There are many methods of making a printed circuit board and over the years I’ve tried most of them. Each of them has the advantages and their disadvantages, some are simple and some are complex. Hopefully this how to make a printed circuit board step by step guide will show you all you need to know.
A PCB is basically just a copper pattern on a fibre glass or SRBP board. It’s all about how you get the copper pattern there in the first place and how complex and accurate you are. The most basic method is to just use etch resist ink and manually draw the circuit and then use etchant to end up with your board.
In terms of complexity you can now end up with a multi layered board with a solder resist mask and screen printed. I’ve tried many of the methods over the years and I’ll attempt to pass on what I’ve learned, the good and the bad.
A single sided PCB is by far the easiest one to manufacture and if your starting out I would highly recommend you make a single sided board first. A single sided board means that there is copper on one side of the board, the bottom, and the components are on the other. A two sided or layered board has copper tracks on the top component side as well, it makes a complicated layout easier in a smaller space but manufacturing them at home is harder as you have to get the two layers to line up and then decide how you will accommodate through plated holes. These are the joins between the two layers.
The easiest board to start with - the single sided board.
First you need to start with a piece of blank copper clad board. This is commonly available from electronic hobbyist suppliers. There are two common types of bare board that you can buy. One is made of fibreglass and the other of SRBP which stands for synthetically resin bonded paper. Fibre glass is more commonly available and is more robust, you can slightly see through it, I think the correct term is translucent. This can help when it comes to fault finding. It is usually more expensive than SRBP and blunts drills fairly quickly. I have some SRBP board which has slightly warped over time maybe due to moisture I’m not really sure. Is not the end of the world and I’ll still be able to use it but for some applications it could cause a problem. Both types of board are usually perfectly fine for most applications but it’s worth knowing the differences.
A sheet of copper clad board.
There are quite a few variations in board thickness but by far the most common is 1.6mm. I’ve never had cause to deviate from this and because it’s the most commonly available it’s usually the cheapest.
The thickness of the copper on a board is also something that is quoted. The most common thickness of copper is 1 oz and that means that for a board the size of a square foot, the copper would weigh 1 oz. It actually works out to be 1.37 thousands of an inch. A thousandth of an inch is also known as a mil, so 1.37 mils = 0.00137 inch. In mm it works out to be 0.0347mm so it’s pretty thin.
You will then need to cut it to size. There are various ways of cutting PCB, s and everyone seems to have their favourite way, which they will tell you is the best. My way is the best though obviously. Depending on how often you need to cut board will also make a difference to what you use and how you do it. If you only need to cut it once in a blue moon you can probably make do with tools you have lying around. When I was working at Leicester University we cut board all the time and we used to have a dedicated guillotine just for the job. That was the best way to cut board. It was quick, as accurate as your measurement was and because of the side edges you got a perfect cut at ninety digress every time. Not everyone can afford a dedicated PCB guillotine though.
You can use a steel ruler and score a line with a craft knife and then snap it against a flat edge. One of the problems with this though is you have to cut completely along the board and you can’t cut a little bit off a corner for instance.
One of the most popular methods is to use a hand saw. You need something with very fine teeth to do a decent job. Most people have got a hacksaw of some kind and they work pretty well for smallish boards. You can then tidy them up with a file, again something most people will have in there toolkit.
My favoured method is to use an electric tile cutter. I have written an article about using one to cut board here if you want to give it a try.
Once you have your board cut to size you will need to have the copper side extremely clean for two reasons. First if you are going to apply anything to the copper which you will do in most of these techniques, stuff will stick better to the copper giving you better results. Any photo resits or ink will apply better and bare clean copper will also etch better. Any dirty patches or contaminated bits may not completely etch giving you track bridges and all sorts of problems. Believe me your much better off with a clean and shiny copper surface.
On the left is a cleaned copper clad board, on the right is a board that has been cleaned and had a PCB design ironed on from a sheet of magazine paper. You can see how being exposed to the air for a few days before etching has oxidised the board.
How do we obtain this cleanliness? Again there are a few methods depending on how frequently you’re going to do it. At the university we used a fine pumice powder and a scrubbing brush in the sink with some water. Scrubbing until the boards copper was shiny and, well, copper coloured. Once clean it went vertically into a heater to quickly dry it. If you use anything like this method where the board gets wet you need something to quickly dry it because if you leave it to the air it will quickly start to oxidise and all different colours will start to appear in patches on the copper which is no good.
