Will these heatsinks be sufficient for the mosfets

dc motorh-bridgeheatsinkmosfetmotor

I need to control 10 12VDC motors at ~25Amps, so I decided to make my own mosfet H bridges to control it ( with 2 n chan et 2 p chan ).
I will need 10 H-Bridge, so 40 Mosfets. ( 20 n chan and 20 p chan )
The mosfets which I'd like to buy:

These mosfets have 62.5 degrees per watt thermal resistance to ambient, and the N-channel one has 0.045 ohm maximum resistance drain to source. The p-channel has 0.07 ohm

So I will have 0.045*25*25 = ~28 watts for N-channel and 0.07*25*25 = ~43 watts for p-channel

43 * 62.5 is a very big value so I was asking myself if a heatsink would be enough to absorb this heat ?

I've found these heatsinks: http://www.ebay.com/itm/10pcs-IC-Aluminum-Heat-Sink-With-Needle-fit-for-TO-220-Mosfet-Transistors-HM-/181411561757

I'm gonna have 40 of these, knowing that I will use 8 mosfets maximum at the same time ( 2 motors max at the same time ) if I put all of the 40 heatsinks in contact the 8 mosfets would be able to dissipate on the 40 heatsinks. ( which makes one very big heatsink )

I could also put 1 or 2 cooler fans.

would this be possible ?

Best Answer

I would suggest using a beefier mosfet, like one of these for example: IRLB8748 or IRFB7546, these mosfets have very low Rds(on) of under 10mOhm.

I would also suggest using only N channel mosfets, this makes driving the high side harder but N channel mosfets have lower Rds(on).

With a 10mOhm mosfet you dissipate 6.25W at 25A, which is easy with a proper heatsink and there's no need for active cooling (a fan).

The heatsink you've linked on ebay doesn't specify it's thermal resistance so it may or may not be enough.