I’m testing LED diodes – life test.

Can anyone help me with determination of upper test temperature?

Operational temperature is -40°C to +50°C.

Can I exceed upper temperature and if so for how much?

Kind regards,
Bla¾
blaz.kramer@yahoo.com

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3 Responses to LED diodes – Life test

  • Greg Nuttall says:

    For an LED diode life test, the industry metric is L70. That is the time at which the LED will only output 70% of its original lumens. You will need a photometric test set to monitor this. IESNA has some great standards you can use such as LM-80.

    The temperature of an LED is usually based on the junction temperature (Tj) of the LED. You will need to consult the manufacturer about how to best measure the Tj and there will be a maximum rating for which the Tj is acceptable while operating.

  • kew says:

    Yes, you can exceed 50′C. There are two limit to consider, firstly, the plastic glass transition temperature. Usually the manufacturer does not share this, but it is over 100′C. Secondly, is the LED Die Junction Temperature (usually 100′C to 125′C). This is usually shared in the LED datasheet. As long as you do not exceed either of these two temperatures, you will not kill the device prematurely.

  • admin says:

    If it is a HALT, sure you can. But for a life test, it gets a bit dicey as you start pushing the temperature because LEDs do have a predominant wearout mechanism. You better check with the manufacturer to find out what life tests they have already done and what they are comfortable with from a physics of failure point of view. It all comes down to the failure mechanism and your use profile – what environment, what power level, etc.

    Mike Silverman

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