PCB Transfer methods

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thebeardedone
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PCB Transfer methods

Post by thebeardedone »

What methods do you use for PCB transfer?

I have never done DIY PCBs before (although I have thought about it a lot but never got around to buying the materials). Well, now I have everything I need to start so I am looking for some advice on the transfer methods I should try.

I have purchase a sharpie pen and I am going to try that first. I have also heard of some people using a blender pen by printing the circuit onto coated paper and rubbing the blender pen over the back of it on the CC Board. Then the final method is Toner Transfer.

Unfortunately, I don't have a laser printer but I believe that I will be able to pick one up easily enough if this is going to be the best method.

Any advice to be given?

Regards,
Sam
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BeligerAnt
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Post by BeligerAnt »

(Sorry for the late reply, I must have missed this post at the time)
I have used just about everything available on the amateur and professional markets :o

For DIY boards:

The rub-down transfers and tape that Maplins (used to?) do work but are tedious and error-prone. Only for small boards.

Drawing the tracks with a Sharpie (or similar marker pen) is even more difficult than the tape & transfers. Most important thing is to get a really good thick layer of ink down, otherwise the tracks start to etch away and you end up with a load of open-circuits to fix on the board before you even start building. Only recommended for really simple quick & dirty boards. Probably better off using "ugly", "dead bug" or "Manhatten" construction.

Masking the whole board with spray lacquer or paint, then scratching off the paint where you DON'T want any copper works really well, and can provide you with "maximum copper" which can be useful sometimes. The big problem is that you have to mark out a negative circuit, which can be a bit hard on the brain.

Not heard of the blender pen method before - not too sure how that one works.

Photomasks and light-sensitive copper-clad board. I haven't actually tried this one, but I think it's the method Peter Waller uses. Print the track pattern onto OHP film (a laser printer is much better than ink-jet) then expose the board in a UV light box. The disadvantage is that you need a UV light box and some developer for the photo-resist.

Toner transfer works really well, I think it is as good as light-sensitive board without the need for extra equipment and special board. If you don't have a laser printer, a photocopier works just as well, just check that it is producing clean copies before you start.

I have used toner transfer to produce quite complex boards with fairly fine pitch SMT components. Certainly standard SOICs and 0805 passives are no problem.

All of the boards for my minisumo robot were produced using toner transfer, and I think they all came out OK first time. (Doesn't mean the design was right first time though!)

Top tip: Use double-sided copper-clad board. Design the circuit on one side and use the other side for 0V, then you don't have to worry about routing the 0V track (just stick in a via hole). Mask the 0V side using spray paint. Use tinned copper wire or old component leads to link through the via holes (remember to solder both sides!)

Hope this helps.
Gary, Team BeligerAnt
thebeardedone
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Post by thebeardedone »

Thank you, Gary.

I can see that the toner method is probably the way forward. I still haven't had the chance to try any other method yet, so this is my order of experimenting:
1) Plain ol' sharpie
2) Blender method (similar to the toner transfer actually)
3) Toner Transfer

I know the stuff you are talking about from Maplin (Press-n-Peel but I have heard that you get poor results from this.

I was wondering how to properly implement a ground plane though. Is it totally necessary? I have been doing many searches on google but I can't find any really good information on it.

Regards,
Sam
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Post by peterwaller »

I use an old PCB package call Protel 98 (as in 1998). It enables me to put in the circuit diagram see below Radio Link controller board:
http://i109.photobucket.com/albums/n66/ ... ircuit.jpg
I then generate a net list which holds all the component pad layouts and interconnection information. From that you produce a layout as below, red is top layer, blue is bottom layer and grey is both layers:
http://i109.photobucket.com/albums/n66/ ... layout.jpg
I manually layout the components and tracks but the system does check all the connections are made and minimum clearance and track widths are maintained.
I then print out the two layers on a transparency material and stick the two sides together on three edges making sure all the holes are aligned.
I then Place the photo resist board between the transparency sides and expose it to UV light. The board is then developed in caustic soda solution until all the copper to be removed is exposed.
I then etch the board in ferric chloride.
It is then just a matter of drilling the holes and fitting small hollow rivits where a through board connection is reqired.
http://i109.photobucket.com/albums/n66/ ... /rivet.jpg
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Post by slurp »

I keep the marker pen for fixing toner transfer blips and the simplest of PCBs.

