A PCB (Printed Circuit Board) is arguably the highest form of fabrication in the field of electronics. It was once a thought that it is almost impossible to make them at home but later Ferric chloride etc. were used. But Ferric chloride isn’t a commonly available chemical in a locality. So this article is about how you can make your own PCB with easily available materials.
To start off, you need to generate a PCB layout. There are many softwares available but I suggest using EagleCAD from Cadsoft. It’s easy to learn and has everything a hobbyist would ever need. The following are useful links to learning the software:
Once you have a layout, like this one (I constructed a 555 astable multivibrator PCB).
Now in Eagle’s print dialog box, you will find options like black etc. We want the print to be in black so tick it. For all PCB implementations keep the scale to be 1. Use glossy paper like magazine paper and print the PCB layout using a Laser printer only. Cut it to suitable proportions. The only high profile thing that you will need is a copper clad board. But you can get that easily these days at ebay.
Keep the printed side facing the copper and simply iron it. Keep the iron box over the paper and board, to heat it. As you heat it, the laser toner (which is like a plastic material) will melt and get stuck onto the copper. Be careful not to move the paper over the copper and smudge the ink. Do it as gently as possible and repeatedly just press over the paper. Also, never leave the iron box over the paper and board. Do that for about 15-25 times and after you are done let the board cool down before carefully remove the paper. It should come off easily but if it doesn’t come off use water to rub it off. Don’t rip it out. Once you are done with it, you must end up with something like this.
If all this seems too ‘out of hand’, you can simply draw your board with your hand. Use the layout as a reference and sketch it on the board with pencil (and scale too!). Then use a permanent marker to simply draw the board. If you draw with your hand, the circuit lining will not be perfect but you can get the job done easily. The advantage with permanent markers is that you can also add your initials like what I have done.
Let it dry overnight and meanwhile we can prepare the etchant. The etch process can be described as follows. The laser toner or the permanent marker transferred onto the copper serves as a mask. The etchant acts on copper and dissolves it. So all the surrounding copper is dissolved except the one underneath the mask which gives the required copper lining. Usually Ferric Chloride is used for etching but its often difficult to get it and it is also relatively costly to the current method.
The etchant I have used is a mixture of conc. Hydrochloric acid (which every household has) and Hydrogen Peroxide (I got it for Rs. 20 from a medical shop). The key here is the pH of the solution. If the concentration of acid is too high (pH<1), the copper etching will be too aggressive that the mask will be rendered useless and if it is too low (ph>3), the etching will take ages to complete. So, the optimum level is to use 1 part of conc. Hydrochloric acid (pH < 1.1) with 1 part of Hydrogen Peroxide (ones sold in medical shops are 2% solution, so the extra water will dilute the acid suitably). If by variation of some quantity, the etchant fumes (still very concentrated), carefully add water by drops along the side of the container (to avoid a rapid increase in exothermic enthalpy). Keep adding until the etchant just stops fuming. But this involves keen observation, so if you are a starter stick with measurements and be extremely careful while pouring the acid!!!!
Use the board only after it has completely dried. Then wrap the board with wire to serve as a holder. Make sure that the metal in the wire never comes in contact with the etching solution. Then just immerse the board into the etchant using the wires and make sure the board is completely immersed in the etchant.
Now all you have to do is agitate the solution every 5 mins or so. Do so gently because you don’t want anything coming out of that container.
Within 5 minutes, you must observe a nice turquoise (blue-green) color. This is due to the reaction between hydrochloric acid and the unmasked copper with hydrogen peroxide as the oxidizing agent. This results in the formation of copper (II) chloride. For people interested in advanced Inorganic chemistry – Copper tetrachloride ions also play a role as a mediating agent.
After about 15 mins with constant agitation in regular intervals of time, the board will becomes something like this.
Keep observing, don’t let the board simply rest in the solution for a long time. Remove the board as soon as the etching is complete. A complete board should look something like this.
Remove the board carefully, dripping any remaining solution back into the container. Do this near a sink and wash the board with excess of water under a tap. This is to drive off any remaining etchant on the board and wire and then dry the board.
One the board is dried, we need to remove the permanent marking. Again we use a commonly available material – nail polish remover. The cheap ones will be more than sufficient. Add drops of the remover on the board, it should start dilating and the copper should be visible.
Rub the ink and it will be removed. Do this with some gloves, so that ink does not stick to your fingers. Once you have all the ink removed, you will still have the laser toner (only because I used that too, not if you use only permanent markers). Use steel wool (steel rug used for dish washing) and carefully rub of the toner while having the board under a steady flow of water from a tap. Dry the board again and you must have a raw PCB.
To make things a little attractive, print another image (preferably color) of the layout and cut it to the same dimensions as the board. Stick the printed paper on the non- copper side of the board. if your measurements are correct, the copper linings underneath will exactly coincide with the printed content on the non copper side.
Drill holes wherever necessary either using a drill machine and fine drill bits or a PCB hand drill. A drill machine (the one I used) costs a lot and I got the fine drill bits – 0.6 mm, 0.8 mm & 1 mm from ebay. If you are not gonna use a Drill machine for anything else, don’t buy it. Instead go for a hand drill also available at ebay since it is significantly economical. Once the holes are drill you have a complete PCB now.
Non copper side:
Copper lining side:
If the holes vary by a little, it can be rectified during soldering. If the variation is large then you got your measurements wrong.
Now all that remains is to add the components and solder it. While using IC based circuits, it is better if you use a IC holder rather than soldering the IC directly. Soldering is arguably the toughest part because it requires a lot of skill. But like everything else it is attainable by practice.
The shiny powder like thing in between two solder joints is not lead, its actually the reflection of the plastic which slightly melted while soldering. A tip while soldering is to scratch the copper junction and the component terminals with a sharp object. This removes the oxide coating and also enables the lead to adhere strongly with the copper and the component. As you can see I am not great at soldering. But as long as you can get the junctions in proper electrical contact without short-circuiting (especially near the IC holder pins which are very close to each other), it is more than enough.
The finished neat PCB with components:
You could attach a battery holder with it and make it a self containing board, but I coupled it with a breadboard using the soldered wires.
When you switch the supply on (5V), the LED blinks and you know the circuit is working correctly and there is nothing wrong with the PCB or the soldering.
I have uploaded the video of its ‘blinking’ operation. Do look at it and my other circuits too!
There are actually hundreds of ways of making PCB’s but I hope you find this one useful too. Good luck for your circuits!