Summary of The Saltwater etch process using PIC16F54 microcontroller
This article details a beginner-friendly tutorial for creating a custom 18-pin PIC microcontroller circuit board using a saltwater electrolysis etching process. The guide covers cutting copper-clad laminate to size, scoring and breaking the board along marked lines, and cleaning the surface before etching. It specifically addresses design choices for an 18-pin PIC (like the PC16F54), including connector spacing and component placement for breadboard compatibility.
Parts used in the Saltwater Etch Process:
- Copper clad board
- Ruler or straightedge
- Knife
- Sandpaper
- Abrasive cleaning pad
- Saltwater solution
- 18-pin PIC microcontroller (e.g., PC16F54)
- Crystal oscillator
- Capacitors
- Resistor
- .1" pitch connectors
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).
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
Step 2
Score a line on the copper
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
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
This is the copper side, with a deep groove.
Step 5
Groove on the plain side
Step 6
Break it apart
Step 7
The cut piece of PCB laminate
Step 8
Decide how large it has to be
Arranging them all on the board, it seems that about 2″ will be sufficient.
Step 9
Clean the board
- How do you cut the copper clad board to size?
Score the line multiple times with a knife while holding a ruler firmly, then deepen the groove on both sides before snapping the board. - What is the minimum width required for the 13-connection side?
The board needs at least 1.3 inches to accommodate 13 pins spaced 0.1 inch apart, though 1.5 inches is recommended. - Can I use a kitchen abrasive pad for cleaning the copper?
You can use one, but it should not be returned to the kitchen because copper is toxic. - Which signals are excluded from the board design?
The two programming pins and the Master clear signal are not brought out to avoid signal conflicts. - Why is the crystal made pluggable?
Making the crystal pluggable allows the user to experiment with different clock frequencies. - How do you ensure the board breaks neatly after scoring?
You must score deep grooves on both the copper side and the plain side of the laminate so bending causes a clean break. - What components fit on the estimated 2-inch length of the board?
The two connectors, the PIC, the crystal, some capacitors, and one resistor fit within this dimension.
