Printed circuit board or PCB is one of the important things to assemble an electronic circuit. It provides support to the components and makes electrical connection between the parts. In PCB assembling, the components are placed on one side of the Copper laminate passing their pins or leads to the other side through the holes. The pins/leads are then soldered to connect with the PCB tracks. Here explains the easiest method to make a homemade PCB for prototyping.
Part To be Required
Copper clad board This is available in different sizes. Select a suitable size to accommodate all the components. If the copper clad board is large in size, cut it to the required size using a knife/Hacksaw blade. The copper clad board has a copper coated side which forms the soldering side. The other side is the component side on which the components are placed. If there is any dirt or copper oxide on the copper side, clean it thoroughly using a steel wool and scrubber. Etchant (Ferric chloride) This is the Etching crystals of Ferric chloride. It removes the unwanted copper layers from the copper clad board. The Etching solution can be prepared by dissolving 75gms Ferric chloride powder in 100 ml Luke warm water.
PCB drill and bits PCB drill is used to drill holes in the PCB. A hand drill with suitable bits is sufficient for the purpose. Use drill bits of the following size to make holes for different components A. 0.8mm OR 1mm –for, Pots, Resistor, capacitor, transistor, IC pins etc. B. 1.2mm and 1.5mm –for Switches, trimmer, rectifier diodes, and components, this requires bigger holes.
Step 1 - Cutting copper clad to size
Step 2 - Cleaning the copper clad with scrubber
Method 1 - Pasting Layout Print out on copper clad
Method 2 - Drawing
1. Draw the circuit diagram as compact as possible on a paper. Mark the points (component pins) to be drilled, this side is called ‘component side’ of the board. The mirror image of this diagram is called ‘pattern side’ of the board i.e., for pattern drawing (drawing lines and pads) on the copper clad board.
2. Overlap the tracing / butter paper on the paper explained in step 1. Draw the same diagram on tracing / butter paper using the permanent marker pen. Draw the diagram carefully without any overlapping or shorting of tracks or components. The neatness of the PCB lies in the pattern drawing. After drawing, see the other side of the paper. There is a Mirror Sketch of the tracks. This is the actual ‘pattern of the PCB side’.
3. Place the carbon paper on the copper side of the copper clad board. The layout side of the carbon paper should face the copper layer.
4. Place the tracing paper with diagram over the carbon paper. The diagram should be in the middle part of the copper clad board. Fold the sides of the tracing and carbon papers and stick it using cello tape. This prevents the movement while drawing.
5. Once again redraw the diagram using the permanent marker pen so that the carbon ink will create a mirror sketch on the copper clad board.
6. Remove the tracing paper and carbon paper. Using the permanent marker pen, redraw the carbon pattern of the mirror sketch on the copper laminate, so that the tracks will be created using the permanent marker ink. Keep it for 10 minutes to dry the ink.
The Hanger Tool
Ferric chloride etchant is cheap, can be reused many times, can be used with warm water. The down side of this stuff is It stains permanently everything it gets in contact with: not only clothes or skin (never wear your best clothes when working with it!), but also furniture, floor tiles, tools, everything, that it’s incredibly mess. It is concentrated enough to corrode any metal –including your chrome-plated sink accessories. Even vapours are highly any tool or metallic shelf nearby into rust. Rinse method: For etching, place the container on the floor (some scrap cardboard or newspaper to protect the floor from drops). Fit the board on the hanger, and submerge the PCB. Stir occasionally by waving the hanger. First impression may be that nothing happens, but in less than 10 minutes some copper is removed, making first tracks to appear. From now on, stir continuously and check often, as the process completes rather quick otherwise thinner tracks start being eroded sideways. As a rule of thumb, stop 30 seconds after you don’t see any copper. Rinse the board with plenty, plenty, plenty of water. Store the etching solution in the same plastic box used for etching. When the job is done just put the hermetic lid on. To further minimize risks of leakage, put the container inside the bigger one I use for rinsing, put the second lid, and store it in a safe place.
A few drops of thinner (nail polish remover works well) on a pinch of cotton wool will remove completely the ink, bringing back the copper surface. Rinse carefully and dry with a clean cloth or kitchen paper. Trim to final size and refine edges with sandpaper.