Replacing laptop EC without hot air station.

[SuperGiachi]

So I have to scratch the trace to reveal copper and solder a thin wire to the missing pad footprint, right?

[wraper]

yep

[SuperGiachi]

How can I secure the wire to the pad so that it doesn't move? Do i have to solder the wire all along the trace?

[wraper]

How can I secure the wire to the pad so that it doesn't move? Do i have to solder the wire all along the trace?

It would be preferable to solder all along the trace. But it does not really need to be secured as it will be fixed in place once you solder it to the terminal of IC.

[SuperGiachi]

I scratched the trace till i saw exposed copper.
https://drive.google.com/file/d/0B_r8p2JWpx1DcmRUTGtSNVA4Ynl0T1ZvcmFmeGdLcnByUDk4/view?usp=sharing
Is it good enough should I scratch it more? Is the thin wire in the video(it is not solder, it is one core of a multi-core wire) thin enough?
Is it possible to drag solder the chip without bridging everything?

[wraper]

Exposed copper is enough. It is possible to drag solder. You may need some solder wick to remove bridges on the corner terminals. Of course you should not use drag soldering on damaged pads. Wire on the photo is way too thick. Search for some wire with thinner strands.
Aso solder the wire to terminal among the first (after touching up some corner pins so chip does not move) so you can fix it without desoldering the whole chip if something goes wrong. Also do it fast to avoid wire heating up and desoldering from the trace on the other end.

[SuperGiachi]

Is this still too big?
https://drive.google.com/file/d/0B_r8p2JWpx1DcmRUTGtSNVA4Ynl0T1ZvcmFmeGdLcnByUDk4/view?usp=sharing
Should i tape it down on one side to get it in position while soldering? Also, can i clean the solder pads using solder wick or do i risk damaging them?
Will a wire from solder wick be thin enough?

[wraper]

It's the same picture.

[SuperGiachi]

My bad, uploaded the wrong one
https://drive.google.com/file/d/0B_r8p2JWpx1DajFETkcyVm9WN0dCZFVKeHMzdEV2V3B1aHlR/view?usp=sharing

[wraper]

Well, you could use it if you really don't have anything else. But it's thick as a pad width. You could tape it down for convenience and then cut the end of it after soldering.

[Gyro]

Use a strand from your solder wick.

[SuperGiachi]

I tried soldering the solder wick wire, but solder doesn't adhere to the substrate. Can i solder a wire to the trace and run it through a corner of the chip and then solder directly to the pin by routing it on the top of the chip? I would glue the wire down to the pcb underneath the chip to avoid unwanted contacts.

[Gyro]

Yes, the solder won't adhere to the substrate once the pad has gone. Soldering it to the track and then bringing it out to the pin position should be fine. You ought to be able to just bring it out where the pad would have been and then just solder it to the underside of the pin. Just make sure it is correctly located when you place the chip.

[SuperGiachi]

I'm back again with another question
I have to replace the power supply controller IC(3.3V and 5V in one chip) and this chip happens to be a 20 pin QFN with a thermal pad, so I can't solder/desolder it with a soldering iron. Since I can't afford a good hot air rework station and don't want to buy a cheap one that will need to be replaced and/or has dangerous wiring, would it be possible to get by with an heat gun(like the one you find in hardware stores)? I wouldn't use it often, just for the replacements that I can't perform with a soldering iron alone.

[wraper]

would it be possible to get by with an heat gun(like the one you find in hardware stores)?

If your goal is instant death of motherboard, then go on. FWIW cheap 858D hot air station from aliexpress is a good choice if you don't have money for something better.

[SuperGiachi]

Would it damage something even at the lowest setting(350°C)?

[wraper]

Would it damage something even at the lowest setting(350°C)?

You will melt the solder all around and most likely blow off many components. Not that there is actual temperature regulation to begin with.