How do I etch PC boards?

[jdcolombo]

Etching PC boards is a skill I need to learn.  I vaguely understand the process - you "mask off" the parts of the board you want to leave, then etch away the rest using a chemical.  But that's about the extent of my knowledge.  So . . .

1.  What do I need to do this?  Are there "starter kits" available?
2.  Are there good instructions somewhere on how to do this?  I've seen several summaries on the web, but all of them seem to have a slightly different process; if there's a go-to resource for this, please let me know.

Thanks!

John C.

[crusader27529]

From my experience, the easiest and cheapest way to etch PCBs is to use the Laset Printer transfer method. It takes a bit of experimentation to get it to work well, and is only usable for single sider boards, but it's do-able.

Google the process, but basically using shiny photo paper, the image is transferred to the copper plated board. The laser toner is a black polymer(plastic), and after it's on the paper, re-heating it with an iron of laminating machine, the toner softens enough to transfer to the copper. Most laminating machines need to be modified to produce the required heat, but it's more consistent than using an iron.....

Good Luck.....depending on how many boards you need, it may be cost effective to get it done professionally.

I use https://easyeda.com/. Shipping vaies, but the overall process is very professional allowing 2-sided boards, and takes about a week TOTAL.

[railnerd]

Short run prototype PCB production, either in China or USA is really cheap now:

https://oshpark.com
$5/square inch for 3 2-layer boards, other options available
USA (PDX/Oregon)

https://www.seeedstudio.com/fusion_pcb.html
10 10cmx10cm PCBs for $4.90 + shipping
(don't bother ordering until after Lunar new year)

My friends at MRCS use seeedstudio for all their PCB production— a bunch of us combine orders to save on shipping

[ednadolski]

Can they do boards to mount SMD parts?  My thought is if it would be useful to etch PCB boards for mounting the small SMD IR chips as discussed in this thread:

https://www.therailwire.net/forum/index.php?topic=43970.msg563170#msg563170

Ed

[railnerd]

Can they do boards to mount SMD parts?  My thought is if it would be useful to etch PCB boards for mounting the small SMD IR chips as discussed in this thread:

https://www.therailwire.net/forum/index.php?topic=43970.msg563170#msg563170

Ed

Yup.  BTW: a board to hold the IR LED and Photo transistor would be pretty easy to do.

-Dave

[mmagliaro]

If you still want to do it yourself, the iron-on transfer stuff is called PnP Blue.  You basically draw out your board,
with the areas you want PROTECTED (the areas where you want the copper to REMAIN on the board) in black,
and the test in white.  Then you "flip" the image in your favorite editor so it is a mirror image.

Then you print the pattern on a sheet of PnP Blue.  You have to use a laser printer, no ink jet.  If you don't have one,
you can print out the pattern and then get somebody to photocopy it onto a sheet of PnP Blue.  The hitch there is that office stores where they do copying may not want to put a sheet of "something from you" in their machine to print on,
but I was able to get Office Depot to do it many many years ago when I did this.

When you're done, you scrub your copper board very very clean with a scrubby (steel wool is okay, but be sure to wash the board and let it dry really well afterward, because steel wool sometimes has coatings or oils in it to keep it from rusting).

Now, you place the PnP Blue sheet on your board, and use an iron to iron-on the pattern to the copper.

That's it!  Now you place the board in a GLASS tray of ferric chloride solution (can be bought at many on-line electronics supply places), and gently rock the tray back and forth until all the unwanted areas are etched away.

It works fine for hobby-grade boards and can handle 0.1" spaced IC pins, but nothing finer than that, and I don't think I'd trust it to do really tiny surface mount pads and traces.  The problem is that when you iron it on, there is always some "mushing" and "spreading" of the pattern.  It isn't a lot, but might make very tight pads mush together.

======================
After that long-winded diatribe... These days, there are enough places on line that will take your pattern and etch boards for you, that I don't think I'd do this myself again.  They will also DRILL the boards for you, and that can save you a lot of time if you've got 50, 100, (or hundreds!) of component holes to drill.

[C855B]

Yup.  BTW: a board to hold the IR LED and Photo transistor would be pretty easy to do.

Wellllllll... yes and no. There are physical attributes to consider, including chip proximity and line-of-sight issues. I've been trying to go down this path since the weekend, and one of the keys (I believe) is finding a prototyping house that will do 0.010" substrate for any board that will mount on the roadbed surface, whether replacing a tie or nestling down between ties. Thinnest I'm finding so far is 0.6mm, or 0.025". The proof-of-concept has the IR LED in a hole which shields the phototransistor from direct line-of-sight. This is important to prevent falsing.

Dave, I checked your two favored PCB houses and they don't go that thin, nor do the others such as dirtypcbs.com. Do you know of anybody who handles 0.010"?

The concept I'm after is building a replacement tie. Atlas and ME ties are 0.050", so the idea is a .010 board will be topped by an .040 hunk of plastic which provides the shielding.

[peteski]

For small, simple, one-off boards I do those at home. I have done this type of etching for around 40 years.  A short tutorial is in this post.

For more complex boards I recommended https://pcbfx.com/ to few friends and they liked it.  Laser printer is needed.

Then, as mentioned by others, there are many PC-board fabrication houses which will produce the boards from your design. You do have to learn to design them first.  The process is a bit daunting.  @nscaleSPF2 used this process to make his PRR signal heads.  He documented some of it here.

