Homebrew PCBs

Hi,
  First of all, I'm new to this group, so please go easy on me. I've been
etching PCBs for a good five years, and have just exhausted my first batch of
ferric chloride (just need to order some sodium carbonate from a pool
chemical supplier, then I can finally dispose of it). I used to use a tray to
etch my boards (55 minutes!), then I moved onto etching the boards vertically
in a bottle (40 minutes), and now I'm using a heated bubble etcher that
etches a 1 square inch board in around seven minutes. I guess the etch times
for larger boards would be similar.
  I built my etch tank out of a 2-litre plastic (polypropylene) cereal box,
an aquarium air bubbler and a 50-watt Visi-Therm aquarium heater. This
combination seems to work quite well - the rubber suction-cups that hold the
heater in place are firmly stuck to the (curved) side of the tank and I can
etch any PCB up to about Eurocard size. If anyone wants to take a look at my
etching setup, let me know and I'll upload some photos. The etchant does seem
to produce a lot of fine mist - using removable adhesive putty (Blu-Tack) to
block the gaps seems to have done a reasonably good job of keeping it in the
etching tank.
  I'm using some "Super-Activated Ferric Chloride" (basically 40% FeCl3 with
0.1% hydrochloric acid as an anti-sludging and etch-assisting additive). It's
sold by Mega Electronics (www.megauk.com - code 600-015) and by Farnell
(www.farnell.com - code 413-8697). I've also got the MSDS for it (the MSDS on
the Farnell website is for the PELLETS, not the liquid - Mega will email a
copy of the MSDS and usage guide to anyone that emails them and asks).
  But that's not the problem. 
  I've run out of Press-n-Peel, so I decided to try a bit of HP "Premium
Inkjet Coated Paper" out, just for a laugh. I cleaned the board with a green
scouring pad until it changed colour from "sewage brown" to "metallic
orange". Next, I dried the board and placed the transfer on top. This was
followed by a sheet of A4 copier paper.
  I ironed the transfer for a good minute or so, with the iron set to
maximum, no steam. This seems to have worked fairly well. To get the transfer
off the board, I submerged it into a sink full of hot water with a bit of
"Fairy" washing up liquid added (to help remove the paper). The paper rubbed
off quite easily with light thumb pressure. My printer is a Panasonic
KX-P7110 "LASER PCL6+Network" using original Panasonic toner.
  The problem is, there seem to be a lot of sections missing from the tracks.
Is this something that might be curable using a different type of paper?
Are there any British members on this list? If anyone can suggest a type of
paper that works better than the HP stuff and is available in the UK (the
local Staples store doesn't seem to have the stuff Tom Gootee mentions, nor
do they carry any of the JetPrint papers).
  I've uploaded a scan of the board (one of my "resolution test" patterns) to
<http://www.philpem.me.uk/pcb1.jpg>. Note the "dropouts". BTW, the "x/y" text
relates to the track width and spacing - x=track width, y=spacing. I wanted
to see just how fine I could make the PCB tracks on this paper without ending
up with a blotchy, smeared mess. Seems the lower limit for my printer and
this paper is 10 mil track width with 10 mil spacing.
  Any suggestions?

Thanks.
-- 
Phil.                              | Acorn Risc PC600 Mk3, SA202, 64MB, 6GB,
philpem@...              | ViewFinder, 10BaseT Ethernet, 2-slice,
http://www.philpem.me.uk/          | 48xCD, ARCINv6c IDE, SCSI
... Profanity, the language programmers know.

I'd use the iron for about 3 minutes - 1 min is probably too short. 
It looks to me like you didn't get hot enough everywhere - make sure
you move it around as irons have hot and cold spots.  I've also found
that moderate to firm pressure really helps with inkjet paper.  More
so than PNP.  I recall checking with a scale and was using about 30
lbs of pressure.  The inkjet paper is pretty forgiving in this regard
so press on. Finally, I've had good luck with turning off the iron and
leaving it weighing down the board while it cools.  My theory there is
that it keeps the toner in contact with the copper as it cools down
and hardens.

