Oznog
Active Member
I'm looking to build a MOSFET replacement for a diode-based battery isolator for a high current car DC system. For now, let's please just assume "I have my reasons". I have a high side driver that can drive an NMOS.
I'm really liking this Power SO-10 pkg. Very, very good rDS-on and the dissipation through the tab can be pretty high.
https://www.st.com/stonline/products/literature/ds/6654/stv160nf03l.pdf
So the system can be around 160 amps here and I was figuring 2 in parallel would be best, keeps the voltage drop and heat down. That's 12W per device if they're cool, if rDS increases due to temp rise we could be up to 19W at max junction temp. The case will not have a fan and will not be vented since it's "under the hood" and could get splashed.
OK, I now have 3 issues:
1. Even if I use 3 oz board, can the traces be made large enough to handle the current?
2. How can the traces be made to dissipate the devices' heat?
3. I will probably be lugged 1/0 cable here too. Mechanically, standard board can't take this kind of stress. Nor do I want to have to use 2 wrenches to ge it on. Using a stud attached with 2 permanently affixed nuts is a bit hoakey even if mounting stress weren't the issue since the contact area with the lug is reduced when the lug grabs the nut.
I've seen "aluminum core PCBs" but I don't think this is going to be possible to do at home and it would be expensive to mfg. Should I cut out copper sheet to lay over the high heat/current areas? I'm thinking the lugs themselves could be used to conduct away most of the heat, does that sound right?
How much does 3oz board insulation between sides? I could make the bottom of the board below the components all copper, grounded, and stick a flat heatsink on it. But that means a layer of fiberglass between the component and sink which is hardly ideal.
I'm really liking this Power SO-10 pkg. Very, very good rDS-on and the dissipation through the tab can be pretty high.
https://www.st.com/stonline/products/literature/ds/6654/stv160nf03l.pdf
So the system can be around 160 amps here and I was figuring 2 in parallel would be best, keeps the voltage drop and heat down. That's 12W per device if they're cool, if rDS increases due to temp rise we could be up to 19W at max junction temp. The case will not have a fan and will not be vented since it's "under the hood" and could get splashed.
OK, I now have 3 issues:
1. Even if I use 3 oz board, can the traces be made large enough to handle the current?
2. How can the traces be made to dissipate the devices' heat?
3. I will probably be lugged 1/0 cable here too. Mechanically, standard board can't take this kind of stress. Nor do I want to have to use 2 wrenches to ge it on. Using a stud attached with 2 permanently affixed nuts is a bit hoakey even if mounting stress weren't the issue since the contact area with the lug is reduced when the lug grabs the nut.
I've seen "aluminum core PCBs" but I don't think this is going to be possible to do at home and it would be expensive to mfg. Should I cut out copper sheet to lay over the high heat/current areas? I'm thinking the lugs themselves could be used to conduct away most of the heat, does that sound right?
How much does 3oz board insulation between sides? I could make the bottom of the board below the components all copper, grounded, and stick a flat heatsink on it. But that means a layer of fiberglass between the component and sink which is hardly ideal.