PCB Etching

User avatar
John Bateson
Posts: 808
Joined: Wed Jul 02, 2008 6:39 pm

PCB Etching

Postby John Bateson » Sat Jan 16, 2021 11:26 am

I needed a few small PCBs but did not want to get too complicated with laser printers and light sources etc. My cupboards of shame have far too many unused tools in them.

The board is rectangular with a gap along the centre of the long side and 4 holes.
241 Tender PCB P4 Single.PNG


This is easy to make multiple copies on an A4 sheet of sticky paperwith a small gap so they can be separated.

Usually once separated and filed to size and the holes drilled and countersunk (OK - I could use C/H but I wanted a flat surface to protect them from stray wires and DCC bits and pieces), ready for fitting with 10BA C/S brass bolts.
Then I replace the sticky paper with sellotape with a cleaning session in between. Followed by a dunking sessin in ferric chloride, but I have no idea how long this should take especially when it is 3 degrees in the shed/hobbyroom.

The results are untidy and I am very tempted to resume the "gouging out the centre line" method. At least I can get that tidy.

Any thoughts - for the number I need it is not economic to get them made professionally, but I would like them to look the part.

John
You do not have the required permissions to view the files attached to this post.
Slaving away still on GCR stuff ...

JFS
Posts: 813
Joined: Wed Dec 16, 2009 3:47 pm

Re: PCB Etching

Postby JFS » Sat Jan 16, 2021 4:12 pm

Well, I am not sure I fully understand the problem to be solved here, but if you want to get good results by etching you need a good mask - I hear you don't want to use a laser printer, but the job is actually very easy given that you have a drawing package; I used press n peel blue. It is dead easy, though I had the odd failure but then mine were more complex than yours.

It is pretty cheap (loads of on line sources - http://www.fortex.co.uk/product/press-n ... -transfer/) and just needs to be run through your laser printer and ironed-on

This bloke sort-of explains what is what:-
https://www.instructables.com/Etching-P ... ressnPeel/

Needless to say, the cleaning is the tricky bit.

If you don't have narrow tracks on your board, you can leave it in the etchant as long as you like as there are no down sides to over-etching. But you should pre-heat the etchant at 3 deg! Or put a fan heater on it!

I had about 60 to do and in hindsight, our friends in China could have done the job for about the same price as I paid for the materials ... ...

jasp
Posts: 141
Joined: Thu Dec 04, 2008 9:24 am

Re: PCB Etching

Postby jasp » Sat Jan 16, 2021 7:55 pm

There is nothing to stop you using sticky tap but the edges must be well rubbed down. You can stick the tape on and then trim to size and cut wee holes where required.
I would use a plastic based tape, not Sellotape type as it is not impervious to water based solutions like ferric chloride.
As stated, the ferric chloride will work better warmed up.
Jim P

Terry Bendall
Forum Team
Posts: 2420
Joined: Sun Jul 27, 2008 7:46 am

Re: PCB Etching

Postby Terry Bendall » Sun Jan 17, 2021 9:49 am

One solution would be PCB tape which can be obtained from the more specialist suppliers of electronic components. Those that we might expect to see at model railway exhibitions don't seem to stock this. An etch resist pen, or even a permanent market is another solution.

My solution would be to make a groove on the milling machine but first catch your machine. :) A fine saw cut along each side through the copper, perhaps with a piece of wood clamped to the board to get the cut straight and then remove the copper with a narrow wood chisel or the edge of a file is another possibility.

Ferric chloride needs to be reasonably warm (i.e. room temperature) to work effectively but a new solution should do the job is a few minutes

Terry Bendall

Alan Turner
Posts: 643
Joined: Sun Jul 20, 2008 4:24 pm

Re: PCB Etching

Postby Alan Turner » Sun Jan 17, 2021 11:55 am

I suggest you get it drawn up in a PCB software package and get China to produce them for you. With your dimensions you would get about 40 for£12 ish.

Try SEEED Fusion (https://www.seeedstudio.com/fusion_pcb.html) or JLCPCB (https://jlcpcb.com).

regards

Alan

User avatar
ICollett
Posts: 39
Joined: Wed Nov 20, 2013 10:46 am

Re: PCB Etching

Postby ICollett » Sun Jan 17, 2021 12:21 pm

You can get good results from Ferric Chloride etch using a tape stencil mask, also by using spirit marker pen ('Sharpie') as the etch resist. However, the FC needs a reasonable temperature to be active (30-50 degrees C) and the solution needs agitation as oxides form on the target area that inhibit contact between etchant and the material to be removed. On PCB the copper layer is measured in microns and I would estimate 10-15 minutes would do it, but as you should be agitating the bath (gently tipping to and fro) then you will see when the etch is complete.

NB: ALWAYS WEAR PROTECTIVE EYE WEAR WHEN USING ETCHING CHEMISTRY

I've used a Bain Marie arrangement to heat the etch solution, put the etch bath in a larger bath filled with hot water so the water cannot spill over into the etch batch - that should give the temperature the FC needs to get to work.

Another way to overcome the oxidation problem along with agitation is to use FC in an 'Edinburgh Etch' mixture - the recipe is on the internet but it's just a case of adding 20% of Citric Acid to the FC. A small bottle of supermarket concentrated Lemon Juice would do the job. This not only speeds the etch process by removing the oxides from the etch, but is reported as extending the lifespan of the FC mix.

https://www.nontoxicprint.com/etchcopperandbrass.htm

Good luck and happy etching.

Enigma
Posts: 533
Joined: Tue Aug 13, 2013 2:49 pm

Re: PCB Etching

Postby Enigma » Tue Jan 19, 2021 11:53 am

I've etched nameplates using Letraset, magic marker and/or nail varnish. Just left the item in the ferric chloride at normal room temperature (with occasional agitation) until it was sufficiently etched for the letters to stand out. I've also used the edging from Letraset sheets to etch straight lines with the area outside the straight line filled in with nail varnish etc. as a resist.

User avatar
ICollett
Posts: 39
Joined: Wed Nov 20, 2013 10:46 am

Re: PCB Etching

Postby ICollett » Tue Jan 19, 2021 12:42 pm

Enigma wrote:I've etched nameplates using Letraset, magic marker and/or nail varnish. Just left the item in the ferric chloride at normal room temperature (with occasional agitation) until it was sufficiently etched for the letters to stand out. I've also used the edging from Letraset sheets to etch straight lines with the area outside the straight line filled in with nail varnish etc. as a resist.


Thanks for the pointer Enigma. Can I just confirm, you're not using the Letraset lines as an etch resist but as a mask for the nail varnish? Do you then peel off the Letraset to leave the metal open to the Ferric Chloride? Or does the FC eat away the Letraset and then attack the metal that's not protected by the nail varnish?

I have to admit I used to use tons of Letraset back in the last century, but I hadn't thought of it for etch resist purposes.

Cheers.

Enigma
Posts: 533
Joined: Tue Aug 13, 2013 2:49 pm

Re: PCB Etching

Postby Enigma » Tue Jan 19, 2021 1:39 pm

The Letraset is the resist to create the raised letters as are the straight lines used to delineate the edges of the nameplate etc. Nail varnish etc. is just a rough 'infil' to cover areas of brass etc. not required to be etched. After etching the Letraset is removed with glass fibre brush, scraping etc. Nail varnish is removed with cellulose thinners - or nail varnish remover. Permanent marker also works as a resist to fill in 'general' areas not requied to be etched.


Return to “Other Workshop Practice”

Who is online

Users browsing this forum: ClaudeBot and 0 guests