From: Spehro Pefhany
Subject: Re: luxeon star leds
References: <3DE15871.EF8FF9EA@RobertsResearchInc.com> <3DE224D3.81EFBA3C@RobertsResearchInc.com> <3DE4C4C1.50072B92@RobertsResearchInc.com> <3DE62B7B.53D088E8@RobertsResearchInc.com>
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Date: Fri, 29 Nov 2002 18:46:19 GMT
NNTP-Posting-Date: Fri, 29 Nov 2002 13:46:19 EST
On Fri, 29 Nov 2002 18:25:14 -0000, the renowned "R. Lewis"
>"Leeper" wrote in message
>> This thread is kinda scary, folks, you really need to heatsink these
>> devices very well.
>> At the seminar, LumiLeds (Luxeon), mentioned there have been
>> many cases where engineers have claimed they were keeping the
>> devices cool. Analysis of the failed devices, then taking a look
>> at the devices in their application showed they were not being kept
>> cool enough, causing subsequent early failures of the devices.
>At the beginning of this thread I asked the question as to how to know the
>die temp on a luxeon emitter and/or star.
>Luxeon quote a tempco of 2mV degC but I found some problem in that the temp
>rise on the (star) mcpcb was grater than the temp rise of the junction
>calculated on this figure.
>Or I did something wrong.
Yes, exactly. You're trying to verify their numbers in a responsible
manner. Could you use a lab oven or environmental chamber to take a
number of measurements at different temperatures, looking at the
beginning of short pulses of current so the die temperature is
essentially ambient temperature in the chamber. If you do, I hope you
post your findings.
Alternatively, you could inquire at Luxeon and try to get ahold of
someone technical. I'm sure they've have a lot more information than
that raw number on the datasheet. Especially if you tell them what you
are trying to do- make their product reliable in your application-
they should be cooperative.
"it's the network..." "The Journey is the reward"
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