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I recently purchased LEDs on ebay that were supposed to come attached to star PCB (as a heat sink). The items I received are just the LEDs (no PCB). They are listed as 3W LEDs, with a forward voltage of 3.0-3.4V, and current at 700mA.

I received a partial refund. Will I damage / destroy the LEDs if I use them without a heat sink? If not, what is the best way to mount these to preserve their life during operation?

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  • \$\begingroup\$ Do you have a part number or data sheet? \$\endgroup\$ – Scott Seidman Jan 14 '15 at 17:27
  • \$\begingroup\$ Unfortunately, the only "datasheet" is what's listed on ebay. It's not really a data sheet. Just gives the info that I posted int the question (forward voltage and such). \$\endgroup\$ – snapfractalpop Jan 14 '15 at 18:53
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If you received actual 3 W LEDs and were to run them at 3.5 V, 700 mA without a heatsink, then yes, you will sooner-rather-than-later kill them.

You have three options.

  1. Run them at a lower voltage/current.
  2. Heat sink them, perhaps improvised out of some aluminum bar stock and metal epoxy (Home Depot)
  3. Buy star PCB heat sinks and assemble them yourself.
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  • \$\begingroup\$ Can something like gorilla epoxy work? It's a two-part epoxy, but doesn't say on the packaging what its thermal conductive properties are. \$\endgroup\$ – snapfractalpop Jan 16 '15 at 20:48
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Related: What is the purpose of star pcb?

At the very least, running them without a heat sink would degrade their operating life. You can buy cheap bare star PCBs off of eBay. Most are from China, but I see at least one set in the U.S. Soldering might be difficult unless you have a reflow oven or hot air station. You could try using a thermal paste, but I doubt it would conduct heat as well as solder.

If you design your own PCB, you can add a thermal pad connected to a ground plane. That won't work as well as a star PCB since star PCBs have an aluminum substrate.

If you don't care about light output, you could try reducing the current and using no heat sink. Start at 25mA and monitor the temperature of the thermal pad with an IR thermometer. The LED datasheet should give a maximum operating temperature for the rated lifetime.

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  • \$\begingroup\$ Do you think something like gorilla epoxy can work? It's a two-part mixture, but the packaging has no information about its thermal conductive properties. \$\endgroup\$ – snapfractalpop Jan 21 '15 at 3:03
  • \$\begingroup\$ I don't know for certain, but I doubt it. \$\endgroup\$ – Adam Haun Jan 21 '15 at 7:18

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