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what do you think of these bricks?

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LAN_403

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Thu Aug 03 2006, 08:14PM

Registered Member #76 Joined: Thu Feb 09 2006, 10:04AM
Location: Hemer, Germany
Posts: 458

mhh, interesting, so the "smaller" igbts are better than the 800A peak monsters?? mhh, when my halfbridge modules arrive i can build a fullbridge for testing and compare the fujis to the siemens. i have a great dealer on ebay who sells them for a few bucks each, maybe i should write a mail to him to get more of these halfbridge modules

HV Enthusiast

Fri Aug 04 2006, 02:37AM

Registered Member #15 Joined: Thu Feb 02 2006, 01:11PM
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Posts: 3068

Not necessarily. To evaluate an IGBT, a lot of different things need to be taken into consideration - thermal interface, electrical parameters, etc...

Big thing with the small packages is cooling. If you can provide a coldplate that can maintain a decent temperature, along with a good thermal interface between the components and the coldplate, then you can definitely run them like i've been doing. My thermal interface between component and coldplate is quite good. During operation, i only measure a 5 degree difference between component and coldplate so the thermal impedance is quite good.

Steve Ward

Fri Aug 04 2006, 04:20AM

Registered Member #146 Joined: Sun Feb 12 2006, 04:21AM
Location: Austin Tx
Posts: 1055

I take it you are referring to your new modules, Dan? Just out of curiousity, what is the thermal interface between the surface mount device, the heatspreading plate, and heatsink?

Of course every device has its thermal limit when the peak die temp starts to exceed 150*C. The transient is so fast, that the best you can do is keep the die cool before it hits. Of course, the more massive your IGBT die, the more energy it can soak up before hitting critical temperatures. This is why Dan's surface mount IGBT bridge probably wont beat out a CM300 bridge, but because its newer technology, it's still more "bang" for your silicon.

Newer bricks from powerex and semikron, etc, are looking really great now, offering greater frequency operation, lower gate charge, and lower package inductance. If you could get ahold of these, then you are set.

HV Enthusiast

Fri Aug 04 2006, 12:41PM

Registered Member #15 Joined: Thu Feb 02 2006, 01:11PM
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The interface is an aluminum substrate board and grafoil pad.

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Sat Aug 05 2006, 12:04PM

Registered Member #76 Joined: Thu Feb 09 2006, 10:04AM
Location: Hemer, Germany
Posts: 458

hehe, for cooling my igbts i got a very huge heatsink from my fathers company. it is 75cm long and 16x16cm in diameter, its a so called "kÃ¼hlprofil" with rails on one side to screw 120mm fans on it. i want to cut this thing in 3 pieces, one piece for other projects and the remaining two pieces for the fullbridge, eeach heatsink with 2x 120mm fans, should stay cool

here is it .

HV Enthusiast

Sat Aug 05 2006, 04:00PM

Registered Member #15 Joined: Thu Feb 02 2006, 01:11PM
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Keep in mind, that you could have a heatsink one mile wide, by 50 feet high, and it would be useless. The limiting factor is almost always the thermal impedance at the interface between heatsink and device. This thermal impedance will determine the temperature drop between device and heatsink, and if its too high, then doesn't matter what kind of heatsink you are using.

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Sat Aug 05 2006, 05:45PM

Registered Member #76 Joined: Thu Feb 09 2006, 10:04AM
Location: Hemer, Germany
Posts: 458

yeah sure, but the thermal impendance of the device is an unchangeable factor in the datasheet, the only thing i can do is to screw the devices strong onto the heatsink with a small amount of thermal compound "wÃ¤rmeleitpaste" between igbt and heatsink in hope the thermal factor wont change much.

HV Enthusiast

Sat Aug 05 2006, 08:02PM

Registered Member #15 Joined: Thu Feb 02 2006, 01:11PM
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Posts: 3068

I'm referring to the interface between device and heatsink, not the thermal impedance between case and die. Depending on application, one might need an electrically isolated pad between device and heatsink, or use an inferior thermal substrate, and this just kills the thermal performance.

...

Sat Aug 05 2006, 08:18PM

Registered Member #56 Joined: Thu Feb 09 2006, 05:02AM
Location: Southern Califorina, USA
Posts: 2445

But for our drsstc's isn't the average power way lower than it would be if the device was being used for a 'normal' application, so we don't really need to worry about that? I mean, a brick that sized would normally be mounted on a copper waterblock with a big radiator to cool it... Then you would be worried about a perfect thermal contact, but if we only have a few hundred watts (you are gonna need a pretty big fan cooled heat sink to handle that) we should be fine with mediocre thermal contact?

JimG

Sat Aug 05 2006, 09:30PM

Registered Member #52 Joined: Thu Feb 09 2006, 04:22AM
Location: Austin TX
Posts: 57

When your device has only .13" square inches of surface area to dissipate heat out of how it is connected is pretty important no matter what the average power is. If you can't cool it down while its off then heat will just build up. Even with 100us pulses my surface mount bridge can get hot pretty fast.

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