This is klunky but should work.
There could be one or two heat spreaders, depending on whether the fet substrates are electrically common. The compression of the gap-pad determines the force on the fets.
I want the heat to go down, into the PCB, not up into the air. In still air, small heat sinks don't do much anyhow.
This miniaturization lead us into progressive insanity. Have a look at the real problem: how to spread one watt. Mere one watt.
Electrically neat, mechanically Rube Goldberg. The problem is that it is not your fault. Is the correct word "progress"? :-/
Maybe a board-scale radiator would be an option then? IMS is my favourite material nowadays.
Best regards, Piotr
Ouch, OK I have no idea, but I think three devices and one screw in the middle would be better, you could have one or two devices and a pivot point.. or one with a clip.
George H.
That's a good idea. The springs could be external, pressing the heatsink onto the dice. They might even be something like Belleville, lock, or other springy-thingy washers.
Cheers, James Arthur
Who uses vias with thermal relief? o_o
I've seen tons of commercial production (100ku+) without thermal relief. Lead free. I don't see that it's a problem for SMT.
The DFM and assy people tell me they're more worried about thermal balance on small parts causing tombstoning.
Tim
My production people want through-holes, like connector pins, to have thermals, to make them easier to solder by hand. Vias and mounting holes, we pave over.
The ones I normally encounter eiter use plastic push rivets with coil springs, or use springy wires that hook onto U-pin headers [1].
[1:
If you have a cooling pad connection that is peppered with full-metal vias for heat conducting purposes and top and target layer are 2oz or heavier the assemblers sometimes have a hard time. When contracting out the assembly it can mean that a more expensive shop needs to be used.
With a good oven profile, the entire board gets hot, top and bottom, so thermal vias don't affect soldering. They can affect rework, but we have rework gear that heats a board top and bottom to take care of that.
My PCB will probably have a gap-pad between the board and the enclosure, or in the extreme a cold plate. That really sucks heat out of a board. Other things will get hot too, kind of all over the board.
Smallish PCBs with internal copper planes tend to be fairly isothermal across their surface, so gap-pad everywhere helps keep everything cool. Of course, the silly GaN parts are so small they will have local hot spots.
Higher thermal conductivity laminate would help transport heat from topside parts to the bottom and the gap-pad, but vias can do that too, and vias are essentially free.
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Measure, I guess. EPCC are on their fifth generation--maybe this varies by part number or generation.
Cheers, James
------ "Measurement--accept no substitutes."
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