Can hot air be used for LED reflow?

Flashlight Modding and DIY Parts
1

Question 1: Can hot air (such as a hot air rework station) be used to reflow LEDs to MCPCBs?

If YES, then:

Question 2: What about if the MCPCB is soldered to a pill? Could hot air still remove the LED from the MCPCB/pill combination?

I have a copper pill with MCPCB soldered to it, and LED installed. I’m curious if hot air would allow me to remove the LED and reflow a different one without needing to fully de-solder the MCPCB from the pill.

2

1) yes, have done it before

2) not sure - depending how much heat will go through the pill. But I’d say it will work. hot air rework stations are very good in focusing hot air to one spot.

3

Copper pill, you will need a lot of power, copper is good at heat dissipated

4

Look in the datasheet of the LED and see how long and to what temperature you are allowed to pre-heat the LED.

Take full advantage of that, if there is nothing else that can melt, pre-heat the whole assembly to the allowed temp, that will spare you a lot of trouble with hot air.

5

Good observations, it didn’t even register to me that I could preheat the pill so that the hot air didn’t have to do all of the work.

The Cree data sheet says:
Maximum LED junction temp: 150*C
Soldering Profile:
Preheat: 120-170* C
Peak temp: 245*C (for 40s max)
Time from 25* C to peak: 4minute max

There’s no way I can get the large copper hunk of P60 quad up to 245*C within 4 minutes, but I don’t need to.

Based on a highly educated (pulled out of my butt) guess, I can probably safely bring the pill up to… 130*C (?) for an indefinite amount of time?

Melt point of the 63/37 solder is 183*C

Then a hot air gun would hopefully be enough to apply local heat to the LED that needs to be swapped.

6

I am still waiting for my hot air rework station. This is exactly what I want to do with it. Please let me know if you have been successful, sac02! Thanks!

7

This was my hot air gun for along time and the only item I used to solder leds to MCPCB’s. The distance the MCPCB from the end of the heat gun was the way I controlled the temperature.

8

My intention is to mod a drop in that is totally potted. So I want to heat and remove the LED from the top, through the reflector opening. Do you think that this is possible without any damage to the dome of the LED due to the hot air?