- SAFETY NOTICE -
It is important to follow current safety procedures and guidelines
when handling or working with the chemicals and materials mentioned below.
Making
Your Own Printed Circuit Board
(A
10-step process using the photographic technique)
1,
After you have produced your PCB layout with OnTrack's System's
Designer, use a printer and clear transparent film to produce
your photographic mask. You can either do this with the subsystems connected
for individual work, or separated for group work (this is so the subsystem modules can
be interconnected later on).
Ex.
1 - Subsystems Closed |
Ex.
2 - Subsystems Open (for group work) |
2, Using 50mm wide PCB with a "photo-resist" layer, cut a length
of the board to fit between the corner marks of your mask (see above).
Either use a guillotine, tin snips, or hacksaw to do this and then smooth
the edges with emery cloth or a file.
PCB
with photoresist layer |
3,
Place the mask onto an Ultra Violet (UV) light box ensuring it is the
correct way up and not upside down!
Peel
off the protective plastic film from the PCB and place it face down
onto the mask. After closing the lid, set the UV Light Box timer for
approximately 2 minutes and wait for areas of the board, not masked by
the black areas on the mask, to be exposed to the U.V. light.
UV
Timer Box (Remember to close the lid!) |
4, When the time is up lift up the lid (but never
look into the light box when the UV is switched on). Remove the
board and keep your mask safe, just in case you need to use it again.
5, The board should now be given to a qualified technician
who will place it into a suitable tank or tray containing developer
or alkali solution. This will strip away the photo-resist layer that
had been exposed to the UV light. The circuit tracks on your PCB will be saved,
however, as they were covered by the mask's black areas. Remember
the developer can be harmful and necessary safety precautions such as
eye, clothing, inhalation and skin protection have to be taken. (See
COSHH details associated with the products before use).
Bubble
Etch Tank with 2 Compartments |
6, Wash the board in water to remove all the chemicals
used in this process.
7, The copper layer underneath can now be removed
by transferring the PCB to a heated tank of etchant - ferric chloride
or sodium persulphate. This acid will react more quickly with
the heat and remove the exposed copper on the board. After approximately
ten minutes your circuit board will be produced.
It
is very important to follow the recommended safety precautions when
working with these chemicals and expert help should be sought before
carrying out this work - Never
mix these two chemicals. As part of "Quality
Assurance" procedures, it is important that the chemical solutions
are made
to the correct strength, maintained at the correct temperature and replaced
from time-to-time after continued use.
8, Wash the finished circuit board thoroughly
and rub with either a pan scourer or very fine wire wool to remove any
left-over resist or residue that might still be covering the copper
tracks and pads. Any contaminated water should
be disposed of carefully and responsibly.
9, So that the component legs may be pushed through
the board, you will now need to drill holes through the PCB pads on
the circuit board (details are also shown on OnTrack's circuit
legends).
PCB
Legend |
You
can use a 1mm drill bit held in a mini-PCB drill + stand to do this
- Remember to wear safety glasses as the small
drill bit can easily break if the work is not done gently.
10, To finish, visibly check with a magnifying
glass that there are no breaks in the Copper tracks or short circuits.
These faults can occur if the printed mask is of poor quality or the
copper has been left for too short, or too long, in the developer/etchant
solutions.
A
multimeter set to measure
resistance, or conductivity, will further help you check for continuity
or breaks. These checking procedures are part of "Quality Control" and avoid unseen manufacturing errors preventing your circuit from working
later on.