How to clean oxidation from BGA pads?

[dicky96]

I have about a dozen motherboards here that need new LGA 1151 sockets

I am able to remove the old socket but I have a problem with some sort of oxidisation that is getting onto some of the BGA pads and I am struggling to clean it off. Even dragging a solder ball around with my T12 doesn't shift it. See attached video

I assume that I need to get all these pads clean before attempting to solder the replacement socket? So how do I get them clean and shiny?



Another problem - So far I have not been able to fit a new socket successfully.

After soldering and checking for continuity from the LGA pins to 0V or Vcore it is obvious that only some pins are soldering. if I remove the socket again it is obvious that many of the balls did not melt because a lot of the PCB pads are still 'flat' with no solder on them. And this is when I get this oxidation problem even worse.

After a bit of experimentation I created a profile that will desolder LGA sockets from gaming motherboards, as the one I use for standard motherboards wouldn't do it.

But that profile will not attach the new socket properly. I then created a profile that is 10C hotter on the final ramp up and it still isn't soldering the new sockets. IIRC, with this profile, the probe near to the LGA on the top of the PCB is getting up to around 260C-265C on the final ramp up.

I will have to try a hotter profile for sure, it seems my probe isn't reading the actual temperature at the LGA to PCB junction. But how much more heat?

Also should I apply flux to just the PCB or to the PCB and the LGA socket? I'm using NC-559-ASM from Aliexpress. Can too much flux be as problematic as not enough? What is the correct amount?

video https://youtu.be/uMiCsbOJ-ZU
The cleaning liquid is Iso Propyl

Pics
Profile 'LGA Gamer' used to remove
Profile 'LGA Gamer Mount' used to solder.


Questions Questions lol

Rich

[diif]

Re: How to clean oxidation from BGA pads?

Are you using flux when you remove the old socket ?

[dicky96]

Re: How to clean oxidation from BGA pads?

Yes mate - I have some Topnik TK83 liquid flux that I try my best to run under the old socket by holding the PCB vertically and rubbung the apllicator brush under the edges

[stj]

Re: How to clean oxidation from BGA pads?

if you put the flux on the socket contacts and heat it with air it should run down onto the board,

soldering profiles for the sockets are on intel's site but you may have to search a bit.

[diif]

Re: How to clean oxidation from BGA pads?

Maybe try some Topnik AC81 it's a more active flux and use a pipette or syringe with needle to ensure the area is flooded.
You can scratch the surface with the tip of an iron if your careful.

[dicky96]

Re: How to clean oxidation from BGA pads?

That AC81 flux seems really hard to get, I can't find any sellers on ebay that post here, or on Aliexpress. The only way I'm likely to get some is to order to the UK and get a friend or family to bring it here when they visit - which is gonna be no time soon!!

So to clean this PCB ready to fit a new socket I am going to have to scrape that residue off? Would very fine emery cloth or something similar do the job?

I think the problem with soldering the new socket is that it isn't in full contact with the PCB so the balls don't conduct the heat from the PCB and melt like they do when using the same profile to remove the old socket.

Rich

[R_J]

Re: How to clean oxidation from BGA pads?

I've seen them use flux and solder wick under the iron tip to clean the pads, but you need to be carefull not to damage them.

[stj]

Re: How to clean oxidation from BGA pads?

that flux is probably sold at TME

[dicky96]

Re: How to clean oxidation from BGA pads?

@R J
OK I will give that a go with various fluxes I have

@stj
I will give them a try - not that the postal service seems to be actually functioning here at the moment - I have had one delivery on Tuesday this week, the only one in 3 weeks. On the plus side diesel is 90 cents (0.9 euro) a litre here now. Shame that Correos (post office) is not open for me to go collect my mail

[clearchris]

Re: How to clean oxidation from BGA pads?

For cleaning off residues and oxidation, I really haven't found anything better than brake cleaner and a q-tip. Just make sure you clean it all off before soldering, the fumes when burned are highly toxic. And be careful when you spray it, it comes out very, very fast. If you splash it, and it ends up in your eyes, you will go blind for about 5 minutes or so. At least my vision came back, um, I mean, my friend was fine after having that happen to him.

[Deusjevoo]

Re: How to clean oxidation from BGA pads?

To clean pads use a GEL FLUX, not liquid. Liquid evaporates and looses activation too fast.
To get rid of that oxidation higher activation (gel) flux types can give better results but they have to be cleaned off thoroughly as they're more acidic.
Reason for the the dark pads can also be a bad finishing, hard to fix sometimes.
But using gel flux and touching it with some solder, even rubbing it slightly but don't sratch, can help. Or soak a solder wick with solder, add gel flux to the pcb and go over it with soaked solder wick eventually cleaning again.
Gel fluxes:
Good no clean ones which often help out switching between them:
Amtech NC-559-TV, NC-559-V2-TF, Amtech Syntec, Amtech VS-213A-TF

Very agressive one for oxidized pads: Amtech NWS-4400-HA-LF must be cleaned !!!
Other brands will have same types of flux probably.

Even many so called "fake" Chinese fluxes can do a good job.
I often use Kingbo for cleaning, cheap and does a good job, even reballing not a problem althoug I do use Amtech for it mostly, NC-559 or VS-213A, most often Syntech now.
Kingfull Kingbo seems ok.

[dicky96]

Re: How to clean oxidation from BGA pads?

