PCB etching technique

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PCB etching technique

In the previous post we have elaborately discussed how we can prepare the etching solution observing all precautions involved in that. Once you have prepared the etching chemical and kept ready, the next process of etching the CCB starts. In this post we shall discus the detailed process of etching.

Etching process

The circuit pattern transferred CCB is slowly immersed in the chemical solution kept in the plastic tray. Care should be taken while placing the board in the tray. The pattern side of CCB should face up and not upside down. The board should be completely immersed in the solution. The chemical in the tray should be given gentle shake either by shaking the tray itself or the solution is stirred with a spoon or glass rod. Then and there one should give the stirring movement so as to quicken the etching process and for uniformity of etching. Stirring also helps in preventing the deposition of dissolved copper over the design and thereby prevents it settling over it. The deposition may obstruct the copper to face direct contact with the etchant.

Completion of the task

The etching will take some time to complete. The board can be lifted out from the tray gently and observe the progress of etching, that is dissolution of unwanted copper from the CCB. The time taken will be longer or shorter depends upon the strength of the solution and the density of the pattern on the board. Please ensure that all the unwanted copper is dissolved from the board before taking out. One can view the board against bright light behind it to confirm whether the process is over or not. If incomplete the process should continue for some more time and get assured the completeness. 

Once confirmed the CCB can be taken out of the tray and thoroughly washed with plain water under the tap to remove all the chemicals sticking to it. Now the surface is cleaned with gentle sponge to remove the printer ink, so that the copper track is visible with clean brightness. Then the PCB is washed and dried for further fabrication work.

Finishing touches

Here one important task is one should carefully compare the etching finished pattern with the circuit diagram and get assured that there is no short in the copper track with adjacent tracks. So also one can observe for any missing links in the track. Though this has been verified earlier when we transferred the pattern to the CCB, it is imperative to verify this after the etching process is over in the PCB. This will avoid complications in future when the board is assembled and put to operation.

Drilling Holes 

One more task with the PCB is left over. It is nothing but drilling the appropriate holes on the PCB pattern so as to enable to insert the circuit elements from the other side of the board and get them soldered on the copper track side to make firm electrical contact.  A small hand operated or electrical drill with PCB drill bit can be used for finer holes. It is necessary that holes should be drilled wherever necessary with utmost care and especially one should be careful with holes for IC pins are to be made. It should be uniform in shape and distance as IC pins should be inserted with ease. If necessary holes edges should be smoothed with thin emery paper as this avoids chipping of copper layer when handling the components.

Protective layer

Now the PCB is ready for hooking up of the components on the board with soldering process. If one wants that the board may be coated with a thin coat of transparent varnish to prevent the copper track becoming oxidized in course of time as it is exposed to open atmosphere.

One should practice this etching process initially with small designs to develop the skill in this field. Practice makes one good at fabrication technique of entire PCB making work. In our next post we shall discus a few important assembling hints for successful building of one’s favourite project.