Soldering a MCPCB vs Thermal Adhesive (test results)

[Fritz_t_Cat]

@Lothar

Hey pflexpro, I’m assuming you still have to the lights and hardware you used to do this test. I see the test was done at 3.8A. Would it be possible to redo the test ±2.8A and ±3.8A to see what the difference would be between direct soldering and adhesive at different amp levels?

Thnx

Air flow may be complicated, but the heat conductivity of solids varies only slowly with temperature. I think it is safe to assume that the result would extrapolate simply to different powers.

[pflexpro]

@Fritz t. Cat

@Lothar

Hey pflexpro, I’m assuming you still have to the lights and hardware you used to do this test. I see the test was done at 3.8A. Would it be possible to redo the test ±2.8A and ±3.8A to see what the difference would be between direct soldering and adhesive at different amp levels?

Thnx

Air flow may be complicated, but the heat conductivity of solids varies only slowly with temperature. I think it is safe to assume that the result would extrapolate simply to different powers.

I should mention air flow and my method: I cool the tested flashlight with a 75mm cooling fan -I’ve adjusted the speed and distance from the flashlight to closely match the thermal properties as if the light were being hand held. I adjusted the air flow based on a 3.04A flashlight. Since I’ve started building 3.8A as my max, I did not make any adjustments to the air flow…I thought this would complicate things.
I also agree, the thermal properties could be accurately calculated or estimated at 2.8A, but it may be easier to just test it.
My only concern: If I current limit the input power on a 3.8A light to 2.8A, would it be the same as running a flashlight with a 2.8A driver.

[JonnyC]

Stupid question, but when you solder the MCPCB to the pill are you reflowing the emitter at the same time?

[pflexpro]

@JonnyC

Stupid question, but when you solder the MCPCB to the pill are you reflowing the emitter at the same time?

Questions are never stupid…but, some answers are.

When I solder a MCPCB on, it is bare. I use a high temp solder for the mcpcb. I also drill a small divot in the board, in the case of a Noctigon, right where it says ‘xm’ (on the xm-l boards). I think the bit I use is 1/8” and I drill just deep enough to expose copper and for my solder tip in fit in. Then I install and pot the driver. I do not solder the lead wires until I reflow the LED, if I do, they will ‘pop off’.
So I have several of these pills with drivers installed, potted and MCPCB installed. When I receive an order, I put a dab of solder on the tip of my gun and stick it in the divot to do the reflow…then solder the lead wires.

I will make a few where I solder the board and reflow the emitter at the same time…it’s tricky, but it saves me from the 1 minute heating of the pill through the divot. Doing it this way increases the chance of the led getting damaged when I solder in the driver and do the potting.

[Lothar]

@Fritz t. Cat

I think it is safe to assume that the result would extrapolate simply to different powers.

Yeah, thinking about it, the extra effort of doing more tests at different amps will not justify the slightly different magnitude of the graphs.

Thnx for the graphs and the info on soldering the PCB

[mattjk]

Old thread but nice tests. I always solder the MCPCBs in anyway when i can (ie not to aluminium) but just confirming what i thought so ill continue to do so