Etching Small PCBs at Home

 
Electronic hobbyists are deeply interested to know how to indigenously make a DIY homemade small PCB. Boards can be made at home; however, etching is only a part of a much holistic process which also includes designing and creating a layout. Etching is a step that comes after an enthusiast has completed the other basic procedures. Have you always been in interested in knowing how to etch a home-produced small PCB? To start off, such boards can be manufactured at home by following 2 unique procedures;
 

Toner Transfer Method

The designed layout of the circuit can be printed with the help of a laser printer on a paper which is placed facing downwards on the small PCB. Boards will get the impressions on them when the toner of the printed paper is transferred to them by pressing it against a heated cloth iron. A glossy paper or photo paper ought to be used for printing the design. in addition to this, the temperature of the iron is also quite tricky to adjust. A high temperature would blur out the traces while a low temperature would leave out open connections in the circuit.

After the application of heat, the photo/glossy paper cannot be removed easily and you will have to use water to submerge the small PCB. Boards need to be scrubbed with a toothbrush while running water is poured over it so that the paper can be removed.
 

Photo-resistive Laminates

The second way to print the mask on the small PCB is through the application of a UV light. Before you choose this method, you should bear in mind that this process is far more expensive that the other methods. The mask is first printed separately on a foil or a transparent paper and then on the laminates of the small PCB. Board laminates have a light sensitive coating which allows images to be printed on them. The protective coating wears off at portions where the light is allowed to strike which makes the copper foil at those areas soluble in an etchant later on in the process.

Follow these steps in order to create UV images on the small PCB;

1. Print the layout in high resolution on a foil or transparent paper without selecting the option of ‘scale to fit’.
2. Special care needs to be taken when printing is done on foil. This includes making use of a toner dissolver which is used to make the density of the toner even. The toner is applied soon after printing and allowed to dry. The foil is then kept in an imaging frame with the toner surface facing upwards.
3. The laminate is then placed in the imaging from on top of the foil. It is important that the copper surface should face the transparent film/foil. Too much light exposure in the developmental stage on the light sensitive layer is not favorable.
4. Shut the imaging frame’s lid and set an appropriate timer (approximately 4 minutes) and start the light exposure.
5. When the exposure to light is complete, place the small PCB in a development tank for a couple of minutes.
6. Lastly, place the small PCB in a distilled tank water for rinsing.

Etching Small PCB

Etching of small PCBs is done to remove unwanted copper from the boards so that only copper traces remain. Before etching small PCBs at home, you must take safety precautions as you will be working with corrosive chemicals. So don protective goggles and gloves and work in a ventilated space because the chemicals used in etching release pungent fumes.

Ferric chloride and a solution of hydrogen peroxide and hydrochloric acid (in a ratio of 2:3) are popular amongst hobbyists to etch small PCBs. Boards should be immersed in a plastic container filled with the etchant. Keep the board immersed for at least 20 minutes. You will know that the process is done when the board changes its color to a yellowish shade. Rinse the board with water or make use of isopropanol spray.  Fry the board with a paper towel and use acetone to remove the toner mark to reveal the copper traces on the board. Do not dispose the chemical in the sink as it is illegal to do that. Either reuse it or give it to a chemical disposal facility.