Making own PCBs?

Jeremy Leach

Senior Member
Hi

This is a pretty general electronics question really, although I've definitely got PicAxes in mind.

I'm currently constructing my PicAxe projects on stripboard because this is what I've always been used to. However I know the results aren't as professional looking as an etched PCB (LOTs of wire !) plus overall board space is probably much greater.

So I'm considering a simple PCB etching kit. Not sure though how easy and cheap it really is to produce own PCBs. For instance I can imagine a good pillar drill is essential to drill out all the holes, plus drilling accurately for many holes could be tricky and time-consuming to say the least.

Or would I be better sticking to what I know (and it works !).

I'd be interested in what you think.
 

hippy

Technical Support
Staff member
Never tried etching, but I suspect you can use a normal "Dremmel" type drill to do the holes. To get neat 0.1" pitch holes, you can probably use a sheet of vero-board ( strip-board ) clamped in place, then drill the entire set in one go. You can drill them out to a larger size later if need be. Make the pads as large as possible so a little bit of error can be tolerated.

Can holes be drilled first, or would the etching eat under the copper where the holes are ?
 

Charliem

Senior Member
HI Jeremy Leach,
I have made quite a afew PCB at home and its not as bad as you might thing,Although it has its moments.You can do a search for "homemade PCBs" and you will get a lot of good info.The first thing you will need if you don't already have it is the Layout software.ExpressPCB has a Free program the you can download and use to draw the stencil.
 

Rickharris

Senior Member
HM PCBs are not difficult but it is worth using a CAD package to make a mask and UV sensitive PCB although it is a bit more costly.

Chemicals can be nasty, Ferric chloride stains everything so kitchen sink is out, There are none staining systems but they dont work as well IMHO.

Holes need to be 1 mmm or 1.5 mm in Dia, They are not too bad to drill with a standard dremmel or a cheap low voltage PCB drill available from several suppliers, Bettere yet lash out for a stand which makes the process more accurate and less of a pain.

A standard piller drill and a pin vice for the drill (1mm is not going to fit your standard chuck, ) would work. As the pad will have a hole in the middle you have something to aim for.
The chemicals also do not store forever so you may find they have to be replaced every time you wish to make a new PCB - cost is an issue. There are system which are a one off in a plastic bag that you may look at - more costly but in the long run not much more and a lot cleaner.

Personally I tend to:
Minimise the amount of copper I remove leaving large areas of coper if necessary.

Use wide tracks wherever I can - this makes the etching process less criical.

Use big pads to make soldering and drilling easier.


And finally, you can etch away the excess copper using a milling machine. This could make a good project and there is a lot of information on the web about making lightweight stepper motor based systems that read standard file formats such as HP and Gerber. Such an engraver/miller also has other applications beyond PCB manufacture.
 

bgrabowski

Senior Member
I have made hundreds of small PCBs at home even though I have access to an etch tank at the school I teach at!

My top tips are:
*Use PCB Wizard (it has Picaxe parts as standard) or similar software to design the artwork.

*Print out the mask with a laser printer on A4 tracing paper - much cheaper than OHP acetate and equally effective.

*Invest in a proper (ie safe) Ultra Violet exposure unit, preferably with a timer.

*Use "economy" photo etch PCB available from Rapid (pre-treated with photo resist, only needs half-strength developer).

*Use PCB developer code 34-0790 from Rapid - one bottle will last you years.

*Avoid Ferric Choloride etchant - use Press-n-Peel Sodium Persulphate based etchant. Two teaspoons of this dissolved in about a mugful of water at 40 to 50 degrees C will etch a 50mm x 75mm PBC in about 20 mins. This can be stored and reheated in a microwave to etch further PCBs. Mix a new batch when the etchant turns blue.

*Wear disposable polythene gloves and eye protection when using chemicals.

