Electronics > Repair
Soldering ESD-sensitive components without grounded soldering iron
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Ian.M:
Personally I get good results with a catalytic gas iron, a literal ''firestick', even with fairly fine pitch boards.  However as it *is* a 'firestick' with no temperature control, albeit variable power, and there is quite a lag between adjusting it and the gas flow change taking effect, one needs considerable experience and skill to avoid overheating stuff.   Probably on balance if you need a portable mains-free iron, the less experienced should get a low voltage temperature controlled one, possibly powered by a USB C power bank or a common power tool battery so you can easily swap battery packs if you run out of juice at an inconvenient time.  Do not get suckered into buying anything less than 40W max. power to the tip at the nom. battery voltage you intend to use.

Not a resistor in *series* with your DMM, a resistor in parallel with it!  i.e. to make a low impedance voltage measurement, put the resistor across the points you want to measure voltage between then apply the probes.

A mains soldering iron bit should be hard grounded - as close to zero ohms* to mains PE as you can manage.  This may be problematic in some parts of Norway where the shallow soil depth and underlying rock type makes getting a good ground for the mains supply difficult, so you may not actually have a grounded socket.  In that case, it should be grounded to wherever your ESD ground goes#, but without any series resistor.  It may be possible to refit your iron with a three wire mains cord and three pin grounded plug, or you may need to use a small metal spring clip on the shaft of the iron to connect the ground, as close as possible to the handle so it doesn't get too hot.

* Ref: NASA-STD-8739.3, section 6.4.3 (page 30):

--- Quote ---6.4 Tool and Equipment Control
...
   3. Power tools used during the soldering process shall comply to the tool requirements herein and have a three-wire grounded power cord. The area making contact with the workpiece shall be grounded. When measured from the workpiece contact point to ground, the resistance shall not exceed 2.0 ohms and the potential difference shall not exceed 2 millivolts root mean squared (RMS) using methods indicated in the supplier's engineering documentation.
--- End quote ---

# Do *NOT* ground to a water pipe in a multi-household building.   Unless you control all plumbing from the point of entry to the point you wish to ground to, you cannot guarantee its integrity as a ground which may have to carry a fault current.  It is unethical to risk a fault in your equipment making someone else's pipes mains live!
wraper:
Don't bother, it will be fine. Unless you start manufacturing in volume, very unlikely you'll ever see any of them fail because of lack of ESD precautions.
analogix:

--- Quote from: Ian.M on June 19, 2024, 10:39:15 pm ---# Do *NOT* ground to a water pipe in a multi-household building.   Unless you control all plumbing from the point of entry to the point you wish to ground to, you cannot guarantee its integrity as a ground which may have to carry a fault current.  It is unethical to risk a fault in your equipment making someone else's pipes mains live!

--- End quote ---

I completely agree, but I believe it's mandatory to have "earth circuit breakers" installed in every home's electrical installation -shouldn't that prevent situations like that if AC voltages from the soldering iron accidently goes to ground?

As far as I know, current building regulations demand that all AC sockets are to be grounded in new buildings, but that's not the case with older housing, so in my case there's grounded AC sockets in the bathroom and kitchen, but not elsewhere. So I'll have to use a grounded extension cord, then attach a wire with crocodile clips at each end between the soldering iron and the extension cord's ground pin.
The soldering iron is plugged into an (ungrounded) AC socket where I have my work desk.


UPDATE: success! I did my best with the ESD-protection and went ahead with the desoldering/soldering -and the new display is working perfectly!  :)
I grounded the ESD-mat and wrist strap, but didn't do anything with the soldering iron, but it might be good to learn what I should do the next time for the ultimate in ESD protection (I suppose that would be to buy a proper ESD-safe soldering station and all).
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