Jun 22

Homemade PCBs for Effects Pedal Projects

Homemade PCB - Thumbnail

This article looks at a common alternative method to using press ‘n’ peel transfers, hand drawn layouts, or routed boards. This will cover each stage of the process in detail, showing you how to get a good result. You need access to a laser printer, and some copper clad board.

Because the normal methods of making a PCB can be relativly expensive, or quite crude (when hand drawn) this provides a cheap, accurate alternative. The basic concept is to replace the press’n’peel system for transfering a PCB design layout onto a copper clad board, and use a laser printout instead. A laser printer uses heat to transfer the toner "ink" onto the paper. This article looks at reversing this process, by heating the paper printout and forcing the toner onto the copper clad board. The laser printer gives a sharp accurate print that will transfer cleanly onto the board.

Firstly we need to look at the print out. Many websites will provide you with a PCB layout for an effects pedal (but this is also true for any electronics PCB layout).

Homemade PCB - Layout

We need to take this image and prepare it for printing. Generally they will be a good quality so you can print them out straight away, but you need to check the dimensions are correct (so that they print out at the correct size). Secondly, it’s worth checking areas that could transfer badly: thin lines, lines close together etc. These may need cleaning up in a graphics application. You will notice that they are also reversed. This is so that when they are transfered to the copper board- they appear the right way around. All will become clear.

Homemade PCB - Printout

Many other sites will discuss the types of paper for the best results. A glossy paper is apparently the best to use. My attempt was using standard plain paper and providing you iron the board properly (explained later), it should give good results all the same. The secret here is to try out some different paper. You must use a laser printer as well. Inkjet printers use normal dye ink and this is useless for our purposes. Laser printers use heat to transfter a special toner ink onto the paper. We rely on this and heat to reverse the process.

Copper boards come in serveral different types. Show below are a perforated "perfboard" and the standard PCB copper clad board.

Homemade PCB - Copper Boards

Once you have the printed PCB layout on paper, you can cut out a section of copper board.

Homemade PCB - Ready to Cut

Line up the paper to an edge of the board, and mark out a line to cut out. The next setep is to get your drill ready. I use a Black & Decker RT650 rotary tool -- like a Dremel but cheaper and possibly better. Shown here is the tool, safely glasses, and the compressed grit cutting wheels.

Homemade PCB - Rotary Tool

Please use safety glasses if you have them. Whilst they may seem a bit lame and over the top (as I used to think), I managed to get a metal spark directly onto my eyeball when cutting some metal. It’s not pleasant, and really not worth the risk. If you can’t get hold of any, at least cut with your face away from the wheel (not directly over it in the line of dust and sparks). Also remember that the grit cutting wheels often shatter.

The next step is to sand down the copper board to remove the oxide layer and also any grease or dirt.

Homemade PCB - Dirty

This is vital to help the laser toner stick properly to the board. I use a fine P600 grit wet or dry paper with a bit of water to help clean the board up. Just run the board and paper under the tap and begin to sand in the same direction. The board goes from a brown / pink to a very pale salmon colour.

Homemade PCB - Sanded Smooth

After this, you can use tape to stick the paper printout to the copper board. Make sure you don’t get the tape over the design as when you come to iron it -- you will melt the tape and make a mess!

Homemade PCB - Transfer Taped On

Use a normal household iron set to almost the hottest setting. Wrap the board in a doubled layer of kitchen paper or use an old tea-cloth. This protects the surface of the iron.

Homemade PCB - Ready to Iron

Start by ironing over the board with the broad part of the iron. Press down quite firmly and gently run the iron from side to side. Be careful not to burn yourself. This is stating the obvious really, but I like to look out for you :) After a minute or so of doing this, open up the paper.

Homemade PCB - Transfer

The next step is to use the tip of the iron, to detail over the layout (you should see it through the paper). Use the tip to trace over the lines -- being careful to not tare the paper. I then cover up the board again and iron it over for another minute or so.