Other methods I’ve used or seen others do are to use a dry abrasive paper, a sanding block or steel wool. Whatever you use make sure that it’s a fine abrasive as you only want to clean the copper surface not sand it away. It’s not as thick as you might think. Also anything to abrasive will leave scratches, not something that you want. You just want to end up with smooth bare copper.
The method I use is to apply a sprinkling of Vim, the powder cleaner and use a small brush or cloth to clean the board. The liquid versions of this abrasive cleaner also work well.
If you have a very simple printed circuit board layout or if you are a beginner and have never made your own PCB the simplest way to start is to use transfers and draw the layout yourself directly on to the bare circuit board.
I’m assuming that you have a PCB design that you are ready to put on to a board, either from a magazine or your own finished design. Actually designing a PCB is an article all on its own which is why I’ve written an article all on its own here.
Let’s take a look at an actual design and how we could go about producing a PCB.
The picture above shows a very simple board design.
So starting with a cut to size and cleaned bare copper board and a designed layout, the simplest method is to manually draw the circuit directly onto the copper side of the board. If you have a designed layout make sure that you have the correct side of the layout. If it’s a picture or a copy the last thing you want to do is to make a perfect PCB only to realise when you come to populate it with components that you’ve made a useless mirror image of what you needed. We’ve all done it at some point but that never ceased to make it hilarious when a student showed us what they’d done and enquired if there was anything that could be done to salvage it.
So once you’re sure your copying the right picture the right way round take a look at the various things on the layout design. The starting point for me when I used this method was to look for the integrated circuits or IC’s. These need the pins in exactly the right places. Fortunately you can get rub on transfers of dual in line circuits so you can easily make up any size you need. If you’ve never used these transfers before they are simply to use, follow the manufactures instructions but they usually just tell you to apply a fair amount of pressure and not to move the transfer as you’re doing it.
The PCB rub down transfers above are available from Rapid Electronics.
The transfers are excellent for making simply layouts. You can also use them for component pads as well. I used to use Edding transfers and my local stationers even had PCB layout transfers along with their letters and numbers ones, so they were readily available.
Once you’ve got your pads in place you can link then up by drawing the tracks in. The simplest way is to use one of the dedicated PCB pens available from the electronics hobbyist suppliers.
Incidentally once when I made a board using different method, which ill mention later, some bits were missing and I hadn’t got a pen. I’d just been doing some painting in the house and I’d left the tin of white emulsion and I wondered if that would work as etch resist. It was water based emulsion and didn’t take long to dry. I tried it and it worked. It stopped the etchant eating away the track. I’m not sure which paints work and which don’t it’s just an idea if your pens dry.
Using this method you can easily create boards like the one below.
The major problem with making a PCB this way though is it’s only possible for simple layouts. You’re not going to be able to make complex boards. Copying designs is difficult and prone to errors and it’s also difficult to make the same board again. Using a photographic method not only means you can make more complex boards but you can reuse the artwork to make another copy of the PCB. You can also use this method for reproducing circuit designs from magazines and articles on the internet.
The photographic method was actually the first method I learnt at Leicester University as a trainee technician. You take your finished design and then produce artwork on a transparency. The artwork consists of black image where your tracks and pads and stuff are and clear transparent film where there not, so anywhere you want copper needs to be black and anywhere you want etching need to be clear. You then take a cleaned copper clad board and dip it in a photo resist solution. This is to make sure you get a complete and even coverage. It is then put in a heater to dry. The transparency was then placed onto the boards copper side, which had a covering of the photo resist chemical. It was then placed in a machine that basically held the transparency flat and firmly down against the board by means of a vacuum then exposed the board to ultra violet light for a timed period.
You then ended up with a board that had been exposed to UV light but the parts of the transparency that were black i.e. the pads and tracks that you wanted to remain as copper had been shielded from the UV by the transparency.
It was then a case of using a developing solution by putting the board in a tray and agitating it until the image started to appear on the board. You then continued this until the parts exposed to the UV light became a clear copper colour. This was a question of timing and experience because if the board was underdeveloped it would be difficult to etch and not all the copper would get removed from the right places. If the board was over developed some of the bits you wanted would get etched away.
