Etching - all the facts you should know

courtesy: flickr.com

Etching - all the facts you should know

We have so far discussed two simple and easy methods of transformation of circuit design to CCB in the PCB fabrication process. One can follow any of these methods depending upon the individual skill, capacity and need of the project. For simple designs not involving much complicated components such as ICs, one can adopt manual method. If the drawing contains a little bit complicated multi pin ICs, then laser print method will give good results. As such the ready made PCB designs for popular projects are provided to adopt this near professional technique. It all involves one’s talent, need and time factors.

In this post we shall move on to the next step involved in fabrication process, namely ‘etching’ the CCB. The etched CCB is the actual PCB by which hooking up the circuit elements will be carried out. So let us understand this process before actually step in.

Etching process

CCBs

CCB, as already discussed, is nothing but copper laminated Hylam sheet. The surface is coated with thin layer of copper. There are two types of CCBs are available, one is single sided and the other is double sided. In the double sided CCB, both sides are laminated with copper layer. The double sided CCBs are used in complicated circuit designs involving high density of circuit elements and for technical reasons. But here we are mostly going to deal with single sided CCBs. It is sufficient for our purpose. One can procure these CCBs from the electronics market and from local dealers.

So what is etching?

On the copper laminated side of the CCB, the circuit design in the form of drawing is transferred through two different methods as we discussed earlier.  The drawing is actually called the ‘pattern’ of the schematic circuit diagram. The pattern is transferred on the copper surface of the CCB. We want only the copper area underneath the pattern and we do not want the copper other than that. Etching keeps the copper areas underneath the pattern and removes the unwanted copper by dissolving it by the chemical. Hence etching is a chemical process. 

Retaining the pattern in the form of copper track and removing the unwanted copper areas by the chemical is known as etching. This pattern is intact even after etching. This means that the copper portion of the drawing lines does not dissolve by the chemical and we get the actual conductive copper track of the circuit. The transferred printed pattern in the form of printing ink protects the copper from dissolving by the chemical whereas the unprotected areas will be dissolved out.

In our next post we shall discuss the etching chemical and the process in detail.