Building your own PCB's

Using stripboard or veroboard (or whatever it is called by your supplier) is an easy approach to most circuit board solutions. However it has two main disadvantages:

a) Circuits can be quite large due to the restrictive nature of pre-built tracks
b) Some components will not easily fit into these boards without excessive bending of pins which can lead to damage of the component.

Stripboard - home made PCB comparision

Since I have learnt to make my own PCB's, I have used them as replacements for stripboard in many circuit cases (except for the simplest where stripboard provides the easiest means of construction. Left illustrates a stripboard design against a design of my own. Although these are not the same circuits, it is easy to see that the board on the right is far neater. Building your own circuits boards isn't very easy and can be time consuming, but it is not an extremely difficult task and I would recommend it to even quite a novice in electronics (as I am one myself) and the result you get afterwards is of huge benefit when it comes to finally soldering the components and constructing the final appliance/system. Below is a list of what you will need for basic freehand style PCB construction:

1) A copper board (this can be fibreglass or standard type, fibreglass ones a stronger but wear down the drill bits faster)
2) A copper etchant (this is a ferrite chloride solution that will be used to 'eat away' at copper, personally I prefer the ferrite chloride crystals which dissolve in hot water to make a solution)
3) A suitable (old) plastic or glass container for etching the board in (THIS MUST NOT BE METAL)
4) Rubber gloves (its also a good idea to work on an old surface, preferably outdoors)
5) A copper board cleaner (I use a cleaning block which nicely removes oxidisation from the copper)
6) An etch resistant pen (this is used to protect areas of copper that you do not want to etch, i.e. the tracks)
7) A method for cleaning the board after etching (personally I use thinners)

Using the copper etchant

There are many different etchants available, most of these are far too dangerous for the home user so ferrite chloride is recommended, however...

FERRITE CHLORIDE IS VERY CORROSIVE, ESPECIALLY TO METALS. Do not get this solution on hands, clothes and never pour it down drains or sinks. It and the the solution it makes after etching (copper chloride) are also poisonous and you should seek medical advice immediately if any solution gets in eyes or mouth etc.

Safe use of this chemical however and it should not cause you any problems. These guidelines give you a quick description of how to make it but I strongly suggest you read up more on this topic so it is specific to your etchant that you brought. My method of etching may differ from others too and I only aim to provide additional and summarised information on this topic.

Along with pre-cautions above, I also recommend these actions are also taken when using this chemical:
a) If possible, use it outdoors - its far safer and won't cause half as many problems if an accident does occur
b) Where old clothes. If you get a slight drop on your clothes, there is no way that you will be removing the stain, whatever cleaning agent you use. I have ruined decent clothes just by getting one small drop on them - a small yellow stain will always be there now.
c) Never get this chemical near metal. That means do not wash it down sinks, drains or anything like that - it will corrode them and ruin them, particularly aluminium. If you must discard of this, dilute it as much as possible so it is less likely to react.
d) Do not bring this anywhere near the kitchen - it is poisonous and should be kept away from food or anything that is used for food preparation.

Most versions of ferrite chloride come in bottles or as rock crystals. I have not used bottles yet, but a bottle will contain about 250ml of the solution and will probably need to be diluted, to make 500ml usually. Follow the instructions on the side of the bottle for specific details (I am not providing these). I prefer to buy the ferrite chloride crystals (or "rocks"). These come in a bag with the instructions on a sticker (read them :P) for how to dilute and use.

My ones come in a 250g pack, and if I remember correctly (I do not aim to remember as I always read the instructions every time I have brought them), I add these crystals to half a litre of warm water and stir rapidly with a wooden stick (well last time I done it was with an old felt tip pen which I then discarded). When stirring, never use anything metal, or anything you intend to keep clean and use on something else. At first site, it doesn't look like the crystals will dissolve at all (as they are huge), but warm water and lots of stirring, and they soon disappear. The result is a very orange looking amount of water - this is your etchant solution. Ferrite chloride is also available as anhydrous ferrite chloride. I do NOT RECOMMEND this and it should be avoided for these reasons:

a) Its undiluted without any water content, therefore is a powder. Powders can be easily breathed in and since this chemical is poisonous, its hard to recommend.
b) When mixing it with water, lots of heat is produced. The energy released by this chemical can heat up cold water to a point where it can melt some plastic containers.
c) Although the above statement seems to imply the chemical dissolves well, it does not. It easy to have lots of powder that won't dissolve and you get a solution that looks like it should work, but actually doesn't.

Since anhydrous ferrite chloride is hard to recommend, I will not give details about using it.

Now that you (should) have an etchant solution to work with, here is how to make the circuit boards...

