[Elecraft] SMT and the K3 - Nerves

[Dave Lankshear]

I'm surprised no-one has mentioned Chipquik to ease the pain of SMT removal.
It is a low temperature alloy (something like Wood's metal - the melting
teaspoon in a hot drink prank etc.), supplied in small diameter "wires"
together with a special flux.  Melt a little Chipquik onto an existing
soldered joint and then melt the other end with the iron.  The Chipquik-ed
end stays molten, so removal is a breeze, as is cleanup.  I've removed and
replaced a 64-pin chip quite easily with it.  I won't say more, but visit
the website, www.chipquik.com <http://www.chipquik.com/>  and take up their
free sample offer; it's enough to help remove several components.

 

As for crunching up SMT's, that doesn't sit easy with me, but the quality of
Elecraft's boards means they will take some hammer before foil separates
from the substrate. I sure have hammered, but to date, I've never lifted a
trace or pad on an Elecraft PCB, although I know a few folks who have.  Just
tonight, I removed a diode on a small, made in China PCB.  Simply heating
both ends of the component's solder caused the pads to separate from the
board; such was its dire quality.  I used a wire ended diode to replace the
dud and had to be a bit crafty as to where the ends were tacked, but it's
working again. 

 

For a quick hold-down of a component, I often use a cocktail stick, taking
care to keep it absolutely vertical above the component.  Use tweezers with
care because they make fine component launchers and tracking down the
launched component is like looking for a needle in a haystack.  Little
vacuum pencils are sold on Ebay for a couple of bucks and are handy for
lifting or keeping hold of stuff like SMT ICs - the big stuff Hi!

 

While I'm on a roll, here are more tips, qualified by the usual disclaimer -
YMMV.

 

Small wattage soldering irons have so much thermal lag that components can
be barbecued before the solder melts.  I use and recommend a temperature
controlled iron of around 50 watts.  Go for something that has a fine tip,
but not a needle tip, as there's not much metal to conduct heat to the tip,
so thermal lag again.  Look for a short taper.

 

Get a GOOD solder sucker.  I have a small stock of Soldapullts from Edsyn.
Take a look at www.edsyn.com <http://www.edsyn.com/>  and check out the last
few pages of their clearance items.  You should find some very inexpensive,
end of line, high quality solder suckers listed.  Get a spare tip or two
with the order.

 

Invest in a liquid flux pen.  It makes such a difference to have wiped a
spot on pads before soldering and wiping along the next bit of solder braid
you're using makes the braid much more effective.

 

73 Dave G3TJP