We've broken the code on how to etch proto-boards in under one minute! It's called "Contact Etch".

This technique was discovered one day in early 2003, when I drove my car through one of those "no brush" car washes because I was feeling incredibly lazy. I noticed, not surprisingly, how the car went in dirty and came out dirty (less a tiny-weeny bit of dust)... then it hit me! Is the reason for a resultant 'still-dirty' vehicle the same for why PCB's take so long to etch? (This should really make you wonder about those of us who can't turn our minds off of our passion for perfecting everything.)

What does this mean specifically? It's only a revolutionary idea! Consider this... what's the only difference between a "bucket of soapy water and a sponge attached to a hand" to a "spray only car wash"? The one and only difference is the physical touching of the paint to break the surface tension (that allows the dirt to cling to the painted surface in the first place).

I think we've misunderstood what is really required to etch a circuit board. Over the years we've always heard "agitation" when it came to etching tanks. Etchant agitation has always been either by rocking a tray, sending bubbles up a tall white "can't see what's happening" type of tank or a very expensive "spray" tank. (We even developed a fourth method of agitation by flowing a "wave" of etchant over the PCB which was almost as efficient as the expensive "spray" tank - well, until this revelation happened, of course).

From a purely unprofessional, non-technical point of view, it's very clear that the microscopic layer where the etchant just touches the copper surface becomes nearly instantaneously saturated with copper ions and that means the etching process basically grinds to a halt in just a few seconds. To keep the etchant eating away at the copper we must some how move this saturated layer away to allow for fresh chemical (or less saturated chemical) to get at the copper surface. This is what all tanks are TRYING to do (but fail miserably) using either their rising air bubbles, or rocking trays or even spray nozzles of etchant directed at the surface of the copper. True, agitation does move some of the saturated layer... but very little. This is why it takes so long to etch a board. The one main problem still remains even with these different methods of agitation, and this is, you aren't physically touching the copper surface to break the "surface tension" which is what's responsible for holding the dead/saturated etchant clinging to the copper surface.

So after the idea hit me, I dropped it in 1st and laid rubber back to the office to try out the idea. It's so simple it hurts. I tested both etchant types (sodium/ammonium persulfate and ferric chloride). It became clear that we must use a "corrosive" chemical vs an "oxidizer", so persulfates are out. This trick just doesn't work with either sodium or ammonium persulfate. I would assume it has something to do with the way in which the chemical reacts to the copper. All I know is, it doesn't work anything like FeCl does!

A couple of truly nice things to say about using ferric chloride, (I know, hard to believe there is anything nice to say about this "nasty" chemical). For starters, we're only going to be using an ounce or two. That's such a small amount, there is no offensive odor or corrosive "atmosphere" to speak of. Secondly, it's available everywhere... in every city, coast to coast, at your local Radio Shack. One small pint will last you through quite a few boards and at $3.99 for the pint-sized bottle, this is an extremely economical way to go. As far as the "staining" problem associated with FeCl, put on an apron if you're wearing good clothes. All stains on cloth are basically permanent!

And the best part of all of the above... it's done at room temperature! You do not have to heat up the etchant.

1) ROAD TRIP! ...for Gloves, Sponge & Etchant: Get a small box of "surgical" type disposable gloves from your local drug store – a box of 50 is only a few bucks. While there, buy some 3-M ScotchBrite scouring pads and a box of "Zip Lock" bags. Next stop, Radio Shack for a pint-size bottle of Ferric Chloride and last but not least, to one of those cleaning supply stores (like "Smart & Final" if you have them in your area) for a 1 to 1-1/2 gallon container with a wide-mouth lid.

2) PREPARE THE PCB: Print and transfer your TTS image to the copper surface and most important, transfer a piece of our "GreenTRF" on top of the toner image. (Without this GreenTRF, you can not perform this technique).

3) DON THE GLOVES: Slip on a pair because you will be holding the PCB in one hand and rubbing the sponge with the other.

