Using the ultra-violet light box, etching tank and mini drill for
Mr Reynalds
The King Edward VI School, Morpeth
Once your PCB layout ‘artwork’ has been checked, print it out onto acetate.
Cut out the printed PCB layout.
Make sure the etch tank is switched on, so that it has time to heat up to around 37°C.
Carefully cut a piece of PCB to the right size for the circuit, using the guillotine. Remember to leave the black film on.
Put the offcuts of the PCB in the PCB box.
Open ultra-violet (UV) lightbox.
Make sure the glass is clean.
Put in acetate upside down. (The writing on it should be backwards.)
Remove black film from the PCB quickly, then place face down covering the acetate.
Close lid.
Turn timer dial to 2 minutes to expose the PCB.
Put on an apron.
Put on goggles.
Put on rubber gloves.
The developer solution is harmful.
Mix 1 part developer to 9 parts water using the measuring cylinder: Add 10ml developer Add 90ml water at
approx 20°C Pour into the tray Repeat these steps once more Replace the lid of the developer bottle
Put PCB, with copper side up, into developer solution. It will turn black.
Move tub to wash developer back and forward over PCB until you see the tracks and the blackness has come off the surface.
Remove PCB immediately and rinse thoroughly under tap.
Dry the PCB with paper towel.
Make sure you still have an apron on.
Put on goggles.
Put on rubber gloves.
The Ferric Chloride in the tank is corrosive.
Secure PCB into the rack of the etch tank, so that it cannot fall out in the tank.
Put rack into tank and close lid.
Check temperature reading of the etch tank – it should be around 37°C.
Press button to start machine timer.
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You may have to run the machine more than once – stop it once the tracks are all visible, and the rest of the surface is white.
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Do not open the lid while it is running.
Stop the etch tank.
Switch on the rinser.
Open lid, lift up rack with PCB in and allow liquid to drain into tank.
Place rack into rinser until all Ferric Chloride is washed off.
Put rack in sink and undo fastenings to remove PCB.
Dry off PCB with paper towel.
Put rack in rinser of the etch tank.
Dry your hands and switch off etch tank.
You can now take off gloves and goggles.
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Make sure there are no smudges.
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Make sure there are no broken tracks.
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Rub copper tracks with wire wool until they are bright and shiny.
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Wipe with paper towel to remove wire wool fragments.
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Make sure you still have an apron on.
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Put on goggles.
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Set up mini drill with correct size drill bit for your copper pads.
Place PCB under drill and, while switched off, lower it to make sure it is lined up with the pad you need to drill.
Hold PCB, switch on drill and lower it to drill out the pad. Raise drill bit out of the hole before switching off.
Remember strain holes for the battery wires.
Set up a solder station with: Plenty of space Soldering iron stand Soldering iron Soldering mat
Solder
Always solder in shortest components first e.g. resistors.
Use IC holders so that heat of the soldering iron cannot damage the ICs.
Switch off soldering iron and leave in the stand to cool.
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Put on goggles.
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Use wire snips to cut legs off components on solder side of PCB. (You must hold legs as you cut them so they do not fly off and hit someone else.)