Toner Transfer PCB Fabrication Guide

Introduction:

First off, I should give credit where it is deserved.  Thomas P. Gootee is the man who got me started in this.  His website is located at http://www.fullnet.com/u/tomg/gooteepc.htm  His site is the single most informative guide to the toner transfer method that I have ever found.  The main reason I am making this site is that while informative, his site is very long and detailed and doesn't read as much like a tutorial as I'd like.  So, I'm going to try to keep this guide more concise to help make this information easy to swallow so some people will be able to use it more easily.

Step 1: Generating artwork

   Design:

    Generating proper PCB artwork is an important step in the process, because the way you design the board can have an impact on how easily and effectively it can be transferred and etched.

    The first and probably most important design tip is to use pours.  A pour is a way to fill in the empty space in a board; most importantly, filling in large open areas, and provide a border around the edges.  The reasoning behind this is that traces on the edges of the board, and around large open areas, tend to be more likely to be broken or chipped when the paper is removed.  By filling open areas and making a border, the amount of trace chipping and lifting is GREATLY minimized.  

       

The board on the left has no pour, the board on the right has a pour.

    To do a pour in eagle, first select the "polygon" button on the left toolbar.  Then you need to select the proper settings.  I use a trace width of 0.016", isolate of 0.024", and spacing of 0.05".  You also need to set the fill, thermals, and orphans buttons as indicated above.  For Fill, I usually use a hatched fill; this saves toner, and also looks better since laser printers rarely do a good job printing perfectly evenly when you have large solid black areas.  Thermals are the little isolated areas around any pin that is connected to the fill.  These aren't necessary but they do make it easier to see where the holes are so you don't miss any when it's time to drill.  Finally, Orphans are areas of fill that are not physically connected to the main fill (such as small patches appearing between traces, etc).  I recommend turning orphans ON, since most of the reason for using a fill is to aid in toner transfer, so you want to fill in all empty areas.  Once you have the settings chosen, then you just draw a line around the outer edge of the board (okay to draw it outside the board outline, it will only appear on the actual board).  Press the "ratsnest" button (X icon in bottom of left toolbar) and your pour is complete.

    One optional step is connecting the pour to some part of the circuit.  Typically you would connect the pour to ground, so that it will form a ground plane, and help maintain signal integrity.  Although for most hobby projects it's complete overkill, if you're going to have the ground plane in there, you might as well take the easy step and do it.  Besides, if your project has both analog and digital circuitry, and you aren't running separate grounds for them, it will provide a better ground connection for the analog portions.  To connect the pour to something, you simply choose the "name" button in the left toolbar, click on the EDGE of the polygon you drew for the pour (which is usually going to be outside the board outline, although invisible when you do ratsnest, you'll find it), and type in the name of the net that you want to connect it to.  (ie - GND or 0V) if you got the right name, it will prompt you asking if you want to connect the nets.

    Next, you need to pick appropriate values for trace widths, etc. And bear in mind how close you can reliably place traces to other things, etc.  Values that I typically use are 0.012" for trace widths, and 0.016" spacing minimum between traces and other traces/pads.  Getting smaller traces and tighter spacing can be done with experimentation.  Printing very darkly, for example, will tend to make the transfer easier, but you will usually see the traces/etc expanding outwards as the expand, and if things are too close together then they will come in contact, which is not good.

    The only paper I recommend for toner transfer is Staples brand "Picture Paper".  It has apparently changed names recently, and is now called "Photo Basic Gloss", but still bears the original SKU (item number) of 471861.  It is not very expensive, but it is just about the perfect paper for this process. (typically $10 for a 30 pack and $30 for a 100 pack)

    Printing:

    Getting your layout onto the paper can be done a couple different ways.  You can print it on a regular printer, take it to a copy shop and get it photocopied onto the picture paper, or you can print it directly onto the paper if you have a laser printer.  Photocopying it onto the paper is a little tricky, since copiers sometimes don't give the most high-quality images.  Also, I've run into a LOT of problems with the copier not being able to handle the photo paper.  Since the paper is so glossy, the copier often has a lot of trouble feeding it properly and as such, will often jam.  This doesn't make a good impression at a copy shop.  Printing on a laser printer is easier if you have access to one.  You will want to use a relatively dark print setting if you can, but you will have to experiment with darkness when you start dealing with intricate boards.

