Hi
I have a PCB, 50mm x 50mm, and I need to optimize cooling of the PCB. A num ber of dissipating components are spread out on the PCB to produce an unifo rm temperature across the PCB.
Currently I am using 0.5 Oz PCB thickness, but it is possible to increase t hat to 1 Oz.
So I was looking for a graph of the thermal resistance on a certain area of PCB versus the copper thickness. My initial feeling would be that the incr ease of the copper thickness would be insignificant with respect to the Rth .
Found this graph, figure 3 on page 2:
Increasing the copper from 0.5oz to 1oz would reduce the thermal resistance from 260K/W to 180K/W
But, is this valid. If we take the example of a single hotspot device in th e center of the board, the increased thickness would reduce the thermal res istance from the device to the rest of the board, so the temperature would be close to uniform.
If on the other hand, with a PCB with decreased copper thickness, I have a number of devices spread evenly on the PCB and dissipating individually the same amount of power, the heat would then also be uniform. But the transfe r of the heat to the surroundings are convection and conduction, and these should not be affected by the thickness of the copper layer.
So, for the actual design, evenly spaced components would not benefit from thicker copper thickness. Is this a valid assumption?
Cheers
Klaus