Direct Thermal Transfer is a system that we have designed for use with the latest
high output LEDs; XML, SST-50 and SS-T90.
These LEDs have a very high concentrated thermal problem because of their small
thermal pads.
Without proper thermal management output and LED life could be a problem. Normally
those LEDs are mounted on an aluminum base that is screwed onto the head of the flashlight.
That is where the problem starts. There is an insulating membrane between the LED and
the aluminum base, then there is the gap between the base and the flashlight head that
should have thermal grease to help with heat transfer. If we look at the thermal radiation
patterns what we see is a series of shallow spherical sections radiating outward from the LED.
This gives a hot spot under the LED. The result is that while this works fine for a Seoul P7
type of LED, an improvement is needed for the Cree XML and Luminus LEDs.
What we have done is taken the basic idea of the Heat Pipe for heat removal and incorporated
that design principal in our flashlights. We Silver solder our modified heat pipe directly to the
thermal pad on the LED. (The circuit board is used only for electrical connection of power to
the LED). The LED assembly is then inserted into the flashlight head with an interference fit.
This method pulls the LEDs generated heat down into the head and radiates the heat outward
in a pattern that resembles a cone and not that the the typical shallow circular segment.
Curt
high output LEDs; XML, SST-50 and SS-T90.
These LEDs have a very high concentrated thermal problem because of their small
thermal pads.
Without proper thermal management output and LED life could be a problem. Normally
those LEDs are mounted on an aluminum base that is screwed onto the head of the flashlight.
That is where the problem starts. There is an insulating membrane between the LED and
the aluminum base, then there is the gap between the base and the flashlight head that
should have thermal grease to help with heat transfer. If we look at the thermal radiation
patterns what we see is a series of shallow spherical sections radiating outward from the LED.
This gives a hot spot under the LED. The result is that while this works fine for a Seoul P7
type of LED, an improvement is needed for the Cree XML and Luminus LEDs.
What we have done is taken the basic idea of the Heat Pipe for heat removal and incorporated
that design principal in our flashlights. We Silver solder our modified heat pipe directly to the
thermal pad on the LED. (The circuit board is used only for electrical connection of power to
the LED). The LED assembly is then inserted into the flashlight head with an interference fit.
This method pulls the LEDs generated heat down into the head and radiates the heat outward
in a pattern that resembles a cone and not that the the typical shallow circular segment.
Curt