it MUST be compatible. You want a liquid (not paste) water-based no-clean flux. Kester 951
is ideal, if you can get it. Chip-Quik sells little 2ml tubes for about $2 each (unfortunately they
sell them in 6-packs, you can’t just get one) which works very well. If you decide to add flux,
you must use only a tiny amount. A few drops will suffice for the entire board. DO NOT use
Rosin Core flux, or you will make a mess of the board and possibly damage components. We
have built many kits without using any additional flux without any issues, the board is pre-
tinned to make solder adhesion easier so in general you should not need to use additional flux.
For soldering components on a board like the Quark, we recommend a small pencil soldering
iron, about 15W. If you are only going to use it occasionally, Weller makes a decent cheap
12W iron, it’s about $15. There is also a similar iron that’s sold by ECG. We like those, but
the copper tips seem to oxidize and corrode rather quickly compared to some more expensive
irons; fortunately, the tips are replaceable and cheap. Better would be a fancier soldering
pencil with iron tips; those run about $30, but they’ll last forever. The best iron would be a
temperature-controlled solder station, they typically start at about $50 for a cheap one and can
go to a few hundred dollars if you want to get really fancy. Weller makes a good one for about
$50, if you make the investment that will probably be the last soldering iron you will ever need
to buy. These solder stations usually have a little well with a tip-cleaning sponge, so they end
up taking less room on your workstation too. Get the smallest tip you can find, preferably a
small conical tip. It should be just about the same width as the processor’s pads.