Recently I gave up with the laser printer at work. It was chewing and crumpling the paper I was using for transefer... I print as normal and use the photocopiers manual feed now!

I'm a bit hit an miss at getting the ironing right (despite lots of practice on Shirts for Work :wink: ) you really need to be careful not to slide the paper across the copper.

Paper is a big factor for the method. Copy paper is a pain, it leaves lots of fibre and impacts on the etching. I used the waxed paper from sticky lables, I've generally left a strip on the leading edge to help the feed. if their a larger PCB the're occasionally a ghost from earlier parts of the board - think about orientation and volume of mask printed in one go.

If you get it wrong you can always scrub the board and try again.

regards,
Colin
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Post by thebeardedone »

Have you tried using magazine paper, Colin?

I have heard that you get good results from the coating that is on it.

Sam
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BeligerAnt
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Post by BeligerAnt »

Press-n-Peel is a toner transfer method. It works just as well (probably better) than using ordinary paper. I have always had very good results with it, but see Colin's notes about ironing skills above! Anyone that has poor results with this is likely to have worse results with toner on ordinary paper!

I was actually referring to some rub-down transfers that Maplin used to do, like Letraset, with predefined symbols for ICs etc.

Personally I would never design a PCB without a ground plane. I suppose it comes from getting used to professional multi-layer PCBs and building RF boards at home. Anyway, it makes life much simpler in many ways as it means you don't have to route the biggest net on the board. Also you get a much better quality design as your supply decoupling is so much better.
For modern high-speed logic a ground plane is just about essential. You can do without it, but you just store up problems for yourself later. Don't forget nice wide power tracks too!

I have used Protel 98 in the past and the only thing it has going for it is that it is now free. Try using it for a while and you will see why it's free!
There are free limited versions of many of the professional tools available, usually limited to a few 10's of components or a few hundred pins. Enough for most home projects. I use Cadstar Express, mainly because I use Cadstar at work so I know all its quirks!
Eagle from Cadsoft is popular but I have never tried it. A friend of mine uses Autocad, but I wouldn't recommend it - a bit like using a hammer to put in a screw (possible, but far from ideal)
Gary, Team BeligerAnt
thebeardedone
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Post by thebeardedone »

BeligerAnt wrote: I was actually referring to some rub-down transfers that Maplin used to do, like Letraset, with predefined symbols for ICs etc.
)
Hmm, I have never seen or heard of this. I had a look but the searches were fruitless.

I need a really good book/tutorial on PCB design.

Sam
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BeligerAnt
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Post by BeligerAnt »

Although Cadstar is a bit quirky ( I think most CAD packages are! ) it does come with a pretty good self-teach guide. There should also be some good stuff around for Eagle as it is very popular amongst hobbyists.

Laying out and routing a PCB is a bit like doing a complicated jigsaw puzzle. Using a decent CAD package that shows you the "rats nest" connections between the components makes life somewhat easier. Move bits around until you reduce the number of crossovers as far as possible.

Most of the following I have learned the hard way...
You can use wire links to make crossovers - it's easier to add a few wire links than spend days trying to find a way to route an impossibly complex board! Use insulated wire!
Don't forget decoupling capacitors - ideally one 10nF or 100nF ceramic for each IC plus a few uF bulk decoupling, either aluminium electrolytic or ceramic.
If using SPI, don't run the clock and data lines close together for long distances. This is a sure-fire recipe for disaster! If they do have to run together, run a 0V trace between them.

Apologies if some of this is already obvious...
Gary, Team BeligerAnt
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Post by Andrew_Hibberd »

I bought the book a while ago called making printed circuit boards, it was fairly useful but with enough googleing you should find everything you need to know.

I wouldn't recommend designing your own board using a pen and/or the pre made parts. You are likely to make a mistake and you won't be able to repeat the board easily.

I have used the high gloss paper for printers with some sucess you need a laser printer or can photocopy it over to the glossy paper, print with the tracks in black and inversed image. Iron on the paper to the copper clean well to remove greasy finger prints etc. Then soak off the paper, etch and with a fine sanding block remove the ink from the tracks.

I did start looking into making a UV box using leds from ebay, 100 for ?6. A box from maplin for ?5 and then just odds and ends and tin foil reflectors. But i started using the baby-orangutan board which was much smaller than i can make boards and can do everything i need.


For board design i used eagle cad, there are lots of tutorials online on how to use it. I even found a autorouter to route tracks. With a few modifications afterwards it produced perfect designs.
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