DIY Prototype Printed Circuit Board (PCB) Manufacture

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Introduction: DIY Prototype Printed Circuit Board (PCB) Manufacture

I have built a number of projects that required PCBs to work as well as they do, I produced a number of boards for my Ultimaker 3D Printer project and I thought I would document the process of making PCBs from scratch! For the prototype stage I manufactured the boards myself as it would have been too costly to send the board designs to be professionally manufactured on a one off basis. I produced the boards myself using these basic techniques and was able to save a substantial cost whilst ending up with a good end result.

Step 1: Circuit Board CAD Design

The first stage of manufacture was to design the board layout using a CAD package. I chose to use Eagle CAD which has a free version that was appropriate for my needs and is very popular within the maker community, I also have used it in the past so was pretty fluent in its operation and feature set. I created schematics of the basic circuit which I then routed into a board file.

Step 2: Board Layout

The next stage of the design process was to convert the circuit diagrams to a board layout that could be transferred to copper clad fibreglass circuit board. The software allowed me to see which pins needed to be connected to each part, this made it easier to ensure the correct electrical connections were being made. I always try to make board single sided to enable a simplified manufacture workflow, however because the switches were on the top of the board and the Arduino was on the bottom I needed to solder on both sides. I could have used SMD tact switches but I already had a load of through hole ones I wanted to use.

Step 3: Stencil Printing

After the computer design stage the Pads, Vias and Top layers were exported from Eagle for single sided boards and an extra Bottom layer for the double sided boards. The artwork was then mirrored and printed on to clear acetate sheet; I printed two copy’s so 2 sheets could be layered on top to eliminate and light leaks that could happen because of uneven toner coverage.

I got the acetate sheet from WHSmiths in the UK, you can buy it online too.

Step 4: UV Exposure

I then cut the photo sensitive copper clad board to a size just larger than the acetate artwork which was then affixed to the photoresist side of the board with tape after removing the black protective film the circuit board. It was important to do this in a darkened room to prevent unwanted exposure. The board was then placed in the UV exposure unit for about 15 minutes to sensitise the area where there were no traces or pads.

Step 5: Developing

After being exposed, the boards needed to be developed, this is done using a strong alkaline solution such as 1% diluted sodium hydroxide. However I had better success using a Seno developer which I bought in an applicator bottle similar to a shoe polish container with a sponge pad on the end. This made it much easier to develop areas of the board in a more localised way as I found using the sodium hydroxide solution created uneven results.

Step 6: Etching

After successfully developing the boards the traces and pads turned a green colour which could then be used as an etch resist. Green parts would stay copper and anything not green would be etched away, leaving just the fibreglass board remaining. The etching process is fairly easy but involves some hazardous chemicals and needs to be handled carefully. I used Clear PCB Etchant from Mega Electronics which is a relatively safe etchant but takes a little longer than Ferric Chloride which is the traditional choice and is stronger. However the clear is much less toxic and does not stain clothing. It comes in a powder which requires mixing with hot water to make a solution for etching PC boards. Once a solution is made up, the board can be submerged and the etchant will start removing the copper in the un-masked parts of the board. A small PCB usually takes about 30 minutes for the etchant to fully remove the unwanted copper, I found rubbing the board using an old toothbrush helped to speed the process up.

Step 7: Special Treatments

The last stage was to finish the board by removing the etch resist with isopropanol alcohol or nail polish remover, this then exposes the shiny copper which can be soldered to straight away or finished with a solder mask. I bought a tube of green UV curable solder mask online relatively cheaply. This requires a similar process to the photo etch method to apply the mask to the board. Another product that could be used was Liquid Tin which coats the copper traces and pads with a very thin layer of tin which helps with the soldering process and stops the coper oxidising.

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22 Comments

Hello,

Nice project - Ferric gets a bad press, but it is very effective as an etchant. It all comes down to proper handling and a good understanding of what you are working with. Any iron compound is going to stain and is a sod to get off - oxalic acid does work, or EDTA. The free hydrochloric acid (after hydrolysis) is doing the etching and dry Ferric Chloride is a safer way to provide the acid than mixing or using neat HCl solution.

Years ago I used to produce prototype PCB's using EasiPC software on an IBM XT. This churned out a Gerber file which was sent to a Versatronics robot arm. This was a neat bit of kit at a relatively low cost which used a drafting pen (Staedtler) and India ink (waterproof) to draw the tracks directly onto the copper. The pen was swapped for a mini-drill with TCT drill bits to do the holes - double-sided was just as easy. The board went into aerated ferric which took off all the copper except the inked tracks. The results were flawless, very professional PCB's. The final stage which really makes life easy for soldering, was a dip in a tin-plating solution.

With so many X-Y tables around, it would be relatively easy to draw the tracks - just like an X-Y plotter (I used a Roland A3). The drill just went through FR4 boards under it's own weight, so no third axis needed - the pens operated the same.

