[sdiy] SMD experiences

[Matthew Smith]

Quoth Dave Manley at 10/09/11 06:27...
> In my experience there's no need for liquid flux on anything except for ICs,
> and there it is absolutely required for drag-soldering.

I've found that flux pen on capacitor pads gets flow a lot faster than 
just applying resin-core solder to part on a bare pad. So I just take 
the easy route - if there's going to be a joint, I flux it.  Most of my 
boards are so small and have such a tight layout that it's hard to avoid 
fluxing the whole lot :-)

And don't get me going on the Pb-free solder that has the same rated 
melting point but just doesn't wan to flow. Ugh! (And which is why I am 
avoiding using Pb-free until such time as I have to.) Maybe I'm doing 
something wrong and need a different technique, but gimme that good ol' 
lead any day!

> Often solder bridges can be cleared with the clean tip of the iron, drawing the
> solder down towards the pads and then outwards, but Matthew is correct, solder 
> braid is another essential.

I've certainly found that a cleaned bit can whip off any blobs that 
might have formed on capacitor joints, and can sort out the majority of 
bridges on broader-pitched parts like PLC44s. However, I've been unable 
to do 0.5mm pitch ICs without braid - which accounts for the majority of 
the parts I am now using. (SO8 opamps look HUGE after LQFP 
microcontrollers!)

So, flux pen, braid, tweezers, magnification, decent soldering iron with 
a fine bit (I *love* my Hakko FX-888.)  If you want to go for a 
binocular loupe for the latter, do NOT use high magnification like 3.5x, 
as you'll never hold your head still enough.


-- 
Matthew Smith

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