- Make sure that there will be a thermal path between the LED and the peltier plate. If there is an area on the component side, you should avoid thermal vias.
- You need a thermal pad that attaches to the case or leads of the LED.
- The thermal pad should be as large as possible.
- Shorten the distance between the LED and peltier plate.
- The thickness of the PCB copper should be at least 2 oz.
More reading: Guide of LED PCB Assembly