4) SPONGE: Soak the sponge with a few ounces of etchant and begin rubbing in a VERY ORDERLY manner. Overlapping passes by a sponge that is too small will give you DOUBLE the efficiency where you overlapped your passes! This will result in etching times for that section to be too fast! Developing your rubbing technique is the only difficult part of this process. You obviously want to have the entire board finished at about the same time. It will never be perfect... but close.

5) TOUCH UP: If you notice that the edges are not etching as fast as the center, you are not dedicating enough rubbing to the entire board evenly! When this happens, concentrate your rubbing over the areas that are not done.

6) COPPER DENSITY: Obviously, the more copper to etch off, the longer it will take. We sell "1/2" ounce copper laminated FR-104 epoxy boards. This technique will etch a 1/2oz board in under 1 minute! For 1oz boards it'll take a whopping 2 minutes and closer to 4 minutes for 2oz board (very cheap board found mostly in the "surplus" market. 2oz copper is a LOT of copper to try to remove.) Keep in mind that because the efficiency is very high, heavier copper boards are going to "saturate" the etchant (making it look very black), obviously using up more etchant at a faster rate which is why we promote our 1/2oz board. It's not expensive, etches in about 45 seconds and enbles you to make extremely fine trace lines with very little undercutting. Check our prices for blank circuit board under the "Where To Buy" (last menu button). Our 1/2 ounce board gives you the best "bang for the buck" over all other copper weights for speed vs. efficiency vs. cost.

7) CLEAN UP: It would not be a good idea to simply toss the sponge in the trash. Even though the chemical is basically "spent", a portion isn't plus what you have left over is copper ions which would be considered a "heavy metal" if it got into the water system. What we've found that works best is to fill the gallon size jar half way with water. When you are done etching a board and your gloves are still on, put the sponge into the water and squeeze the sponge several times to get almost all of the copper ions out. Put the sponge in a Zip Lock bag to keep it soft and ready for the next board. The idea is to keep the water bottle for some time, letting the water get more and more saturated, then you only have one trip to dispose of all etching by-product. For companies the EPA says you must dispose of waste material properly. There are other methods besides calling for an expensive "Hazardous Waste" pickup. The simplest method for disposal we've come across is to visit your local automotive garage or quick-change oil service and ask them if you can pour your gallon of diluted etchant into their hazardous waste container. Most if not all will have no problem. If they hesitate, maybe that would be a good time to offer that you'll have your oil changed too.

We'd like to hear your comments and constructive criticism on this technique! Send a quick note to Pulsar what you think about this.

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#2: Better "Double-Sided" Circuit Artwork Alignment Techniques

One thing I did to help get an excellent image transfer on larger board sizes, using just a household iron, was to use a wooden dowel under the circuit board as a way to achieve a high pressure point. What I do is to cut out my circuit board to the exact final size (this helps me line things up on double sided boards... I do one side at a time).

I place the TTS paper down on a smooth, heat resistant surface, toner facing up.

Next, I lay the circuit board down on top of the TTS paper, copper side facing down. Line up the board edges with the board outline that is on the TTS paper (I make sure to have a board outline present on the layout).

Then, I heat the board with the iron for about 15 seconds, just long enough to get the TTS paper with the toner to "tack" adhere to the board.

Now, I place a wooden dowel down on the smooth surface (I use a 7/8 inch diameter dowel that is 8 inches long). Next place the circuit board with the "tack" attached TTS paper on top of the wooden dowel, board down, TTS paper on top.

Put the iron on top of this, and slowly move the iron, TTS paper, and circuit board back and forth several times while pressing down with a goodly amount of pressure. To help with "slowly moving" the iron, TTS paper, and circuit board, use one hand on the dowel and slowly rotate the dowel. If the circuit board you are doing is larger than the bottom surface of your iron, move the iron over a bit relative to the circuit board/TTS paper and roll the dowel some more.

Its actually not too difficult to do all of this at once, and it really makes a big improvement in getting high pressure applied for a nice clean solid toner transfer! And, its even cheap!

You can check out a bit of what we are doing, for the Oregon Coast Repeater Group, at www.ocrg.org