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Etching Your Own Circuit Board

This tutorial will outline the process for etching your own circuit board.

While breadboards are good for prototyping and perf boards are swell for creating a simple, robust circuit, etching your own circuit board provides the opportunity for inexpensive fabrication of more complex circuits. It allows you to create multiples of the same circuit, and your design is no longer tied to the grid of the perf board. This opens the door for creativity in the design of your circuitboard.

(:toc Table of Contents:)

Safety Precautions

This process involves the use of a chemical etchant called Ferric Chloride. It is to be treated with the utmost respect and care. This means that it has to be handled with caution and disposed of properly.

Ferric Chloride is an etchant which means that it eats metal. In addition, it stains fingers and clothes, and the vapors are toxic.

A few things to remember about handling ferric chloride:

  • Use PLASTIC containers when using ferric chloride.
  • use in a well ventilated space.
  • be careful to avoid contact with your skin or eyes.

When finished etching, store your used etchant in a plastic bottle with a cap and place in the hazmat area of the shop. DO NOT pour down the sink or flush down the toilet.

Let's begin

First we will want to assemble our tools and chemicals. Here is a small shopping list:

  • Ferric Chloride/etchant - this will remove unwanted copper from the board.
  • Copper clad - this is the term for the unetched board that will eventually be your circuit. Copper clad comes in varying thicknesses and can be one or two sided.
  • Acetone - we will use this to prime the unetched board.
  • Lacquer solvent - this is for one of the final stages of the process where in we remove the resist.
  • Staples photo paper for inkjet printers OR Techniks Press-N-Peel PCB Film.
  • Steel Wool - for preparing the copper.
  • Toothbrush - for cleaning the paper from the board before etching.
  • Several plastic containers - these containers should be larger than the board you are etching. I use three: two for soapy water and one for the etchant.
  • Iron or Heat Press - this is used to apply the resist to the copper clad.

Access to a laser printer.

Now that everything is assembled it's time to design your circuit in our favorite program. This can be anything from eagle PCB to Illustrator. As long as you can print the design, it's all good. You will be printing on Staples photo paper. Try to find the cheapest available, but feel free to experiment with all kinds. If possible, run the paper through the printer twice to double up on the print. This can be tricky because the paper doesn't always move through the printer the same way twice. I found that putting the paper in the same corner of the paper tray helped.

In many cases there was little or no doubling of the design. Here is what's happening: laser toner contains plastic fibers. These fibers are what we call the resist as it resists the ferric chloride in the etching process. Being plastic, they are sensitive to heat, which will come in handy when we apply the design to the copper clad.

Prep the board

Before applying our design, it's important to prep the copper clad. Take the steel wool and rub down the copper until it has a well brushed look. This puts little grooves in the copper and creates a greater surface area for the resist to attach to and the ferrich chloride to react with.

After the steel wool, clean the board with the acetone. It will pick up all the fine copper dust created by the steel wool. Though it's just dust, it will save on the ferric chloride. There's no sense int he chemical eatiing away material that's not on the board.

Iron on the circuit pattern

Once the board is clean use the iron or heat press to apply the design to the copper clad. Preheat the iron to approx. 350 degrees. Place the design, printed side to the copper, and with the iron, press the design to the copper. This will take some time and a lot of pressure. Move over the design, making sure that the entire circuit is covered equally with heat and pressure. Here is where the plastic in the laser toner is melting, and adhering itself to the brushed copper. Here there may need to be some experiementation to find the right time/heat needed for a good transfer. Approx. fifteen to twenty minutes of constant pressure with an iron is the average.

Remove the photo paper

Time for the first plastic container. The first container should have enough warm soapy water to completely submerge the board. Becareful in picking up the board after using the iron. It will be pretty hot. Use the tongs or similar to place the board with paper attached into the soapy water and let it sit. The water will loosen and fall away. If you are impatient, give it a little help

When the paper starts to come off the the board, peel the rest away and take the tooth brush and scrub away the remainder. The design should be free of any paper lint when you are finnished and the design crisp and clear on the board.

In the event that part of the design did not transfer, take a Sharpie or whiteout and repair the broken traces or pads.

Etch the board

Take the second plastic container and pour enough ferric chloride in to completely submerge the board.

If the container has a lid, put it on and gently rock the container to agitate the etchant.

If you have no lid, then find a piece of plastic to use as a stirring stick and move the ferric chloride with this.

After ten minutes has passed check the copper clad for progress. There should be patches where the copper has been completely etched away.

The ferric chloride will turn completely black and the design will be all that remain. continue to agitate the chemical until only the design is on the board.

Once the unwanted copper is completely removed, use the tongs to move the board from the etchant and into the last container of soapy water for rinsing.

When the last of the etchant is removed from the board, take the laquer thinner and with a cloth remove the resist until your design in copper is revealed.

If you don't like the smearing of the laser toner on the boeard, you might try submerging the board in the thinner until the toner peels off. I've tried this with smaller boards and it's worked really well.

Drill the holes for your components and you have made your first circuitboard.

Congratulations! You've just etched your first printed circuit board.

Dispose of supplies

Remember, the etchant is toxic, and cannot be flushed or poured down the train. Put the used etchant in a sealed plastic bottle, label it clearly "USED FERRIC CHLORIDE ETCHANT" and place it in the hazmat area of the shop for disposal.

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