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Thermal management of through-hole leds

I have some leds in 8 mm through-hole packages, rated for 0.5 W, maximum steady current 100 mA. The legs are extra wide at the top, but there is no other built-in heat sink. These are chinese cheapos from ebay and no proper datasheet was supplied.

I intend to lay these out in a lattice on a stripboard, but I'm worried about thermal issues. How closely can I position the leds? Do copper strips provide enough additional heat dissipation area, or do I need to etch and drill a PCB? At the very least I suspect I should leave the legs sticking out from the board instead of cutting them.

Also, is there some way to measure the temperature of the led to check if heat dissipation is sufficient?

Typical through-hole leds are low-power so heat isn't much of an issue, and typical power leds are SMD and have dedicated heat sinks.

0.5 watt through-hole leds seem to be in a grey area and I can't find much information on them. Any advice is appreciated.

Thanks,

Lauri

Reply to
Lauri Alanko
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I don't know about the 8mm leds. But for the 5mm ones if you look into the package you can see that the lead going to the anode (more positve end in normal operation) is mounted right to the device, whereas the cathode lead is a wire bound. (I don't know if this is universal or just the most commo n configuration). So I'm thinking that if you make a big copper pour for t he anode side of the led that will help conduct some of the heat out of the led. Of course you still need to get rid of the heat in the copper on the pcb. To measure the temp you might try sticking a little thermocouple on the same anode leg.

George H.

Reply to
George Herold

Hi, what do you mean by "stripboard?" Not those plug-in plastic breadboards, I hope.

but I'm

The legs will help a little, but their surface area is small. Best thing would be to solder the chip-side leg (as George says) to as much copper as possible, as close to the LED as possible.

Air flow would help a lot, like a small fan.

A small thermocouple or thermistor glued to an LED in the middle of the array. Wrap the lead wires around the LED a turn or two.

What are you making?

--

John Larkin                  Highland Technology Inc 
www.highlandtechnology.com   jlarkin at highlandtechnology dot com    

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Reply to
John Larkin

From the period reading electronic hobby magazines from the UK, "stripboard" is perfboard with strips of foil along the holes along one axis. So it's not perfboard with copper all over, but perfboard with strips of copper. You cut where you don't need continuity.

Michael

Reply to
Michael Black

It used to be a reliable indication that the cathode was always the "pedestal" lead frame, but around the 80's or 90's they came up with a new material for ultra-bright LEDs with the "pedestal" lead frame was the anode.

So I'm thinking that if you make a big copper pour for the anode side of the led that will help conduct some of the heat out of the led. Of course you still need to get rid of the heat in the copper on the pcb. To measure the temp you might try sticking a little thermocouple on the same anode leg.

A good idea in principle - but melting loads of solder on carries the risk of cooking the LED before current flow gets anywhere near it.

Low melting point solder maybe, but the last time I saw any it was cadmium based - probably banned by RoHS.

Reply to
Ian Field

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