I have been instructing for more years than I would like to think about.
One area was, has, and is about soldering irons and what we should check
them periodically. I instruct my students (operators) on daily checks and
maintenance, such as removing the tip at the start of the day to remove the
oxidation build up between the metal portion of the tip to the metal contact
portion of the handle. This insures the best you can that the resistance
will be low (<5 ohms). If you have someone do the checking (audit) I have
usually found that person will automatically remove the tip and do what I
call a scrubbing action to get good contact or if test bad will go ahead and
do it then. This way the just have to record it as good. It is the
operators who must do this not wait to the test. The purpose of checking
the tip's resistance and potential to ground to prevent damage to components
by injecting an unwanted voltage. There was a case sometime back that a
soldering iron injected a voltage that fired a circuit called a squib that
was a firing mechanism if I remember correctly. It was alert issued by the
government. I believe soldering iron manufactures who deal with folks like
you make very excellent irons. All will do a good job provide you monitor
and maintain them. You can always reduce your checks based on past history
on almost anything if you have data that shows you have things in control.
What you find, if the finding are recorded as found, resistance out,
temperature too high or too low, damaged cords, etc. If an iron just melts
solder does not really give you the whole picture. Ask your soldering iron
reps or read their manuals and you will see changing the tip affects
temperature, and you should not take a handle from iron to another with out
checking temperature. That will be in most iron manuals. Even new irons
should be checked. The one you have is very stable, tip's regulate
temperature, etc. but you probably paid a higher price for them. I have
seen soldering iron holder where the sponge was held started to corrode due
to bad plating but would not be noticed by operators. They did not
understand it was a form of aluminum rust that now allowed the possibility
of contaminants to enter the solder joint. I know I became long winded but
this is what I seen, read, and discovered over the years working in the
electronic field and growing up with where and what this requirements were
first implemented for government products. So not only are you checking
resistance but the temperature control and controllers can go bad. My 2
cents worth. I think J-STD-001 handbook may have some of the whys. Jon
-----Original Message-----
From: Kane, Joseph [mailto:[log in to unmask]]
Sent: Friday, October 13, 2000 1:50 PM
To: [log in to unmask]
Subject: [TN] Soldering Iron Testing
Anyone have an opinion about whether periodic testing of irons is warranted,
and if so,
how often? Newer specs and handbooks don't address this.
For the record, we still apply an old military requirement, and test each
iron every 3
months for tip-to-ground resistance (<2 ohms), potential from tip to ground
(<2 millivolts),
and temperature variation at rest (+/- 10 degrees). Most of ours are
Metcal, and the
pass rate is better than 98%. Those that fail usually do so for tip
resistance slightly OHL.
Iron manufacturers have told me (off the record) that these limits don't
mean a whole
lot in practice; when DOD came after them years ago, the manufacturers
proposed these
numbers because they knew they could meet them.
Joe Kane
BAE Systems Controls
Johnson City, NY
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