It was quicker to do these than mess about with wire-wrap or other prototyping methods

Hi Phil thanks for your comment, some great info there. I have a Shapeoko 2 CNC router that I've been wanting to use for drawing the tracks onto FR4, I'm sure once setup its a really quick way to prototype. If you have anymore info about that I would be really interested to lean more. Cheers, Jack

Hello Jack
Not really much more I can add, but the inking technique really did work well. These were low volume boards, mainly eurocards, but going into an industrial environment, they need to be reasonably professional.
The Versatronics robot was just a two link arm on a vertical spindle with facility for either the Staedtler Mars 707 drawing pen or a mini-drill to take 1/8" tungsten carbide drills - all this could be done on an X-Y machine - the ink was Staedtler Mars 747 TL, basically a standard India ink for drawing on drafting film. The pen also had a weighted carrier to make sure it was in good contact with the board. Any touching up (rare) was easily done. Nothing seemed to affect the dried ink.
Ink was laid down first, then the drilling.
Standard Ferric etching followed by a tin plating dip - otherwise protect your fresh copper after ink removal (glass fibre pen or meths) with a spray flux.
I used to use reconditioned carbide drills and a random selection of drills, burrs and milling bits was quite cheap.
Some of the finest drills were amazing and hardly ever broke in use.
The only other thing to add was about the via's - I used via pins from Vero which came as a long "wire" of pins that you simply pushed into the via hole and snapped off - any wire or component will do as well.
Even a basic PCB beats the other methods hands down, though I still rate wire-wrapping for complex layouts like multi segment displays and drivers at the prototype stage.
Good luck, Phil

Ref disposal of depleted etchant solutions.

It doesn't matter how the elemental copper is removed/etched, you are still faced with the disposal problem. If you are a law-abiding individual, you will consult your local authorities (liquid and solid waste authorities, usually landfill or sewage works operators). You could elect to go to a licenced waste disposal who will relieve you of a lot of money. I wonder how some of the very cheap Chinese PCB producers do it?

Copper ultimately comes from the ground, as an insoluble ore, usually an oxide or carbonate. Taking the ferric example, the kindest and safest way to dispose, is first neutralise with common soda (sodium carbonate), adding slowly while the residual acid and carbonate react. A cloudy suspension of copper carbonate will form - at this stage, the copper is effectively bound up (the most toxic form of copper is when it is present as a soluble salt such as chloride, cuprammonium sulphate, nitrate).

At this stage, you could bottle it up, let it settle and pour off the supernatent liquid either on some waste ground or with plenty of dilution to the household drain (shock, horror, but in reality, insignificant). If you are blessed with a warm climate, you could let the solids dry out then dispose of the solid in the household waste.

Another more complex route is to use Ethylene Diamine Tetraacetic Acid (EDTA or Versene) which chelates or binds the copper - this is how lead is removed from the body in poisoning cases.

Copper is not in the same league as mercury, cadmium (batteries) or beryllium (heat sinks). It is an essential element (blood of crustaceans) and has been legitimately used in horticulture (Bordeaux mixture) for years. My argument is that this is the closest to returning copper to the environment in it's native form. Ultimately, this is what the licenced operators do.

From a moralistic point of view, how does anyone justify sending huge quantities of electronic waste to China or Bangladesh? Out of sight out of mind.

Hope this helps

Further to your post Phill I've just found this neutraliser for ferric chloride from Maplins. http://www.maplin.co.uk/p/pcb-etchant-neutraliser-...

Looks like you just mix the ferric chloride and it turns into a 'cake' that you just dispose of in your household rubbish. Along with the tinned pasta this is turning into a very food themed instructable!

How the chinese do stuff, well, they don't, they appear to have no regard for enviromental stuff, even the living breathing kind too, one my ex bosses, went out to china to install a exhibition stand,, Behjing I htink, about the time of the olympics, aka the Birds Nest, he seen a person hit by a car, ..... the driver just got out the car, moved the person to the pavement, and carried on with their journey..............................

Could you please post the links for the items used:

PCB?
Developer?
Etching?

Not sure how you calculate the good timing for expose on UV, do you need to wait until you see some trace on the film?
what about developing? You said when the traces get green, so just leave in the solution until you see green traces? Do you shake the board or leave it there?

Thanks :)

Hi, I got the sensitised PCB from my high school a number of years ago. I have about 50 a3 sheets of that stuff so would be willing to send some out for a small cost. The sodium hydroxide can be bought from your local hardware store, usually sold as lye drain cleaner. The etchant can be bought from an electronic store or online. If your in the UK Maplins sell it.

The UV timing really depends on how your exposing the board. It really does take some experimenting to get just right, just keep checking until you see it change colour.

Developing also depends on how concentrated your developer solution is. You will want to agitate the board gently so you can see when its done.

Good luck with your boards! Cheers, Jack

Why is so much copper removed from boards? Would not leaving large isolated pads be okay to do?

It sure would reduce copper that has to be disposed of.

Granted at the EOL of the board, the disposal of the copper will still need to be reckoned with.

Nice ible!

Yes having ground planes or larger isolations on the board is fine. I just chose to leave the traces for no good reason except that I was drilling large holes in the board. It mainly reduces the time the board has to be left in the etchant for, which speeds up the process a bit. Cheers, Jack