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other/additional
variants:
when things go wrong:
there are many different ways to produce homemade
PCB's
here i'm describing my way using printer, halogen-lamp and
corrosive-bath
bill of materials:
|
1-101€ |
tanks for liquids
(100€ professional solution -
recommendet) |
|
20€ |
el. multitool |
|
10€ |
set of drills |
|
10€ |
e.g. halogen lamp 500W |
|
2,4€ /120g |
acid, Sodium persulfate Na2S2O8
natriumpersulfat |
|
1€ |
handgloves |
|
1€ |
plastic-tweezers |
|
1€ |
white spirit (Spiritus) |
|
0,9€ |
PCB e.g. 100mmx160mm photopositive
coated |
|
0,6€ / 10g |
developer, Sodium hydroxide NaOH
natriumhydroxid |
|
?€ |
protection-goggles |
|
?€ |
piece of glas |
->150€ for your own PCB development laboratory
see security documents for your acid !! e.g. Sodium
persulfate Na2S2O8 or Iron(III)chloride Fe3Cl
sicherheitsdatenblätter für
Säuren beachten !! z.B. natriumpersulfat Na2S2O8 or Eisen(III)-chlorid
Fe3Cl
they are dangerous! for your health and raise burning, various
allergies may arise and stay by contact with Na2S2O8
even more dangerous is
your Sodium hydroxide, NaOH(natriumhydroxid) used for developing the PCB
a
little splash can make you blind, it's corrosive -see security
documents!
always wear handgloves and
protection-goggles - these informations are not complete! be careful! it's on
your health!
>>> i'm not responsible for any possible damages on
everything <<<
and of course bring chemicals after use to a
collection of problem materials!!
if your acid is salt-based like Sodium
persulfate or Sodium hydroxide you can let evaporate the biggest part of it
(water)
choose a save place and bring the rest to a waste disposal
place
ok, let's start:
picture of an finished homemade PCB
first you have to draw your shematic/PCB with the software of
your trust (e.g. eagle/target)
inactivate the layers which you don't want to
have on your print (top, top-place, bottom-place)
sorry for the bad layout, but we were in a
hurry
now you have to print(inkjet) your
pcb-layout on a premium plus inkjet transparency film - available in most
shops
make shure you print with best quality and your printer is set to this
type of "paper"
(i recommend hp ink -it has a higher concentration of
pigments than the other inks - don't use the cheap refilling ink)
check your
printed film by holding it against light, the routing should be solid
black
be careful to print it mirrored, later the ink should lie directly on
the PCB (no foil between ink and PCB)
otherwise your PCB would have no sharp
edges and they would be thinner because your lamp is not a punctual
lightsource
printed film
ok, lets get
the routing on the PCB:
first you have to cut your photopositive-coated
basematerial in the right dimension (e.g. with el.multitool)
now you have to
expose the PCB to light through your film:
make shure your lamp has a fixed
distance to your PCB
i'm using a cheap 500W halogen lamp in a distance of
about 35cm for 8,5 minutes
i removed the protective glas of the lamp, because
glas filters the light with the needed spectrum
(the right exposureduration
depends on distance,basematerial and most on the lamp itself)
be careful,
such a lamp (500W halogen) gets very hot in short time
now darken the room, remove the protective foil and put your film with the right
side on the PCB
during light is on, the temperature will rise by the lamp and
eventually will bulge your film
against that i'm putting a thin glas on it to
make shure the outlines will be exposed sharply to the light
consider the
absolute maximum temperature ratings of your PCB basematerial
maybe you have
to fan or put a metal plate for cooling under your PCB
after exposing the PCB to the lamp it will be warm
put it in a dark place
(or upside down on a clean surface) until it has cooled down
(duration of
chemical reactions depend on temperature, and we want a reproducable developing
time)
meanwhile you can mix the Sodium hydroxide, (caution! see the beginning
of the dokument)
NaOh 10g for 1 liter H2O, for 2 euro-PCB's(160x100mm) 0,25l
should be enough
gently put your PCB in this bath, be careful not to produce
splashes, use tweezers
you should see the chemical process after a few
seconds
gently move the PCB about every 30seconds
remove it after 1:30 to 2:30
(depends on the basematerial)
wash it with water, after that rub it gently
with the skin of your fingers
-the last protectivecoat-parts of the
lamp-exposed regions should loosen
you should be able to see the routing on
the PCB very clear
hold it under a lamp for checking
wash the PCB after removing from the acid, be careful!! (see description on top
of the page)
congratulations! let's corrode the now not photopositivecoat-protected parts
away from your PCB
the cheapest way is to use Iron(III)chloride Fe3Cl in a
suitable flat container
corroding time depends on temperature and how used is
your acid (20min to 1h)
better and faster results (less undercorroding) are
reached with Sodium persulfate
i recoment a professional corrodingtank,
Sodium persulfate has to be temperatured to 40°C,
it is clear (gets more and
more blue by using it), so checking the progress is mush more easier
use 100g
of na2s2o8 for one liter H2O
calming like an aquarium
almost finished
wash the
PCB after removing from the acid, be careful!! (see description on top of the
page)
so now you have to remove the remaining photopositivecoat, the
easiest way is to use a brush and white spirit
(other way is to expose it to
light a second time and develope it)
it looks nice isn't it?
(if you don't
want so solder your PCB now you can conserve it by a solderlack-spray)
lets
drill the holes - a set of 0,8mm 1,0mm 1,2mm and 3,5mm should do it for the
beginning
you will have to use e.g. an el. multitool because of the needed
high turns/s
begin with the smallest holes
so now lets solder, begin with e.g. resistors because of the less hight, it will
be easier in this order
after that you will have to wash the soldering flux
off the PCB by white spirit (Spiritus)
the final conservation can be done by
clearlack
a washed and conserved PCB lookes quiet good and lasts
"forever"
without protective-lack the PCB will be slightly corrode by air,
think of Verdigris (Grünspan)
>>> congratulation for your first selfmade PCB <<<
other/additional
variants:
bring on a photonegativecoat after development for
protectioncoat of the copper
(soldering regions left out)
when you
use SMD technic a print of values can be made with this
technic
when things go wrong:
upper PCB:
- too short developing time
there is still a photopositive coat on the mid-dark
parts
eventually you can re-develope this PCB, wash it before
redeveloping
do not expose it too long to light!
lower PCB:
(upper picture)
- too high concentrated NaOH
- (you have been too rude with rubbing)
- (too long light exposure)
there is no cure for this PCB
problems with
soldering:
- you have forgotten to clean your PCB with white
spirit?
- you have already conserved it with plastic-spray, and want to
resolder for e.g. repair?
remove the plastic-spray with white
spirit
- your PCB has already corrodet? long time without protection, got
wet...
clean the surface -white spirit and brush - very fine sandpaper
for not yet soldered PCB's
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