Hey guys,
I'm currently designing a new PCB using BSC100N06LS3GATMA1 mosfets. I want to connect them to power planes and my question is : should I use thermal relief or should I connect them directly to the plane? I've attached a picture where you guys can see the two options where on the lift side they are fully connected and on the right side they are connected through thermal reliefs.
How do I know why solutions is better? My concern is mainly regarding the soldering. I did not find any layout recommandations about this package.
Thank you very much !

 

In general, it does not matter, but there are some power supply topologies in which tiny amounts of parasitic resistance or inductance can have a great effect on performance.

What does the engineer who designed the circuit think about this?

If you are relying upon us as the engineer, it is only fair to spell out the circuit topology and operating frequency.

 

This seems to be TDSON-8 package. The MOSFET bottom pad is for heat transfer reasons and PCB-thermals usage would just destroy its purpose. So my suggestion to this question is 'without thermals'
It depends how are you going to solder them, do you have an oven, or manually?, anyhow, soldering them even by hand isn't very difficult, you need a heat gun and solder paste.

 

I do not use thermals. I want to get the heat out and away from the part. Also want to get the electrons out with the lowest resistance and inductance.

No thermals make hand soldering a bitch. Often I heat the entire board to solder all the parts at one time. A hot air gun heats the transistor and a little more up to the milting point. With the right equipment no thermals are fine.