On semi MJL3281A mounting Question

[Fritz]

Im ordering some MJL3281-TO264 packages and I was wondering what I need to mount these to the heat sink.

This is my first time building an amp

Do I need washers and bushings and grease Or?

Fritz

 

[UrSv]

You need a screw that fits the hole and washer (or similar "pressure spreader"). Then you need one of the following:

1. Mica and heat conducting paste applied to both sides.
2. Silicon rubber/Kapton or similar mounting pad.

1. Is good 2. is good and easy and I would use that.

/UrSv

 

[peranders]

Yes, use mica washer only if you are going to dissipate much power. Most of the time normal amps don't need mica + silicone grease. One thing though, Kapton is very thin, smooth surface is a must, otherwise it's very easy to get bad (or no) isolation.

Mica + grease is for heavy duty applications.

 

[Fritz]

Ok, It will be a high power situation. I see the mica kit for a TO220 package. It looks like it will fit a lot of these single bolt packages. Do you think this would be big enough? ,it doesnt give a dimension. Do I need a bushing?

Newark calls it a type 4880 it is part 46F4081

Thanks,

Fritz

 

[Jean]

To-220 is too small, look at 3p or 247 style.

 

[UrSv]

To-220 is too small, look at 3p or 247 style.

Exactly. Why would you use a mounting pad of the wrong size? MJL3281 is TO-247/TO-264 if you check the specs which means that anything designed for TO-247/TO-264/TO-218/TO-3P will be OK. TO-220 is smaller...

/UrSv

 

[Fritz]

Ok I'll hunt for those,

Thank you