Re: The goo inside of IGBT modules.

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Original poster: "Steve Ward" <steve.ward-at-gmail-dot-com> 

Hi Jan,


 > The monkey snort is silicone gel. Which is not silicon, but the bathroom
 > fixture type sealant resin. Not a good thermal conductor really. It just
 > helps keep moisture and corrosives outside. Heat is mainly removed via the
 > substrate and baseplate. The low-hardness gel also reduces thermal stress
 > on the bonding wires as they can move more freely than in e.g. hard 
epoxy fill.

Ok, so basically what i had figured.

 >
 > Btw, it doesn't damp those explosions, the gel is too "soft" for this,
 > shrapnel just shoots right through it, with a nasty little scorched crater
 > left behind... :) (at work, one wall is decorated with some dramatically
 > exloded 3-phase IGBT modules, some with all gel and guts sticking out,
 > quite gory... ;-)

Haha, well all of the failures i have seen (they usually have about
1300j behind them when they fail) have resulted with the tops of the
IGBT blocks broken right off, but the actual stuff inside was all
trapped up in the goo.  Actually, there were large air bubbles from
where the dies vaporized, and also a large amount of carbon (or some
other black stuff).

 >
 > You're not by any chance contemplating to remove the gel and adding a pump
 > and internal forced oil cooling to your IGBT modules, are you?  ;-)

Hehe... it had been considered.  The manner which im using the IGBTs
can cause a lot of transient heating, and i was really curious if
there was some other way of getting the dies even cooler (increase my
thermal headroom).  Im not sure if im willing to go so far as oil
cooled though.  Maybe just get the baseplates further below ambient
temp.

Steve

 >
 > cheers,
 >  - Jan
 >
 > --
 > ****************************************************
 >  Helsinki University of Technology
 >  Dept. of Electrical and Communications Engineering
 >  http://www.hut.fi/~jwagner/ - jwagner-at-cc.hut.fi