Make your own Printed Circuit Boards

dynamag By dynamag, 7th Aug 2015 | Follow this author | RSS Feed
Posted in Wikinut>Guides>DIY>Electrical

A method to make Printed circuit boards for use at home/workshop, with the added benefit of being able to keep using the etching solution repeatedly, and not having to throw it away every time.

Introduction, Materials Used, Statutory warning

Introduction
Most electronics needs a Printed Circuit Board, and this is one way to get a fast PCB done, which gives a professional touch to your DIY project in electronics.

This is a project that requires the use of relatively strong chemicals, therefore

1. PLEASE USE GLOVES,
and
2. IF YOU ARE NOT AN ADULT, PLEASE GET ADULT SUPERVISION.

Materials required

A. Consumables
1. Hydrogen Peroxide - commercial strength solution, which should be at 6% V/V. One litre will work for hundreds of PCBs.
2. Hydrochloric Acid - commercial strength, which should be at 30% V/V. One litre will work for hundreds of PCBs.
3. Acetone - or Nail Polish remover can be used also, though it may be costlier. One litre will work for hundreds of PCBs.
4, Copper Clad Board, single sided or double sided. Here the quantity depends on the size of your boards. I fo for the bigger 400 mm square, which I cut to my board size.
5. Toner Ink used in a Laser printer only. One cartridge should go for ages.
6. Good quantity of clean Water.
7. Cotton Waste - small packet will do for many boards.

B. Tools
1. Drilling machine, a small one is better, and gives faster results. I have used hand drills before, but then completing a board becomes very slow on account of the time each hole takes to be drilled and the number of holes to be drilled.
2. PCB cutter, which can be managed with either a band saw or a hand router. The band saw is faster and somewhat cleaner, without a doubt.

Print your PCB layout

This section starts with the PCB layout that you have already created, with your favourite PCB layout package. If this is not yet done, then you need to make a layout first. I will be making a guide here to make a layout later.
See the image attached as an example of the PCB layout I have printed
Once you have the PCB layout, a print out on LASER PHOTO PAPER is to be taken. This paper is suitable for our use, since the plastic layout printed on the paper (by us) can be removed by applying heat, which is what we want, anyway.
Before taking the print, set the laser printer to print in the highest resolution possible, since we want clear tracks. The resolution I use in my pcb layout is normally 0.5 mm spacing with 0.5 mm tracks, or sometimes 1 mm tracks with 0.5 mm spacing. This is so that I can drive more current, and do not have to worry about tracks evaporating when I need more drive. The resistance of the tracks also reduces, so that is an added plus point. Thicker tracks are also easier to print and etch, though the number of tracks reduces. Well, some pros, and some cons are to be expected every time.
Some basic rules to be followed. I make most of my boards single sided, since I find it easier than double sided with its alignment and Plated Through Hole (PTH) complications. I also make my component pads a bit bigger. Since the boards are single sided, there isn't any through hole material to hold the pads in place, which tends to lift tracks and damage pads in case of component change or replacement. So the bigger the pad on the board, the less damage there will be after soldering.

So, now, you have the print out, then you need to transfer the toner to the copper board.

Clean Your Copper clad Board

First cut the copper clad plain board to a little more than the correct size. The clean the board thoroughly with fresh water, and a "Scotch Brite" utensil cleaner brush, which I have found is the ideal thing to use to clean copper clad boards without scratching them. Clean/Rub the board till they shine, keeping the direction of motion of your brush in one direction, so that you have an even looking board :) Okay, board is clean, what next?

Toner Transfer

Now place the laser print out - cut to slightly bigger than board size - track side face down on the board. Fold the excess paper over the blank copper clad on one side, and tape the folded bit firmly to the back of the board. Now make sure the print out sits squarely on the board, and the paper folds over the board on one side only. The fold is there so that the transfer ironing is done in the direction away from the fold, which serves to hold the paper while the transfer takes place. The transfer is done using an ordinary clothes iron, heated to maximum. The iron is pressed on the paper firmly while moving it in the direction away from the fold. So the sequence of your board from table upwards is 1. table top, 2. board with taped fold, 3. actual board, 4. the layout with inked tracks pointing downwards, and 5. your pressing iron.
Press the iron onto the paper, with as much force as you can muster. The heat will melt the track underneath the paper and separate it from it (the paper), and the track transfers to the copper and sticks there. Strokes away from the fold will make sure all parts of the layout are pressed into the paper, and that cracks in tracks do not form.
Keep doing for about ten minutes, or till your arms get tired( whichever takes longer) :)

Removing the paper from the copper clad board

Now you need to remove the paper from the board. This can be done in many ways, but the easiest way I have is to immerse the entire board with paper and tape into a tray of cold water, where the board will cool, the paper will absorb the water, and in a few minutes, we can start slowly pulling the wet, weakened paper away from the board, while the plastic toner tracks remain on the board. Remove all the paper from the board, as much as possible, anyway. The image shows how the board dipped in the tray of water.

