How to prepare the solvent for etching

courtesy:commons.wikimedia.org 

How to prepare the solvent for etching

We have discussed elaborately ‘what is etching’ in our last post and its end result of getting our final product namely PCB for our assembling work. As such we understand clearly that removing the unwanted copper and retaining the wanted copper portion only in the form copper track by chemical treatment of CCB is the process of etching to obtain PCB. Now we are ready to know how the chemical process is taking place.

The Chemical

In order to remove the unwanted copper in the CCB, a chemical called ‘etchant’ is used. This etchant is nothing but Ferric chloride. Ferric chloride is the chemical name of the etchant and is toxic in nature. It is harmful to eyes and skin if you are in direct contact with it. You should avoid inhaling the fumes that emanates when the chemical is dissolved in water. Hence it is advisable to use hand gloves and mask to cover face and hands. You can procure Ferric chloride from chemical shops in your town or from online. It is available in the powder form and kept closed in the plastic container.   

Preparation of etching solvent

For etching the CCB, the ferric chloride solution is required in which the CCB has to be immersed and kept for some time until all the unwanted copper is dissolved.  Ferric chloride dissolves the unwanted copper and to one’s wonder, the copper underneath the pattern of the circuit that is the art work of the design drawn over the CCB remains intact un-dissolved. This is what we want actually for our purpose.

Solvent

Take a wide mouth plastic tray of the size at least 3 times bigger than the size of the CCB to be etched and pour at least a glassful of water into it. It is desirable to take just sufficient water in the tray so as the CCB has to be immersed in the solution. Ordinary tap water will do for the purpose. Add 2 or 3 spoonful ferric chloride chemical in the powder form slowly into the water with stirring. Do not try to add water to the chemical. The reverse process is always not preferable as heavy toxic fumes emanate while mixing powder with water. Always add water to the chemical. The fumes are very dangerous to eyes and nose. Hence do not inhale and safe guard the eyes. A plastic spoon or glass rod can be used for stirring. 

This solution is called solvent. One should be very cautious in handling the solution and the remaining solvent after the process is over may be discarded. It is preferable to prepare fresh solution every time when you want to etch a CCB. Overnight solution may not give good result apart from slow downing the etching process as the etchant tend to become weak and loses its strength. 

Once the chemical solution is ready, you can proceed with etching process with the CCB. The detailed process will be discussed in the next.