One of the most discouraging things about making a hardware project (apart from obtaining all of the components) is building the printed circuit board - PCB.  It is sometimes possible to use strip board or some other pre-fabricated board but more often than not the circuit complexity and performance requires a proper PCB to be made.  The good news is that due to improvements in printing and processing technologies it is now relatively easy to make inexpensive high quality PCB's at home.

WARNING: Making PCB's requires the use of Ferric Chloride (FeCI3) which is corrosive so avoid skin and eye contact. Remember safety first use glasses, gloves and protective overalls. Ferric Chloride is also very good at distorting cloths weeks after you think you have washed it off. If you do get any on your skin then wash it off immediately with lots of water and soap.

The Shopping List

This is the minimum things you will heed,

1. Access to a PC with a Laser printer eg: HP Laser Jet
2. Cloths iron
3. Kettle
4. Water bucket
5. A one litre glash jar with plastic screw top (biscuit jar)
6. PCB hand drill with 0.8mm and 1mm drill bits - FR84F, QY64U
7. Copper-Clad fiberglass board - WF40T
8. Press-n-Peel PCB transfer system - AB15R
9. Ferric Chloride Copper etching fluid 250ml - WF10L
10. Two plastic etching trays (ideally different sizes) - CH38R
11. PCB cleaning rubber - HX04E
12. PCB solvent cleaner - LL59P
13. Safety glasses, latex gloves, old clothes/overalls - KE83E, YJ84C

All part numbers are from the Maplin Electronics catalogue.

The Artwork

Until recently the artwork had been an area of DIY PCB manufacture which caused the biggest problems. But now by combining high quality laser printing with the Press-n-Peel PCB transfer system these problems have been solved.  The first stage is to transfer the circuit layout from the PC to the special Press-n-Peel film. You will find that my projects provide Laser print files (.prn) for printing the circuit layout direct onto this film,
 

1. I cut the Press-n-Peel film in half for small boards so it lasts longer 2. Put the film in the laser printer so that the print will appear on matt blue side 3. At a DOS command prompt type: copy filename.prn lpt1 to print onto the film

This will produce a contact print where the black image will end up as Copper on the final PCB. Now to transfer the artwork to the Copper board by following the instructions with the Press-n-Peel film,
 

1. Clean the Copper board very well with the PCB cleaning rubber 2. Heat the cloths iron to 300 deg.F (Acrylic to Polyester setting) 3. Hold the film with the print in contact to the Copper and smoothly iron the film     down until the print appears black through the film (about 1min) 4. Allow 5mins to cool down (or speed this up with water) then peel the film off

This should produce a clean black print onto the Copper. If you let the film move or overheat then you will find that the tracks and writing will be smeared and out of focus also the film may be wrinkled up. If you don't use enough heat or heat unevenly then the film may not stick or be dark enough. In either case clean off the PCB and try again, you should get it right after a couple of goes.

The Etching

Now for the messy bit, etching the PCB to remove the unwanted Copper. Please read the warning at the top of the page as it is important to take appropriate precautions before handling the etch chemicals. I recommend you do this outside or in a shed and you must ware glasses and gloves. Keeping the etch chemicals warm (45deg C) is essential as it reduces the etch time from over an hour to about 15mins.
 

1. Dilute the concentrated Ferric Chloride fluid with water (1:1) and pour into the     one letre glass jar and screw the top on 3. Place a sheet of news paper on a flat surface and put the trays on this 2. Fill the kettle with water and boil 3. Heat the Ferric Chloride jar in a bucket of hot water. Caution don't spill any     drops and keep away from food

 

1. Pour 1cm of boiling water into the bottom tray then place the other tray on top 2. Put the PCB copper side up on the top tray and pour all the Ferric Chloride on top 3. Gently rock the top tray to keep the etch fluid moving avoiding spillage 4. After about 15mins all of the unwanted Copper should have disappeared 5. Remove the board and drop it into a bucket of cold water to clean off

Usefull tip: For small boards just drill a 1mm hole in the corner of the board and tie 2ft of strong cotton to this. Now put the board straight into the Ferric Chloride jar with the end of the cotton outside and put the top on the jar. Keep the jar hot by heating in a tray of boiling water and gently rock to keep the etch fluid moving. Every 5mins use the cotton to lift the board out and check progress. This method is much less messy as the Ferric Chloride is always left in the glass jar.

Drilling

Drilling with 0.8mm drill bits can be a bit tricky as it's easy to break the drill bits. Always hold the drill straight and do not bend it when the hole has started. Putting a soft block of wood under the PCB provides a good base to drill into. Once you have become experienced at drilling I would recommend using Tungsten Carbide drills (FE49D) which easily break but last much longer,
 

1. Dry off the board and clean away the blue etch resist with PCB solvent cleaner 2. Using a 0.8mm PCB drill bit drill out all of the component holes 3. Some 1mm holes may need to be made for connectors, 3mm for corner fixings 4. Finally use a PCB rubber to clean the copper ready for soldering

So now your PCB's finished and you can start soldering the components in. You should do this soon after you have cleaned the PCB (within 1 hour) as the copper soon oxidises and becomes hard to solder onto.

Links

Maplin Electronics home page
Frontier Engineering the U.S. Distributor for Maplin Electronics
UK based low cost Press-n-Peel sheets
EAGLE PCB software
Olimex PCB manufacture