Yeah, I've only seen TO-220's with the isolated tab.
IN general, the thermal resistance may or may not be up to par for your requirements.
We see FET representatives all the time and will ask next time I see them. Now you have my curiousity up.
Lasse reminded me about AlN thermal jumpers, which really helps the heat sharing situation between the two dpak heat sinks.
With 8 programmable load circuits on a board, and some air flow, I'm thinking 10 watts per channel should be OK.
torsdag den 24. juni 2021 kl. 05.46.56 UTC+2 skrev snipped-for-privacy@highlandsniptechnology.com:
include some through hole pads in the footprint for an easy upgrade with TO220/TO247
There are d and d2 pak fets rated for hundreds of watts; my limit is heat sinking. I think I want to get the tabs of the fets as close as possible and squeeze 2 or 3 of the AlN thermal bridges between them. If I go with 1 oz copper on layer 1, that's 70K/W per square, so I need to minimize that spreading thermal resistance. The tabs are nice chunks of copper.
How hot should I let the fets get? 80C?
torsdag den 24. juni 2021 kl. 18.40.20 UTC+2 skrev snipped-for-privacy@highlandsniptechnology.com:
sure, but adding more heatsinking is a lot easier with a part you can bolt to a heat sink
The challenge is to do everything with one pick-and-place pass.
If I do a single-channel high power dummy load, that would have one big finned heat sink and some TO-247 fets bolted on. Not as much fun to think about, or to build.
We just got a selective solder machine, which frees us up to use more thru-hole parts.
TCA0372Ps can't be far behind.
Cheers
Phil Hobbs
Digikey shows it as obsolete with 318,160 in stock.
Digikey is not making sense lately.
The problem with dips is just soldering, it's insertion.
Hint: You can also put a heat-sink on the bottom side of the PCB (opposite side than the FET's tab is on.)
We do it with D2PAKs. Should work OK with DPAKs as well.
Just gotta think about it for a few minutes.
Mounting directly to a heat-sink is better but not bad this way either.
boB
Few minutes!!!??? We've been obcessing on this for weeks.
I'd like to pick-and-place everything, fets and heatsinks both, on the
8-channel load board. We can have a giant extruded heat sink and a few TO-247's on the high power, single channel version.We're thinking 10 boards on 1.2" centers, and won't allow tall parts on the bottom. Heat sinks on the bottom wouldn't help much anyhow, because it's hard to transport the heat from the fets on the top side. Here's the general idea:
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