PCBs on glass

Possibly slightly odd question here - I'd like to use glass (as in the stuff you have in windows, not fibreglass) as a PCB substrate, approximately A5 (210x150 mm) sized. As far as I can see, there's three options. The first is to stick some copper foil on, the second option would be to evaporate copper onto the glass, and the final option would be to use electrolysis. Afterwards I'd do the usual photoresist/etch steps to get a PCB. I can't seem to find much information at all on any of these. The main things I'm looking for are surface preparation tips, and things to avoid due to them reacting badly with the photoresist.

One thing that makes it slightly more complicated is that the glass must remain transparent (outside of the tracks). Roughing the surface will probably be OK as I'm going to be using an optical epoxy to sandwich the PCB side (with SMT components) to another piece of glass, but I don't want the copper to bleed into the glass (which would presumably result in a green tint).

Any tips/links appreciated, or if anyone knows where pre-coated glass can be obtained from in Australia let me know.

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Michael Brown
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Reply to
Michael Brown
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If the copper part doesn't have to be transparent, just stick the foil onto the glass and etch it or use a press-n-peel premade copper pattern.

Otherwise, if it needs to be transparent, then you're getting into vapor deposition and molecular-beam epitaxy and stuff like that.

But somebody's got transparent conductive stuff (like the touch-screen folks), but you'd have to look that up. )-;

Maybe

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or similar.

Good Luck! Rich

Reply to
Rich Grise

Actually, printed wiring on glass is a known technology; porcelain-on-steel circuit boards and additive copper (silk screen applied, I believe, possibly electroplated to add thickness) is a rugged-duty standard. Last time I saw it used, was for relays (too heavy for a flimsy plastic board).

As far as adhesion is concerned, the porcelain is just a kind of glass.

Surface mount soldering to such a board, however, may require some finesse.

Reply to
whit3rd

Actually, printed wiring on glass is a known technology; porcelain-on-steel circuit boards and additive copper (silk screen applied, I believe, possibly electroplated to add thickness) is a rugged-duty standard. Last time I saw it used, was for relays (too heavy for a flimsy plastic board).

As far as adhesion is concerned, the porcelain is just a kind of glass.

Surface mount soldering to such a board, however, may require some finesse.

Reply to
whit3rd

You could look into how the astronomy guys silver home-made mirrors. I know I've seen at least one do-it-yourself vacuum deposition project on the web. There are also chemical methods, but I'm not sure how the chemistry would transfer over to copper.

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Ben Jackson AD7GD

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Reply to
Ben Jackson

Actually there's a fourth - silk screen silver loaded epoxy (conductive ink) directly onto the glass. I did this over 20 years ago on a coke can and the front of Electronics Weekly. I framed the mag with a working flashing LED circuit and sent it to the mag. Got an article and interview out of it. 3D circuits were all the rage then but nothing came of it.

ian

Reply to
Ian Bell

Come out of the PCB thinking. Take a glass used for solar-panels, print(silkscreen) silver paste on it, cure it at high temperature. Have a look at Hybrid manufaction for the paste.

Probably the epoxy will tear off the components due to different thermal expansion. it is actually a big problem to even find some suitable backside coating for solar panels, let alone hard and transparent stuff.

Schott, Germany

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ciao Ban
Apricale, Italy
Reply to
Ban

How are you going to make the holes in the glass? Feedthroughs, crossovers, etc.

Tam

Reply to
Tam/WB2TT

Could you use transparent flex pc boards? That's a very common thing. They even come with peel-off adhesive, so you could just slap it down on the other piece of glass. Multilayers with vias are standard.

John

Reply to
John Larkin

What do you need it for?

If you can stick a normal but very thin fibreglass PCB to the glass I would expect that to be most convenient. If you really need to metallise the glass, and if you can afford to have this done professionally then it might be worth asking Lintek

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whether they would do this, as their PCB process is based on vacuum deposition.

Chris Jones

Reply to
Chris Jones

No matter how you might manage to get conductive traces onto the glass substrate there is a slight problem when trying to make connections to items which require soldering. In my experience glass doesn't take too kindly to sudden and localised heating as you would get from a soldering iron. Then there is the problem if you need holes in the glass...

Now ceramic substrate is a different matter, and this is used in specific circumstances. I would forget about glass if I were you and go for a more commonly used method which will work and will be far cheaper.

Reply to
Ross Herbert

I've never managed to damage it that way, OTOH could always use a reflow oven, or hot air.

IIRC I've see spade lugs soldered to rear window demisters.

the mirror guys know how to do that, and I've seem the windscreen repairers do small holes.

Bye. Jasen

Reply to
jasen

You seem to have it all sorted out, go for it!

Specialised glass - no doubt with pre-cut shape & size (bugger! I should have made that a bit smaller, now it won't fit the case) Specialised technique for applying conductive material. Specialised techniques for attaching connections. Specialised hole drilling.

All in all, just the sort of facilities one would have available in a small scale electronics production workshop.

Oh, did you say you would get these things done by outside contractors?

I wonder how interested a company would be (ie. one which might have similar facilities to those which make car windscreens with heated wiring and connectors attached) would be in your project. "Sure, we can rejig our equipment which is set up to make windscreens to manufacture your non-standard clear glass circuit mounting substrate - how many millions do you want?"

Bye.

Reply to
Ross Herbert

Pyrex?

Its probably worthwhile investigating the different types of glass available and their properties.

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Paul Hovnanian     mailto:Paul@Hovnanian.com
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Reply to
Paul Hovnanian P.E.

Using glass for a PC board is nothing new. It was done in the '70s for CATV notch filter traps for pay TV. Any attempt to open the filter caused a sharp steel spring to shatter the glass, in an attempt to keep it from being reverse engineered.

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Reply to
Michael A. Terrell

be

Maybe a borosilicate glass (pyrex) that's silvered and then etched? Or more likely have copper evapourated onto it as a mirror. Won't carry much current in the traces but maybe OK low low frequency cmos

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Dirk

http://www.onetribe.me.uk - The UK\'s only occult talk show
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Reply to
Dirk Bruere at NeoPax

Just bonding a copper sheet to it and etching would seem pretty easy. Vias are another matter.

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Dirk

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Dirk Bruere at NeoPax

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