which adhesive to use to make copper clad circuit board?

[darron]

hey guys.


i've looked around and someone with proper experience might be able to tell me straight up what i need to do it correctly.



how should i adhere the cooper foil to the material? it seems like a UV glue or a heat/pressure bonding epoxy is the trick. i think if i just buy any two part epoxy i might have a failed experiment.



i'm in australia but i'm also happy to ship from UK/US etc.


RS usually have a nice wide catalogue for stuff like this.



thanks!

[John Lyons]

I've use epoxy to laminate thin FR4 copper clad to various sheet material.
This way you don't have to deal with heat issues with the bare copper on your
base material.

[darron]

Thanks John. If it's good enough for your standard of work then I reckon I should give it a go


Sounds like fun really... Maybe next I can look into rolling my own caps and casting my own aluminium enclosures.... or.. or.. nah..

[R.G.]

Commercial copper clad is made with epoxy adhesives to hold copper to glass-epoxy.

That being said, "epoxy" is not a single thing. It's a whole class of things, with varying compositions and performances. The epoxies used to hold copper to glass-epoxy are special formulations for holding, peel strength, and heat resistance under soldering. We used to have a circuit board fab house at TIC* that did many acres of 4 to 10 layer PCB stock per day. They kept a cadre of mechanical, manufacturing and chemical engineers busy keeping it running right. I believe it was a heat/pressure cure stuff, but usually the epoxy precursors were impregnated into the surface of the raw stock (see "pre-preg").

Heat softens epoxies. Soldering is heat. RoHS made it worse.

So all this is no help, just a bit of info on the size of the problem.

* Three Initial Corporation

[gritz]

@ R.G. - pre-preg sounds familiar - like carbon fibre fab. where parts are assembled dry and curing is done with heat / pressure in an autoclave.

Thanks John. If it's good enough for your standard of work then I reckon I should give it a go


Sounds like fun really... Maybe next I can look into rolling my own caps and casting my own aluminium enclosures.... or.. or.. nah..

Being an old fart I remember  a project in EW+WW magazine (a self-build Tesla coil) that involved literally rolling a 100nF 4kV capacitor from polyethylene sheet and tinfoil.  

[darron]

Good points R.G.


which makes me think, once the copper gets hot I don't want it to expel nasty fumes from the adhesive into my lungs too!

the appeal is that i'd like to try some different materials. i saw a youtube video of a guy using tempered glass for example: http://www.youtube.com/watch?v=Rf5HBLzDGQA

also, i think it would be cool for once to cut the material stock to size THEN bond on the copper.

might have to hit some suppliers for some advise on what they can sell me. i'm willing to have a bit of trial and error because it can be great for learning.

Being an old fart I remember  a project in EW+WW magazine (a self-build Tesla coil) that involved literally rolling a 100nF 4kV capacitor from polyethylene sheet and tinfoil.  

i've heard you tesla guys need to wrap your own caps for the high voltage rating! i imagine going to the kitchen and getting a roll of wax paper and a roll of foil and getting stuck into it.

perhaps you could strip back some pencils and shave them to get resistors too? hold on, i'm going to need an enormous chassis to build this now...

[frank_p]

Radio ham guys who build Manhattan style (copper clad on top of copper ground plane) use Super Glue (cyanoacrylate, Krazy Glue).  It's supposed to be less sensitive to heat than epoxies and less wait time between preparing and soldering.  I use it once in a while and it's relatively solid.  Epoxy is sensitive to too much heat.

[darron]

i'd probably try a test batch with different glues.


someone asked on that youtube video if cyanoacrylate would work and he said not very well, but then, i'm not stressing the traces much or doing heavy work or smd work.... i bet that might be okay

[R.G.]

the appeal is that i'd like to try some different materials. i saw a youtube video of a guy using tempered glass for example

I'm guessing that would make drilling difficult.  

i've heard you tesla guys need to wrap your own caps for the high voltage rating! i imagine going to the kitchen and getting a roll of wax paper and a roll of foil and getting stuck into it.

