Are some components spot-welded to the MBs?

[paulo66]

Re: Are some components spot-welded to the MBs?

Honestly Paulo, nearby components will not fly around the board-

Yes they will. And honestly I think you overestimate the ability of the solder surface tension to keep the components in place.

[paulo66]

Re: Are some components spot-welded to the MBs?

And there goes the fourth x550 motherboard. Fuck Asus. I´m convinced this is the proper way to deal with them:

https://youtu.be/bifOI4MbHVU

[paulo66]

Re: Are some components spot-welded to the MBs?

Ordered the Atten ST862D this morning. Thanks all for the recommendations. Vengeance will be sweet (fingers crossed).

[dellxps15]

Re: Are some components spot-welded to the MBs?

next mosfet u encounter some difficulty to desolder:

flux and put some solder both side.... with tweezer let solder get into mosfet... u should remove it easy

[paulo66]

Re: Are some components spot-welded to the MBs?

Thanks. Yes, part of the problem is the leadfree solder. I will try that with the mosfet shown in the first post. Which btw is the high one. It sits on the B+ track. The low mosfet is the one with ground plane underneath, so it will be even more difficult to remove.

I´m trying to remove them to track down a strange short circuit in the +19V path. It´s showing unusual readings. The voltage fluctuates cyclically as if some auto-protect mode keeps turning on and off...

[paulo66]

Re: Are some components spot-welded to the MBs?

That is what's left from the coil that the 858 couldn't remove. The "casing" which is actually all ferrite was eaten by the tweezers.

With the 862 it took only 30 seconds. I´m amazed.

Now, how do I get the nozzle off the handle? I think it's stuck!

[paulo66]

Re: Are some components spot-welded to the MBs?

The mosfet in the ot took another 30 seconds, or less. This machine rules. I'm "blown" away. Sorry

[tobbyhush]

Re: Are some components spot-welded to the MBs?

No components are ever spot welded in any motherboard. It can be done with RF shields, but you'll rarely find those in consumer electronics since it's easier to just use solder or bent tabs. I've only seen those in modules of old military equipment with large "Replace Card, Do Not Service" stickers, and in one HP oscilloscope.

Some manufacturers, depending on the application (specially in cars where there's lots of vibrations, or high amperage power supplies), they will glue components before soldering. You'll typically see it looking at any resistor or SMT capacitor, oozing out the sides. Typically a red or black glue:



What I think it's happening on your case, though, is that you're shielding the entire motherboard too well. You shouldn't unless there's a good reason to do so (i.e. nearby plastic connector, crystal oscillator, or electrolytic capacitor). The motherboard will soak all your heat and you could even burn off the solder mask, and maybe the solder you are trying to melt would still not reach enough temperature.

You need to uncover all that, apply 350º heat at 5cm (high fan speed) in large circles around what you want to remove for around 40-50 seconds. When the entire area is nice and toasty (100-140ºC) point your gun to the component you intend to pull (you can drop your fan speed to a medium setting).
Always remember that anything that is connected to the ground plane or a large copper pour for power delivery will be harder to remove.

TLDR: Unless you get yourself a preheater, you should preheat your board with the hot air gun itself before attempting to pull any component from it. Otherwise bad or very bad things will happen specially in boards with 4 or more layers. You could even delaminate the layers by applying a lot of heat in a small area, which would totally write off any vias in sight.

[paulo66]

Re: Are some components spot-welded to the MBs?

Thank you for the thorough reply. I liked the encyclopedical style.
Those questions have all been addressed throughout the thread by various posters and some have been rebated.
Note on the second picture the mosfet was replaced using the st862d and the shielding was still in place.
I've since done some rework without any shielding and I'll eat crow after insisting with another poster nearby pieces would fly off the board with the new station none has so far.

[Bigfoot]

Re: Are some components spot-welded to the MBs?

Hi guys
Read all the posts diligently, I have a similar issue to OP.
I'm trying to de-solder 32 pin PLCC BIOS chip from XW9300 workstation.
Trying to clone it. And then re-insert another 32 PLCC chip.
I'm using the Quick 861DW station. Granted I haven't had much experience with it. But I have it on 370 Celsius around 90 airflow. I spent about 1:30 minutes on chip. I see smoke coming off the board (probably some silicon/plastic burning off), but chip won't come off. I'm using CHIP QUICK NC191 Flux. It's a soft paste in syringe.

Like OP I have covered the surrounding with aluminum tape to protect plastic jumper and what looks like a silicon insulated crystal. I'll start by taking the tape off. And pre-heat the back of board with my gun.

If that doesn't work. Anyone has any better ideas?

Thank you 🙏🏼