LED temperature range

Try some! The big problem is that the transparent plastics tend to soften up at high temps, and the leads/chips can move around and break wirebonds. But 135C isn't very hot; we reflow solder boards with surface-mount LEDs at well over 200C.

Infineon makes some nice surface-mount led's with inner transparent plastic and an outer white shell of high-temp stuff. They hold up to heat very well.

John

Is an LED absolutely necessary? Seems like there are alternatives that will work just fine. The main problem with the LED's is going to be the packaging. Most of the time they are made of clear plastic like material that is not designed for high temp. Possibly there are some with glass bulbs rather than plastic. Potentially you could make your own housed in a small glass build if your really up to it.

Richard Rasker wibbled on Sunday 11 April 2010 20:53

Don't they usually use peristaltic pumps to get around this - the only bit of the pump in contact with fluids or the patient or sterile field is a removable bit of tube. The rest gets treated same as any other bit of electronic kit, eg wiped over with surgical spirit or whatever the disinfectant of the day is.

Most LEDs use packages that aren't appropriate (plastic lens); and the autoclave, in addition to heat, applies condensing moisture, which is a corrosion issue. Can you put the LEDs in a separate box, and use light pipes (plastic optical fiber) to get the light into the sterilized unit? There are connectors that accept light-emitter 'pins'.

Otherwise, I'd think of using grain-of-wheat incandescent lamps.

Sure, but these devices will have to withstand not just one short reflow cycle, but dozens of 5-minute sterilization cycles at 135C.

OK, if the transparent plastic is the main problem, I guess I'll have to look for LED's with a ceramic substrate to ensure stability of the semiconductor chip, and a heat-resistant outer shell like you mention.

Thanks for the swift response, best regards,

Richard Rasker

Lumex has ceramic-substrate (non-hermetic, though) SMT LEDs with storage temperature ratings of 120°C. Steam is fairly aggressive at corroding aluminum bonding wires AFAIUI-- you may not be able to find a part that is actually guaranteed for this kind of service. There used to be visible LEDs in the old hermetic TO-46 package, but perhaps no more, at least not at an affordable price. Here's one that's rated for 150°C storage.

Best regards, Spehro Pefhany

The die itself shouldn't be the problem, so it's not a fundamental barrier. I don't suppose this is an infusion pump, as those generally require some means by which to measure cam rotation angles, which implies quadrature detection to me. I don't know what your volumes might be, but some companies making diode detectors have been fairly cooperative about accomodating specific needs at surprisingly reasonable quantities. Not exactly the same business area as LEDs, but perhaps close enough. You might contact a few LED manufacturers and at least give them a chance to suggest their thoughts about meeting your specs. You might be pleasantly surprised by the response. (My contacts have been with both US and Japanese manufacturers. I believe Spehro Pefhany has more personal experience than many here about Chinese sources and may be able to reflect a little on that possibility.)

Jon

If the LED was captured and sealed, how would you connect the leads to the outside ?

How is this usually done with internal wiring ?

hamilton

That low temperature rating is for the clear epoxy case. You can probably heat them to 130C as long as there's no stress on the pins and you don't mind the lens degrading.

Power LEDs have a ceramic and silicone case that has no problem with high temperatures. The sapphire chips (green, blue, white) can even operate moderately well at 135C. They'll cost you dearly - maybe $4 to $10 each. Keep moisture out of them or they'll blister when they get hot.

Try: optekinc.com

There is another one that makes ultra-bright hermetic leds in metal cases, but it may take me a while to find it.

Steve

TO-66 cased leds,

Roithner is a reseller, but I cannot for the life of me remember the manufacturer. They do a lot of mil-spec work and often advertise in Photonics-Spectra and Laser Focus World. They also make stuff smaller then the TO-66.

Steve

And then I remember. Ah the joys of being 40 in a world of 23 year old Engineers..

Here it is:

Steve

Have you looked at some power LEDs designed for 0,7-1,5 A operation, which are claimed to work at very high temperatures and running such devices at much lower currents for indicator purposes ?

For instance the Luxeon K2 the claimed storage temperatures range of

-40 to +185 C.

The data sheet also claim:

Is this sufficient for your application ?

On a sunny day (Sun, 11 Apr 2010 19:54:18 -0700 (PDT)) it happened snipped-for-privacy@uakron.edu wrote in :

Now that is nice, a 3055 with build in headlights :-)

Yes, these temperature specifications would definitely suffice, and I'll certainly take these devices into consideration -- although the relatively high cost (some $5 each) may put the customer off. Ah well, that's not my problem :-)

Thanks for your suggestion, best regards,

Richard Rasker

K2 is out of production, take a look at Luxeon Rebel.. Then look at Seoul Semiconductor to get the costs down!

Steve

Rolling on the floor laughing my posterior off... Thanks Jan, that was exactly what I was thinking when I posted that.

Steve

From what I can find, LED's are specified for a maximum of

What's wrong with cobbling up a board that has maybe 25-30 of them and running them through a hundred autoclave cycles to see how many of them fail?

Jim