There were ways to help such as washing all the developer of the board and just rubbing a bit on the stubborn bits to fully develop areas and scratching bits off to expose copper if there were obvious bridges but generally this method worked pretty well.
The advantages of this system were that the artwork could be used again and again to make multiple printed circuit boards. You could also modify the artwork if it was made using dots and tapes which could be lifted with a craft knife. It was also pretty repeatable with the same chemicals.
The disadvantage was the extra chemicals and equipment that were required. Also the processes after completion of the artwork had to be done in a darkroom environment as obviously exposure to daylight would render the work useless. I say obviously but it clearly wasn’t obvious to all of the students as every term you would get at least one who would bring the board out of the darkroom before it was developed to ask if it was going ok. Yes up until the point you brought it out into the daylight!
Depending upon how serious you are about making PCB’s this is probably the most professional and costly in terms of equipment and chemicals required. I have heard of people using this basic method and managing to short cut some of the stages.
You can use a normal copper clad board and spray it with positive photoresist spray. You can also get pre sensitised boards which have a plastic peel off when you’re ready to expose them. You can place your transparency on the board and then expose it to preferable bright sunlight. Thus bypassing the exposure machine. Obviously you need to experiment with the timings and such but it is possible. You have to be careful that your transparency is perfectly flat though otherwise light will get under even if it’s slightly raised. I know of people who have made their own cheap versions of the machine we used by basically building some UV tubes into a box and having a sheet of glass to hold the artwork against the board. This adds consistence to the exposure procedure part as the box when closed is light proof so the UV light generated won’t be affected by daylight.
Once you’ve sorted out the timing it should be easily repeatable and the glass holding the artwork stops it moving and stops light getting under it. You still have to make sure that no daylight gets into the process until it is developed so a dark room is nice but failing that, working in a darkened room at night will do the job with a lamp with one of those red non UV producing bulbs. With a bit of ingenuity it’s possible to go the photographic route and not have to spend too much.
Once developed its ok to expose the board to daylight. It’s then just a case of etching the board and then cleaning off the photo resist to reveal your hopefully perfectly reproduced copper image.
This is a cheap and pretty reliable way of producing PCB’s. You need a laser printer though as it won’t work with any other type. It’s all to do with the way a laser printer works in fusing the ink on to the paper.
First you need to get your PCB design and get it as a mirror image. If you are using a PCB design package this is easy as its available as an option when you come to do a print out. You will probably have to calibrate your print outs as well. There are usually options for this as you need the print out to be exactly actual size or things like dual in line packages won’t fit. Next set your printer to print in its darkest mode. You can usually find this option somewhere in your settings depending on which printer you have.
Once you have got your printer sorted you need to sort out your paper. You are again going to have to do some experimenting to find out what works best.
I find that using old magazines worked best, seriously that’s the paper you’re looking for. The thin glossy magazine paper. It doesn’t matter that it’s already printed on because that’s a different type of ink to what we are going to be using. We are using toner that melts with heat.
Take a sheet of the magazine paper and print out your PC design as a mirror image on its darkest blackest setting. Some of this type of paper is really thin and you may have a problem getting it to feed. On my laser printer there is an option to open the front and manually feed a single sheet. This is the best way I’ve found of printing on to this thin magazine paper. I have heard of other people without this manual feed option that have success by taping the magazine paper onto a normal A4 sheet of paper and then separating it after it’s printed.
Once you’ve got your mirror image print out you need to get your cleaned copper clad board and tape the edge of the print out to the edge of the board. This is to stop it moving but also so you can flip it up to see what’s happening. Obviously the printout side needs to be facing the copper.
Then you need an iron. Not a soldering iron, a clothes iron. Don’t use the steam setting if it has one. You just need a hot flat dry iron. Set it to its hottest temperature and on a flat surface with the board facing down and the paper on top. Apply an even pressure to the paper for several minutes taking care not to touch the board.
What you are doing is melting the toner from the magazine print out onto the copper. After a few minutes you can lift the paper and see what’s happening. Hopefully you will have transferred your printout onto the copper. You may find that the paper has totally stuck to the copper, don’t worry some types of paper do, it will still hopefully have melted the toner onto the board you just have to remove the paper by soaking it in a bowl of water and gently rubbing the paper away. It will disintegrate leaving the toner on the board.
