Old 04-25-2013, 06:46 PM #1
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Default Failure Temperature for 445nm diodes.

I am looking for the general failure temperature of blue diodes like m140, 9mm, and osram diodes. I have a digital probe thermometer that will be used to determine the efficiency of my heat sink cooling system, but I need to know the temperature limit I should avoid first. Does anyone know the temperature specs?


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Old 04-26-2013, 04:07 PM #2
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Default Re: Failure Temperature for 445nm diodes.

Depends where you measure .. the thin gold wires connecting the chip with electrodes will give way first usually .. but it would be pretty hard to measure temperature of those. How well that translates to temperature of the chip or the case is hard to tell.
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Old 04-26-2013, 04:16 PM #3
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Default Re: Failure Temperature for 445nm diodes.

I'm talking about the temperature of the outside of the diode. I know that the temperature of the chip is going to be greater than the outside temperature, but there must be some threshold of max temperature that can be taken from the outside of the diode.
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Old 04-26-2013, 06:19 PM #4
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Default Re: Failure Temperature for 445nm diodes.

It doesn't work like that. If someone said 80C (arbitrary value) was the limit, that doesn't mean 79.9C is perfectly safe and 80.1C means instant death. That's absurd. Besides, it's more about keeping efficiency high than not killing the diode. You'll never top 10 hours actual diode run-time in a pointer, so the life reduction means nothing to you. The hotter it gets, the lower the efficiency though.

TL;DR: Don't worry about it.
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Old 04-27-2013, 05:27 AM #5
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Default Re: Failure Temperature for 445nm diodes.

I'm not talking about an exact temperature. I'm talking about a general threshold. I'm making precision heat sinking. I guess I'll spend the money on a diode to blow out. I'll let you guys know.
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Old 04-27-2013, 08:25 AM #6
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Default Re: Failure Temperature for 445nm diodes.

First, i would just like to qualify the below post by stating that i am no expert on diodes, but I would actually like to know a little more about this topic too.

If you were to measure temp on the heat sink I know you would want to stabilize the heat sink temp before you could get any measurement that would give you insight into the temp of the diode..... and to make that situation repeatable when switching in and out diodes with a common press fit module would be tough.

Would it be better to measure it indirectly through efficiency with a LPM and power supply? modeling it sort of like a heating element that also gives off light?

edit: now that i think of it...maybe a combination of the two methods would be best for measuring the efficiency of your heat sinking system? any thoughts?...then maybe work backwards to the temp?



As for life of the diode, the common consensus here seems to be that it is a crap shoot, but i would think that you would at least be able to approximate the life of the diode maybe proportional to it's efficiency? ..assuming all other things being equal like duty cycle and heat sinking.
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Old 04-29-2013, 04:50 PM #7
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Default Re: Failure Temperature for 445nm diodes.

Don't waste your money on blowing a diode. Use the datasheet case temperature as your guide. It can be found here.

http://laserpointerforums.com/f65/9m...eet-80177.html
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Old 04-29-2013, 05:34 PM #8
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Default Re: Failure Temperature for 445nm diodes.

Quote:
Originally Posted by TheDukeAnumber1 View Post
Don't waste your money on blowing a diode. Use the datasheet case temperature as your guide. It can be found here.
Thank you sir. 50c
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Old 04-30-2013, 02:35 AM #9
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Default Re: Failure Temperature for 445nm diodes.

Thanks, Duke. That datasheet is helpful. you don't know of any diode life time data, do you?

Quote:
Originally Posted by TheDukeAnumber1 View Post
Don't waste your money on blowing a diode. Use the datasheet case temperature as your guide. It can be found here.

http://laserpointerforums.com/f65/9m...eet-80177.html
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