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Hand-soldering SMD for fun and profit

If you want to inspire fear/admiration/incredulity(* - delete as applicable) in people, simply tell them that you solder surface-mount components by hand. Go on, try it ... I'll wait.

What if I told you that it's easier, and a hell of a sight quicker, than solding through-hole components?

When you mention surface mount technology, most people will immediately think of the insanely small components that you'd typically find on a PC motherboard or in your phone, and they'd be right. However, not all surface-mount devices are created equal ... the insanely small stuff in phones and on motherboards is picked, placed and soldered by machines, however 'bigger' surface mount components are easily soldered up by mere mortals given a few basic tools.

Over time, it has been quite gratifying to watch my module designs evolve from rather nasty looking through-hole prototypes on perfboard to professionally fabbed boards with hand-soldered surface-mount components. I haven't abandoned through-hole construction altogether - it still has it's uses, and in some cases a through-hole component may cost considerably less than the SMD equivalent (case in point: the LF398 sample and hold amplifier - the SOIC version is about twice the cost of the PTH chip)

At this point I have absolutely no desire to get into a dick-swinging contest with those people who claim that they can hand-solder 0402-sized components blindfolded with one arm tied behind their back. If you can do that, great. Me? I'm in my mid-40s, my eyesight isn't the greatest and I know my limits. Those limits? 0805 and SOIC.

You only need four things to solder SMD:

Technically, you need five things but 'a steady hand' is kind of implied (I'm serious too - do not attempt SMD soldering if you've hit the coffee a bit too hard. Don't ask how I know this)

Hit your favourite video sharing site and you'll find a whole host of tutorial videos, but the techique boils down to this:

Easy! If you've done it right, you should have nice, shiny and rounded solder joints - if any of them look dull, pop a bit of flux on the offending joint and re-melt the solder.

The technique for ICs really isn't much different:

Again, if you've done it right you should see nice, bright joints. Using this method it's easy to solder 'standard' SOIC or TSSOP packages (150mil pitch) providing you have a steady hand - larger TQFP packages (think in terms of the Atmega 328 TQFP) are also relatively straightforward. BGA? Forget it.

Why use SMD though? Here's a few reasons:

But what about the downsides?

Well, prototyping with SMD is a bit hit and miss - if you're using 0805 or similar components then you can use regular perfboard if you're enthusiastic enough. A few companies used to do SMD prototyping systems but these seem to have been discontinued. Fortunately, the Internet rode to the rescue - I stumbled across this article on surface mount soldering (worth a read) and it would appear that the author had similar issues - I had a bunch of these fabbed up and now I have everything I need for building prototype SMD circuits prior to committing them to a 'real' board.


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