This transferring stage will probably need a bit of experimenting with to get right along with the ironing. The good thing is that if you mess it up you can just clean the board and try it again with another print out. You will need to experiment to find the best paper and the correct ironing pressure but it’s possible to produce some really good PCB’s for hardly any out lay.
Once etched you’ll need to use acetone to remove the toner.
The picture above shows a finished single sided PCB made using the laser transfer method.
There are many types of PCB transfer paper being produced now for exactly this process although at this time I’ve not tried any as the magazine paper is working fine for me. I’d like to think that you could get even better results using this and I’m sure I’ll get round to giving it a go at some stage.
One that I’ve been looking at is the “Fab in a box”. They do mention using a laminator and then using another layer to seal the image before etching so it seems a more complex process. Once I've tried it I'll do an article about it.
I’ve etched boards in pretty much the same way for years, never really questioning the technique. While working at the university we used to have a bubble etching tank. The etchant (I can’t remember what the etchant was but it was green and pretty unpleasant) went in the tank and a pump blew air out of tiny holes in the pipes inside the tank to produce bubbles in the heated etchant. The heating and the bubbling speeded up the process.
At home I used ferric chloride in a tray and rocked it while observing the etching process, known as the agitation method. I’m sure loads of people do it the same way or use similar techniques integrating both methods. However I’ve recently stumbled across a different technique claiming to etch better, quicker and more cheaply. I’ve tried it and guess what its great and I’ll never use the agitation method again.
The full article is here on the website of a company selling PCB toner transfer paper. You need a surface to do the etching. I use a piece of chipboard on top of my work area. You also need rubber or throw away latex gloves and a thin sponge and a bottle of ferric chloride.
You just pour a little amount of ferric chloride onto the sponge and wipe the board to be etched. I found it easier to put the ferric chloride into a saucer and dab the sponge into it.
You’ll find the board etches really quickly compared to the submersion and agitation method. Not only is it quicker but it’s more controllable. The problem with traditional etching is that once the etchant starts etching, the etchant on the copper slows down as it becomes saturated with copper. Agitating moves it but it only moves it around the board. It’s better than not moving it but it’s only a compromise and agitating means the edges of the board get done quicker than the middle, leading to over etching at the edges and a barely touched board in the middle.
Shown above is ferric chloride in solid form - you can also buy it as a liquid.
Using the “contact etch” technique you can see areas etch evenly. The lesser contact time also means less undercutting. This is where the etchant eats into the side of the copper under the resist which sits on top of it. You’ll also use less etchant with this method. The problem I had before was that I ended up with ferric chloride getting weaker and weaker each time I used it. This way you just use what’s on the sponge so it only gets used once.
You are best using a thin sponge and don’t rub too vigorously. Once you’ve etched a board using the contact etch method you won’t go back to using the traditional methods. The first time I read about it I wanted to make a board just to try it.
A PCB produced by contact etching with a sponge.
As you can see from the above picture, you can etch the areas you want and not the whole board. You can see there were large ares of copper above and below the required area. With contact etching you just leave them as they are going to be trimmed anyway. Once an area has etched you can see it and leave it alone to concentrate on the unetched areas.
You can see the basic equipment that you need, sponge, etchant, gloves and something to protect the table!
You’ve got the copper pattern on you board and now comes the drilling process. I’ve tried a few different methods of drilling a PCB. Once again there are advantages and disadvantages and lots of people swear by their techniques so I’ll try and explain why some are better and the reason I like them. Hopefully this will guide you if you are unsure.
The first way I drilled PCB’s in my naivety was with a little hand held drill and some thin steel bits that came with it from a hobbyist supplier. It was little more than a motor holding a drill bit but never the less it drilled holes in the board, which is what I wanted and I was fairly happy at the time. I had just one drill bit and drilled the whole board with it. What I didn’t realise at the time was this wasn’t the best thing to do.
My first PCB drill (like my first pony).
I also found that the drilling perhaps wasn’t as easy as it should have been. The drills didn’t seem to want to go through the boards quite as easily as there should. I also broke quite a few as hand holding the drill leads to too much flexing and broken drills. Once I got more experience I realised that although it did the job steel drill bits were quite poor at drilling fibreglass which is the main material for PCB’s.
