Welcome to Chiphacker

Question

1

More components are only available in SMD packages. For hobbyist assembly the options are to buy breakout boards or solder SMD.

Since components are usually packaged in a couple of SMD package types I am trying to put together a set of guidelines for choosing packages that are compatible with hobbyist skills and tools. I would consider hobbyist level tools for SMD assembly as -- soldering iron in the $50-$100 range (new), for magnification a $40 visor (like the B&L) and tweezers.

For the kits I make now I use the following guidelines --

Passives 0805 or larger
Min Lead Pitch for SOIC or QFP -- 0.5mm
No QFN, LGA or BGA
Prefered package for gates, BJT, FET --- SOT23
Diodes SOD123 (or larger)

I am interested in recommendations on component selection, minimum tool requirements and assembly issues. Specific tool changes (like solder tip size) that enabled you to do SMD assembly with your existing tools would be useful too.

Thanks.

(* jcl *)

http://www.wiblocks.com

flag	asked Jan 26 at 17:32 jluciani 2,611●1●10

3

Typically signatures are not allowed - your user page is a more appropriate place for such things. – Adam Davis Jan 26 at 18:16

Jason S · Accepted Answer · 2010-01-26 23:31:05Z UTC

0603 isn't too bad to solder by hand (I won't do 0402 or smaller though).

SOT23 is probably a good guideline (for diodes too, not just transistors); there are some SOT323s that are smaller that are a pain.

I would avoid certain SOT23-6 parts because it can be very difficult to determine which way the package is supposed to go. (For some dual MOSFET packages it doesn't matter.) We had one where there was a slight bevel along one edge. Grrr.

I would also avoid SOD123 because of the backwards nature, if possible. SMA/SMB/SMC aren't as much of a problem.

And avoid those cylindrical diodes (LL-34 / MELF) like the plague! they will roll off the board.

davr · Answer 2 · 2010-01-27 00:29:41Z UTC

As far as my skills, to add a point of data. Using a $40 soldering iron, and lots of flux (I have a 'pen' with the liquid kind inside), and the occasional desoldering braid.

Easy: 0805 passives , 0.7mm pitch ICs

Doable if careful, but have ruined a couple: 0603, 0.5mm pitch ICs

Haven't tried smaller than those yet, I think that's about my limit.

Steve · Answer 3 · 2010-01-28 10:58:45Z UTC

I would recommend using a SMD rework tool for small projects, and a reflow oven (you can make one from a toaster oven) for larger boards.

Reflow makes sense because you have far less problems with solder bridges and it's actually harder to destroy components. Components tend to pull themselves into position, so placement of smaller components becomes less critical (than with soldering by hand). 0805 and 0603 are a breeze.

For reflow it makes sense if you have a tool to deposit accurate amounts of solder. Using a syringe by hand and really a bad idea. The smaller the component the more critical this is.

Sizing SMD components for Hobbyist Kits

3 Answers