RE: Discrete Mosfets/IGBTs mounting techniques ...

["Tesla list" <tesla-at-pupman-dot-com>]

Original poster: "Mccauley, Daniel H" <daniel.h.mccauley-at-lmco-dot-com> 


1.  Correct.  The PCB traces have to rated accordingly as well.  40A is
a LOT of current.
Even a trace that has a resistance of 0.005 (not too uncommon) will
dissipate 8 Watts at 40A ! ! !

Also, if you are planning on running 40A through some FETs, you may be
connecting them only electrically to
a PCB board.  The FET itself will be connected to a large heatsink or
coldplate.  Not one of those dinky
fin-type heatsinks either.  I'm talking big aluminum extrusions.

Typically, you would use high oz. copper planes, not traces.  For
example, for that current, we might use 4 to 8 oz
copper.  Your typically economical PCB boards are usually rated at 1oz
copper.

For boards with external layers (top or bottom), you can use the
following equations.  I'll try to get the summary
sheet but each equation is listed as:

10degRise:    Amps = 0.1651 * (Area^0.6746)
where:  Area of 1oz trace = 1.2
         Area of 2oz trace = 2.4
            and so forth . . .

They have a different equation for each degRise.

As far as mounting, for those type of currents, I would recommend either
an isolated TO-247 package or
Isotop such as the IXFN44N50 (IXYS)



Dan



Hello experts,

I have few discrete power mosfets (TO-247 package) with me. I am
planning
to design high power inverter for tesla coils.
Some mosfets are capable of handling up to 40 Amps. But the problem is
how
do I mount those power mosfets in a PCB ?
Because, even though the mosfets can handle 40 Amps or even higher, the
PCB
tracks cannot handle that much current ?
Should I have tracks which are several inches wide ?
Are there any other mounting techniques for Power mosfets (other than
PCB
mounting) ?
Thanks in advance.