Archive for March, 2009

DIY PCB Boards – Toner transfer method

Saturday, March 21st, 2009

I know this is nothing new,  the toner transfer method has been around for years.  One of the pioneers was probably Thomas Gootee.  He discovered the miracle of the Staples paper and described the method of making a board really well.

While i don’t want to undermine what beautiful work he has done  (in fact, if you have come here without seeing his page first, i strongly reccomend you follow the link above before going further here) I would like to document some of my experiences using this method and what i use to produce repeatable results.

Primarily, the problem for us Aussies is that the staples paper is simply not available here.  I have gone through several brands of paper and just could not find any that released well enough.  Most of the papers coating also got stuck to the board and was hard to almost impossible to remove without damaging the toner.  I have used generic papers such as OfficeWorks brand, Avery, Canon and Kodak papers.  None of which produced good results.  All were cheap and only 15x10cm papers so fortunately it has not cost me a mint in research but the one i have settled on with PERFECT results is:

HP Everyday photo paper

The item number of the papers i have (in 10X15cm) is Q5441A.  This is plenty big enough for all my projects.  It releases PERFECTLY with no residue, even on the toner.  I only soak for about 5 mins in hot water and it simply slides off.  If some is left behind, soak for a little more and it will all come off – NO scrubbing with toothbrush, heavy rubbing etc.  it just glides off the board.  I was absolutely amazed at how well this paper worked compared to all the others i have tried.  There is simply no better paper in Australia.  To make things even better – the pack of 100 sheets only cost me $6!!  that’s right, the paper is so cheap it’s not funny.  Compare that to press ‘n’ peel or other commercial toner transfer paper which is not any better and WELL above that price.

That is not the only key to this system working consistantly, the other important factor is how the toner is transferred with heat and pressure.  Irons can and do work ok but repaeatable results are hard to achieve with them.  I generally found that i eneded up applying too much heat and/or the paper tended to slide and smudge the toner which meant starting again.  The answer to this is to use a laminator but even still, not just any laminator.  90% (if not more) of laminators heat, then squeeze the laminator pocket.  They do this by having 2 heat plates before the rollers to warm it up and the rollers then squeeze it all together.  What i have found is that the heat and pressure need to be applied at the SAME TIME for it to work well.

The key here is, find a laminator that utilizes a heater INSIDE the roller.  AFAIK, the only company that produces this type of laminator is GBC and even not all of thiers work like this.  I can confirm however that the GBC ‘Creative Laminator’ available at K-Mart DOES.  I believe this is also the same as the one available from Dick Smith stores and even Australia Post.  K-Mart is the cheapest however, i paid just under $40 for mine from there.

The method of using the laminator is pretty straightforward but there are some points that should be observed:

1, Make sure the laminators ‘ready’ light is on.  It takes about 5 mins to heat up…
2, Run the board through the laminator with a piece of ordinary blank paper over the copper to pre-heat the board.  The piece of paper is important as i have found that the toner does not stick as well if you don’t.  I presume this has something to do with the rubber rollers possibly having some oil residue on them.  It could go away after time.
3, Once the board is preheated, attach your PCB design and carefully feed the two through the laminator at least two, probably 3 times
4, Dunk board and paper in hot water and leave for about 5 mins then peel slowly. 
5, Etch as normal with your favourite echant
6, Clean toner off with Acetone 

So far using this combination of the HP paper and the GBC laminator i can consistantly produce boards with tracks at 0.4mm and even less between tracks/pads.  it’s possible that it could go less but i have not tried.

Below is some pics of a board i have just done… This is for a pic based li-po monitor i found over at http://www.plmsdevelopments.com (look for the link right down the end of the text about Martin’s Electic RC exploits).

I am using a HP Laserjet 1320 with density set to 5 (maximum).  I still get some pitting in the toner as you can see in the pics but it is not evident in the final product.  I’m hoping to find a better printer that can pile up the toner – something like a HP Laserjet 4 but they are hard to find in good enough condition on the cheap.

UPDATE: I’ve since slightly changed the way i do this.  One thing is that i now tend to print my PCB’s using a very dark blue (on a colour laser)  rather than black.  It could really be any colour i spose but my theory is the darker it is, the more toner is used.  I have found this to be the best way to avoid pitts in the copper after etching as it fills all the gaps.

The problem with this is, the colour toner tends to be a little harder to melt in the laminator. Basically, it doesn’t.  It’s very hard to get it to bond.  However, Ahmad Tabbouch has written an excellent guide on bumping up the temp on the GBC laminator, as well as another mod that should help it last a bit longer.  I won’t re-hash what he has done, but here’s a link to the guide on his site – http://www.ultrakeet.com.au/index.php?id=article&name=superfuser.  Even if you don’t use colour toner, it’s still a great mod.  No pre-warming the PCB and you only need to feed it once! Highly reccomended mod, you could even substitute the resistor with a trimpot and have variable temp if you ever need to use the laminator for it’s actual intended purpose.  However, the outer shell will get a little deformed from the extra heat and i would not reccomend leaving it on for more than is needed for a few boards.