Hi Jay
First point is that the data sheet covers the use of double sided PCB with conventional through plated holes. The thermal data relates to boards that have either through plated holes that are left vacant prior reflow and those that have been filled with resin and then plated over. The penultimate sentence on page 10 indicates that filling the vias with thermal paste achieves little when added to the copper pipe left by the through plating.
This leads to the conclusion that the data sheet is aimed at mass production PCB manufacture using electroplating to build the heat path through the vias and supplementing this by copper plating over the vias as a method of decreasing the thermal route away from LED to the exposed PCB copper. This process is not compatible with the DIY milling of the isolating lands on a PCB as the copper plating is integral to the drill plate drill cycle. The use of PCB bonded to a metal backing plate is your way forward. However the insulating material between the copper and the alloy backing will be very thin and hence the milling accuracy will have to be high if the insulation is not to be compromised. Suggest you use this material but photo etch - not too difficult as a DIY operation provided you mask the alloy well!
Your next problem will be to position and reflow the chips in place with out frying them.
There are other chips and mounting solutions out there and these might give the optical / physical features. You might strike lucky and find a source of ultra thick single sided copper clad board - where thick means copper thickness. This could give improved thermal conduction to the exposed copper to the cooling air. You will need to experiment but you will be doing this anyway as the data sheet is not a completed design as the case and cooling air will play a great part in the final application.
Hope this helps you reach a satisfactory conclusion.
Regds Pat  |