Steve,

I guess the flat pad surface is crucial for heat transfer more than for
current. I don't know what IGBT package you are using but usually its metal
tab is electrically common with the collector pin. That means the majority
of the 90Amps goes through the bolt to the busbar while connections with
other circuit elements (snubber, sensing, etc.) are made via the PC board.
The collector pin of the device is sufficient for these connections. If
heat transfer is the major issue, conformance of the mating surfaces would
be important. However, you cannot guarantee both the device surface and the
pad are absolutely flat. Some thermal interface material is thus necessary.

Hope this helps.

K.K. Chin
Mfg Engg Mgr
Artesyn Technologies,
Fremont, CA
www.artesyn.com




Steve Plant <[log in to unmask]> on 08/10/98 04:31:52 PM

Please respond to "\"TechNet E-Mail Forum.\" <[log in to unmask]>,
      Steve Plant" <[log in to unmask]>

To:   [log in to unmask]
cc:    (bcc: KK Chin)
Subject:  [TN] Solder on pads




Hi all,

Wondering if any of you could help me out.

We are currently assembling a product which requires us to bolt
busbars on top of PC boards into the IGBT's below the board. This
connection can pass up to 90 AMPs through it. Some of the
boards we are receiving have solder build-up on the pads and we
are spending some time clearing it off to provide us with a flat
surface.

My question is : Does anyone have any experience with this type
of sandwiching of PC boards and the effects of solder on the pads?

Is there any standards which we can use?

Any help would be most appreciated.


Regards


Steve Plant
Electronic Production Engineer.
PDL Electronics LTD.
New Zealand.
Ph (06) 843-5855       Fax (06) 843-5185
Email   [log in to unmask]

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