Author Topic: Using a heatsink on a PCB, clear the copper under it?  (Read 776 times)

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Offline corrado33Topic starter

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Using a heatsink on a PCB, clear the copper under it?
« on: August 01, 2011, 06:13:14 PM »
When using a heatsink that's on a vertical T220 or T247 and that rests on the board below it, should you clear the copper under the heatsink?  I'm thinking this type of sink.  I mean the transistor SHOULD be isolated from the sink (if you use an isolating washer), so it shouldn't be a problem.  But is it good practice to do it anyway? 

http://www.ohmite.com/catalog/pdf/w-sink.pdf


Yes, this does involve the thread I created a few days ago, but that one had nothing to do with heat sinks.  Well, it kinda did but it wasn't searchable. 

Offline Soeren

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Re: Using a heatsink on a PCB, clear the copper under it?
« Reply #1 on: August 02, 2011, 08:35:37 AM »
Hi,

When using a heatsink that's on a vertical T220 or T247 and that rests on the board below it, should you clear the copper under the heatsink?  I'm thinking this type of sink.  I mean the transistor SHOULD be isolated from the sink (if you use an isolating washer), so it shouldn't be a problem.  But is it good practice to do it anyway? 
It's isolated if you ensure that the clip is isolated too. With screw on heatsinks, you use a nylon bushing (not unlike the cheap LED holders) to isolate the screw. With this clip, I don't know if it is, but you could use a silicone TO-220 isolating washer to go in between the spring holder and the tab.

The heatsink itself can be grounded as long as you ensure complete isolation (check with an Ohmmeter if in doubt.
Regards,
Søren

A rather fast and fairly heavy robot with quite large wheels needs what? A lot of power?
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