To what temperature can safely heat up the radiator?

Good day!
I put together a lamp on a powerful 6-watt LEDs, they are secured with hot melt glue on the heatsink with longitudinal ribs. During operation, according to the Datasheet, they are heated to 100 degrees. The radiator eventually becomes too serious. I want to know will it heat up so indefinitely, yet did not warm up to the temperature of the diodes and will not be able to keep them cool? How to check?
March 23rd 20 at 19:18
4 answers
March 23rd 20 at 19:20
Solution
https://electronics.stackexchange.com/questions/30...
There is still a lot of links.
In short, the way you are trying to estimate is not considered. And 100 degrees for LEDs - a lot. So they are not degraded faster than incandescent lamps, they must be hot 70 degrees.

Will add some details.
- "In the Datasheet are heated to 100 degrees" is incorrect. Is the maximum, not nominal operating temperature.
- To judge the effectiveness of the radiator only by its temperature - it is impossible, because the thermal transition resistance between led and radiator is an unknown quantity. At high resistance, the led may, conventionally, have to burn out and the radiator will still be barely warm. To judge the effectiveness of cooling in temperature, if only to measure the temperature of the led. This temperature is the only baseline that matters.
- Because the lamp in question is not described, nor is it clear how in General to consider the situation. Because, for example, a short activation, the radiator (a device that performs intensive heat exchange with the environment through convection and radiation) - not needed. I was doing some lighting for macro photography and microscopy for such a regime, where the role of sink carried out the piece of metal with a high heat capacity but low heat (so corny it was cheaper and faster). But for a situation of constant work, this trick wouldn't have worked, because quickly enough the heat sink heated up, and ceased to provide the low voltage of the LEDs because heat dissipation from its surface would be manifestly inadequate.
my diodes operating temperature 85, the maximum 104
thanks for the link! - Gardner34 commented on March 23rd 20 at 19:23
March 23rd 20 at 19:22
Solution
they are secured with hot melt glue
Where something heats up above 35 degrees, there should be no glue! You don't want to have it all off after half an hour of work. In addition, the hotmelt awful neteploprovodnym. To transfer the heat mount has to be mechanical, with a tight nip gap is minimal (less than 0.1 mm) and filled with thermal compound. Best of all screws, but can be a flat spring pressed, as is sometimes done with transistors.

In some datasheets mention the maximum permissible temperature, and it does not mean that it should be working. On the contrary, the lower it is, the longer it will live your light bulb (led by strong heating degraded). The conclusion is that the radiator must be of such dimensions, which maximally fit in your case. It is also useful not just holes in the case to make for the flow of air, but also forced to drive his cooler (well, this is only in case of real overheating).

Finally, all of this is easily calculated, there is an elementary formula, somewhat similar to Ohm's law.
is hot melt glue on it and glue to fall off? - Gardner34 commented on March 23rd 20 at 19:25
and, it is necessary to clarify, this is not glue, but thermal adhesive here - Gardner34 commented on March 23rd 20 at 19:28
@Gardner34, if the solidified hotmelt to heat, it loses its strength and adhesion to the surface on which applied. Glued falls off.
A thermally conductive adhesive is another matter, but it is not so simple. Its layer should do the minimum possible thickness, and still he would be worse than thermal grease. - Gerry_Rowe commented on March 23rd 20 at 19:31
March 23rd 20 at 19:24
The radiator will try to warm to the temperature of the LEDs. Endlessly. But since it will be dissipating at least as something warm, with sufficient ribbing and size temperature will be slightly below the current of the diodes.
To test, use two temperature sensors, one on the side wall of the led, the second at the base of the heatsink.
Then turn the LEDs on 90% of the planned capacity. Well, then look at the temperature difference. As soon as will be over 80 on the diode it is desirable that the radiator was 70 or less.

PS usually the specs indicate the dissipation. You can count in special calculators required radiator
and do not tell more specific, what sensors? - Gardner34 commented on March 23rd 20 at 19:27
March 23rd 20 at 19:26
Is there a simple solution to power open upon reaching a certain temperature?

Apparently, this is done using the thermostat. But I don't know which one to choose. I have 2 6-watt diode

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