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PCBs for Dummies

Posted 19th February 2011 at 12:49 AM by NYCOne

WARNING:


The following method uses deadly, strong chemicals. Do not proceed as you could die, or lose a part of your body you value (eyes, face, hands, other). The following is for entertainment purposes ONLY. Following this method is taking extraordinary risk and you could get gravely injured, or die.

Yes, I was a dummy when it came to PCBs. In fact, I was a dummy when I came to anything DIY Audio a few months ago. Of course, now I’m an expert in all things.

All the information you could ever want is in the forum – “Just search the forum…”

It really irks me when people post that. “Hey, I already searched the forum, and now I’m asking…” As a newbie, I knew NOTHING about circuits, PCBs, soldering, resistors, you name it. I always wonder if the “experts” realize that new people enter the hobby now and again.

After trying lots of things, buying lots things, and running some experiments, I know a little bit about DIY Audio.

Now, on to etching PCBs for Dummies:

1. Don’t be a cheapskate.
a. I live every aspect of my life with the presumption that I can do what the next guy can do with no tools or experience as long as I try really hard. To put it bluntly, I can’t. As the result of this predisposition, I usually try a new build, effort, or idea with none of the right equipment, and then I sequentially buy equipment piece by piece until I achieve my goal. This way, I spend relatively little on tools and materials, and rarely buy things I don’t really need.
b. Things you need based on my cheapskate efforts
i. Chemical Safety Goggles – the full wrap around kind. They’re like $3. If you’re not willing to buy these, move on to another hobby
ii. Thick rubber gloves that fit - $3 or 4
iii. PCB – I buy off eBay. There a fellow in NH that will sell you his leftovers by the pound. I bought 4 lbs of 2oz double sided PCB for $10 shipped! 4 lbs of PCB is a lot of PCB!
iv. HCl – I get this at the local hardware store for $4 a quart. It can be had a lot cheaper, but I live in Manhattan.
v. H2O2 – local drug store, buy by the quart - $2
vi. Toner transfer paper – Staples item 633215. I bought an open ream for $8. That’s more transfer paper than I can use in a lifetime.
vii. Acetone – Local hardware store ~$4
viii. Isopropyl Alcohol (NOT rubbing alcohol) ~$2
ix. A home iron – I had this already
x. A sharpie pen – I had this already
xi. Oven mitt – I had this
xii. Drill Press or Dremel (I had a Dremel, then bought a drill press)
xiii. 1500 grit sandpaper
xiv. Harbor Freight Micro Carbide drill bits - $4 with coupon
xv. Possibly Green TRF foil (I’m trying it for the first time this week) - $8.50 for a bunch of it
c. The design. Basically you need a pattern for printing your PCB. I was able to pull most of what I needed off the web. My first PCB was a Borbely pre-amp. Erno actually publishes the PCB patterns in his papers. In the case of the F5, Juma gave me a one sided PCB pattern and I was able to modify it in MS Paint to the pattern I wanted.
i. As I mentioned, I use Paint to make new traces, or erase traces, etc. If you want to get fancy, you can design from scratch with many of the free PCB design programs.
ii. After I save the pattern from Paint, I import it to Photoshop. In Photoshop, I set the image to 2400DPI and shrink or enlarge to the size I want (you need to match the distances of the legs of Mosfets, trimmers, etc. I then flip the image and print to the toner transfer paper (Staples item 633215)
d. Once I have the image on paper, I iron it to the PCB.
i. I first rough up the surface with the 1500 grit sandpaper
ii. Clean the surface with acetone until all dirt is off
iii. Place PCB on a stack of regular paper (20 or so sheets as a cushion underneath the PCB.
iv. Center the pattern where I want it on the PCBN (toner side to copper)
v. Hold the pattern in place with a oven mitted hand
vi. Iron the pattern in place, gently at first until it starts to stick to the copper, then I put my full body weight on the iron as I hold it in one place over the transfer paper.
vii. With the oven mitted hand, drop the PCB into HOT water
viii. Let sit for 30 min, and then gently rub the paper away with a finger tip.
ix. Use a toothbrush (soft) to get the last bits of paper off.
x. Let the board dry, fill in any defects with a Sharpie marker.
xi. (I may add Green TRF at this point)
e. Etching (wear goggles and gloves, perform in a well ventilated area)
i. Mix HCl with H2O2 (only add acid to H2O2, NEVER the other way round – I like living). The proportion I use is 2 parts H2O2 to one part HCl.
ii. I use a plastic coated 12 gauge copper Romex wire to make a PCB holder. I bend a loop in each end and use that to hold the PCB as I handle the board into the etchant. Put the PCB into the etchant.
iii. I jostle it around now and again.
iv. When the mixture turns dark black, you need to pour out the etchant and make a new batch. Some save the etchant and rejuvant it, I have not had luck with that method.
v. Eventually, you’ll be done etching
f. Take out your board, rinse in H2O
g. Dry
h. Use acetone to remove the toner from the copper
i. Use the Micro carbide bits to drill the PCB – I use a drill press, but before I had a drill press, I used a Dremel with the flexible shaft – both work well.
j. Now, I’d mentioned I bought two sided PCBs. I have made two sided boards. To do so I put holes in each pattern as fiducials to line up the patterns on the opposing sides of the board. Mostly, I make one sided patterns, and use the second side to write something decorative, like “Balanced F5”. As long as the decoration is not over important traces on the other side, you’re OK.
2. Using this method, I’ve gotten excellent results. The only minor complaint I’ve had is I get a little pinholing in some broad copper traces. That’s why I’m going to try the Green TRF. It supposed to get rid of the pinholing.

