We are encountering problems with solder irons (brand unidentified for now)
and I would like your thoughts. This is one of the new generation of irons
with heaters in the tips like Hakko, JBC, Metcal, Pace and even Weller are
offering.

1. While attempting to measure the tip temperature we discovered an offset
from the measured tip temp and the displayed tip temperature on two of our
eight solder stations. The offset was the same for any tip. Six other solder
stations of the same brand did not exhibit the offset. The amount of offset
was temperature dependent.  The two stations did not have the same
temperature offset. I concluded that there must be a DC voltage on the tip
and verified this with a DMM. The station with the higher DC had a higher
temperature offset. We measured a maximum of about 1 VDC from the tip to
ground. The manufacturer was aware of "a random temperature offset" when
measuring the tip temperature with a thermocouple but had not, I presume,
associated the issue with a DC voltage on the tip.


2. We had been checking all the solder stations performance at a calibration
station with a single tip. The above discovery prompted us to check all the
tips in the house. We found numerous tips with tip to ground resistance
exceeding 5 ohms (the maximum J-STD-001D recommendation). Several tips
measured in the 10 to 30 ohm range. No new tips were identified with high
tip to ground resistance, suggesting that this resistance develops as the
tips age.



I find that the IPC-J-STD-001D recommends tip transients should not exceed 2
VP but merely states AC and DC leakage should not create deleterious
effects. As a voting member of the committee, this phrase formed an easy
consensus. As a user, this phrase in the standard is less than helpful.



Mil-STD-2000 limited leakage to 2 millivolts RMS. I wonder what data moved
us from 2 millivolts RMS to 2 Volts Peak or no deleterious effects.



What do you think:

Of the solder station performance?

Of the standard recommendations?


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