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| Soldering ESD-sensitive components without grounded soldering iron |
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| Krotow:
You totally overcomplicate things. ANY soldering iron/station with soldering tip grounding is sufficient. You can even connect 1 MOhm resistor to ungrounded soldering iron tip with other end to mains socket ground pin and be fine. Honestly in your case I would never bother about ESD at all. --- Quote from: analogix on June 19, 2024, 11:36:48 am ---Will it be safe to use my existing soldering iron to solder those ESD-sensitive components or do I need to buy a gas powered soldering iron (like the Dremel Versatip I mentioned earlier)? --- End quote --- Wasn't laughed so loud for a while. Buy a big hammer and smash your device to smithereens. Then go and buy another one. |
| Ian.M:
Modern multimeters are very high impedance (typ. 10 Megaohms for handhelds) and can give a significant AC voltage reading just from the E-field of nearby mains wiring, with the probe leads acting as an antennae. You'll also get phantom voltages on un-powered mains wiring running next to live wires, and from various circuits. The key to figuring out what is actually going on is to shunt the suspect voltage with a resistor to make a low impedance voltage measurement. As you have determined its low voltage, an ordinary 10K resistor in parallel with the meter will do. If you suspect higher voltages will be present,use a higher value, higher wattage resistor e.g 100K 1W will be OK up to 300V (or the voltage rating of the resistor, whichever is lower). Knowing the resistor and the new voltage reading with it in parallel, you can calculate the AC leakage current and decide if it is unsafe for your components. I suspect that your existing iron although not ESD safe is unlikely to damage those LED display modules. That may not be the case if you used it on more delicate parts, e.g. extremely ESD sensitive RF MOSFETs. |
| Kim Christensen:
I'd say you're safe to just solder the LEDs with that iron. It doesn't have any significant AC leakage. Like Ian.M said, your meter will pick up AC out of the air. But there is no harm in grounding the shaft of the iron anyway. I'm not really a fan of gas powered irons for regular soldering jobs because it's hard to control the tip temperature. Not to mention the hot exhaust/flame coming out if it that can burn other components in the vicinity of what your soldering. I'd only use a gas powered iron in remote locations where getting AC power is impossible and if the job was not too delicate. |
| analogix:
--- Quote from: Ian.M on June 19, 2024, 02:51:15 pm ---Modern multimeters are very high impedance (typ. 10 Megaohms for handhelds) and can give a significant AC voltage reading just from the E-field of nearby mains wiring, with the probe leads acting as an antennae. You'll also get phantom voltages on un-powered mains wiring running next to live wires, and from various circuits. --- End quote --- I had no idea about this. Does this mean that with fluctuating/floating voltages like this you can take the reading with a grain of salt? While with "normal" voltage measurements (i.e. connecting the probes directly to a power source etc.) the readings will be more correct without needing to think about having an appropriate resistor in series with the probes? --- Quote ---I suspect that your existing iron although not ESD safe is unlikely to damage those LED display modules. That may not be the case if you used it on more delicate parts, e.g. extremely ESD sensitive RF MOSFETs. --- End quote --- Good to hear as I'm comfortable with this soldering iron after years of use (meaning less risk to do a bad job). The main reason I'm discussing ESD sensitivity is because a section of the display module's (DLR1414) datasheet (see attachement below) warning about ESD sensitivity. --- Quote from: Kim Christensen on June 19, 2024, 03:26:31 pm ---I'd say you're safe to just solder the LEDs with that iron. It doesn't have any significant AC leakage. Like Ian.M said, your meter will pick up AC out of the air. But there is no harm in grounding the shaft of the iron anyway. I'm not really a fan of gas powered irons for regular soldering jobs because it's hard to control the tip temperature. Not to mention the hot exhaust/flame coming out if it that can burn other components in the vicinity of what your soldering. I'd only use a gas powered iron in remote locations where getting AC power is impossible and if the job was not too delicate. --- End quote --- Good point. I've never used one, but what you say sounds reasonable and without the necessary practice I might very well damage both the replacement LED modules and the PCB in question due to excessive heat and a too big tip etc. But the ESD-sensitivity warning in the datasheet has got me worried. It's hard for me as a non-engineer to know if I should take this very seriously or if they're bound to exaggerate and point out all the "in the worst possible case scenario" type things to avoid getting sued or whatever if they hadn't done so. So if I use my regular soldering iron, would you recommend I find a resistor (around 1M Ohm, but I understand that's not a critical value) between the shaft and the ground pin of the nearby AC wall socket? |
| Kim Christensen:
No need for the resistor. You can just ground the shaft directly which is what is done in commercially made irons. By not using a resistor, you'll actually make your iron a bit safer. ie: If it had an internal failure and the element shorted to the casing, then the tip would be live at mains voltage if you'd used a resistor in the ground lead. But with a direct connection, the breaker in your house would have tripped alerting you to the danger. The 1M \$\Omega\$ resistor in the wrist strap is for your safely. What it does is limit the current flow through your body (via the wrist strap) if you accidentally touched a live wire while wearing the strap. Touching a live wire is never a good idea, but if your body was completely insulated from the ground (current return path) then nothing would happen to you. But wearing a static wrist strap provides a guaranteed path to ground. Hence the 1M \$\Omega\$ safety resistor. |
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