pcb lifted traces

[manubali]

so, i was repairing smps and there was a big trace for power diode that my iron was unable to heat, so stupidly  i took hot air gun and started heating it, and the trace got some  bubbles on it. so my question is that will it work fine or should i scrape the solder mask and tin the whole trace with solder?

[KL27x]

If the FR-4 bubbled, it may have gotten hot enough to char. And this can make the board conductive. If you have high voltage on there, the board can conduct and arc and char more, and you get a runaway problem that ends in blown fuse, at best, somewhere down the road.

I have never seen soldermask bubble, so I assume your board substrate may have been damaged.

If you scrape off the mask and there's no brown or dark spots in the FR-4 next to the traces, it is probably fine. I'd tin it to prevent oxidation and call it good. The worst of the heat damage will be on the surface, not underneath. If charred, then what he said. This is just my opinion, not any kind of certifiable repair standard.

[wasyoungonce]

Might be better with a jumper link wire "oversized" a little.  If the trace is lifted and its a high current trace, I'd be a little worried about flexure of it from current and heat and cooling. 

Use a jumper wire (I use insulated wire trimmed at ends for solder joins), glue it too the PCB.  We used TakPack but hell 5min araldyte is ok.

For a burnt PCB to conduct it has to be quite burnt.  I've seen one on a pool controller PSU badly burnt conducting.  It looked quite carbonised yet I didn't consider it an issue!   Until I noticed the area heated due to this carbon resistance and I did ohms checks on it when off...wow I was surprised.

FWIW

[manubali]

If the FR-4 bubbled, it may have gotten hot enough to char. And this can make the board conductive. If you have high voltage on there, the board can conduct and arc and char more, and you get a runaway problem that ends in blown fuse, at best, somewhere down the road.

I have never seen soldermask bubble, so I assume your board substrate may have been damaged.

If you scrape off the mask and there's no brown or dark spots in the FR-4 next to the traces, it is probably fine. I'd tin it to prevent oxidation and call it good. The worst of the heat damage will be on the surface, not underneath. If charred, then what he said. This is just my opinion, not any kind of certifiable repair standard.

its not that bad, have just 2 bubbles underneath the trace and trace itself is around 8 mm wide.
i will try to remove it and add jumper wires to it