl of water
and wait (tick tock) for the paper to literally fall off (takes longer,
but much more consistent results, don't rush this step).

5) Carefully wash everything off the toner surface, and make sure there
are no oils left either.

INSPECTION: if there are any missing areas, clean the copper off with
acetone, go all the way back to step 2 and start over.  DO NOT SKIP ANY
OF STEP 2, do it all over again.

6) Laminate/iron the green film onto the board, let cool, and carefully
peel back the plastic.

INSPECTION: if the film wrinkled and left visible toner on the board, or
if any toner is visible on the peeled off plastic, go back to step 2 and
start over, as per previous inspection step.

7) Grab some gloves, a sponge (combo glove+sponge works great for me),
and a few ounces of FeCl or equivalent.  Get some FeCl on the tip of the
sponge, and lightly *scrub* the board all over until you can see all the
way through the copper-free areas when held against a light.

8) Thoroughly clean the film and toner off with acetone, scrub it down
with steel wool, and clean it again.  Cleaning is your friend.

9) Dump the board in some Liquid Tin (MG Chemicals 421-500ml) for
5-10min.  When removing the board from the liquid tin, do not touch the
copper+tin surface until you've washed it off and let it sit for a
minute.  I kept getting fingerprints on the tin and finally realized it
came from *above*, not underneath the plating.  The stuff is soft.  It's
also extremely nasty stuff, you *MUST* take even small amounts to a
disposal site. MG says even 50ml diluted into 5 gallons of water is too
nasty to dump down the drain.  You can use extremely fine-grade steel
wool, *very* lightly, to clean up the surface a little bit, but as soon
as it shows a little copper tint to it, you're done.  Very nice color
effect though.

10) Use appropriate drill bits, such as the re-ground ones you can get
cheap in sets of 25.  Only problem is that there no guarantee of size
selection with those.  This would be a good time to thank yourself for
cranking up the pad annulus and leaving yourself some room to mess up.

11) SMT components can be soldered by hand, but I've had far better luck
using solder paste and a toaster oven.  Digikey has it (KE1507-ND) but
as a rather high price ($42 for 35g), and you'll need to find a syringe
tip to use, the smaller the better.  I'm still getting a feel for
exactly how much paste to use for different parts, and the
time/temperature constant of my toaster oven is abysmal, so the process
is still evolving, but it's worked fairly well so far.

I've taken a few closeup pics of some of my most recent boards, both
good and bad:

http://www.omegacs.net/misc/pcbs/

It's not in a decent gallery because the software I was using didn't put
up with an upgrade and I haven't figured out what's broken about it yet.

I haven't done any yet, but I plan on doing some attempts eventually.
The process would be to put the toner and film on one side, drill 3+
reference holes, then transfer the other side.  The problem may be what
the laminator will do to the first side when going through the second
time.  It may be necessary to use even more extra dimensions on the PCB
and transfer films and carefully tack the two pieces of transfer paper
down through the drilling process, and laminate the two sides at the
same time.

The through-hole plating problem is another one I need to research.
Pulsar recommended going to International Eyelets (ask for a catalog,
you get it within a few days) who make nothing but "PCB eyelets"
designed to do through-holes.  They're going to be noticably bigger than
your average via, but comparable to a normal through-hole component pad.
   Absolute smallest one their catalog shows a 0.030" hole diameter,
0.020" finished hole, with a 0.046" flange/pad.  That's actually not too
bad.  I'm going to get some trail stuff pretty soon and see what happens.

One thing to note when making your own PCB's.. be careful not to mix
chemicals.. some cleaners can react with the chemicals used to produce some
rather hasty gasses... A friend of mine spent two nights in hospital doing
this.

I think the best bet is to use a proto house.. if they can do a panel it can
be cheap... for me it was AU $270 for 3 x A4 worth of PCB's .. as much as
you can fit on a single A4 sheet and 3 of them. No fuss, no mess, no
chemicals or EPA requirements.

