Homebrew PCBs

Thanks so much for that valuable information. I realize while I was reading, that a lot has changed since I went through electronics school 30 years ago. Electronics now is just a part time hobby.

Thanks again
Joe
  ----- Original Message ----- 
  From: DJ Delorie 
  To: Homebrew_PCBs@yahoogroups.com 
  Sent: Wednesday, April 22, 2009 12:06 AM
  Subject: Re: [Homebrew_PCBs] TIP120 Darlington






  "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.


  

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