Hi,

Can any one plz help me to know how to design the heat sink/ground plane required for MOSFET heat dissipation.

if you could explain with example will helps a lot.

Rgds,
Monty

 

There is typically all the information you need in both the design guide for that specific mosfet as well as in numerous application notes provided by the chip manufacturers..
https://www.vishay.com/mosfets/related/
See AN811-AN822 and more on that page..

 

Yes, the datasheet tells everything.

 

Hi,

Yes it is usually good to look at the data sheet because they often tell you exactly what you need as well as supply a board layout pattern that is recommended.

That aside, the rule of thumb is one square inch per every 60 degrees C rise in temperature for every watt of power dissipation. Since the heat beyond one square inch has to conduct away from that first square inch if there is more than one square inch that means that every square inch after the first one (assuming the device is centered on the area) dissipates less heat than the first square inch so it's only a rule of thumb.
I always meant to calculate a derating factor for wider areas to get a better estimate for board areas that require more than one square inch but did not get to it as of yet. Copper conducts heat pretty well but as the distance from the source increases the heat dissipation ability of course goes down so maybe a quick rule of thumb would be derate by 50 percent for every square inch beyond the first square inch. Then after that, derate another 25 percent for patterns that go beyond 9 square inches, etc.
Of course no matter what method we use we always have to test these things just to be sure they work in the target environment.

 

It might be better to use a fan with a heat sink.
For what wattage are we talking?