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Episode: 1174
Title: HPR1174: Low Tech Fab (PCB Etching)
Source: https://hub.hackerpublicradio.org/ccdn.php?filename=/eps/hpr1174/hpr1174.mp3
Transcribed: 2025-10-17 20:59:41
---
Hello, this is NY Bill and I thought I would talk to everyone today about etching circuit
boards.
I haven't done this since I was in, probably about 1985, a young teen, I used to have a
book on guitar effects so sometimes I would try and build these effects and etch my own
circuit boards.
Then I used to use Radio Shack kits, if anybody remembers them, back when Radio Shack used
to actually sell things besides cell phones.
It is a shell of its former self, but recently I ordered a Raspberry Pi and I was also
given a Bricked Router, a Lynxus E2000.
Well, a friend tried to put DDWRT on it and it didn't fit or something went wrong and
you can log in and access the control panel but once you plug in the WAN or try and do
anything with it, all the lights go crazy and it starts resetting itself.
So the next step with that router is we're going to go in on the J-Tag headers.
Plus these Arduino's and Raspberry Pi's, a lot of interfaces these days are 3.3 volts.
I've heard it referred to as UART or TTL, not the 5 volts coming out of USB.
So looking online, I found lots of sellers that were selling little conversion boards
for about 15 to 20 dollars at USB to 3.3 volts.
But it seems like most of them are sold out.
So this must be the R-Pie craze or people just can't keep stock.
But I noticed that the chip that a lot of them are using is a FTDI chip.
I'm familiar with this chip because at 2600's HOPE conference, Hackers on Planet Earth,
not the one that just went by but the one probably almost three years now, they do it every
two years.
The badges there were basically a microcontroller and they would do things like RFID and they
could track the people walking through the conference, all interesting things like that.
But on the back of this badge, if you soldered on a mini USB and then there was a space
for this FT232RL, which is a USB interface chip, and you could turn the badge into a full
microcontroller.
So at the conference, I did that.
I did a sloppy job because I borrowed someone else's soldering pen and I'm not sure if
I had flocks.
I think we did it.
Yeah, we had flocks.
But the pen had the big tip on it and if you've ever seen some of these surface mount
chips there, it's so tiny.
It's similar to the chips that are on, well, the leg spacing is similar to the chips you'd
see on a memory stick.
It's almost impossible to solder these things.
But I did solder it on to that HOPE badge and I was able to plug it in USB and it identified
itself and well, that's as far as I got.
Now looking into these converters, these USB to the 3.3 volt, I'm seeing they're using
this chip again and I'm familiar with it.
I've looked at the data sheet and I'm somewhat familiar with the functionality of it.
I found a schematic and because I can't order any of these boards at the moment, they're
all everybody's back ordered.
I figured, why don't I try and make one?
So I ordered a few of these ICs and I went to a local electronic supply store.
I can't believe that these guys are still around.
They've been my grandfather used to shop there.
There's this old, big, huge, old, dusty place that's probably got all kinds of neat things
back on the shelves.
But I was able to go there and I picked up a very small soldering tip.
I picked up some single-side copper clad and the rest I either had at home or I was able
to get at hardware stores or pharmacy stores or I'll go into that in a second.
So the first thing you'd need to do in etching a board is to come up with a design.
You can either come up with on your own or look online.
There might be some schematics you can get or board layouts you can get.
I recall back in when I used to do this as a teen, there was a resist pen.
It kind of looked like a sharpie and you could just basically draw a hand draw your layout.
That's what I used to do.
Just hand draw your layout on the copper and you'd have a resist layer.
So when you go to etch it with acids, the acid would either way all the copper except
for where you drew.
It turns out that inkjet and copiers and anything that I want to make sure I'm saying the right
type of printer here.
Anything that uses a toner, not, yep, I said the wrong thing.
These are jet or copier.
So anything that uses that powdered black toner, this will also act as a resist for you.
So you either look for a board layout that you can use or you design your own.
There are some design software specifically for use for making PCB boards and some of
them you can even design your layout and then click a button and order the board and the
file goes off and in the mail comes a pre-made board.
I'm kind of doing it low tech here, but it still works just fine for a low production
home type of hobby thing that this procedure works just fine.
So take your layout and or design it.
I found the 28 pin surface mount breakout board which is what that FT232RL is.
I dragged that into Inkscape, imported it into Inkscape, made it an SVG so I could scale
it up and down because you're going to have to get this just right to the print size.