Making circuit board

As an example, I will use pictures from a recent mixer project I have done. I am unable to provide any schematics for this mixer as it is from a book and therefore providing details would be a copyright issue. I can tell you that it is a 2 channel stereo mixer with fader controls for each input.

There are several steps that I use when making my own PCB's and these are listed in order below, and will be explained after:

1) Obtain the schematic for the circuit and buy all the components first
2) Design an initial layout on paper
3) Use the components pins to make holes in a paper design template
4) Use the paper template to mark holes on the copper board
5) Drills the holes with a drill and a small drill bit
6) Clean the board to remove dirt and oxide.
7) Draw on the tracks with the etch resistant pen
8) Prepare the etchant and then etch the board once the pen has dried
9) Once all exposed copper has been removed, remove the board and clean it.
10) Solder the components in place
11) Test all connections to detect any solder defects (i.e. dry connections or shorts)
12) Connect up and test circuit

I strongly suggest that if you are etching your own board for the first time that you do a small board to practice with. I made a small board for a power LED which is basically a board containing an LED, a small resistor and two holes for the power wires. If you do this successfully, then you may move freely to bigger boards, although I still wouldn't suggest anything huge for a beginner.

1) Obtain the schematic for the circuit and buy all the components first

Although this is common sense, it is easy to forget or avoid. It is a real disappointment if you build a board and then find out a particular component will not fit in it properly and you have to mount it in an unsatisfactory way, or in the worse case waist an entire board and rebuild another one. The schematic is the key to designing the right circuit, although if you are lucky you may find some places on the web giving you a PCB design already.

2) Design an initial layout on paper and 3) Use the components pins to make holes in a paper design template

Paper design template Designing the layout can be quite tricky, again if you have a PCB design already, then use that. However do make sure that this design fits the components that you have brought and what side of the board it is viewed from. If it is an above view (most likely), then you will have to reverse this for drawing the track layout on the back. If you do not have a design already, then you need to do it yourself. My advice is to follow the general layout of the schematic, changing it when necessary (as the symbols for components do not usually represent the pin layouts on the physical component, especially with integrated circuit's).

When designing on paper or card, it is also a very good idea to use the components you have brought in order to create a good template for drilling. This is particularly handy where electrolytic capacitors are involved, as with many IC's, transistors, relays, and other components. Design and components For resistors and diodes or other similar components, use a sharper tool to make holes for these components roughly a 1-1.5 centimetre (1/2 inch) or more apart. I find that it is easier to design the layout viewed from above for this reason and that I seem to be able to make the designs better when looking at the board from above.

You need to keep double checking your layout as you go to make sure that you do not accidentally short tracks or lead them to the wrong components. It may track some time and several attempts to get your desired layout. Also, as you are designing the tracks on one layer of copper board, you may also need to cross tracks. This can be done if you have a break in the track you need to cross (i.e. when there is a capacitor or a resistor etc on the other side) or where this is not the case, often the easiest way is two use a jump wire on the other side of the board to cross the track. Do avoid using lots of these though, otherwise your board will look messy and you will need to drill lots of holes.

Above left: design for TDA2030 amp, Above Right: mixer design and all its components.

4) Use the paper template to mark holes on the copper board

If the paper template you have designed is viewed for above, then you need to reverse this piece of paper and stick it to the back of the board (the copper side) with sticky tape. This now allows you to mark the copper side of the board for drilling by using the holes made in the paper created by the components. I use an old braddle to mark the board and provide a small hole for the drill bit to sink into. This can take some time if you have quite a lot of holes. Be sure you have stuck the template to the board well or it will move about and your marks will not appear in the correct places, potentially making components very difficult to mount.

5) Drills the holes with a drill and a small drill bit

Copper board drilled Most components will happily fit a 1mm hole in the board. Bigger components (potentiometers spring to mind) will require holes of 1.5mm and some small components (such as IC's) fit best into 0.8mm or 0.6mm holes. In the ideal situation, you need a small electric drill in a small stand so you can easily drill straight downwards into the circuit board and make the holes easily and effortlessly. Unfortunately I do not have this situation yet and have the choice of two drills - a heavy duty electric drill or a hand drill. Because the work is very delicate, I use my trusty hand drill as it gives me good control over the drilling process. Because the drill bits are very small, they snap very easily and a little too much pressure, particularly in sideward directions will cause the drill bit to snap, and I also find the after this has happened you will slip and scratch the board with what remains of the drill bit in the drill. I find that this step is the longest and dullest part of the circuit board making, but hopefully I should get a small drill and a stand soon for my next big project.

Above: Mixer Board design with only the holes drilled.

6) Clean the board to remove dirt and oxide.