Step 2: Board Preparation

   Cutting:

        Cutting copper-clad board can be accomplished many ways.  You can try scoring and snapping it with a knife, but don't expect the knife to last long.  For a while, I did it with a dremel rotary tool with a heavy-duty cutoff wheel.  It works, but it's hard to get straight edges.  What I use now is a small table saw.  I have a very small table saw that uses 4" blades.  I am using a carbide-tooth blade with it, and it cuts PCB like butter.  I picked the saw up with blade for about $40 on ebay; after cutting many boards, I still see no signs of wear on the saw teeth.  This isn't surprising, since carbide is the material that most commercial PCB routing and drill bits are made from.

   Cleaning up:

        One ABSOLUTELY necessary step that is easy to neglect is filing the edges of the board after you cut it.  Cutting the board will almost always leave raised copper on the edges.  If you don't get rid of it, it will make it near impossible to properly iron the pattern on.  Taking a simple straight file and cleaning up those edges is all that is required.

   Cleaning/prepping the surface:

   Bare copper will get contaminants on its surface. Also, it's too smooth for good toner adhesion.  The simplest and best way to prepare the surface of the copper is to scrub it with scotch-brite pads.  You can get them at auto parts stores, or you can even find them in the dishwashing section at your local supermarket.  Using steel wool is NOT recommended since iron dust will end up in the board which will react during etching, and/or rust and make a mess of your board.  Scotch-brite is fast and does a great job.  You should simply polish your board until it looks something like this:

After you have polished it up, it will look pretty clean and shiny; however there is a lot of dust you can't see.  Polishing creates extremely fine dust.  To remove it, simply take a clean paper towel and pour some rubbing alcohol on it (acetone or other solvent should work okay too) and wipe down the board once.  You should see the paper towel get pretty black from the dust you're cleaning off.  Fold the paper towel so you expose a clean side, and using some more rubbing alcohol, wipe it down again.  Repeat until after wiping, the paper towel is clean, usually 4 to 6 passes.

You can get by without cleaning the board, which is what I used to do, but I find I get much better results if I do, and besides, it only takes a minute.

Step 3: Toner Transfer

You need a household iron to transfer the toner to the board.  Just about any iron will do, but ideally it should have as few holes in the bottom as possible, to ensure even heat coverage.  This is the iron that I use:

I paid $6.97 for it at Target, as a display model, so you don't need to spend much.  

Also, for very small boards, you may be able to use one of these:


See my Equipment page for more information.

As for iron settings, first off, you should have steam turned OFF.  Some people will tell you to iron on the highest heat setting, often marked "linen".  However, a heat setting of approximately 2/3 of maximum yields good results as well.  You may have to experiment with your particular iron.

You should cut out the printed pattern; I typically either cut it nearly flush on all 4 sides, or flush on 3 sides with a small tab to hold on to while I position it on the board.  

I recommend pre-heating the board by placing a piece of plain paper on it, and laying the iron on top of that for a few minutes.  Then position your pattern where you want it.  Because the board is pre-heated, the pattern will most likely stick where you first put it down, so don't try to move it or it might smear the toner.

Now you iron the pattern on.  Place the iron over the pattern and apply some pressure.  You don't need to stand on the thing, but at least apply some weight to it.  Pressure is required to properly adhere the toner to the board.  If your pattern is small and you iron has a large flat spot like the one above, you may not need to move it around... But if your pattern is large, you should move the iron around a few times a minute to ensure even heat and pressure distribution.  Often it helps to go over the edges and corners a few times pressing rather hard, using just the tip area of the iron.  These are the areas most likely to have transfer issues if you don't adequately iron them.  With the staples picture paper, you will be able to actually see a "ghost" image of the toner pattern start to appear on the rear side of the paper if you go wild enough with the ironing.  By going over an area with the tip, you will almost certainly see some of this, and I take it as a sign that that area is well adhered, so I usually go over all edges until I can see this happening.

