Are some components spot-welded to the MBs?

[paulo66]

Because that's what it looks like. At first I followed advice from a poster here and went easy with 250ºC mid air, then lost my patience and went 500ºC full air. It refuses to come out! What is happening here?SOICs on this same MB are tough to desolder as well and I´ve only managed to remove them by adding solder blobs first. You can't do the same with this type of packages not to mention QFNs. Help

[paulo66]

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

I've thought of adding solder paste so it could reach the short pins and the pads beneath, but it's the same result. Maybe I have to dremel it out?

[dellxps15]

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

use good flux, good air flow, good air temperature, and wait the required time to remove it.

[paulo66]

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

I think I'm using all of that and I've waited longer than necessary for the bloody solder to melt.

[petehall347]

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

are you using a pre heater ?

[dicky96]

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

No - they are all soldered. So most likely it is problems with your desoldering station. Which one do you have?

I second what petewhitehall says - are you using a preheater? If not, then you really should be using one. Or at the very least get a powerful hot air station.

So either

1. Use a preheater, plus a cheap hot air station
2. Use a good hot air station - I recommend the Quick 861DW (and previously I had one of the 858D so I know the difference first hand)

Or preferably get a preheater plus a Quick 861DW - this combo will put far less stress on the PCB and components and desolder anything you are likely to find with no hassle

Rich

[piernov]

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

Get a decent hot air station.

[paulo66]

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

No, I don't use a pre-heater. Never tried one. Isn´t that better suited for one-sided boards?

Aren´t all hot air stations the same? I'm using a ProK DS101A - same as the 858D. It has served well. Until very recently.

So I got your points and will do research.

Thanks all.

P.S - That Quick 861D looks good.

[mon2]

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

Personally have this unit:

https://www.aliexpress.com/item/3296...27424c4dBRM9ca

bought from this vendor. However, you can consider the same brand (BEST) who is a solid manufacturer. We contacted BEST and have met them in HK at trade fairs to confirm that they can supply us service parts for this tool. They said they can as they produce this assembly.

Very pleased with the tool and often use 550 degrees for the heavier ground plane PCBs + flux to desolder the solder by Foxconn / Apple.

You may want to review the spare nozzle kits for BGA removal, etc. - just ask the vendors on the compatibility.

[Smoxx]

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

250ºC is too low while 500ºC is too high. You need to find the sweet spot.

~400ºC + lvl 7 air flow is enough for laptop and desktop boards most of the times but the ideal temperature depends on your location weather, air humidity, etc.

Also, the oxidation level of the board and components can influence the desoldering process.

The best way to find out the right temperature for your rework station+location weather combo is to test soldering on a scrap board. Never on a good one!!

Preheaters are indeed handy and necessary in some cases but not in this one.

Apply flux on the IC, pre-heat underneath the IC with the hot air gun for about 10s at a 5cm distance then flip the board and apply hot air on the IC at a 1cm distance. The solder will melt in about 20s~30s (time may vary depending on the variables previously mentioned).

[piernov]

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

250°C or 500°C doesn't mean anything with an 858D. Even with a decent hot air station exact temperature doesn't mean much, it depends on too many factor so you have to figure out the sweet spot yourself.
Which will also be very different between a cheap garbage 6 layers Compal board that can easily darken and popcorn with heat, and a 14 layers MacBook Pro board that'll sink all the heat in the power planes.
Only way to find out what works is practicing on worthless board.
Also no need to preheat under the board, just heat for a short while around the chip and then you can blast hot air on the chip directly.

[paulo66]

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

The wave of cheap stuff and a number of Tuber videos may contribute to the idea that everyone's a technician these days. And I have my share of guilt. But I like to think I'm not a noob anymore. I've practiced on a few trashed mobos for spares and have never encountered any like these. Even on X550XXs I've managed to get all the parts I wanted using this 858D type. The other day I decided to remove the GPU coil just to see if it would engage the cpu internal gfx, as claimed on some video. Quick test, the coil would soon return to its place. Well I couldn't take it out, the heat even destroyed the grey enclosure leaving the bare copper wire attached to the board. Even the miserable capacitor next to it was almost impossible.

[paulo66]

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

Didn't t think air pressure was critical. I never liked the handle with the built in fan anyway. True, if the fan motor dies you can always buy a new one, but maybe that's where the flaw is? Physical limits? Like inside the box there will be plenty of room to install even a compressor?

[paulo66]

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

Wait a minute! Maybe the fan just needs maintenance? It must be carrying tons of dust by now and probably condensed rosin fumes, due to the nearfield operation. Hey hey!

[ktmmotocross]

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

IT IS A MOSFET!!!!

off course it can be WELDED to pad. Its because of shorted current was so high it WELD pad to MOSFET.

Only way is RIP it off with trace. so i prefferr to jump it and be without power circuit and its protection

[dicky96]

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

@paulo66
If you have not already watched it, here is a youtube video that is worth watching

https://www.youtube.com/watch?v=N_yHkrVYrBE

That should tell you everything you need to know regards the Quick 861DW and the 858D

Also I have seen another model that says it is a Quick 861DW but has a different style case and a carrying handle on top. It's about half the price but personally I would not trust it as having the same performance.

There also seem to be two versions on the 861DW that looks like the one on the attached video too - one has a captive mains lead (same as the one in the video) and the other has a 'kettle lead' socket and different back ventilation grill layout. Personally I went for the one with the captive lead as I considered that to be the 'original' and again I have no idea if the one with a power socket is the same internally or the same performance.

[paulo66]

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

IT IS A MOSFET!!!!

off course it can be WELDED to pad. Its because of shorted current was so high it WELD pad to MOSFET.

Only way is RIP it off with trace. so i prefferr to jump it and be without power circuit and its protection

What do you mean by trace?
Btw these are not arranged as first and second mosfets where vin=vout. Rather hi and lo.

[paulo66]

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

I'm going to wstch the full video after work, thanks.

[piernov]

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

Atten ST-862D is a cheaper alternative to Quick 861DW these days.

[R_J]

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

Just a note:
You may want to check the datasheet on the QFN ic as it my have a large heatsink pad under it which also needs to be released as well as the pins.