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Corrosion issues in stud mounted parts

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Zak28

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Is galvanic corrosion an issue for uninsulated stud mounted parts such as DO-4, DO-5 TO-94 studs?

Heatsinks are typically copper or aluminum, not sure what those packages are made of.
 
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I have used up to 40 Amps.
But I Do use "SILICONE BASED HEAT SINK GREASE".

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    Zak28

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Zak28 said:
Whats the heatsink material?
Click to expand...

almost always Aluminum.

And Silicone Grease is Recommended by Manufactures of these type of parts.
It Increases Heat Transfer from the part to the Heat Sink.
 
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I use lower thermal resistance thermal grease made for PC CPUs - silicone is far less expensive and a worse performer.

chemelec said:
almost always Aluminum.

And Silicone Grease is Recommended by Manufactures of these type of parts.
It Increases Heat Transfer from the part to the Heat Sink.
Click to expand...

Was it anodized?
 

I presume the thread is based on pure speculation rather than observed actual problems. Stud mount parts on aluminium heatsinks have been used in older days power electronics for at least 50 years.
 
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FvM said:
I presume the thread is based on pure speculation rather than observed actual problems. Stud mount parts on aluminium heatsinks have been used in older days power electronics for at least 50 years.
Click to expand...

I wasn't sure if corrosion would be a problem.

Is it fine to simply screw the package into a drilled and tapped heatsink without using a nut?

The hole would be deeper than device package stud to permit all the threads on the package to make contact with the heatsink. Not sure if this is fine since aluminum threads might not have enough strength to permit adequate mounting torque for the device package.
 

If you have the Correct Tap for the Threads, It should work Perfectly OK.
 

"Is it fine to simply screw the package into a drilled and tapped heat-sink without using a nut?"

Not my field so 'IMHO', but I'd worry about getting adequate thermal contact between the package and the heat-sink.

Also, IIRC, setting bolts into a block thus requires some extra machining. In addition to 'base clearance' or a through-hole, I'd expect a shallow counter-sink or counter-bore to allow for incomplete threading of the bolt. That may not leave much thickness for a thread, meaning you'd need a back-nut for security...

Unless you are using a seriously massive block as your heat-sink, which is inefficient unless doubles as structural, IMHO, you'd do better with a 'clearance' hole, heat transfer gel & washers and a correctly torqued back-nut in the usual way...

YMMV.
 

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