ISOTOP vs TO-264 MOSFET

Oneminde

Member
2014-06-22 11:14 pm
This question is related to thermal relief or heat transfer between the devices. So lets look at some specs.

#1: ISOTOP - Pd:
Total Power Dissipation @ T C = 25°C: 500W
Linear Derating Factor: 4 W/°C

#2: TO-264 - Pd:
Total Power Dissipation @ T C = 25°C: 520W
Linear Derating Factor: 4.16 W/°C

If adequate cooling is in place for both, would there be any difference in heat dissipation for these devices.
 

wg_ski

Member
2007-10-10 5:21 pm
The TO-264’s case-to-sink thermal resistance would be unavoidably higher. But the screw terminal package has a whole lot higher inductance, so in practice the switching losses would be higher at a given frequency, generating more heat to get rid of. You would have to fully analyze your system to determine which would actually run cooler. Sometimes a pair or more of TO-220s in parallel will beat a TO-264.
 

wg_ski

Member
2007-10-10 5:21 pm
A lot of very high power IGBTs and Mosfets give case to sink Rth in addition to junction to case. That’s for a perfect greased interface - as good as it could possibly get. To that you have to add the contribution from whatever thermal interface material you use. That will be given in W/m-K and you calculate based on thickness and size. If you do use an insulator it adds a lot at high power levels. The bigger the mounting surface the less it hurts you.
 

PRR

Member
Paid Member
2003-06-12 7:04 pm
Maine USA
www.diyaudio.com
This question is related to thermal relief or heat transfer between the devices.

Between devices? Or between a device(s) and the room?

500W 4 W/°C
520W 4.16 W/°C
If adequate cooling is in place for both, would there be any difference in heat dissipation for these devices.

4 W/°C is also 0.25 °C/W. Almost any "practical" heatsink has thermal resistance so much higher that 4.0 or 4.2 vanishes in the haze.

Heatsink should be appropriate for the device. Not a tin fin for a 1000W amp or a truck radiator for a headphone amp. Let's try a sink with thermal resistance similar to the device. For 0.22 to 0.3C/W I see prices from $50 to $427, and the $50 is for distributed input not one HOT part in the center. I don't know what a TO-264 costs but it is very likely that two devices at half the Watts each can use a cheaper cooling solution and be lower total expense.
 

Oneminde

Member
2014-06-22 11:14 pm
Bad wording from my side. The original question was concerning the heat (or energy) transfer between the MOSFET case to the heat sink and if the TO-267 was considered inferiour SOT-227 "ISOTOP".

Used an online calculator to find the Heat Sink Thermal Resistance using the SOT-227 size (25x38mm), 500W device and with Panasonic EYG Series, 1950 W/m.K, Graphite Sheet

50 °C =0.04995 °C/W
80 °C = 0.11 °C/W
100 °C = 0.15 °C/W
125 °C = 0.2 °C/W

Calculator: Heat Sink Thermal Resistance Calculator