Another possibility is board prep - degreasing is pretty important. 
I've been using 600 grit sandpaper and acetone to clean it off and
have had really great results with this.  The sandpaper (wet-or-dry
brand, I think) creates significantly more surface area for the toner
to stick to and the acetone takes all the oil/grease off.  Toner
sticks to my boards really well.

Phil

--- In Homebrew_PCBs@yahoogroups.com, Philip Pemberton <philpem@d...>
wrote:
> 
> Hi,
>   First of all, I'm new to this group, so please go easy on me. I've
been
> etching PCBs for a good five years, and have just exhausted my first
batch of
> ferric chloride (just need to order some sodium carbonate from a pool
> chemical supplier, then I can finally dispose of it). I used to use
a tray to
> etch my boards (55 minutes!), then I moved onto etching the boards
vertically
> in a bottle (40 minutes), and now I'm using a heated bubble etcher that
> etches a 1 square inch board in around seven minutes. I guess the
etch times
> for larger boards would be similar.
>   I built my etch tank out of a 2-litre plastic (polypropylene)
cereal box,
> an aquarium air bubbler and a 50-watt Visi-Therm aquarium heater. This
> combination seems to work quite well - the rubber suction-cups that
hold the
> heater in place are firmly stuck to the (curved) side of the tank
and I can
> etch any PCB up to about Eurocard size. If anyone wants to take a
look at my
> etching setup, let me know and I'll upload some photos. The etchant
does seem
> to produce a lot of fine mist - using removable adhesive putty
(Blu-Tack) to
> block the gaps seems to have done a reasonably good job of keeping
it in the
> etching tank.
>   I'm using some "Super-Activated Ferric Chloride" (basically 40%
FeCl3 with
> 0.1% hydrochloric acid as an anti-sludging and etch-assisting
additive). It's
> sold by Mega Electronics (www.megauk.com - code 600-015) and by Farnell
> (www.farnell.com - code 413-8697). I've also got the MSDS for it
(the MSDS on
> the Farnell website is for the PELLETS, not the liquid - Mega will
email a
> copy of the MSDS and usage guide to anyone that emails them and asks).
>   But that's not the problem. 
>   I've run out of Press-n-Peel, so I decided to try a bit of HP "Premium
> Inkjet Coated Paper" out, just for a laugh. I cleaned the board with
a green
> scouring pad until it changed colour from "sewage brown" to "metallic
> orange". Next, I dried the board and placed the transfer on top.
This was
> followed by a sheet of A4 copier paper.
>   I ironed the transfer for a good minute or so, with the iron set to
> maximum, no steam. This seems to have worked fairly well. To get the
transfer
> off the board, I submerged it into a sink full of hot water with a
bit of
> "Fairy" washing up liquid added (to help remove the paper). The
paper rubbed
> off quite easily with light thumb pressure. My printer is a Panasonic
> KX-P7110 "LASER PCL6+Network" using original Panasonic toner.
>   The problem is, there seem to be a lot of sections missing from
the tracks.
> Is this something that might be curable using a different type of paper?
> Are there any British members on this list? If anyone can suggest a
type of
> paper that works better than the HP stuff and is available in the UK
(the
> local Staples store doesn't seem to have the stuff Tom Gootee
mentions, nor
> do they carry any of the JetPrint papers).
>   I've uploaded a scan of the board (one of my "resolution test"
patterns) to
> <http://www.philpem.me.uk/pcb1.jpg>. Note the "dropouts". BTW, the
"x/y" text
> relates to the track width and spacing - x=track width, y=spacing. I
wanted
> to see just how fine I could make the PCB tracks on this paper
without ending
> up with a blotchy, smeared mess. Seems the lower limit for my
printer and
> this paper is 10 mil track width with 10 mil spacing.
>   Any suggestions?
> 
> Thanks.
> -- 
> Phil.                              | Acorn Risc PC600 Mk3, SA202,
64MB, 6GB,

> philpem@p...              | ViewFinder, 10BaseT Ethernet, 2-slice,
> http://www.philpem.me.uk/          | 48xCD, ARCINv6c IDE, SCSI
> ... Profanity, the language programmers know.