ICs & Hotplate

[Memductor]

Hello everyone

I'm somewhat new to PCB assembly and I recently had the issue that my circuit failed after connecting it to the input power (15V). The linear regulator at the input "burnt" and after some (long) troubleshooting I figured it was a solder bridge which caused a short circuit at the input of an OpAmp (at least that's what I think caused the failure).

I figured that for the next PCB assembly it might be more useful to solder each part of the circuit after another and check in between if the parts that I already soldered work properly.

Now the question I have is if that could be damaging to some ICs on the PCB. Say if I solder the first part of the PCB (some passives and some OpAmps), then the next one etc. would the ICs that I soldered first take damage from the hotplate (125°C) when I solder the subsequent parts of the PCB?

[mayor]

Personally, I try to leave boards for as little time as possible on the hot plate. I wouldn't return a board multiple times as you are suggesting. Out of curiosity, what is the package for that LDO? I've not had bridges I couldn't correct with an iron on small footprints like 0402 and 48QFN at 0.5mm pitch, sometimes less.

[Siwastaja]

No, the 125degC hotplate won't damage any components (not even most temperature-sensitive components like plastic connectors, electrolytic capacitors etc.) even if you work for dozens on hours on it. Your hotplate temperature is spot on and reduces the risk of soldering issues; also reducing thermal shock to some component types that may be sensitive to quick temperature changes (such as large MLCCs).

125degC is also low enough so that bringing anything on the top of the plate surely won't cause rapid thermal cycling. It would be a different thing to repeatedly bring boards on a 300degC hotplate, for example, due to the sudden thermal shock every time.

Having power applied while hot may be a problem, though, if the junction temperature is close to 125 degC, especially if there is some power dissipation in the components themselves; the circuits won't be designed for operating at Tambient=125 degC. Especially if the thermal design of the circuit is marginal, I would let the board cool down for a few minutes before applying power.