It depends on what you're soldering, and how skilled you are at soldering.
You can, in fact, solder a 0.4mm pitch TQFP with a tip that spans several pins, such as the ETA you mention, but it takes a lot more skill (and flux!).
If you're doing mostly through hole components, the ETA is perfectly fine.
I'm also doing SMT and very fine SMT work, so I also purchased the 0.030" and 0.015" conical tips. I use these under a microscope to do the 0.4mm (about 0.016") pitch TQFP chips.
It is worthwhile getting the biggest chisel tip you can, as well, for the occasional need to deal with soldered heatsinks, or parts soldered to ground planes or PCB heatsinks. These can pump all 40+ watts of your iron into the joint, allowing you to remove it without heating the component up too much.
Keep in mind that typical wet sponge tip cleaners can lower the tip's temperature significantly, especially with the small tips. I use a gold tip cleaner similar to this Hakko product, which doesn't soak as much heat from the iron on each wipe.
I think that using anything to dissipate the heat when doing soldering is just some very nasty folklore, best forgotten unless fully understood.
On surface mount parts, you want to do exactly the opposite. When soldering or desoldering, you ideally want all parts to be at the same temperature: that's why people use preheat plates. When all things are at the same temperature, there's minimal thermal stress on the terminals.
On through-hole parts with just a few terminals and good access, you may find it possible to grab all the pins at once with pliers to sink some heat away. You'll find that in practice you're more likely to mechanically damage your part by doing that, than just quickly desoldering without any heat sinking. For desoldering leaded parts, the important things are:
- Have a high-powered iron. 50W would be bare minimum. Do not use fine tips. The wider the tip, the lower the thermal resistance between the heater and the tip, and the closer the tip temperature will be to your setpoint.
- Have an iron with temperature control based on feedback close to the tip. Otherwise your tip, in presence of a heat sink, will be cold even though you think the temperature is right.
- Ensure that you have good thermal contact with all the pins at the same time. This means that you need to heat up a big blob of solder with your iron, and then roll it over the pins of the device. In less than a second you should be able to pull it out.
- If your device has leads far apart, you will need multiple soldering irons, no way around. Yes, you can try and pull leads out one at a time, but it's a hit or miss if you want to preserve the part.
- Use flux-cored solder with electronics-compatible flux. That really means a rosin-core flux. I find that water based fluxes have too low boiling point for rework, and no-clean fluxes are irrelevant since you'll have to clean stuff anyway.
- If you can avoid it, do not play with pulling the solder out of the holes before you desolder the part. It's easy to damage the PCB and/or the part while doing so. Apply the heat, pull the part out, and only then remove the solder from the holes so that you can replace the part.
Best Answer
Summary:
Don't be worried, unless the voltage is more than say 10 millivolts. In that case, just consider it to be unsuitable for use with electronics, put it to some other use or discard it, and get a "real" one.
It is common enough for low quality soldering irons to have voltage on their tips due to leakage. This is unacceptable and can and does do damage when soldering suitably delicate equipment.
Reputable soldering iron makers take care that their products do not have this problem.
Here is a useful document that discusses tip leakage and other soldering iron factors. Note that where they MAY APPEAR to have written "MV" the original was "mV" (snall m) for milliVolts and the font is rendered incorrectly by your system if you see a large M (as I do). They note -
Tip-to-ground potential: Sometimes called ‘millivolt leakage’. The voltage existing between the soldering iron tip and the workstation common point ground. It should not exceed 2mV per DOD-STD-2000; not specified in J-STD- 001B.
Tip-to-ground resistance: The resistance existing between the tip of the soldering iron and the workstation common point ground. It should not exceed 5 Ohms per J-STD-001B, appendix A, and 2 Ohms per DOD-STD-2000.
Insulation resistance: The resistance between the soldering iron tip and its heating element (applies to Hakko soldering irons, series 900, 903, 907, 908). Properly termed ‘isolation resistance', it is a measurement of the isolation of the tip from the transformer secondary winding.
The last point implies a transformer in the system but an equivalent rating applies to 'direct connection to mains' irons.
ESD association soldering iron test methods
Hakko soldering iron tester one of these you will not be buying. BUT it gives you some good ideas.
leakage voltage testing
tip to ground testing
Hakko maintenance inspection
Note that whereas paper above quoted 2V as acceptable level !!! :-( - Hakko so Mil Std is 2 mV. More likely. Hakko say -
The MIL standard is a US military-based standard and the standard MIL-STD 2000A regarding soldering irons has been abolished.
Measure leak voltage after adjusting the temperature setting to the maximum.
When the leak voltage is measured at the highest temperature, the highest leak voltage will be recorded. If normal results are obtained even in unfavorable conditions such as at the highest temperature, it is judged that normal results will be obtained at other temperature settings. (This method is based on the MIL standard.)