PCB fabrication (homebrew)

PCB is an abbreviation for printed circuit board, the copper clad boards used for mounting and connecting electronic circuit components. Originally PCBs had holes for component leads, pins, wires, etc. which passed through and were soldered to the copper tracks on the underside. From the 1980s surface mount components have been used increasingly instead of through-hole components. Double-sided or multi-layer boards use plated-through holes, called vias to connect the traces on different layers. The most common PCBs are composed of either FR4 (glass fiber and epoxy), or the cheaper and easier to cut and drill but more brittle SRBP (Synthetic Resin Bonded Paper).

PCB layout design

Wikibooks' Practical Electronics PCB Layout and Trace Current Capacity.

PCB fabrication

Homebrew vs. commercial

Etching and printing

Photo resist

How to make really really good homemade PCBs by Mike Harrison

Toner transfer method

This is using a laser printer or copier (not inkjet) to print an image of the PCB tracks on glossy inkjet paper. Laying this printed side onto the de-oxidised and de-greased copper laminate and using an iron at a high temperature, on the rear of the paper to transfer the toner from the paper onto the copper. After soaking in water to remove the paper, the toner now transferred to the copper laminate acts as an etch resist.

Cutting boards

With SRBP use a craft knife and straight edge. Score it deeply on both sides. Clamp one or both sides between wood to prevent the board being scratched. Then snap it off. A craft knife works especially well for perforated prototyping board. Score down the center of a row of holes, line the score line up with the edge of the table, and press down quickly on the overhanging piece.

FR4 boards are much harder to cut and very hard on tools. A PCB guillotine is the right tool for the job. Failing that use a bench shear or an office guillotine that can cut through more than 2mm of paper. Use a nibbling tool for non-straight cuts. If there is going to be any dust a conventional dust mask might be insufficient protection as the dust is extremely fine. Use a vacuum cleaner to catch the dust at source. Safety glasses should always be worn.

Alternately take a straight edge and secure it along the line to cut. Then take a chisel (one set aside for this), and run one of the corners along the straight edge. First pass go lightly to just get a bit of a groove dug in for the tool to follow so it wont jump out on subsequent passes. Next pass or two press hard, and dig in for a deep groove. Score on both sides. Secure the board and snap the piece off. To finish the edge make a pass or two along it with a fine file.

Tinning

Use Seno Immerse Tin Crystals ...

External links

• Printed_Circuit_Boards at Open Circuits

Further reading

• The Circuit Designer's Companion by Peter Wilson, Newnes, 2012, ISBN 0080971385