Page 56 - Build Your Own Quadcopter_ Power Up Your Designs with the Parallax Elev-8

Chapter 3: Building the Ele v-8 35

the investment. Cold solder joints are the bane of any builder, and they are hard to locate.
The key to quality soldering work is to have good soldering technique, keep the soldering
iron tip clean, and to use the highest-quality solder available. Figure 3.1 shows the essence
of good soldering technique. It is vital that the solder joint be hot enough for solder to flow
easily. It takes practice to apply just the right amount of solder; too little could result in a cold
solder joint, and too much could lead to a short between closely spaced components.
Another issue regarding a good solder joint is the use of lead-free solder. Now, please
don’t get down on me. I am all about maintaining a healthful environment, but the elimination
of lead from solder often produces poor solder joints unless some extra precautions are taken.
The simplest, and probably, the best approach is to apply a high-quality, acid-free solder flux
to the joint prior to heating the joint with the iron. This will allow the lead-free solder to flow
more freely and produce a better-soldered connection. Again, it takes practice to perfect
soldering techniques.
I have one final thought that relates to solder joints as well as other types of electrical
connections. A long-running anecdotal observation contends that 90 percent of all electrical/
electronic malfunctions are related to connection malfunctions. This claim makes a lot of
sense when you think about it. We live in an oxygen rich atmosphere, and oxygen is a great
reduction agent: it wants to oxidize every element it can possibly chemically combine with.
Metal oxides are reasonably good insulators because some of their free electrons have been
taken up by oxygen molecules. This leads to higher and higher resistance being built up in a
connection, which will eventually cause a failure. Of course, current flowing through a
resistance produces heat, which in turn can cause a fire if the currents are sufficiently high.
So, what is the solution? One expensive solution is to gold plate electrical contact surfaces.
Gold doesn’t oxidize and is not subject to this type of failure. It is, of course, very expensive
and not practical for large-scale connectors. For the type of projects that I work on, I can
ensure only that solder joints are sound from both a mechanical and electrical perspective. I
also inspect electrical connections for oxidation and foreign matter, and take appropriate
action to replace or repair a damaged component.

Bill of Material
The bill of material (BOM) is reproduced below in Figures 3.2 to 3.5. It is highly recommended
that you cross-check all the material in the kit against the BOM and contact Parallax if
anything is missing. I have always found them very prompt and attentive to requests from
builders, in instances where parts are missing or otherwise incorrect. All of the kit contents

Figure 3.1 Good soldering technique.