IMSAI 8080 System
General Assembly Notes
Solder
Using the proper solder is as important as using the proper
iron, and there are many solders to choose among. In normal
electronics assembly, separate paste or liquid flux is not
used. Rather, .a solder with a "core” of rosin (or resin)
base flux is Used. This flux (contained in the hollow center
of the solder) should be sufficient. Absolutely avoid any
solders using an acid flux. (Or any cans of acid flux -
unless a can of flux says"rosin" you may safely assume it
is an acid flux. Acid fluxes are used for mechanical sold
ering where the surfaces are not as clean as those in elec
tronic assembly. They are corrosive and will typically
damage a printed circuit.
Also very important is the ratio of tin to lead used in the
solder. Best to use is 63% tin, 37% lead, called 63/37 or
eutectic. Much more common is 60/40, which is still a very
good solder. Avoid using 50/50 or 40/60, even though they’re
a little cheaper. The higher-lead ratios solidify gradually,
while the 63/37 solidifies almost instantaneously, making
"cold solder joints" very much less likely.
Also important is the gauge (or diameter) of the solder.
For fine electronics work a fine gauge should be used,
such as #20 (from #19 to #22 is OK). Again, the correct
solder is easy to obtain from any local hobbyist electronics
outlet or TV repair shop. ERSIN Multicore or KESTER are two
brands you can count on for good results. The solder in
cluded in the kit should be sufficient. If for some reason
it is not, and you cannot obtain the proper solder locally,
DO NOT USE any substitutes. More solder of the proper type
can be detained from IMSAI.
Soldering Technique
For a joint to solder correctly, enough heat must be applied
so that both pieces of metal get hot enough to melt the solder.
The tip of the iron should be applied so .that it touches both
the wire and the foil pad on the board. The end of the
solder should then be touched to the junction of the iron,
lead, and pad, so that a small amount melts and "wets" the
joint (flows smoothly on. both the lead and pad). As soon
as the joint has wet, the iron can be removed, and the joint
inspected immediately. Careful inspection of each joint is
the key to successful soldering. While the solder is being
applied, watch the joint carefully. You should be able to
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