Where to buy flexible circuit boards

Something I always wanted to try was sticking copper tape to transparency film to make my own flex circuits.

I suppose sticking packing tape to copper foil would be worth trying too.

Kevin McMurtrie hath wroth:

Page 8 has the start of the thermal calculations.

Ok. That's 35/12 = 2.9 watts/LED. What duty cyle? The calcs in the app note (Pg 9) result in a 10degC/Watt system using FR4 PCB. If you dump 35watts into that, you'll get 350C+25C(ambient) which is sufficient to set fire to your pocket before it destroys the LED's. You'll either need something better than a PCB or reduce the average dissipation by reducing the duty cycle. Apparently, by using optimized components (i.e. thermal epoxy) you can cut that in half, but it will still be too hot.

It doesn't have to be a block of copper. That's overkill. Go to the hardware store and find an overpriced piece of copper roofing flashing. It comes in several thicknesses from 0.010 to about 0.020. That should be thin enough and light enough for your light. How big it needs to be is dependent on the duty cycle at the 35 watt level.

Barf. If you're going *through* the G10 PCB, as in a double sided PCB, the thermal resistance will be horribly high and a function of the number of plated through holes under the LED thermal pad. You're more likely to burn the board before any significant heat goes through the board. You can try doing it on the same side as the PCB, but that's also going to be a bigger problem. The Cu layer is quite thin and will not conduct much heat to the aluminum.

Copper roofing flashing. If you need more dissipation, bolt on a block of finned aluminum heat sink or fold the Cu sheet to get more surface area.

If you're lucky your local hardware shop has Shim-in-a-can. Also try stained glass supply stores.

snipped-for-privacy@netzero.com hath wroth:

I beg to differ somewhat:

Shim-in-a-can is usually available in rather thin foil sheets. Foil will work, but something thicker, such as 0.025" will move more heat. That's why I recommended copper roofing flashing instead of shim stock. It's also cheaper as the thickness doesn't have to be as carefully controlled as shim stock. I guess a roofing supply house or lumber yard might be more appropriate for copper roofing flashing.

The local hardware store has Shim-in-a-can, but only in brass and stainless. Copper is special order.

I once dabbled in stained glass. The suppliers have 1.0 and 1.5 mil copper foil tape, but not copper sheet stock sufficiently thick to make a suitable heatsink.

I have no idea what you're referring to here but it sure threw off the replies. There was never a block of copper, pulse modulation, or G10 boards.

As I said, copper plates are not practical. I used a .062" x 1" copper strip with a pattern of holes drilled in it. It cooled fine but it's nearly impossible to build and it's not durable. Do have any idea how small the Rebel LEDs are? The whole LED is smaller than a soldering iron tip. Maybe I should also mention that the high-binned LEDs are $6 each. After a few practice runs with recycled low-binned LEDs, I need a reliable technique. LEDs mounted on the edge of copper strips are always heavy, unreliable, fragile, and expensive.

Back to the original topic, I'm looking for something like Pyralux sheets. Surface mounting is the only reliable way to use these LEDs. I'm hoping that passing heat downward through a very thin film PCB lets me use close spacing while keeping the LEDs at efficient operating temperatures. I haven't found any place selling thin film/flexible sheets so I haven't been able to experiment with them.

Kevin McMurtrie hath wroth:

Sigh. 2nd try:

DuPont has a product sample request form:

The Mars rovers used Pyralux boards made by Pioneer Circuits in Santa Ana, CA. You might ask if they have a sample:

Sorry, I didn't realize that the LED's were so small and the weight was such a major concern. However, you might want to continue where I left off on the thermal resistance calculations. 35 watts is an awful large amount of heat do move through a few holes and a thin piece of laminated copper.

snip

Well, it's not thin-film, but it's easy enough to get thin-ish PCB stock, I have some that's 9 thou thick and is about as flexible as a business card. Could you etch that, then epoxy it onto the alloy heatsink?

Barry

Thinking out loud: for a proto would conventional copper tape (from digikey or any other electronics supplier) attached to a backer work? You can even various polyimide films from mcmaster-car for a backer .... "Polyimide (Kapton) Film Thermally Conductive"?

I see that Kapton polyimide is used as a heatsink insulator. I guess it conducts heat well enough in thin films.

No, I can't put copper tape on whatever polyamide is around. It has to be thermally stable or it will curl up into a little wad.

Digi-Key, Future Electronics, Jameco... Any others to check?

Kevin McMurtrie snipped-for-privacy@dslextreme.com posted to sci.electronics.design:

Not sure if you are aware of them but there is Allied, Newark, and Mouser, and probably many, many others.

I found those online stores on an electronics hobbyist web page - No flex boards. I contacted DuPont to see if they have any distributors for Pyralux. Insulectro has a distribution office two miles from me. Maybe they'll sell me some of the Pyralux sheets listed on their surplus/promotions page.