[railnerd]

Dave, I checked your two favored PCB houses and they don't go that thin, nor do the others such as dirtypcbs.com. Do you know of anybody who handles 0.010"?

To go that thin, you need to go to a "flex" PCB.  Seeed offers these down to 0.1mm and 0.15mm— but you don't want to pay the prices for those ($316.72 for a 10 10cmx10cm single layer!!)

Either building a 3D printed or resin "holder" for the parts might prove interesting— a normal PCB could still hold the parts if the entire module was a "roadbed" module that *could* be carefully ballasted.

-Dave

[C855B]

Yeah, that's what I'm finding after some headache-y online searching. If I can find somebody who does 0.020" laminate (versus 0.6mm) it would be just thin enough to keep the IR emitter below the plane of the plastic topper. Aside from not soldering wires directly to the SMD, the objective is to not rout the roadbed or otherwise recess the sensor pair.

[Lemosteam]

I have been "watching" this product on ebay for some time for a project i have been contemplating.  I am also wondering if this material could be laser cut as the PCB houses will not make holes as small as I want.

If you scroll down the listing there are various thicknesses and sizes available.



https://www.ebay.com/itm/Pyralux-Kapton-Flexible-Printed-Circuit-Board-Material-Various-Models-9-x-12/152302446652?ssPageName=STRK%3AMEBIDX%3AIT&var=451505655071&_trksid=p2055119.m1438.l2649

[jdcolombo]

Hi everyone.

Thanks for the suggestions.  The reason I wanted to learn how to do this was for "one off" projects, not multiples of things, which I realize would be much easier to do (and not terribly expensive) by using a PC board service.  I'll read up on the laser-printer-transfer process and see where that takes me.

John C.

[peteski]

Hi everyone.

Thanks for the suggestions.  The reason I wanted to learn how to do this was for "one off" projects, not multiples of things, which I realize would be much easier to do (and not terribly expensive) by using a PC board service.  I'll read up on the laser-printer-transfer process and see where that takes me.

John C.

For truly simple one-offs it's hard to beat the all-manual process that I use. No computer, no fuss  - just an old technical drafting pen, some old Testors paint and some etching solution.
 

[Steve Smith]

Etching PC boards is a skill I need to learn.  I vaguely understand the process - you "mask off" the parts of the board you want to leave, then etch away the rest using a chemical.  But that's about the extent of my knowledge.  So . . .

1.  What do I need to do this?  Are there "starter kits" available?
2.  Are there good instructions somewhere on how to do this?  I've seen several summaries on the web, but all of them seem to have a slightly different process; if there's a go-to resource for this, please let me know.

Thanks!

John C.

A quick and easy method for small projects can be found on Youtube at :

/>
A black felt tip marker pen is used to trace or hand draw the schematic on a board cut to size, left to dry, then etched using ferric chloride solution which you should be able to buy from any electronics store or photographic chemical supplier.  You do not need a special etch resist pen, any marker with a pigmented ink will do.

The steps are :
- Design and trace the NEGATIVE copy of the circuit on the copper clad side of a piece of PCB board cut to size, and drill holes for the electronic components to be fitted.
- Properly clean the board.  I use a detergent wash followed by denatured alcohol to remove traces of grease.
- After cleaning, only handle the board with cotton gloves.
- I use a felt tip marker with a 1 mm tip to draw the diagram on the copper clad side, and draw two lines (to 2mm wide), which I then mark over with a second tracing when dry.  Make sure the deposited trace has a reasonably thick layer to prevent undercutting when etching.  Let it dry completely before etching. 
- When working with ferric chloride, wear safety goggles and rubber gloves, it is highly corrosive.
- Pour a little ferric chloride in a flat bottomed plastic tub (do NOT use a metal container), to just cover the board with the copper clad side up.
- Hot water can be used to speed up the process.  Place the etching container in a larger container and fill the larger container with water.
- Gently agitate continuously until the copper has been completely etched away, leaving the marked tracing on the board.  Again, only use plastic tools to agitate/lift the board from the solution.
- When done, remove the board from the solution and dip/wash in clean water to stop the etching.  Complete etching could take anywhere from 10 to 20 minutes.  I lift the board from the solution using plastic tongs, and gently blow the solution off the surface to see how it is progressing.
- Dry the board with paper towels, and clean off the tracing with denatured alcohol.
- Ferric chloride can be reused a few times, but will require longer etching time each time it is reused.  Keep used solution in a separate container and mark how many times it has been used.
- Disposal of ferric chloride may be regulated in the US, please check local regulations.   I dilute with copious quantities of water and pour down an outside drain.
- Clean all containers and tools used for making/handling the board under an outside tap; do NOT clean inside.  Ferric chloride etches copper alloy metals, so pipes and fittings could suffer damage.

Hope this helps.
Steve 

[peteski]

I tried using the permanent marker method few times (years ago) using various brands of markers, but none of them had ink dense enough to fully isolate the copper from etchant. That is why I changed to using a hobby enamel paint.

But that video made me think: nowadays paint markers with fine tips are available. Those might work very well for drawing the resist patterns on a circuit board. I also use a household copper cleaning powder (not just detergent) to get the copper really clean. And like the video shows, one has to be careful not to touch the bare copper. Gloves work well.