Homebrew PCBs

"Joe" <n0pme@...> writes:
> Where can I find a cross reference for standard componants to SMT?
> My other question is. Is there a TIP120 Darlington transisiter in
> Surface mount.

No simple answer from me.  I use digikey's search engine to find parts
with similar characteristics, and hope for the best.  In the case of a
TIP120, I searched for "NPN Darlington", then selected everything 65W
or higher, then selected the one remaining SMT package - a D2PAK (it
looks like a laid-down TO-220).  I found this - it's 80W:

http://www.digikey.com/scripts/DkSearch/dksus.dll?Detail&name=FJB102TMCT-ND

To properly solder that, though, you'd need to reflow it - it uses the
copper on the PCB as a heatsink so you want a full solder joint
between the pad and the pcb, and most irons can't pump that much heat
in there.  I use a cheap hotplate.

For SMT transistors, you're mostly going to be looking for SOT-*
(sot-23, sot-323, etc) for smaller ones, or DPAK/D2PAK for larger
ones.  For resistors, capacitors, ferrites, and LEDs, choose a size
you're comfortable with (I use 0603) and stick with it, unless you
need more power (or capacitance) than the package allows.  ICs will be
SO or *SOP (sop, tsop, tssop, etc; avoid SOJ as the leads are *under*
the chip) for dip-style, or *QFP (tqfp, pqfp, lqpf) for square style.
Avoid QFN (No-lead) unless you're really tight on space and know how
to reflow solder.

Most datasheets have land pattern recommendations you can use, if
they're not standard packages.