IGBT Linear operation

[Randy222]

This is more of a "specs" comment than a "solution" comment.

Specs of the items are almost always come from modeling or of the package. It's rare to see a manufacture do actual testing when it comes to thermal controls.

"watts" almost always means it's a temp related issue. But we don't see maker mounting the package to a 1ton block of aluminum (or ideal finned sink) at room temp to sink heat out during the "max" test.

IIRC, few if any show graphs for "max". It's temp that kills the device, but you could exceed a max number if the time there is very small, because it takes times for temp changes, etc.

We also don't really see spec sheets calling out heatsink specification numbers, they kinda leave the thermal design up to you.

[T3sl4co1l]

This is more of a "specs" comment than a "solution" comment.

Specs of the items are almost always come from modeling or the package. It's rare to see a manufacture do actual testing when it comes to thermal controls.

Do you have a citation for this statement of fact?  Example, have you worked at one and have read process documents to that effect?  Or you've seen appnotes which document it?

"watts" almost always means it's a temp related issue. But we don't see maker mounting the package to a 1ton block of aluminum (or ideal finned sink) at room temp to sink heat out during the "max" test.

Well... no... why would they?  There are much better ways anyway.

The typical standard is nucleated boiling liquid, a bath of Freon stirred aggressively and held at a pressure such that it's just boiling at ambient temperature.  This holds Tc, very literally every exposed point of the case, at 25°C for the test.

This itself is not well documented, to the consternation of many; but IR did at least release an appnote during the peak of the specsmanship era when this started really getting pushed (and, AFAIK, is still the accepted standard outside of SMT devices; though many tabbed SMTs still also have a useless Tc=25°C spec anyway).

Namely, AN-1140: https://www.infineon.com/dgdl/Infineon-ApplicationNote_MOSFET_Continuous_Current_Rating-AN-v01_00-EN.pdf?fileId=5546d462689a790c0169166671e9454c

IIRC, few if any show graphs for "max". It's temp that kills the device, but you could exceed a max number if the time there is very small, because it takes times for temp changes, etc.

We also don't really see spec sheets calling out heatsink specification numbers, they kinda leave the thermal design up to you.

I...guess?  Not sure what max you mean.  SOA plots don't change much with temperature.  (Tempco and thermal resistance change a little with temperature, which can change size of the instability region.)  There's transient thermal resistance for pulses.  Naming a particular heatsink wouldn't be very useful, though one might argue SMT footprint data (minimal, thermal pours of given area, inner plane, etc.; see JESD51 series) is somewhat analogous -- but also more flexible, and (nearly) free of cost in comparison, so is worth documenting.

Tim

[PCB.Wiz]

A problem with linear-anything, is power dissipation.

The new SMD packages are great for low loss switching and have very low on losses, but are not so great at heat removal.

I did see a new isolated power package from IXYS that could be used for more modern Linear MOSFET designs. It just needs the market demand. 
This isolated package is designed for heatsink clip/pressure mount, not soldering.