*Use a hand-held mini-drill to drill the pads but make sure it has a chuck not a collet to accommodate different drill bit diameters.
 

wardbob

Member
I have made dozens of boards. I use Eagle to lay it out. Yes, use large pads. I print the circuit out using an HP laser printer on glossy inkjet photo paper. (In the US, the best I have found is Staples photo basic gloss, item # 471861.) Clean the copper with a mild abrasive. Heat an electric iron to the 'cotton' or higher setting. Cut out the circuit to the size of the board. Put laser toner side down. Press iron down for about 3 - 3.5 minutes. Move it around occasionally. When time is up, you can throw it in water and let it soak for a while. Peel off the loose paper and briskly rub off the rest. You can use a stiff brush to clean off the remaining clay or whatever remains.
Once you get the touch, this works very well. No darkroom, no sensitized boards. I use ammonium persulphate to etch. It is clear and neat unlike ferric chloride. I use it until it works too slowly.
This method is harder with large boards since you need a heat press for them. Also, if you are using tiny traces, the detail is not as good as photographic methods.
I agree on the drilling advice, but I use carbide drills that have a wider base that will fit in most chucks. They are very fragile so hand drilling is out of the question, but they last for many holes.
Here's the guy I learned it from:
http://www.fullnet.com/u/tomg/gooteepc.htm
 

manuka

Senior Member
Picaxe PCB update: Some very nifty general purpose Picaxe-08(M) PCBs are apparently soon likely to be abounding, at prices akin to just bare copper clad board! These are much more usefully laid out than the classic 08 "Starter Pak" version, & suit final 08(M) deisgns -after you've tamed them on solderless breadboards of course!
I've a sample at hand already, but Technical may want to spill the beans on this development...
Stan
 

manuka

Senior Member
The very things! And seeing that SC issue is now out, I'll elaborate & mention schools may even apply for a FREE quota.
 
We use a proper UV set up here which is far superior to anything else for making prototypes or single board runs, but it can be costly to set up even if you make the exposure box yourself. It's not prohibitively costly, but costly if you rarely make PCBs.

The cheap alternative is good ol' ferric chloride and some iron-on 'toner sheets'. Toner sheets are still fairly new and although I've never used them I've heard you can achieve excellent results with some practice. The basic idea is you design the PCB with CAD and print it out onto a special sheet, you then iron on the PCB pattern from the special sheet which creates an etch resist pattern on the blank copper clad, then etch and clean it like you normally would.

More info: <A href='http://www.techniks.com/how_to.htm' Target=_Blank>External Web Link</a> (that company sells the sheets)

A tip for ferric chloride: as others have said it corrodes metal like crazy, including stainless steel, so etch outside away from the sink. Tip 2: gently heat the ferric chloride before and during use - sit the pot containing the ferric chloride inside a larger pot containing boiling water - it will etch faster (avoid breathing the steam).
 

ylp88

Senior Member
I find that you can use an inkjet printer to print PCB images onto a film of plastic. The film I usually use is a cut-up sheet from a clear display folder sheet protector! You have to print it in light greay to ensure that you don't have too much ink which will &quot;bleed&quot;. You will need a mirror image, of course!

As opposed to many other people who have posted, I do not use UV resist PCBs to make my boards. Using a permanent marker (I use Artline), you can draw out your tracks on the plain copper clad and then etch it using ammonium persulphate. Ammonium persulphate is easy to use and is realtively safe (in comparison to ferric chloride) - you just have to use hot water.

The only annoying thing about PCBs is drilling. Snapping drill bits is really annoying and bits tend to get a bit blunt after a while making you prees harder and thus increasing the liklihood of further snapping. I try and make small holes in my &quot;permanent marker resist&quot; to allow the etchant to make a samll hold in the pad so that I need not centre-punch the pad later.

ylp88
 

Jeremy Leach

Senior Member
Well, I've got a lot of info to go on here ! Thanks everyone for your tips. I think I may have a play with etching when I get the time - away from the sink ;-)
 

hax

New Member
Or you could be real lazy and use a dirt cheap PCB making service. But that would be cheating.

http://www.futurlec.com/PCBService.shtml
 
If you go for the foto resist way i've got two extra tips for you:

The amount if time the PCB has to be exposed varies depending on the quality of the transparent sheet, the power of the UV lamp and the brand and age of the PCB.

