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The Copper Diamond is the most interesting because it can be metalized while still electrically non conductive. With 650W/MK thermal conductivity the thermal bottleneck could the solder itself (assuming non gold plated contact used). In my opinion thermal resistance is more relevant since in the end this is what matters.
If an attachment system thermal resistance can be optimized to slightly below the thermal resistance in the LED (which we can do nothing about) then the rest of the system can use that number as the minimum resistance. In my opinion, as long as the cooling still creates negative delta temp copper or aluminum heatsink still doing OK. The higher the thermal conductivity of a material the less delta temp needed to flow the heat. We can make a superior cooling system using available budget friendly material widely available with good design and process. Manufacturers have to compromise the outcome to balance the design for a reasonable total cost.
For example:

- Use the best solder available (Indium is in the top of my list). And don’t forget to make the joint as thin as possible.

- Use the thinnest most rigid substrate possible. Metalized Aluminum Nitride can be made reliably down to 0,2mm without sacrificing rigidity. Although the thermal conductivity is only up to 180 W/MK in most cases, the thin substrate will make up the difference. This is demonstrated clearly in my MCPCB using “low” aluminum oxide dielectric with only 7,5W/MK thermal conductivity. Thermal resistance is what matters.

- Conventional wide and thick copper traces still works to further spread the heat over the entire board substrate as long as the radial thermal resistance still lower than through plane resistance.

- As flat as possible finish in the substrate and heatsink mating surface makes a big difference. Don’t compensate with thermal paste. Get the best possible mating surface first, use the least amount of thermal paste.

  • Bare metal with no paint or anodization at the heat sink joint.

- Clemence