Now you’re an expert PCB maker (not really, since this is for entertainment purposes only).
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Comments

  1. Old Comment
    permalink
    Posted 21st February 2011 at 12:08 AM by NYCOne NYCOne is offline
  2. Old Comment
    tomchr's Avatar
    Properly dispose of the etchant according to local law.

    The etchant can be rejuvenated by bubbling air through it for a day or two. I use a small aquarium pump (I think it's rated at 5 liters/min). After a good 24 hours of that, the fluid is bright green and ready to go again.

    To dispose of the copper-saturated, black etchant either take it to a haz-mat place or mix it with lime (calcium). You can get that in the garden department of a hardware store. Mix the lime into the etchant and allow the slurry to dry. The dried compound is now safe to dispose of in the regular garbage.

    Whatever you do, do NOT pour the used etchant down the drain. The copper content makes the etchant rather toxic.
    permalink
    Posted 26th February 2011 at 02:26 AM by tomchr tomchr is offline
  3. Old Comment
    MJL21193's Avatar
    Not to encourage people to thrown the etchant down the drain (A MUCH bigger risk is an interaction with any household beach that may be in traps, etc.) but there is probably quite a bit more copper introduced to the sewage system from pipe erosion. Many thousands (millions?) of miles of copper pipe plumbs thousands of houses. This amount of copper erosion absolutely dwarfs any contribution from the occasional PCB etch.
    permalink
    Posted 26th February 2011 at 03:15 PM by MJL21193 MJL21193 is offline
  4. Old Comment
    Rodeodave's Avatar
    Check out this guy, he etches pcbs with vinegar, peroxide and salt:

    …still messing with forces I don’t understand – the formula.
    permalink
    Posted 14th March 2011 at 10:25 AM by Rodeodave Rodeodave is online now
  5. Old Comment
    Dmatuszak's Avatar
    I've etched by own PCBs for years and it's a real pain. I'm actually considering building a CNC machine to route my own boards. Curious if you know anyone here who has any experience with DIY CNC machines.
    permalink
    Posted 2nd May 2011 at 07:20 PM by Dmatuszak Dmatuszak is offline
 
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