SPECIAL CARE tips by Hans G0UPL
The QCX-mini kit is very compact. It requires a higher degree of precision than many other
QRP Labs kits, if you are intending to install it in the optional enclosure. It’s not more
difficult. It just requires a bit more care. Pay careful attention to the following points,
throughout the assembly.
1. Board inspection
Even the SMD assembly line is not perfect and mistakes can occur. I recommend a careful
visual inspection before commencing assembly, with a jeweler's loupe or other optical
magnification aid. Look for any solder bridges between IC pins, or solder splashes which
may cause short-circuits.
2. Soldering
In the QCX-mini kit, there are SMD components installed on BOTH sides of the PCB. When
soldering through-hole component leads, you will often be soldering a joint that is very close
to nearby SMD components. In this case, angle the PCB and soldering iron so that you are
approaching the joint, and touching and heating the joint, from the opposite direction to the
SMD component, to avoid heating it and removing it.
In the photograph below, SMD capacitor C4 is very close to the component leads being
soldered; I approached the joint from the right-hand side, away from the SMD component,
and successfully soldered the joint without coming anywhere near C4. I successfully
assembled this PCB even though my soldering iron tip is an enormous 3mm chisel-bit.
3. Mistakes
If you do make a mistake and end up with a solder bridge somewhere, desoldering braid
(a.k.a. solder wick) can really help clean this up, it is well worth having some of this in the
workshop. If you have no braid to hand, you can even use the braid from a piece of old
coax or shielded cable, perhaps soaked in flux first if you have some.
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