Step 4: Removing the Paper

   Removing the paper involves a lot of water and a little work.  After ironing you should allow the board to cool before putting it in water, so the toner will harden... However I often just throw it into the water while still hot.  Allow the board to soak for at least 10 minutes or so to completely saturate the paper.  The longer you let it soak, the better. If you let it soak for an hour or so, it will peel off easier and you'll have less chance of breaking traces; I recommend longer soaking times for larger or more detailed boards.  Now, you can take it out and start peeling layers of paper off.  Be EXTRA careful when you first start peeling at one corner.  Be very gentle and go slowly, to make sure the toner isn't being pulled off the board. Once you get the paper started peeling, it gets much easier.

**paper started peeling off**

    After you have a couple layers of paper removed you can start rubbing off layers of paper with your thumb.  Make sure there are no dry spots, if there are, just soak it again for a minute.  Eventually you'll get it down to just a final layer over the toner and board. That is mostly the coating of the paper that is left.  To get that off, the easiest thing is to take a toothbrush and scrub it while submerging it in water.  The toner is USUALLY pretty solid with this method so you shouldn't be scrubbing any of it off.  Don't go too crazy...  Eventually you should have all the coating removed from the bare copper portions of the board.  (coating left on the toner is fine, don't bother removing it)

Your board should now look something like this:

And here's an example of a larger, less intricate board after a good scrubbing.  Note the discoloration on the board, it is only caused by extended periods of ironing, and should not affect the board.

Step 5: Inspection/Repair of Toner Pattern

   Now you have to inspect the board to check for any problems, such as broken/missing traces, traces that have melted or smeared together, etc.  Now is the time to fix them if you find any!  If traces are blobbed together, you can usually just carefully cut a groove between them again with a knife if you have a steady hand.  If traces are broken or missing, you can repair that using an etch resist pen... aka - a fine-tip sharpie permanent marker.

**blobbed traces** **broken trace repaired**

Step 6: Etching

   Etching can be done with several different chemicals, namely Ferric Chloride, Ammonium Persulfate, and Sodium Persulfate.

    Ferric chloride is usually the easiest to obtain; you can even buy it at radio shack.  The other two are commonly sold in crystal form in larger quantities (I paid $18 for 1 Kilogram of Sodium Persulfate, which makes 4 liters of solution).  The advantages of the Persulfates is that they make a transparent solution.  Ferric chloride is nearly opaque, making it harder to see the etching progress. 

   There are many methods for etching the board.  Here are a few recommended methods:

Step 7: Removing Toner

   Toner can be removed by just scrubbing it off , but that's very labor-intensive.  It can be very easily removed with a solvent.  Lacquer thinner removes it almost instantly, and is only a few dollars for a large can, so I highly recommend it.  I have also heard of various other solvents working, such as engine cleaner.

Step 8: Drilling

   I do all my drilling using repointed (used industrial) carbide drill bits, specifically designed for PCB drilling.  I bought them all on eBay, for a total cost of about $60, for a total of about 80 bits of various sizes.  That is, of course, much better than the $5 or more that they cost PER BIT if you buy them new.

Some people use HSS (high-speed steel) drill bits, which can be found in various small sizes ("wire drill" sizes), however they do not last very long when drilling fiberglass PCB's at all; whereas the carbide bits will last many thousands of holes (more than I could handle without accidentally breaking one, eventually), the steel bits will only last a few dozen from what I've heard.

Carbide bits are incredibly brittle, so there is no way you can use them with a hand drill, you must use a drill press.  Other than that, it's pretty self-explanatory.

See my Equipment page for more information about the drill press and carbide bits that I use.

Now, the board is ready to use.  If you wish to take the extra steps, you can continue on to place component silkscreens on the top side of the board as described in Tom Gootee's site listed at the top, and if you want a more professional touch, and/or added corrosion resistance and easier soldering, you can try tin-plating the board.  See my TINNIT Electroless Tin Plating Tutorial.