Hand Soldering 3W COB Chip LEDs: Best Practices for Flush Mounting & Heat Transfer

What is the correct way to hand solder 3W standard COB chip LEDs like https://www.amazon.com/6000K-6500K-600mA-700mA-Intensity-Components-Lighting/dp/B01DBZICDC ? If there is a lot of solder on the pads already, as you are trying to replace a failed LED, then I find it’s hard to get the LED to be fully flush on the PCB and so dissipate heat well. What I have tried is to solder it on and then, using a small watchmaker's screwdriver, reheat the solder one side and push the leadout fully down onto the pad. Keep pressing till solder cools. Repeat the other side.

Could even slightly bend up the leads first so there is no chance the leads are lower than the heat sinking rear of the LED. The above procedure uses the resulting spring in the lead to add contact pressure.

All done after smearing heatsink compound. I have some >3 W/m-k compound. Is that OK? It’s not the highest possible transfer rate but about average.

Have had a spate of such failed LEDs in commercial LED lights due mainly to poor heatsinking I think.

Hi,
Providing you have at least 25% coverage, you will transfer the heat well enough. This TI app note: http://www.ti.com/lit/an/slma002h/slma002h.pdf details the methods of heat transfer.
has this 
On the back of the PCB do you have any room for a small heatsink?
A Raspberry pi heatsink set has some small adhesive heatsinks, they may fit and they will lower the PCB temperature a few degrees.

Edward,For replacing failed LEDs, I'd first use solderwick to get as much of the solder off the pads as possible. Then bend up the leads on the LED slightly before soldering it down. While soldering, hold the body of the LED in place to maintain good contact with the heatsink.The first method you described sounds a bit more problematic than bending the leads up but should work.

Ian,
Thanks. I think you are referring to LEDs which have their heatsink pad soldered to the PCB. Not the case here as, although one could do it, I have yet to find one of these type soldered at the heatsink pad. Instead they just smear heatsink compound on the pad, but unless the leads are well held down there will be insufficient pressure on the pad to make a nice thin film of compound.

LEDs Soldering are wired in series, LEDs wired in parallel use one wire to connect all the positive electrodes of the LEDs your using to the positive wire of the power supply and use another wire to connect all the negative electrodes of the LEDs your using to the negative wire of the power supply. This is the way you can solder your wire.