Please note. This page refers to the prototype
PCBs that feature on the project pages. The PCB's
sold from the on-line store are professionally
I occasionally get emails from people
asking how I make the PCBs that feature elsewhere on the
site. For the benefit of those people and anyone
else who wants
to know, this is the low down on how I do it. I have
to tell you now though it's not very hi-tech.
I use laser artwork film and a HP
LaserJet 1320 printer (better printers don't seem to
make a difference - I've printed artwork on very
printers and the quality is no different). I've also
used clear OHP transparency film with fairly
I always use pre-coated positive photo
resist boards. My experience suggests it needs to
be kept in the dark,
keep it cool and don't have it sitting around for months
before you use it. I usually buy the board as I need it.
I use both FR4 and economy CEM/1 laminate. The
cheap stuff is easy on drill bits and well...cheaper so
it's good for prototypes.
Don't try and cut the board down to the
size of the artwork, I like to have at least 10-15mm
oversize all round. You can trim the board to size
once it's been etched and drilled.
The artwork needs to be printed so the
toner is facing the copper, in other words you don't
want the thickness of the artwork film between the toner
and the copper otherwise the light blurs the edges of
fine traces. Depending on you PCB CAD program you
may need to mirror the artwork to do this. Also,
make sure you put some text somewhere on the
artwork, then when you get it printed onto the film,
you can easily see which way round it needs to go.
I also use ground planes on my PCB
layouts for the simple reason that it reduces the amount
of copper to be etched away and therefore my etching
The UV light box is one of the few
'proper' pieces of equipment I use. This is
something I would suggest you really need to buy rather
than try and build yourself. I get good results
using an exposure time of 2m40s
The developer lives in a plastic food
container at room temperature, stored with the lid on
and depending on how many boards go through, it can last
for months. I mix it slightly on the weak side so it
doesn't develop too fast, usually goes in about 30-45
seconds. I find gently rubbing the surface of the board
helps lift the photo resist. When I mix a new
batch I always try a small scrap of board to make sure
the concentration is about right.
Always rinse the board in cold water, don't transfer
straight from developer to etching solution or vice versa.
The etchant lives in another plastic food
container. I took a couple of corks from wine bottles,
cut them in half and glued them to the bottom. This
stands in a plastic processing tray which I fill with
boiling water just before I start the etch to raise the
temperature of the etching solution (ferric chloride).
you're etching a lot of boards regularly you really
don't need anything more than this. It also has
the advantage that you don't need to mix up large
quantities of etching solution; I use a 1litre food
container with about 300mL of etching solution in it.
This easily handles a 100mm x 80mm board and I can just
squeeze in a 100mm x 160mm board.
I normally dump the PCB in the etching
and let it sit for a minute before taking it out and
inspecting it - the exposed copper
areas should have gone a matt pinkish colour, if any
areas are still shiny I rinse the board, dump it back in
the developer for 10 seconds and repeat.
Once I'm happy all the exposed copper is
starting to etch away I agitate the board in the solution by
hand (wear a glove obviously). With fresh etching
a reasonable temperature (35oC-45oC)
the boards are done in about 10-12
minutes, if it gets to 20 minutes something isn't right
and I will usually give up on it.
I have a small PCB drill and various
drill bits that I buy from suppliers on e-Bay. The sizes
use a lot are .75mm, 0.85mm, 0.95mm, 1.05mm and I just buy
these in boxes of ten for about 10GBP. I
also have sizes from 1mm up to 3.15mm which covers
everything you are likely to need. The hardest
thing is lining the damn drill bit up with the PCB but
that's an age / eyesight thing:-)
is a bit of an art to getting it right and occasionally I seem to do
everything the same and the finish is lousy, but
generally results are good and I can go from artwork to
drilled PCB in under 45 minutes.
sided boards can also be done, the trick is to get the
top and bottom artwork aligned very accurately to start
with. The second problem when using a single sided
light box is keeping it all aligned when you flip the
board over to expose the other side. The way I do
it is as follows:
sure your board is over size because you will need
to stick one edge to the artwork.
the top and bottom artwork films, then tape one edge
so it forms a hinge.
When you do this you want 6-7cm between the actual
artwork image and the hinge so that when you insert
the board in between the two layers of film it
doesn't misalign them to much.
tape the one edge of the board to the bottom artwork
film so it can't move.
should now be fixed together and will stay aligned
so you can expose one side, then flip the whole lot
over and do the other side.
trick to this is making sure the two films are perfectly
aligned when you tape them together and not having the
hinge too close to the artwork image.
an example of a board I made using this method. Double
The developer and
ferric chloride etchant are not very people friendly
chemicals so avoid contact with skin, wear eye
protection etc. and read the safety information at least
once before you use the stuff - it's really hard to read
it when the stuff is already in your eyes!
If the ferric chloride
gets on to your skin it stains it brown, it will ruin
your stainless steel sink and stain clothing brown, even
making holes in them given enough time. Don't lean
over the etching solution or breath in the fumes rising from it,
it's bad for your lungs. Don't say I didn't warn
Tungsten carbide drill
bits, especially the sub 1.5mm diameter ones, will snap
with the slightest lateral loading so drilling by hand
won't work. Even using a drill press you need to
make sure you hold the PCB firmly and don't move it
while drilling. Sooner or later you're going to
snap a bit so I always buy the ones I use a lot in a box
Since drill bits snap,
you should wear some eye protection.
Fig 1. Artwork, printed
on film using an HP LaserJet 1320n
Fig 2. UV light box,
single sided, very simple, not cheap though. Exposure
timing is done with a kitchen timer and I normally give it 2m40s
Fig 3. Close up of my
etching container. Feet are made from a synthetic wine
bottle cork cut into four and glued to the corners of the
container. This allows the water bath to circulate
Fig 4. This photo shows
the developer (1), a photographic processing tray (2) which I
fill with boiling water a couple of minutes before I start the etch.
ferric chloride etchant in another food container (3). Not
forgetting the glove (4) since I agitate the PCB it in the
etchant by hand.
Fig 5. PCB drill, drill
press, selection of tungsten carbide drill bits (from e-Bay)
Fig 6. All being well
you should finish up with something like this.