So I printed a couple of those and then looking at the data sheet for the chip, I realized
I was, these are so tiny to try and solder these, it was going to help me to take it one
step further and looking at the data sheet I found that it looks like I'm only going
to be using breaking out 11 of these 28 pins and then there are some other pins that
are utilized but they're just one breakout to a ground and then ground traces go through.
So I took that breakout board layout that I found and I brought that into GIMP and I called
away all the traces that I didn't need and then I drew some of my own lines to, because
it's even the board is so small.
So I extended some of the lines and put in spots for resistors and capacitors that are
going to need to go in there.
So I kind of designed my own board.
So in any way you get your file and you get it to size, you're going to want to print
it up on a photo paper like for printing photographs.
It's, I believe, you know, my theory is the shininess isn't going to absorb the toner
like a regular paper would so then it's kind of sitting on the surface and what you've
basically made is an iron on.
Now you're going to have to take special care here.
If like the first image you're going to see the breakout board in the show notes, if
it's symmetrical it doesn't really matter but on the second image that I drew because
of the way the chips going, I'm going to have, I had to invert the image to print because
then when you're going to flip it over and you're going to iron it onto the board, things
are going to get backwards so just take extra care.
If your print goes bad or if your ironing goes bad, if your prints backwards, if the lines
get smudged, if at any point up to this point, things aren't going well, you just take
some lacquer thinner and you can just clean the board right off and just start again.
Print again, iron on again, you haven't gotten to a point where you can't get back yet.
Now I should say here, you might need to do a little experimenting, not all photo papers
seem to be the same.
I had three kinds here, well a few different kinds of cannon, a generic staples and ebson,
I believe.
The staples one ended up, you're going to want glossy in any case, the staples one ended
up being the best, nice clean lines and nice clean transfer, the other ones either didn't
transfer so well or one of them was like, it wasn't even a paper, it was like, it was
like made out of plastic and it just melted right to the copper and that one just made a
total mess.
I also saw online that some people had success using just ordinary glossy magazine paper,
you can cut that out and run it through your printer and there you'll have your iron
on transfer.
I'll also say something here, I'll save everyone a little bit of time, don't try and
run your photo paper through more than once.
I printed such a small design, I thought I could flip the paper over and reuse it, somehow
on the first run through it gets activated in some way that the second time through it
just picks up like random toner and starts to get this gray cast to it and the traces
will be very heavy lines and it's best just to practice on regular paper and once you
think you got everything right then send your photo paper through.
Another trick I was doing was my copper board was 4 inches by 6 inches and I was able
to fit multiple copies of my images on the plate.
So in Inkscape I stacked my images up, then when you are doing your iron transfer depending
on the heat of the iron or how much pressure you're putting some images might come out
too faded, some might too thick, but you should find at least one of your prints came out
nice and clean.
So for transferring the print you just use an ordinary clothes iron, some people used a
laminator but I don't have one, a clothes iron works fine, I don't know if you want to
tell your wife you're using it for this but I just did it discreetly sorry Mrs.
Enwebbel I hope I didn't mess up the iron next time she goes to do a shirt or something
but yeah you just set the iron like pretty up high, I don't I was in between the two
highest settings I don't know what that was linen or something.
At the iron heat up you're going to have to push down on this a bit so you wouldn't
use the ironing board, use an old book or something, have your copper plate on there.
Make sure you got your layout on the board, you don't want any traces leaning off the
boards or left or right and then just put the iron straight down on it and keep the heat
on for, I don't know I guess I did 10 or 12 seconds and that's kind of stick, it's going
to heat up the toner, it's going to heat up the board and it's going to stick the two
together and after that then you can start you know moving back and forth and I gave
it a good, you can push, you can bear down on it a bit and I gave it probably a good
35 or 40 seconds of heat.
You can actually cheat if you want, just lift up the paper slightly in one corner and see
if the traces are sticking, if they're not a little more heat, if they're sticking
you might be good, just give a little more heat for good luck there and let things cool
a little bit and then submerge the board and water.
You'll go back in five minutes and see the photo paper just starting to come translucent
and starting to peel, lift up at a point you feel comfortable, you can just peel the stuff
off.
There's some of it's going to stick and you can rub pretty vigorously on the traces
without damaging them.