Rolling foil in poly sheet is OK for low voltage caps. If you want really high voltage caps, get precut sheets of glass - like maybe the glass for precut picture frames. Make a stack of glass, foil, glass foil, ..... glass. Make the foil be maybe 12mm/0.5" smaller on three sides than the glass, and longer on one side. Foil sticks out of the glass on one end and the other end alternately. These are the electrodes. Add as many layers as you need for capacitance. When you get done, firm up the stack mechanically (with nonconductors...   ) and then pot it in varnish to fill the spaces on the three sides of the glass interstices where the foil holds them apart. Or submerge it in insulating oil to seal out air and contamination.

The dielectric strength of window glass is about 10 MV/m (yep, ten megavolts per meter), so 1mm is 10kV. 1/8"/3.5mm  to 0.2"/5mm is a common thickness for such glasses. That puts the punch through rating for a pane of 3.5mm glass at 35kV. The capacitance rating is simply how many panes and sheets you want to buy.

In practice, glass capacitors hardly ever punchthrough, they fail by surface leakage paths and mechanical shattering. You'd have to either pot or submerse in oil a stacked glass cap to get the full performance out of it.

Although I had a neighbor whose window was punctured by lighting which struck a tree beside his house. It melted a hole about 0.5mm and heat warped some 10-12mm around it.

'Course, glass isn't the best, it's just the best easy stuff. Waxed paper is actually better (40-60 MV/m) but it's inconsistent and hard to get pure enough. Distilled water is better yet, with 65-70 MV/m; of course keeping it pure will be impossible. Over time it'll dissolve the metal or contaminates in the glass. Mica's good at 118MV/m, but it's hard to get big sheets.

[frank_p]

I still use a fuzz face and a Prof. Tweed done with Krazy Glue and the clads islands are still holding.  I had to reglue only one pad but it was because I pulled a wire that was soldered to a clad.  Never tried with epoxy...

i'd probably try a test batch with different glues.

It would be a good idea !

how should i adhere the cooper foil to the material

If you want to glue there are very thin pcb (like a flexible sheet): you glue the fiberglass side and the copper outside of the joint surface.

There is a guy who posted not long ago, he used copper ribbon with the adhesive already on one side.  The kind used for stained glass assemblies.  He sait it worked.

[darron]

i've done a bit of stained glass copper foil work (good for the little detailed areas). i can't recall, but i think both sides are shiny

i'm trying to get some stuff in from ebay made for pcb where one side is matte and course to adhere easier.





i just went through the RS catalogue (so it should be available to you guys in the US/UK/AU)

some candidates:


high temp epoxy. though it's advertised more for coating that adhering:
http://australia.rs-online.com/web/p/pcb-compounds-adhesives/6654830/



locktite 5145. used to bond electronic components. rated to 200deg C it seems:
http://australia.rs-online.com/web/p/pcb-compounds-adhesives/1987166/


this. not much information. hope it dries clear too..
http://australia.rs-online.com/web/p/pcb-compounds-adhesives/0567581/

[SteveG]

Is there a reason not to use the commercially-available CC board?

BTW, (off-topic, but with reference to a comment above) I've been involved in sand-casting enclosures, and it's a nightmare! It's a very painful process getting foundries to produce the desired level of quality.

Steve

[markeebee]

Hmmmm - I've got a roll of this stuff:

http://www.ebay.co.uk/itm/Aluminium-Silver-Foil-Tape-Self-adhesive-Heat-reflecting-Insulation-5m-x-50mm-/250966687087?pt=LH_DefaultDomain_3&hash=item3a6ec7bd6f

The roll I've got is about 150mm wide, if I remember rightly.  It's used by heating installers to seal ductwork, but I use it for shielding amp cabinets.  But......heat resistant, adhesive backed, conductive......I wonder if this'll do the trick?  Should also be able to etch it, I guess.

I'm at work for the next couple of hours, when I get home later I'm gonna do some experimenting.

[John Lyons]

Except that you can't (easily) solder to aluminum.

I've never had a heat problem use of the shelf two part epoxy.
But then I was just laminating two sheets and the copper was
a thin FR4 sheet...

[markeebee]

Results of the experiments are in.......and they say that, as always, John is right. Soldering on aluminium is a total sack-ache.

Hey ho.