S/N marking that won't wash off

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haklesup
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S/N marking that won't wash off

Post by haklesup » Mon Jul 26, 2010 12:47 pm

Does anybody have any recommendations on a system for marking serial numbers on boards that can stand up to wave solder and washing with isopropyl alcohol and Acetone. The numbers can be hand written or stamped just as long as they stay on the board. I've been scribing into the FR4 but that's hard to see.

No, A sharpie is not going to stand up here, neither is a sticker (or at least most of them).

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Externet
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Re: S/N marking that won't wash off

Post by Externet » Mon Jul 26, 2010 1:09 pm

Hello haklesup.
Am very sure there is adhesive stickers that are wash resistant, used them all the time in my workplaces.
Alternatives are Dremel, a embossed copper strip soldered on a trace/pad, true indeleble ink rubber stamp as the postal office uses, silkscreen ink in a rapidograph.

This is the typical industry standard, they are vinyl, kapton or mylar... permanent glue; printed on hot film transfer dedicated machines, no inkjets:
---> http://www.cisco.com/en/US/ts/fn/200/fn25954_hjkk3c.jpg

Suppliers:
---> http://www.ultbarcodes.com/electronic_pcb_labels.html
---> http://www.ablelabel.com/PolyesterLabels.html

For plain paper labels, Avery supplies in many sizes, with permanent adhesive too, but the whole label and sorroundings has to be protected with:
---> http://www.seton.com/labels-decals/cust ... s80-1.html

Look for Dymo products, they may have "harsh environment labels" <---(search term)

Miguel :smile:
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Janitor Tzap
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Re: S/N marking that won't wash off

Post by Janitor Tzap » Mon Jul 26, 2010 1:29 pm

How about etching the numbers on?

Here something: http://www.etching-metal.com/

If you have got to do multiple boards that would be the way to go.

If your only doing one or two boards, then a Dremel to etch to numbers would work.
Or how about using a Wood Burning Iron?


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Re: S/N marking that won't wash off

Post by Bear » Mon Jul 26, 2010 1:40 pm

When I was in sheet metal & electronics we used to use "self etching ink" that we bought from our silkscreen supplier. It was approved by the military as a "permanent marking device". It did not have to be SS on. It could be rubber stamped on as well.

Good luck, take care

Dennis

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Lenp
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Re: S/N marking that won't wash off

Post by Lenp » Tue Jul 27, 2010 4:34 am

haklesup.

I usually do text on the foil layer if there is no silkscreen and the data will all be the same, like part numbers or a copyright notice.
If the data is to be different for each board, I've seen block of non-electrical small pads in a matrix with different pads solder filled to form a code for date, serial, modifications.. etc. If the pad hole is small a quick spot of solder fills them up. Maybe rubber stamping or stenciling the boards with etch resist ink or paste before etching would also work!

Len
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MrAl
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Re: S/N marking that won't wash off

Post by MrAl » Tue Jul 27, 2010 6:52 am

Hi,


I've been searching for something like this for the past 30 years :smile:
Havent found anything that is quick and easy.
Most manufacturers dont know the meaning of the word, "permanent" do they?

An engraving tool comes to mind, where it vibrates and creates little dots. You can go pretty fast with one of those things, just like writing with a pen only the pen is much bigger :smile:

How about burning it in? PC boards burn with enough heat. If you want to get fancy maybe you can invent a burning stamp, something with letters on it that burns them in on contact (might not work though if you need really variable lettering). It might just have to melt the board a little.

They do make stamp sets, where you get a set of tools that all look like center punches only with either a letter or number on the end instead of a point. One quick tap with the hammer and you have a letter. Only problem is you have to do it once for each letter, which takes a little time.
I've also seen a center punch used where you create little dots to make up each letter, but that takes quite a bit of time to do.
LEDs vs Bulbs, LEDs are winning.

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Re: S/N marking that won't wash off

Post by ltx71cm » Tue Jul 27, 2010 10:36 am

What about stamp or permanent marker with a coating of clear solvent resistant paint (for lack of a better word)?

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haklesup
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Re: S/N marking that won't wash off

Post by haklesup » Tue Jul 27, 2010 4:45 pm

Its for PC boards so metal plates, burning or etching won't do. Stickers are fine for after assembly but won't hold up in an oven. Stickers, even good ones often let go when you ultrasonic clean them in solvent.

I noticed the ink they use at the PCB fab on the little round inspection stamps don't come off. It may be the same epoxy ink used by the silkscreen process. But what kind of stamp do they use that dosen't harden and need constant replacement. I plan to ask what they use.

Ultimately a UV cured ink that works with an off the shelf adjustable number rubber stamp would be perfect. Just not sure if that's a fantasy or not.

An acrylic or urethane conformal coat will protect a written number from alcohol but not acetone. Besides, we occasionally need to strip the conformal coat off of hard to repair boards. Thats when the S/N typically gets lost. I don't know of a clear coating that stands up to Acetone. (well, I think silicone would but thats a soft coating)

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Lenp
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Re: S/N marking that won't wash off

Post by Lenp » Tue Jul 27, 2010 7:08 pm

Maybe my post was a bit misleading but I was referring to stamping / screening the serial number, on a designated copper foil area BEFORE etching the bare board. The data would be as permanent as the traces and you could screen over it with it with resist if it is transparent. I have done this with acrylic printer's ink and a rubber 'band' stamper from http://www.1stopsquare.com/number.html. If space is restricted a 'peg stamp' could be used. These stamps are small wooden sticks with a rubber stamp on the end, a standard for years in the telephone trades for marking. They still available from P.K.Neuses http://www.pkneuses.com/www.pkneuses.com/numb.htm You probably don't need the whole kit but replacement rubber sheets of stamps are available for repairs and you could DIY the sticks! The ink must be dry for best results. Both Ferric Chloride and Ammonium Persulfate were used with no problems.
Len
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Re: S/N marking that won't wash off

Post by Externet » Tue Jul 27, 2010 8:09 pm

Hi.
Am constantly rubbing acetone in cotton to remove the flux residue after reworking, and the silkscreening on boards has never been even smeared. That ink has to be something good, stands on the solder tunnel just fine.
That ink on a numeric sequential rubber stamp would be something worth trying. :smile:
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Re: S/N marking that won't wash off

Post by dyarker » Wed Jul 28, 2010 6:56 am

?? Dry erase pen the serial number on film mask before exposing the etch resist. The number will left as copper on the board. Will be as secure as the other traces. Change number before making next board. ??
Dale Y

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haklesup
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Re: S/N marking that won't wash off

Post by haklesup » Wed Jul 28, 2010 11:43 am

I don't know of any PCB fab that can increment a S/N in any layer of a design even the silkscreen. If it is possible it would be expensive. The ink on a silkscreen is an epoxy paint applied through a screen. I am not sure the exact process but most epoxy inks only last a finite time after being mixed and activated.

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Re: S/N marking that won't wash off

Post by ltx71cm » Wed Jul 28, 2010 1:39 pm

These seem to meet all of your needs, adjustable for each number, high temp, chemical resistant and permanent. Traceable PCB labeling in the production process is even clearly listed as a use.

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Re: S/N marking that won't wash off

Post by jwax » Wed Jul 28, 2010 4:51 pm

Laser scribers are another option.

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Re: S/N marking that won't wash off

Post by dyarker » Wed Jul 28, 2010 11:56 pm

Thought you were etching boards yourself because of how sturdy you wanted serial number to be.

Add two drill holes to artwork, emboss number in sheet metal (like dog tags), pop rivet to PCB. That sucker ain't goin NO WHERE!

Cheers,
Dale Y

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