Correcting the errors on the board

There are chances that the tracks have cracks in them, or some gaps are present in zones, or pads are not filled, and so on. These errors need to be corrected, before going in for etching.
The correction can be done using any permanent marker pen, of any colour, though I use black.

Board ready for etching

This is how the board should look, after you have removed all the paper on it, and corrected all errors using the marker pen as mentioned in the previous section. The holes for the pads can also be carefully cleaned to remove paper and to make the copper exposed so it will be etched and show the centre holes for drilling. This may need a magnifying glass, if the hole sizes are small.

Make the Etching Solution

Now comes the part, where, depending on ones' patience, the strength of the etching solution, and ones' ability to multi-task, the process involved can be interesting or boring to the point of making one want to walk away. The materials used are Hydrogen Peroxide and Hydrochloric acid, both of which are strong chemicals that require careful handling.

I repeat here that one must PLEASE USE GLOVES,
and
IF NOT AN ADULT, PLEASE GET ADULT SUPERVISION.

The process of etching is easy, it requires that we use a solution of Hydrogen Peroxide and Hydrochloric acid mixed in the ratio of 2:1, or two parts of Hydrogen Peroxide to one part of Hydrochloric acid. To make the solution, use a measurement cup and pour 100ml of H2O2 into a clean, dry tray. Then using another measuring cup, measure out 50 ml of HCL (Hydrochloric acid) into the Hydrogen Peroxide in the tray. Please make sure you follow the sequence as mentioned above. Always put HCL into H2O2, NOT THE OTHER WAY AROUND!! The image shows the chemicals used to make the etching solution

The first time the etching solution is made, it will be transparent. As we make more and more PCBs, the copper will add to the solution turning it green, and finally black.

The colour will gradually deepen into almost black, which is when we need to "rejuvenate" the solution so that it can etch faster.

When the etching solution darkens to black

After the solution is ready, you can slide the inked copper clad into the tray. as shown in the figure. The image shows the colour of the solution is black, which is because the solution has been used earlier for many PCBs, and it is time for me to "rejuvenate" the solution. The speed of etching, and hence your coefficient of patience/boredom will depend on the solutions strength.

Rejuvenating the copper etching solution

This is how the rejuvenated solution looks like. All I did is add a few caps full of the Hydrogen Peroxide to my etching solution, and it lightens immediately and can be used for a few more boards. As the number of boards made increases, the H2O2 addition will stop giving dividends, and now we need to add a cap full or more of HCL to the solution. When the quantity of solution becomes difficult to sore, then we should think of disposing it safely.

Etching

The first time we etch, the etching will complete in a few seconds, with some heat, minor fumes, and maybe some smell to accompany the etching. As we keep using the same solution to etch more boards, the strength of the solution reduces, and the time required to etch increases.
Depending on the strength of the solution, we have two choices
1. Leave the solution and go do something else. Come back after a few minutes.
or
2. Stay here, slowly shake the tray with the solution and the card in it, like rocking a baby, without violence or splashing, so no clothes and or items are marked with green for a long time.
Either way, we need to check the progress once a while.
Take board out of liquid, but do not remove from tray(the board will drip green yuck around), see if the etching is taking place. We can find this out initially by the colour change in the copper and then the copper will gradually be removed, leaving the phenolic/FR4 bare board and the toner ink with copper in place. Repeat till all the visible copper is gone.
Yay! We have an etched board at last! The figure shows the completely etched board.

Removing the toner from the finished board

Now that the board has been etched, we need to remove the toner and bare the copper tracks for further work.
Wet a little clean cotton waste in Acetone, and wipe the board till the toner material is removed and the copper tracks are visible.
Move the etching solution from the tray into a clean, dry glass bottle for future use.
Cut the board into the appropriate sizes. The example board here has three types of PCBs, three each of two types, and one of the third type.

Board drilling

Depending on the hole sizes, drilling should now be done. I try and keep my holes all at around 1 mm so that the drilling can be finished soon too, rather than having to look for matching holes to drill, which takes longer.
I do the drilling first, before cutting the board, but the sequence should not matter. Using the band saw, I cut the board to the size required.

Board Assembly

Now the work remaining is the assembly of the components, which I do by hand. The polarity of diodes, and capacitors should be noted from the schematic diagram, and the component layout SHOULD show correct placement.

Now its up to you how you want to use the board :-)

Tags

Diy Etching, Diy Pcb, Electrical, Electronics, Etching, Pcb

Meet the author

author avatar dynamag
Interested in everything. My experiences include technology, science, India, religion, Indian politics, morals, ethics, business, DIY stuff, electronics, and many other subjects

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Comments

author avatar Sivaramakrishnan A
14th Aug 2015 (#)

You need a technical mind and supple hands, thanks for this share - siva

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author avatar dynamag
14th Aug 2015 (#)

Thank you Sir. This is my first attempt at publishing. All your help and good wishes are valuable.

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