Use a small strip of PCB and a piece of carton between the film and the PCB leaving only 1 cm. of the PCB uncovered. put on the UV lamp for 30 seconds shift the piece of carton so 2 cm is exposed and repeat the process.

After this you get a PCB which is exposed in steps of 30 seconds. Develop the pcb and check which step gives you the best result. multiply this by 30 seconds and you got the correct exposure time.

I bought a little bottle of developer (20 gr.) which costed me 6 euro's. the developer is NaOh (Natrium - ??? ). It seems you can use caustic soda too, this is the stuff you find in sink-deblocker (sorry, don't know the english word for &quot;gootsteen-ontstopper&quot; hehehe). It wil cost you a few euro for a whole bottle which will last for years.

Good luck !
 

wardbob

Member
Dave_h,
We call it &quot;gootsteen-ontstopper&quot; too! (Joke.)
Yes, NaOH is Sodium (originally Natrium) Hydroxide, which is caustic soda or lye. Some of the fancy drain cleaners have other stuff in them, which you can and should remove. Some have little colored crystals and I don't know what that is. Probably NaOH with dye added to make it look super-special. Some have little chunks of alumin(i)um that help it to generate more heat and bubbles when added to water.
Be careful with mixing your own NaOH. Use glass or plastic containers. It does react nicely with Al and some other metals. Also, it generates quite a bit of heat on its own in water. Treat is as you would concentrated acid. Add it slowly to water, not water to it. The added water can boil and shoot back at you.
 

manuka

Senior Member
Just a plug for the SUN as a UV source!
It's some decades since I used this, but good old sol is rich in UV &amp; even ~30 secs exposure under a clear sky will be enough for PCB use.

Naturally you can't do this at night(!), but it saves the cost of a UV lamp, &amp; can be very productive if a large group are otherwise waiting around for their turn on the UV box.
Stan

 
Just bought a bottle of caustic soda at a DIY shop today, the label say's it natriumhydroxide and contains no other chemicals. I paid 2 euro's for half a kilo. going to try it tomorow.

One thing i forgot to mention is that you have to clean the pcb with some degreaser or else you're getting problems soldering on it (the pcb still contains the foto sensitive layer after it's etched).

Protect your pcb with some print spray (Kontakt SK10 flux or something simular). this will protect your print from coroding and helps you make good solder points.
 

ANJ

Senior Member
I second Stans idea of use the sun.
I use presensitized PCB ( Kinsten brand ), as i can get them locally
http://kalex.net.au/display/text/1098426142937-5357/parentContent/1098424907968-1192/
they are as cheap as std PCB material and they are very flexible in use.
No messy iron ons etc, just a pattern on film or tracing paper, the sun and some draino.

I also print out my trace double size, using a cheap bubblejet printer, then use a good quality photocopier to reduce it down to 50% size on film.
This allows me to use cheap means to create the pattern, and it is reusable.
I can also easily write on the pattern manually ( at 2x ) to denote components etc, and when shrunk, this stays legible and etches most of the time.
Andrew
 

Charliem

Senior Member
seeing how we are discussing Making pcbs I have a question.Is it better to use the iron on method or the UV light method for transfering the layout to the copper board?I use the iron on method and With larger boards My success rate is not so good.Thanks for any replys.

Edited by - charliem on 4/28/2005 9:31:17 AM
 

ylp88

Senior Member
Worth noting is that some photo-resists are designed to NOT be removed after etching as they are &quot;solder-throughable&quot; and save you having to spray the PCB in protective laquer afterwards.

ylp88
 
Charliem, the UV method is far superior to the iron-on method. It's a little bit fiddlier to set up, but once you get your process sorted out you're pretty much guaranteed results every time.

Someone else mentioned Kinston board, that stuff is amazing. It's absolutly bulletproof and it's very understanding about mistakes like leaving it out of it's packet in the sun for a minute or two ;) If you can get your hands on some of that, it's well worth it.
 

pittuck

Senior Member
www.sparkfun.com

$5 per square inch first order, $2.5 after. UK delivary of PCB is $7. U get doubled sided, silk screens etc. etc.

Just make sure to check boards using the DRC rules / online tools (currently in BEAT, but isa working on em)
 
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