General > General Technical Chat

SOT-227(ISOTOP) vs TO-264 heat dissipation

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tszaboo:

--- Quote from: Fauks on March 24, 2024, 07:53:23 pm ---
--- Quote from: T3sl4co1l on March 24, 2024, 06:45:19 pm ---Note that SOT-227 top side is not made to bear force; nuts are captive but loose in the package, and the leads are bent over tabs.  A mounting plate is best.  You might take a slab of hardware store extrusion and drill and tap it for the necessary features, or order a plate machined to the same.  I'm not sure offhand how that would work with the stock brackets; you may be better off finding some spots to drill and tap into the heatsink itself.

Tim

--- End quote ---

Interesting point. What about some aluminum spacers between the tabs and nut for bracing? Or like someone else mentioned, bending the tabs straight and mounting through the PCB so the nuts and making contact instead of the tabs.

Or are you referring to the top of the assembly in general should not bare weight?

--- End quote ---
SOT227 has two mounting holes on the base plate of it. It needs to be bolted down with these.

coppercone2:
but for the other package you can either use a screw hole or put a bar across it that braces it from both sides. i mean that you need a way to screw it down aka a hole in the thing. and when you screw it in the part will twist so you need a way to hold it. your supposed to screw it in before soldering too but it would be good to be able to hold it nicely aligned, which means you need cutouts for pliers to go in or some kinda jig to hold it like a spanner. At least with grease it will, if you use a silpad maybe it stay put while tightening.


the other package has a thick base so screwing it down by the flange is the proper method. But you also wanna put holes there if you can, because otherwise you need specialty low profile screw drivers etc (annoying as fuck)

coppercone2:
for drilling and tapping a heatsink you probobly want to consider using threaded inserts (helicoil) because aluminum and copper threads get damaged very easily and aluminum also makes bolts stuck easily

Usually heatsinks want a proper nut made out of steel

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