OK here is another board. This socket came off cleanly on the first attempt using my LGA GAMER profile that I created for the previous board, Gigabyte Aorus Z270-X. This board is an Asus Strix B250F Gaming.

I added some videos, sorry they are not very exciting. Also sorry there is no sound on these videos, I'm normally quite chatty but I need to get a microphone and with this lock down getting anything but food is a pain the the ass. However if you could watch through them hopefully you can tell me if I am doing this right or wrong.

1. Examine PCB after LGA1151 socket removal
looked like I may have lifted one pad but hoping it was just oxidation on that pad
https://youtu.be/TeVRJc3HWaM

2. Examine PCB after using T12 with BC3 tip to drag a solder ball around the pads. I use piece of desolder braid with NC-559 flux to have a closer look at that iffy looking pad
https://youtu.be/4VxMLnpMtmE

3. Examine PCB after using solder braid with NC-559 gel flux to clean all the residual solder. Then cleaned the PCB with iso propyl. That iffy looking pad looking better now but somehow seems slightly recessed compared with all the other pads
https://youtu.be/DC7dCK1UZvA

That iffy pad looks OK now but I would like to check to make sure it has continuity to wherever it should connect. Hopefully the LGA1151 pinout will help me but of someone has the Strix B250F boardview that would be great.

[Spider1211]

Re: How to clean oxidation from BGA pads?

I have a problem with some sort of oxidisation that is getting onto some of the BGA pads and I am struggling to clean it off. Even dragging a solder ball around with my T12 doesn't shift it.

Use your 559 instead of the liquid flux. Paste is a bit more tricky to run under chips/sockets that liquid, but does a better job since it does not run as much. Liquid is better suited for reflow rather than desoldering.

I assume that I need to get all these pads clean before attempting to solder the replacement socket? So how do I get them clean and shiny?

Yes, definitely. Shiny depends on the solder you are using (lead/unleaded).
1. Apply generous amount of flux & flush old solder with new solder (preferable same as the new chip you plan on soldering back).
2. Wick solder from the board.
3. Clean using IPA and feel for sharp peaks using a swap. (You could also use light at an angle to see uneven surfaces)

Can too much flux be as problematic as not enough? What is the correct amount?

For desoldering/cleaning you can use to you heart content, but for soldering apply a thin film using a soft brush. Too much flux will cause the part so shift when its bubbles.


To clean oxidation on pads you could very lightly scrap it off using a rounded edge blade (if there isn't too many) but risk pulling pads. What works great for me is this soldering grease(see attached picture). Not sure if they still sell those, but all you need to do is apply it to the affected area and using a pointed soldering tip (I use a T12-KU) with solder on it and apply light downward pressure (no scraping) and voila! as good as new.

Although you need to clean it after use, I did not notice and corrosion due to the flux being left on the board (scrap board)

[dicky96]

Re: How to clean oxidation from BGA pads?

This is what I have available at the moment

Post is really slooooow to order anything else right now

[Deusjevoo]

Re: How to clean oxidation from BGA pads?

@spider1211 Think that Felder Lotferr is for plumbing or metal soldering, not for electronics. Wouldn't use it for that.

[Spider1211]

Re: How to clean oxidation from BGA pads?

@Deujevoo I don't use it for soldering, only for removing oxidation. I was initially using it for tinning my soldering iron tips (back in the days when I had crappy soldering iron), but found it works exceptionally well for removing oxidation on BGA. I always clean the area I used it on before soldering any chip even though I never had issue with leaving it on as mentioned.

@dicky96 Slow is better than nothing. We are at a complete stop here :/ , no postal service working due to curfew.

Try them on oxidised pads on scrap boards and see which works best.

[clearchris]

Re: How to clean oxidation from BGA pads?

@dicky96 Slow is better than nothing. We are at a complete stop here :/ , no postal service working due to curfew.

I can't imagine. I'm getting so many things done during my sequester, but it's mostly because of the mail.

[dicky96]

Re: How to clean oxidation from BGA pads?

It is true, I am getting around to doing a lot of things in the workshop myself and improving my skills and knowledge .

But the reality here is everywhere is closed down for the duration, including all shops, bars, cafe's, restaurants, takeaways (delivery or collection) hotels, indoor and outdoor public spaces, parks beaches, hiking trials etc. Week 5 of lockdown starts tomorrow - supermarkets open for food sales only, nothing else. I got stopped at three police roadblocks last week but have the documents to work as self employed (internet, TV, satellite). But I can't even get my hair cut or my van fixed lol and now it has broke down. And post? No chance unless it is sent priority next day UPS or Fedex. Then you will recieve it in 10-14 days. I had three packages arrive in over a month, the rest I have no idea where they are.

[Spider1211]

Re: How to clean oxidation from BGA pads?

Even priority mail is out here. I have a DHL package that came in on the 19th of March and was scheduled to be delivered the following day. Surprise surprise, lockdown start that very next day -_-. Lockdown was supposed to be lifted on 15th of April but as of 2 days back, it has been extended till 3rd of May.

Adding insult to injury, I am running low on flux and therefore cannot do much of anything (especially smd related).

I also wanted to start prototyping a low cost ventilator design but there is no way I can procure parts.

[dicky96]

Re: How to clean oxidation from BGA pads?

@Spider
Don't they have a lot of trees where you are?

https://hackaday.com/2012/09/19/diy-...from-the-tree/