Simon

I still make some myself the classic photographic way, 100% success, takes
me about 15 minutes with fresh, well heated etching liquid (the dirty yellow
one). There are many good tutorials to be found on the web. The hardest
part, I find, is cutting the board and drilling the holes in the right
place.

When I was a kid I used to use an etch-resistant ink pen (and a nail and
hamer for the holes, in fact I did the holes first) but fine-pitched boards
are not easy this way. I remember routing traces in between ic pins (I then
had a small electric drill). The pen was rather annoying since you had to
press the tip to get the ink out and often this resulted is large blobs on
the board.

--DF

About a year ago I bought a Roland SX-8 (vinyl) sign-cutter for some
Scout activity signs AND as stencils for glass etching (via sand
blaster).

Works just ducky for both of those applications, but I'm tempted to
try it as stick-on resist.

Anyone tried such a scheme?

                                       ...Jim Thompson

           
I love to cook with wine.      Sometimes I even put it in the food.

IMHO there is not such a method as the "best" hobby DIY. Both method and
result depends highly on the experience and tools available. I ever started
using nail polish and nitric acid. Did several types of photografic methods
and also tried out toner transfer. The latter worked well as long as I had
access to an HP Laserjet 5000. This one put enough toner on the sheet to
work as an etch resist. Other laserprinters I tried, including the Laserjet
4Si, did not. Now I'm back at the photo method using two overlayed
transparancies for the positive. The best site on the net I'm aware of is:
http://www.electricstuff.co.uk/pcbs.html
(Almost) all you need to know about etching PCBs at home.

petrus bitbyter

I have found that using pre-clad boards with positive resist work
quite well. With the spray on positive resist, it is difficult to get
a nice even coating without any bubbles and dust.
http://www.bungard.com/    have very good quality pre-sensitised
PCBs. (Both single and double sided with a long shelve life)
Print the layout on a transparency using an inkjet printer. Clamp
the transparency against the PCB (photo resist) side with a piece
of transparent glass. Expose in sunlight for about 45 seconds.
(Experiment a bit). Develop PCB, and etch. I have had very good
results with even 10mil tracks and 10 mil spacing.
When doing double sided, one must make very sure of the alignment of
the 2 sides.

Regards
 Anton Erasmus

I've only done this once, a thousand years or so ago, but I made my
originals on plastic with tape and a little bit of india ink. They
were 2X. I took them to a photo shop and got positives, six-up,
registered for double-sided. I stapled the negatives together, got
a piece of photosensitive board at Radio Shack, slid the board
between the negatives, and exposed it to the sun for about a half-
hour on each side. I don't remember what the next step was -
developing the resist and washing it, or some such, but then I
etched it in a cake pan with about an inch (2.5 cm) of Ferric
Chloride solution (also from RS - in their etch kit -- Hey! I
said it was a long time ago!), and did get a little bit of
undercutting, and drilling it right was very, very interesting,
but it did work. :-) (the product died on the vine, however. )-; )

Good Luck!
Rich

I still get 99% success with the transfer method .
I have a HP 1210 laser that I set at 1200 for printing .
The secret is in the paper to use and the copper clad cleaning method .
A ) Get the following photo paper from "STAPLES" Staples brand of photo
paper , 30 sheets for $14 Canadian , stock # 18103 02238 , red package "for
inkjet printers" NO SUBSTITUTE .

B )Get a small bottle of cream cleaner used for glass- ceramic cooktop
"cerama Bryte " , "Cook Top " or similar , a bit pricy but worth it.
USE  a few drops and do a good cleaning of the copper board a paper towell
then rinse under the hot water tap then dry with paper tower . DO NOT TOUCH
THE SURFACE WITH FINGERS .
Then proceed with the iron transfer take all the time needed .
Soak copper plate in soapy water in sink and after a few minutes scrub
first paper layer with fingers and thum soak some more then test for
further paper scrubbing and ensure no paper residue is visible .

Works good for me .
Roma
Home of " Handy Dandy Little Circuits "
http://members.shaw.ca/roma