Copperclad FR4

[fixit7]

What do you think about using copperclad FR4 and a dremel?

https://www.dropbox.com/s/w9umrenr60loyd3/HV_Proto_2.JPG?dl=0

I was wondering what happens if you accidentally cut too much copper off?
If the space is short, can you just solder the joint?

[ogden]

I was wondering what happens if you accidentally cut too much copper off?

Put it back   - Add wire or solder blob.
I suggest to skip this nasty&dusty dremelling that do not look much better than Manhattan style and try UV photoresist film + etching.

[Chriss]

He he...
Interesting. I like your design and idea. :-)

Sent from my SM-J500F using Tapatalk

[Benta]

This is standard procedure and done very often, but mostly with a small CNC mill.
It's costly though, as the FR-4 material will make mince of your cutting tool very quickly.

[Jwillis]

It's not glamorous but if it works for a prototype, why not .It might be cheaper ,easier and more compact to use protoboard but I like your initiative.Well done!

[Mechatrommer]

this will be much cheaper, quicker and neater...ymmv...

[fixit7]

I was wondering what happens if you accidentally cut too much copper off?

Put it back   - Add wire or solder blob.
I suggest to skip this nasty&dusty dremelling that do not look much better than Manhattan style and try UV photoresist film + etching.

O.K. I will stick with solder and wire.

[T3sl4co1l]

Hah, was that a Larkin special?

I prefer a utility blade.  Make a v-shaped cut, as deep as needed to get the width.  Or for wide cuts, or stripping areas, cut the perimeter and try to peel off the copper inbetween.  (Easier on 1oz+ copper, dreadfully hard on 1/2oz, it tears much too easily.)  Afterwards, go over the surface with sandpaper, or a scraper, to reduce high points (the cut turns up a bit of a burr).

Or Manhattan style, where you glue or solder small squares of PCB on top of a flat base (uncut copper).  That's good for making circuits with leaded components, where you need a ground plane that would otherwise be absent in a perfboard build.

But that's fine, using a rotary cutter, yeah.  As mentioned, do mind the dust, which includes conductive copper dust, so, try not to do it over your bench where you handle surface mount components and such.  Don't want anything shorting out.  And don't breathe it, don't want fiberglass dust getting your lungs all itchy from the inside...

Tim

[KL27x]

I usually use very thin copper clad FR-4 for this kind of thing. It's 0.007". You can mix it up with Manhattan style with just scissors. Glue it to a more rigid backing. I'm usually gluing this over existing PCB or protoboard or glueing bits to device housing/structural stuff or whatnot. I've even glued bits to the top of IC's to add SMD components to that bit of real estate.

Scoring is very useful for longer straight lines, but I find a diamond ball bur in a rotary/engraving tool is handy for tight spots and fiberglass doesn't dull it.

[T3sl4co1l]

I don't like using very thin laminate for most purposes -- too easy to cut through, or short out.  If you're doing it reliably though, absolutely.

I have however used it to great effect as low impedance transmission line: a 1/4"-wide strip has an impedance of something like 10 ohms, great for longer distance gate drives for example.

Tim

[KL27x]

a 1/4"-wide strip has an impedance of something like 10 ohms, great for longer distance gate drives for example.

Dunno what you think I'm using. It's 'posedly used for RF shielding and the like. The copper comes in standard thicknesses. I have had it in 1/2 oz and 1 oz pour copper thickness. 0.007" is the total thickness which includes the same copper layer as typical PCB's. I imagine a 1/4" wide track in 1 oz copper would be several meters before you would record 10 ohms?

If you are using high enough voltage, I'm sure you could short across the air gap left by Manhattan islands. I supposed, high enough, and you could arc through the FR-4. Anything low voltage, I imagine would be fine. Around 6 thou clearance "between traces" is not particularly remarkable. I've never had a short or arc.

edit: Oh, you mean impedance of signal propagation due to proximity/capacitance to ground plane? Yeah, I suppose that could be too close/thin for many things. Hot glue or doublestick tape adds some thickness, too, though. I don't know much about high frequency PCB design, how close you can get your layers/pours. To me, 10 Mhz is pretty high. I have never done a manhattan style prototype for speed reasons. Just convenience.

[bd139]

Manhattan works fine. Regularly use it up to 150MHz or so RF stuff without resorting to anything special. Can go deadbug as well.

I use 1.6mm stuff for the substrate and then 0.8mm stuff for the traces. The 0.8mm stuff is cut with some decent Fiskars scissors and the 1.6mm stuff with aviation shears. If you really want impedance control, based on the average Er of FR4, cutting 1.5mm strip of 0.8mm thick stuff is around 50 ohms. Loctite superglue is used to glue it.

Here's a pile of crap I have lying around that was done with it. The filter in that is a 70MHz low pass which is the fastest thing there and it has no weird responses up to 520MHz which is as high as I can go with my signal generator



Edit: if you don't want shorts, cut the 0.8mm stuff upside down with one blade of the scissors flat on the bottom blade. That stops the copper getting folded down. Never shorts.

[fixit7]

What are those 3 copper coils?

[Kalvin]

What are those 3 copper coils?

Looks like lowpass filter.

[bd139]

Yep low pass. 3dB at 70Mhz.

[Zero999]

I've done a similar thing before, but with a knife. It's much better than strip-board for high current circuits.

[bd139]

Yeah stripboard is basically made of fuse wire. Many a bit did I set fire to as a kid

[T3sl4co1l]

a 1/4"-wide strip has an impedance of something like 10 ohms, great for longer distance gate drives for example.

Dunno what you think I'm using. It's 'posedly used for RF shielding and the like. The copper comes in standard thicknesses. I have had it in 1/2 oz and 1 oz pour copper thickness. 0.007" is the total thickness which includes the same copper layer as typical PCB's. I imagine a 1/4" wide track in 1 oz copper would be several meters before you would record 10 ohms?

Sorry, characteristic impedance, as a transmission line.

If you are using high enough voltage, I'm sure you could short across the air gap left by Manhattan islands. I supposed, high enough, and you could arc through the FR-4. Anything low voltage, I imagine would be fine. Around 6 thou clearance "between traces" is not particularly remarkable. I've never had a short or arc.

I just mean it's not much distance for a stray goober of solder, or a fleck of metal, to cover.  Manhattan style pads can get quite thick with solder as you move things around, and you can drain that off the top, onto the surrounding board, but you have to be that much more careful you aren't leaving a tiny web shorting across.


Incidentally, I've seen a 4-layer ExpressPCB board used to prototype an industrial inverter.  That's 7 mil prepreg and the designer forgot to set internal clearance other than 7 mil.  Amazingly, most of those boards survived 650V, only one or two failed in the laminate!

OTOH, I had a job where they insisted on 40 mil internal clearance for 1.5kV transient rating only, and I can't possibly seem to make them understand that their outer dielectrics are only 20 mils thick...

Tim