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Routing Under Heat-sinks
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Spark-Doctor:
Hi All

I am laying out the PCB for a electronic load and have hit a snag. I need to route several large traces under a long heat sink.

Is it OK to place the heat sink flat on the board or should i place a few few small stand-offs under the heat sink?

I just worry that over time with small amounts of vibration, it will rub through the board coating and the magic smoke will appear.

Many thanks in advance  :-+
Benta:
Yes to standoffs, your concerns are justified. Alternatively, you could place a sheet of silicone rubber (the type used for transistor/heatsink isolation) between PCB and heat sink.
The Al-oxide surface on the heat sink is an isolator, but not a reliable one.

T3sl4co1l:
Yeah, that, or some polyimide tape say.

You probably can't get a PC-mount heatsink big enough, but spacing it off with washers would be enough already.

Tim
Conrad Hoffman:
As above, you would never rely on the soldermask for insulation, regardless of voltage or anything else. Standoffs or a sheet of proper insulation. Standoffs might give you a tiny bit of extra cooling because of the gap.
coppercone2:
i always meant to simulate what vias do for cooling if under a low heat sink, can they get better convection ging
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