Lumotrix LED heat transfer grease is designed to be used on the back of COB LEDs and the Lumoclip. These LEDs should be fixed on an absolutely flat surface of aluminium or copper. Surfaces with visible grooves (such as those cut with a circular saw) are not adequate. The bond line must be as thin as possible. This is achieved by using a grease that is thin when it is applied, so most of it can be squeezed out of the heat transfer gap. Later it will become more solid as the gumminess of the compound increases. It is also washable which is a great benefit. It contains no silicon, and no solids so it will not cake. It remains flexible for the life of the joint, yet experiments have shown that it will not pump out and leave a void.
It is possible to use a flexible glue or adhesive compound that will act as a heat transfer medium for the LED, but when the bond line is very thin these undergo large shear strains due to the differential expansion between the ceramic of the LED and the metal of the heatsink. The corresponding stress could crack the ceramic. Sometimes they have fillers designed to prevent the bond line being too thin which means that the heat transfer capability is reduced, whereas in this case it is critical due to the large amounts of heat being transferred in a small area. Heatsink glues are best for metal to metal heat transfer.
Similarly it is possible to use thermal pad material for LEDs. Often this is too thick to be good for this application, but would be OK for the LEDisk which has a much larger heat transfer area, and is not so critical.
A 0.5cm3 syringe of compound contains 10 applications of 0.05cm3 each. Each application contains approximately double the amount required for the 20mm x 24mm ceramic surface of a Sharp MegaZeni LED. This ensures complete coverage of the ceramic surface. Order Code: HG1.