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I have been looking into the stackexchange searchbar and also I have been searching for a day or two globally, even the "similiar dialog on this website" when I was creating this post.

I have a bit experience with AMTECH and the NC 599 flux to do small stuff (yes there is better flux.)

I am trying to figure out what flux I should use for desoldering an LGA socket on my PCB bench.

I have done some homework around it since its my first to do something like this.

The AMTECH NC 599 flux is no good for rework, RMA 223 is garbage as well as the burning smell as I'm noticing from other people in their postings.

So with all the types of flux, what are your experiences?

I want to do it just about right from the first start with the motherboard i have here.

Can anyone suggest me the right/good flux to desolder the socket in no time so I can replace it with the new one (I know the steps.)

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  • \$\begingroup\$ Trim the fluff and put links to what you’re loosely mentioning - what is 599? Sure we can Google, but you should save us the trouble and be explicit so we are clear as to what you are referring to. \$\endgroup\$
    – Kartman
    Apr 16, 2021 at 10:25
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    \$\begingroup\$ I've never used flux in desoldering. \$\endgroup\$
    – jwh20
    Apr 16, 2021 at 10:25
  • \$\begingroup\$ Was desoldering LCAs the other day - no way of getting flux underneath. \$\endgroup\$
    – Kartman
    Apr 16, 2021 at 10:25
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    \$\begingroup\$ @Ketske: Flux is needed for soldering. For desoldering, it is less of a concern. \$\endgroup\$
    – JRE
    Apr 16, 2021 at 10:25
  • \$\begingroup\$ @JRE, yes thats true and i know that. So for the desoldering of this type there is no flux needed then you say ? Because i watched some people who desoldered the sockets using some flux to help with the soldering joints underneath the socket. So i am a bit confused right now. \$\endgroup\$
    – Ketske
    Apr 16, 2021 at 10:29

1 Answer 1

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Type of flux isn't really important when desoldering.

It is very important for wicking solder (as it removes oxides from the solder wick, aiding in solder wettage of the wick.)

I realize that there are plenty of videos from quite famous youtubers that absolutely drown the electronics in flux when (de)soldering, but there is absolutely no need for that. Solder flux removes oxides that build up on any exposed metal. This oxide prevents the intermetallic layer to form properly and you will get weak joints when soldering. During desoldering there isn't really any point to remove oxides at the surface of the solder joint.

The key to a good desolder, especially of LGA and BGA, is even heat and enough, but not excessive heat. Preheat the board to 70-80 degC and use hot air at 350-380 degC.

Never, ever use force. Heat+force will ruin your pads.

The component should just smoothly come off. Any amount of prying with a tweezer or screwdriver will ruin both your part and board.

Once the part is removed you can (carefully!) clean with solderwick drenched in flux, but once again, you don't need flux on the board (but a pool of flux on the board drenches the solder-wick, so why not.)

Finally the board can be cleaned with IPA.

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  • \$\begingroup\$ This is the answer i am quite looking for. Yes there are alot of videos, which from here and there and some forums i noted some things to get steps into the right place and from what i am reading, i am into the right spot with my steps. And there is no force needed for sure which is logical, so that is another good thing to notice here for other people to visit, learn and read. So i was thinking almost the same, besides from the temperature, i read in a technical book on google that a socket is between 230-250 the joints should be on point. So you shoud adjust that to a higher temp ? \$\endgroup\$
    – Ketske
    Apr 16, 2021 at 12:21
  • \$\begingroup\$ Or that may be because of the materials used in the solder or this is only for BGA CHIPS, but i know for sure that the book showed a socket.. If i can find the book again on Google, i will add this to the page. Thank you @Arcatus for your decent answer. \$\endgroup\$
    – Ketske
    Apr 16, 2021 at 12:35
  • \$\begingroup\$ @Ketske Note quite sure on what kind of socket you describe. Desoldering should be done at the lowest possible temperature. Practically I have found this to be around the 350degC mark, but if there are plastic parts you might need even lower temperatures, and then it might be difficult to desolder from a GND plane. However: Might you be thinking of the "solder balls" on BGA's? These melt around that temperature if they are lead-containing. Reballing BGA's after desoldering sometimes required. \$\endgroup\$
    – Arcatus
    Apr 16, 2021 at 12:50
  • \$\begingroup\$ Allright, yes i find, that is true about desoldering at low temps which i do also. But the socket section is quite new to me even when i have the specs and steps to apply heat on the bottom and top . I have disassembled all the plastics and o rings on the board. And applied some heat resistant (yellow-ish) tape on the components around the socket. And applied the tape tight together so when there is a bit of flux travelling it stays just about a mm or 3 outside around to socket. Sorry about the clearance in what i described about the socket above. i need to find that book. Thank you Arcatus! \$\endgroup\$
    – Ketske
    Apr 16, 2021 at 13:16
  • \$\begingroup\$ To be more clear into the last answer btw. *Might you be thinking of the "solder balls" on BGA's? These melt around that temperature if they are lead-containing. Reballing BGA's after desoldering sometimes required. -Yes that was probably the thing i was thinking about too, because of the lower temps in lead solder. But the picture/descriptio in that confused me somewhat. \$\endgroup\$
    – Ketske
    Apr 16, 2021 at 13:21

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