PCB FABRICATION
STEP-1:DESIGNING
Sofware simulation using “Easy EDA”.
Manually using trackers, donuts,acrylic sheet.
The output of this step is positive film.
STEP-2: DARK ROOM
Photo bunt machine: A lith film (shouldnot be exposed to
light) is placed on the acrylic sheet inside the photobunt
machine.
We manually count for 10 seconds after placing them
inside.
We get a negative film now.This negative is dipped in a
tray consisting A+B solution.
A is sodium carbonate and B is butyl carbonate ( 1 tbsp
A+1 tbsp B + 200 ml of water)
The negative is placed in A+B solution for 1-2 minutes by
moving it gently in the solution until the traces are visible.
Next we clean this negative with water and dip it other tray
containing fixer.
Again wash it with water and place it in oven for drying.
Until this dries, cut the copper board using cutting machine.
Using a scrubber clean the copper clad so that there are no
unwanted materials and fingerprints.
Dip coat machine: It consists of photo liquid resist (1 lt)
and thinner (250 ml) .
This machine ensures uniform controlled thickness of
photo-resist on copper clad.
Precaution- excess layer shouldnot form on copper clad.
After dip coat machine, place the copper clad in the oven
for drying.
UV Exposure: Place the copper clad with copper side on
top in the machine, then place the negative film on the top.
Switch on the vacuum so that our circuit is printed
correctly.
Next switch on the main there will be a timer appearing for
1 min 40 sec and the down counting starts immediately but
for our chemical considerations we require it to be exposed
to UV for 2 min 20 sec so we add additional 40 seconds.
Next we place our board in photo liquid resist developer
because we cant see the circuit with our naked eye.
Rotate the timer nob and fix to maximum and place the
board inside using tongs.
After the timer is off we’ll get a sounf, then wash the board
gently with water.
Next dip this board in dye for 1 second and wash it gently
with water.
STEP-3: ETCHING
It consists ferric chloride.
It removes unwanted extra copper apart from circuit.
By displacement reaction copper will be removed.
Place the board inside the liquid and fix the nob to its
maximum position and it comes to minimum automatically.
STEP-4: TINNING
As the board still contains copper to avoid environmental
reactions and corrosion we coat it with tin.
After etching wash the copper board with water and scrub
it.Apply flux on the board.
Keep the board between the roller and rotate it in anti-
clockwise direction.
Tin layer is coated on the board.
STEP-5: DRILLING
Drill on the places where donuts are present to place the
terminals of the components.
STEP-6:SOLDERING
We place all the components and fix them on the board
permanently.
STEP-7:TESTING
We test the circuit by connecting it to the supply.