You can get drill bits that are specifically manufactured for drilling circuit boards. They don’t blunt as quickly and do a better job but the problem is they are more susceptible to break with any flexing. At the university we had a proper PCB drill. It was a high speed drill and the higher the speed the less pressure you need. Being better quality throughout I realised it didn’t vibrate the drill bit like mine did. It was very stable when it rotated.
It was also stand mounted and as the board was on a flat surface the drill holes were also exactly at 180 degrees. Drilling with it was a joy to be honest, I was also introduced to the idea of drilling smaller holes for some components, like dual in line circuits and small resistors and capacitors. This in turn made soldering them in better as there was less “hole” around the component. Back then it was .8mm for IC’s and 1mm for other components.
While at the university we also used a foot operated PCB drill. It worked the opposite way around to most drills I had seen. It was mounted in a box with a lift up lid that became the surface that the board went on and boards were drilled from the bottom with the drill coming up through the board.
The drill had a lens and a cross hair like on a gun sight. You held the PCB with both hands and moved it around the flat surface then you lined up the board with the lens and then pressed a peddle and up came the drill through the board drilling a hole where the lens was. Being able to use two hands to position and hold the board meant that with a bit of practice you could get pretty quick at drilling.
If you just want to experiment in making a PCB a hand held drill means you will be able to do the job but if your serious and want to make your own boards you’ll probably want something a bit more robust and stand mounted.
You can use various methods of producing a screen overlay. You don’t have to have an overlay but it does make assembling the finished PCB easier. There are companies that supply heat transfer paper that you use in pretty much the same way as the method used to make the copper side of the board. You can get them in black or white but I haven’t tried them. It’s the added expense and lining it up in the right place. I simply print the component overlay out on a piece of ordinary paper. I uses the same program that designs the layout so the print outs are calibrated in the same way as the printout for the layout of the board.
A printed out component overlay.
It’s easy to line up by cutting it out and then inserting a component in one corner of the board through the paper layout and through the drilled holes and then doing the same at the opposite corner. I then lift the paper away and put some glue stick on the PCB and then put the paper and components back over it again and let the glue dry, it only takes a few minutes. Yes I agree it’s a bit amateurish but it certainly helps to see where the components go.
If I wanted to make it more professional I would get the whole board manufactured by a company. This is just for cheap and cheerful when I need a board when I want to test something out quickly.
You can still make a PCB even if you don’t want to go to the trouble of manufacturing it yourself. There are companies that will manufacture PCB’s to your design. You may even design a PCB that is too complex for you to produce with the techniques you use at home. You can get something made that is multilayer, not a lot of people have that capability at home.
If you are going down this route you will have to give the manufactures the design. As they are used to making PCB’s from standard types of files you are going to have to go along with it and provide your design to those standards.
To produce a design you’ll have to use a PCB design package. There are several around including some excellent free ones. You need to make sure that the one you settle for will produce files in the format that is required, most of them will do that but just make sure you’re not using one that won’t.
The one I use is the excellent and free DesignSpark. A PCB manufacture will require your printed circuit design to follow certain requirements, such as the minimum thickness track size you can use and the minimum distance you can have between tracks and pads. Drill sizes may also be specified.
To help you many manufactures will supply you with a DRC or design rule check. You can load this into your chosen PCB design package. It will then check to see that your design complies with their manufacturing specifications and capabilities.
It may seem complex at first but once you get used to it you’ll know how to easily stay within manufacturing limits and you’ll find all you design will sail through the DRC check.
If your design passes you will still need to output in in a form that manufactures will be able to use. That format is Gerber and it’s also referred to as RS_274X.
As well as the copper track pattern on the board you can also produce a solder mask and a screen print for the component side. Your design package will probably give you the option to produces these automatically. It should also be able to produce an Excellon format drilling file. It’s all basically a case of exporting the correct files into a folder.
Once you have all your files in the Gerber format you can take a look at what they will look like to the board manufacturer by using a Gerber viewer. There are various free programs that you can download and also an online viewer. You can just reassure yourself that you have not done anything silly before you send them.
There are various manufacturers online so it’s just a question of looking for something that suits you and giving it a try. There are lots of good reports about a company called SeedStudio. They are based in china so you have to wait a couple of weeks but looking at the prices they charge this does seem to be quite reasonable and I’m going to give them a try for my next PCB’s.