Ok, I've got a little project started (not automotive) with a few Rebels. I need some confirmation on heat transfer to avoid frying these little pricey babies.
Anyways, the numbers I've come up with so far are:
Rebel @350mA (1W)
Max Ambient Temp: 40 ºC
Junction Transfer: 10.5 ºC/W
Base Transfer: 1.2 ºC/W
Adhesive Transfer: 4.5 ºC/W
Heatsink Transfer: 1.4 ºC/W
Which would give me a junction temperature of approx 57.6 ºC. Nice and safe. The confusion for me starts with adding additional 1W LEDs to the array. As I see it, for each LED I add to the array (approx 1.5 - 2 cm between them), the heatsink should increase in temperature by Ambient + (1.4 ºC * n), where n is the number of LEDs.
Now, what I'm unsure about is how that heat transfers to the other LEDs. Since the heatsink is only increasing by 1.4 ºC, does that mean that the junction temperature of each LED is also only increasing by 1.4? IE: 57.6 + (1.4 * n) ?
Basically I just need to know what my max heatsink temperature can be and how it relates to the junction temperature so that I can set up a thermal switch as a safety feature.