PCB FAB LAB

PCB Fab Lab allows you to quickly prototype with a few simple steps in making your own Printed Circuit board, we do use ACID in this production so it is not suitable for kids.

To complete this workshop you will need to have an understanding of electronics introduction to electronics and also have experience designing Circuits Introduction to designing a PCB workshop

What you Need

• Iron
• Laser printer
• Transfer paper
• non fiberglass 2.5mm copper sheet
• 1 large tub
• 1 smaller tub to fit inside the large one (this will contain the ACID and the PCB)
• Safety Goggles
• Ammonium Persulfate (Etching ACID)

Designing by Hand/Computer

Two ways to do this, you can just draw directly on the copper sheet with a fine markerpen (not good for reproducing) or use a layout tool such as Illustrator/ink scape or if you have specific parts that have specific spacing Eagle CAD (Freemium version is fine for this workshop).

Design your Circuit, once ready just print it out and check it is correctly orientated (upside down?)

Printing

Use toner transfer paper, we've experimented with magazine paper but have not had good results, basically you need to transfer the toner onto the Circuit board with Heat, the waxy surface really does help in this. Print out your finalized design, remember it will be mirrored onto the board, so you need to flip it both horizontally and vertically.

Circuit board

Clean the surface!!! very important!! dont touch the surface after cleaning!!

Transfer

With an Iron and the correct heat apply pressure for about 20 seconds with the toner transfer paper and remove heat, wait for it to cool then place the entire board with paper on into a large tub filled with water and let soak for about 30 minutes. Rub surface slowly to make sure the water has been absorbed by the paper, then carefully peal.

Inspection

Inspect every line, you want to make sure nothing is broken, if it is fix with your marker pen, this is your last chance, if the transfer was not 95% you might want to sand off the last attempt and try again.

Etching *ventilate the area*

Fill the large tub with hot water, this will be a hot water bath. fill the small tub up with water and carefully add the Etchant ACID, slowly place the small tub into the large tub making sure it is not floating around. add your Circuit board that you inspected into the ACID solution, it's strongly advisable to use rubber gloves and never directly handle the ACID, always have a water bath/running water to quickly rinse any item that comes into contact with the ACID solution.

Wait about 10-15 minutes the etching should be done on the bottom, flip it over and have a look and wait another 10-15 minutes, once all the copper has been removed then quickly and carefully take the PCB out the ACID and straight into the water bath to stop over etching, wash and rinse under running water.. do not discard the ACID it can be reused and needs to be neutralized before discarding.

Lessons learned

Printing on the wrong side of the PCB

Causes catastrophic failure quickly

Two Sided PCB Production

holes need to line up exactly, 1mm is a huge problem, avoid doing two sided PCBS

Making Arduino Shields

the holes need to be exactly drilled, use a drill press, this is a lot of work, buy a blank shield, it'll save you a day.

trace width

try to have trace width at minimum 1mm but 2mm is preferred, keep spacing to a minimum of 1mm but you will have to verify each trace, use 2mm to be sure

Sean PCB recipe

Tools:

• tape
• magazine paper
• plastic container
• sulfuric acid (18%)
• laser printer
• white pater
• vector format image (reversed)
• sponge
• paper towel

Ferrichloride solution:

• 130ml of water
• one cube of ferrichloride (crushed)
• one half soupspoon sulfuric acid (18%)

Additional:

• a bit of 18% sulfuric acid to clean layer

Steps:

• print out reverse circuit image on piece of magazine paper
• clean PCB copper with sulfuric acid and paper towel
• iron on PCB (press down with the iron tip) - the part that takes the most skils.
• soak in soapy water for 5 minutes
• gently rub until paper falls away
• soak sponge in ferrichloride solution
• rub gently on the board, refreshing with sponge until circuit is visible
• rinse with water
• clean with paint thinner