I wouldn't use your fingernail or any metal tool or anything but you can just, as much
as you want with your thumb, just roll this paper off until you get a clean board.
So the next part is going to be etching and this is more, oh, I just realized I left
out.
Well, I'm sure you're not doing this as I'm talking so let me just backtrack a little
bit.
After you've printed your photo, printed your traces, don't touch the traces what
your finger, oils will come off and that's no good.
When you get your copper board, you're going to want to scuff it up probably with Scotch
Bright.
I suppose you could use sandpaper, but you don't want to introduce impurities but some
copper boards have a coating on them to keep them from tarnishing or oxidizing in the
package.
So you want to clean that off and then right before you iron on, use rubbing alcohol just
to make sure you get all the oils and impurities off so keep everything nice and clean.
Okay, now we fast forward back to where I was a minute ago.
So it's on to etching.
I used to use ferric chloride way back when it's still around.
It's a brown nasty acid that will stain your fingers and your clothes and whatever else
you get it on and you can actually, I recall seeing like vapors coming off stuff you don't
want to breathe in.
You're going to want to do all this in a safe ventilated area anyways.
Some newer methods I saw online, one seemed pretty tame.
It was hydrogen peroxide, vinegar and salt and the people claimed you could do that right
on your kitchen table.
I'm going to go for a middle ground which is one part eriotic acid and two parts hydrogen
peroxide.
And you have your etching solution.
So I did mine in a glass pyrex and I just, you slip the board in.
It's going to be clear.
The mixture is going to be clear and as the board is etching, it kind of turns green.
It actually, I wouldn't get down there and smell it but it reminds me of actually the
ocean when the tide is out and there's all the tidal pools and the seaweeds and stuff
for some reason it smells like that but I'm getting off track.
So stick your board in there.
You're going to want to wear some heavy latex gloves or chemical gloves.
Then just rock, rock, whatever dish you're using back and forth.
You can't use any metals or metal tongs or try and stick with plastics or glasses.
And slowly the copper will start to fade away.
It starts to fade away at the edges first and slowly goes in and what you'll be left
with is just the black toner traces that you had.
So reaching with your gloves or however you're going to get this board out and then clean
it up with water mixed with baking soda that'll neutralize the acid and clean the board.
Get it ready so you can hand handle it.
And then the next step is to clean the toner off.
So that's just a lacquer thinner.
It just the couple of swipes and it goes away.
Now you should have a nice clean PCB with nice clean copper traces that will oxidize
on you.
So depending on the size of your traces again, if you can cover them with flux, get out
your soldering pen, some solder and go over the whole top of them.
Another thing you can get is tinning fluid.
So it's a, well the one I bought is a two-part powder.
I guess one's a salt and who knows what's in there.
And you mix it with hot water and you stick your board in there and all the copper traces
will get tinned and this method really gives a nice clean professional looking result.
The next step would be drilling out your holes.
They have special bits for this because at the hardware store I could only go down to
one-sixteenth but some of these holes are quite tiny.
So I went back over to that local electronics place or you can get these online.
They have special little bits for drilling out PCBs.
So you're going to want to look into those because when I tried to do it with a sixteenth
inch bit, even though it looked like it would drill a slightly large hole but it looked
like there would be enough copper around the pad to still solder to.
Once the larger bits start hitting the copper, it just starts ripping it off the board.
So there you have it.
It's a few steps besides design wise, the actual ironing on traces and etching probably
takes 20 minutes.
You can get fancier with this, you can do two sided boards, you're going to have to watch
how you lay your traces and design.
There is another method of getting traces onto a board.
They sell pre-sensitized copper plates which have a photo resist on top of them, that's
UV-sensitive.
I haven't tried this yet but I'm looking forward to it.
I bought a few of the plates and the developer that's needed, you can print on a clear acetate
and then lay that over the photo-sensitive resist, hit it with UV light and anywhere the
light is penetrating, we'll soften the resist and that can be cleaned off of the developer
and then you can bring that board to etching.
I guess what I'm saying is the hardest part is layout and design and the etching is just
a few chemicals a little bit of time and you are fabricating circuit boards at home.
So like I said, check the show notes if you're interested, I'll put up links to some of
the places I found designs or parts and I'll link to some photos of my process here.
So if anybody has any questions or wants to contact me, I am NYDIL at gunmonkeynet.net.
I know the two nets are redundant but everything else was taken and I find it kind of funny
but okay, till next time, see you later guys.
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