Re: TI UC2710 vs. Microchip TC4422 FET drivers

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

Original poster: "rob by way of Terry Fritz <twftesla-at-qwest-dot-net>" <rob-at-pythonemproject-dot-com>

Tesla list wrote:
> 
> Original poster: "Jim Lux by way of Terry Fritz <twftesla-at-qwest-dot-net>"
<jimlux-at-earthlink-dot-net>
> 
> 
> 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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