RE: TI UC2710 vs. Microchip TC4422 FET drivers SMT

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Original poster: "Mccauley, Daniel H by way of Terry Fritz <twftesla-at-qwest-dot-net>" <daniel.h.mccauley-at-lmco-dot-com>


You should try to stay away from SMT high current FET drivers unless you can
provide adequate heat sinking.  Most of the SMT FET drivers on the market
are designed for high power power supplies (DC-DC converters) which are
typically built on this special type of PCB board which is actually 1/16 to
1/4 inch aluminum.  This would then be attached to some sort of cold plate
etc... to remove the heat.

Even with my new SSTC, thru-hole (larger mass) TC442x drivers get pretty
damn hot and require fan cooling.

Dan





> > I have soldered some of the tiny parts (although not an 0201)...
> > 
> > I was thinking more of standard SMT ICs with 50 or 25 mil lead pitch. A
> > decent fine tip (like a Weller PTH or PTO, maybe filed down a bit from
> the
> > stock 0.031") on a standard soldering iron will work, and if you are
> using
> > the right (read cheap) chips, then rework consists of cutting all leads
> and
> > throwing away the part.  A hot plate and a heat gun with a suitable tips
> > can also work for desoldering (a bit more tedious, but a lot cheaper
> than
> $2K).
> > 
> > True, for "spaceflight quality" work, or for large volumes, you DO need
> the
> > microscope and hot air rework, vapor phase setup, etc.  But, a decent
> > magnifying headset(around $25), fine tweezers, and some hypodermic
> syringes
> > works just fine.
> > 
> > It aso helps to not try for ultimate in compact design.. 1206 and 0402
> > sized parts are fine.  Mostly, the idea is to get your "hobby process
> > flows" so that you can turn around the board reasonably quickly at low
> > cost, and use all the nifty chips available these days. I'm also a BIG
> fan
> > of the eval boards available for most parts.  Nothing says you can't do
> > some trace cutting, etc. on the boards.
> > 
> > Unless you need a wire bonder and are working with bare dice, I would
> think
> > that you could get everything you need for SMT prototyping for under
> $500,
> > brand new.  Scrounged at hamfests and surplus, much, much cheaper. The
> run
> > of the mill WTCPT soldering iron will take the SMT adapters ($16 for the
> > SMTA-7) and then the various SMT tips (around $20-30 each).
> > 
> > The one SMT peculiar thing you ARE going to need is syringes of solder
> > paste, but they're readily available from the suppliers, and you just
> keep
> > it in the freezer next to your bench in the garage (next to the cold
> beer,
> > right?)
> > 
> 
> I've done SMT at home as you describe, but it was very difficult, as I
> was building a circuit using a quad flat pack type chip with 128 leads,
> a DDS circuit.  If you have the money to burn, the equipment is worth
> it, esp. the microscope.  With circuits >500Mhz, you won't get any of
> the SMT advantages unless you can get the parts really close to the
> chips.  Also, large 0805 and 1206 size components have a large
> self-inductance and high pad capacitance which tends to spoil their
> usage at RF- but for Tesla work, should be just fine. Rob.
> 
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