Homemade PCB - Ironed On

The longer you iron it, the better the chance of the ink setting properly against the copper board. Clearly don’t sit there for 30 minutes with the iron presseed hard against the board. This should only take 3 minutes.

The next step is to remove the paper. Firstly, let the copper board cool down to room temperature. Be careful as it will be very hot from the iron. When it is sufficiently cooled, place it in a glass of water.

Homemade PCB - Board in Water

After 10 minutes, the paper should have soaked up the water and will be easy to peel away. Gently peel off the paper.

Homemade PCB - Peeling 1

This will leave some residue behind. Soak it for a bit longer, and then use your thumb to rub off the last of the paper. A wet cloth can help to GENTLY remove and clean up the last little stubborn bits of paper.

Homemade PCB - Peeling 2

At this stage, try not to rub too hard so that you wipe off the black ink lines. If this happens, dry off the board and touch up the breaks in the tracks with a marker pen. Use an acetate / overhead projector marker pen.

Homemade PCB - Cleaned

The finished transfer. We’re now ready to etch the unwanted copper away. There are several different chemicals that achieve the same goal, but I am using sodium persulphate. You can get this from maplin here:

  • 1KG -- £14.99 -- http://www.maplin.co.uk/Module.aspx?ModuleNo=17355
  • 100g -- £1.99 -- http://www.maplin.co.uk/Module.aspx?ModuleNo=47464

Heat some water in a kettle to boiling. I am using an etching tray, so this uses about 4 or 5 heaped spoons of powder to a few hundred ml of water. I just do it by eye, but it’s probably worth measuring it out! I think 100g mixes with 500ml hot water. You need to half fill the container with cold water (250ml) and then add the boiling water. The idea is to get the solution to about 50°C but adding boling water first will destroy the chemical.

Plunge the board into the solution, and use plastic tweezers to move it about. You may notice bubbles appearing. This is the copper dissolving into the solution. The liquid will start to turn blue (copper in solution)

Homemade PCB - Etching 1

This process take 10 minutes or so, depending on the water temperature and the concentration of the solution.

Homemade PCB - Etching 2Homemade PCB - Etching 3

Homemade PCB - Etching 4Homemade PCB - Etching 5

Homemade PCB - Etching 6Homemade PCB - Etching 7

After the copper has all dissolved off the board, leaving you with the black lines only -- remove it from the solution and wash it thoroughly with water. You can store the etch solution for several weeks -- handy if you want to make other boards.

Homemade PCB - Etched

Next, take some wet or dry paper and sand over the black lines. This will reveal the copper track below.

Homemade PCB - Ready to Drill

You are now ready to drill out the holes for the components. The smallest drill bit I had was still too large. I took a grinding wheel on my Black & Decker tool and ground down a spare small drill bit until it was the right diameter for the component legs. It needs to be a little larger to allow for wires to be soldered in as well. Here is the drill bit:

Homemade PCB - Custom Drill Bit

I doubled over some tape onto an old magazine / newspaper / book and then stuck the board down onto this. Carefully line up each hole and hold the drill firmly to prevent it from slipping out of position.

Homemade PCB - Drilled

After drilling, I sanded over the back and front with some of the P600 wet or dry paper to clean up the holes.

Homemade PCB - Drilled Out

Here’s the finished article, ready to be wired up and placed into a project box. Metal enclosures look great and are very strong. Plastic project boxes are far cheaper, and easier to drill out for jacks but don’t look as cool!

Homemade PCB - Project Boxes

Good luck making your own. There are many designs out there, you just need to search for "guitar effects pedal PCB layout" and you will find many schematics and guides on how to build your own effects pedals for a fraction of the cost of other units on the market. If you have any questions, please e-mail me or come chat on the forums. We love to read about projects that you guys try. Have fun

Written by Alex on Thursday 22nd June 2006 at 9:37pm and posted in Technical, Workbench

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