Dirty Board Cleaned Board

A relatively simple step. I just use my cleaning block and rub it over the entire board until it is shinning a nice copper colour (as illustrated). If you want to clean the board further, a good cleaning agent will help. Above shows a copper board that has been sitting away for quite some time left, the image on the right shows the same board after a quick bit of cleaning with the cleaning block (also shown).

7) Draw on the tracks with the etch resistant pen

Etch resist pen

Layouts drawn A much longer step. Chances are that you have your circuit board design viewed from above, in this case, you will need to reserve it for drawing the track layout on the back of the board. Rather then trying to reserve the image in my head every time, I find it much easier to scan my design into a computer, then use a suitable image package to flip the image horizontally (even MS paint will do this) and then print it out so I have a good reserve template to copy from. With this reversed image, its simply a case of drawing this image onto the back of the board with the etch resistant pen.

Make sure that as you are drawing the image that you avoid leaning on the board with your wrists and fingers as this will cause the copper to quickly oxidise which will cause problems when itcomes to etching. Keep shaking the pen as you use it too to get the best ink solution when you draw on the board. With my particular pen, ink is not released until you press hard on the tip, where ink flows out when this happens. When performing this, do it on an area of low track density on on a separate piece of paper (do make sure this is several layers as the ink will soak through). Once you have all you tracks drawn on the board, check to make sure that the ink does not bridge two tracks in any way and that you layout is satisfactory. To correct small mistakes, I usually find a sharp tool like an old braddle can be used to scratch away unwanted ink. Larger mistakes will need to be corrected by use of thinners or something similar that will remove the pen. Leave to dry for about an hour after you have finished.

Above: Mixer board with tracks drawn on with the pen shown above.

8) Prepare the etchant and then etch the board once the pen has dried

Copper Etchant Now you are about to etch the board, if you have not done so before, prepare the etchant as mentioned earlier or if it is already made and you are reusing etchant from before, give it a quick shake or stir (naturally the container it is in must be tight) and transfer it into a container that you will use to etch the board in. I usually use a glass coffee jar and a piece of string. The piece of string or thread is used through on of the holes in the board and then left outside the jar, this allows me to quickly and easily remove the board so I can clearly check on the etching process. After etching, the etchant can be reused quite a few times, you will notice it will start at a very orange/brown colour and then turn to a blue/green colour as the ferrite chloride is replaced by copper chloride. You will also notice that some iron will start to lay at the bottom of the solution after time too, an understanding of simple chemistry tells you why. That is the copper is more reactive then the iron (ferrite) and the chlorine reacts with the more reactive metal, that being copper. Like any chemical reaction, you can speed up the process by applying more heat and stirring, hence your etching will go faster on a hot day then a cold winters day (especially here in the UK).

9)   Once all exposed copper has been removed, remove the board and clean it.

Etched board After the etching process is complete (this may take over 30 minutes, please be patient), all copper that was not protected by the etch resistant ink should have been removed. If this is the case, you can now remove the board (with rubber gloves on) and begin the cleaning process. There will still be copper etchant left on the board when you remove this, do your best of remove as much as possible with tissues/kitchen roll then use fast flowing water to remove the rest. I like to use some thinners to remove the pen from the board and lots of water and this is quick and easy. Once the board is clean, dry it and examine it. If there are any small defeats, excess copper can be removed by using a sharp knife to break any wanted contacts. If you find there is not contact where there should be, then you can try to use solder or small wire to bridge the gap. If your etching was good, this shouldn't happen. If the board is very badly done, it may be a good idea to redo it.

Above: Mixer board after etching and cleaning.

10) Solder the components in place

Soldered board bottom Soldered board top

I am not about to provide tips for soldering here because you should have soldered things before moving onto making your own boards. I bet there are lots of sites on the web for soldering techniques and practice with stripboard first. If you have designed your PCB well though, then you should find soldering components to it a lot easier then to stripboard as I find that with my designs, it is much harder to short tracks with excess solder.

Above: Mixer board with components soldered in place viewed from below and above.

11) Test all connections to detect any solder defects (i.e. dry connections or shorts)

Good soldering should not suffer from these problems, but I do always suggest that you use a multimeter to test all your connections are correct.

12) Connect up and test circuit

TDA2003 amp Mixer

Finally, you may solder the connection wires to the board and test your circuit, if all is fine, congratulations. Otherwise you will need to go back, check your circuit designs, check your soldering and board construction and check whether all your components are in the right way. Good luck

Above: (left) TDA2003 amp (mono) circuit board, (right) Completed mixer circuit board.

REFERENCES:
1) How to Design and Make Your Own PCBs by R.A. Penfold (Babani Electronics Books) ISBN 0-85934-096-1
2) ESP: www.sound.au.com