The Saltwater etch process using PIC16F54 microcontroller




The Saltwater etch process

This is a one-off process to produce one printed circuit board by removing unwanted copper by electrolysis in a saltwater solution.

I shall illustrate the process by etching and building a board for 18-pin PIC (for the PC16F54, but any 18 pin PIC will fit in it) in the figure. It has to plug into my breadboard and accept the programming signals from my PIC programmer (just go to http://geocities.com/it2n/circuits.html and look at it).

Saltwater etch process schematics

To avoid battling with signal conflicts, the two programming pins shall not be brought to the breadboard. To play around with the clock frequency, the crystal shall be made pluggable. The Master clear signal will not be brought out.

These decisions mean a board with two .1″ pitch connectors, one with 13 connections and the other with five connections, one pin spaced apart from the rest.

This is a tutorial intended for the absolute beginner, and almost every step shall be illustrated. I’ve even included a video of the etching process.

Step 1

Decide how large the board has to be

From the diagram, the side that plugs into the breadboard has 13 connections, and the holes in the bb are spaced 0.1 inch apart. So we need at least 1.3 inches to accommodate 13 pins.Say one and a half inches, a nice figure. Take a piece of copper clad board larger than 1.5 inches a side. Draw a line at one and a half inches.

Step 2

Score a line on the copper

Hold your ruler or straightedge firmly down on the board. Hold a knife lightly and draw across the line many times.After some time, there will be a gouge on the copper, dividing it into two.

If you bear down with the knife, chances are that it might wander and cut the board deeply where you do not want it cut – and you will be looking ruefully down on your ruined PCB stock. Be patient. Being patient has its own virtues, as life will invariably teach you.

Step 3

Make that line a deeper groove

Now, you can take the ruler away and with a little more pressure on the knife, go over the line a few more times. It will be guided by the cut, and you need a groove on that side.
Then at each edge, mark the plain surface of the board and draw a line there, too, exactly on the other side.

Step 4

Score the other side

The Saltwater etch process

Now you need a groove on the other side of the laminate, too.You will have a board with grooves on both the sides, and bending it with the fingers will be sufficient to cause it to break neatly at this line.

This is the copper side, with a deep groove.

Step 5

Groove on the plain side

This is the plain side of the laminate, with that deep groove.

Step 6

Break it apart

If you look at the edge, you will see that the two grooves on the top and bottom of the sheet has made it weak at the line and it will break easily.

Step 7

The cut piece of PCB laminate

So we have cut the laminate to about one and a half inches. It is actually a bit more than that, and that is for allowances in finishing.It will need to be sanded down to make those edges smooth and that will take away a bit of material.

Step 8

Decide how large it has to be

Now we have to decide how large the board has to be on the other dimension.We need the two connectors, the PIC, the crystal, and some capacitors and one resistor.

Arranging them all on the board, it seems that about 2″ will be sufficient.

Step 9

Clean the board

Remove rough edges of the board using a sandpaper (Or go out and rub it on a level rough cement surface).Clean the copper surface using an abrasive cleaning pad – the one I use is intended for use in the kitchen, and copper is toxic so do not let your wife or mum relocate it to the kitchen after you have used it – it would also be a good idea not to borrow the one in the kitchen for this purpose.




Current Project / Post can also be found using:

  • 16f54 circuit
  • what are pic 16f54 pcb diagram

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