De-soldering caps on a GPU help

[Pandora]

Hi, Let me preface this by saying i'm not a total noob with things like this. I have never done anything other than low power components with my experience capping out at replacing smd components on laptops.

I have a dead gpu and after some testing i am 99% sure that there are 2 bad caps right next to each other. I bought another dead GPU to steal caps from test de soldering with lead-free solder.

 

I have been unable to remove any caps so far. Heck I can't even get the lead-free solder to properly tin the end of my soldering iron (hakko 888d at 790c).

 

I know lead-free stuff sucks to work with and i know the these caps are going to have a large grounding trace that will be sucking away a good bit of the heat but i feel like i'm running into a fundamental issue or missing a key piece of knowledge.

 

Thank you for your help

 

[Average Nerd]

1 minute ago, Pandora said:

Heck I can't even get the lead-free solder to properly tin the end of my soldering iron (hakko 888d at 790c)

Maybe turn the temperature down to 450°C, that usually works for me.

[BiotechBen]

I have also found lead-free solder to have a much more temperamental temperature preference. A good lead-free with a rosin-flux core should help.

[Needfuldoer]

Are they surface mount, or through-hole?

 

Either way, good flux is your friend when it comes to doing rework. (And especially rework with lead-free solder. That stuff is sticky and acts like it has a lot of surface tension.)

 

If they're through-hole, you need enough heat to wet the entire joint, all the way through the via. Don't pull too hard, or you can pull the plated via out of the hole in the fiberglass board.

 

This may be a controversial take, but the twist/wiggle method is the most reliable method I've found for desoldering surface-mount electrolytic caps. You just grab the cap with pliers and wiggle it back and forth until the legs break from metal fatigue. Most of the time they break where they bend, sometimes they break up inside the can. Either way, the chance of lifting pads is far less than if you use hot air.

 

(Timestamped to the relevant part.)

 

11 minutes ago, Pandora said:

I have been unable to remove any caps so far. Heck I can't even get the lead-free solder to properly tin the end of my soldering iron (hakko 888d at 790c).

I think you're burning all the flux off before it has a chance to work properly. Try somewhere between 650 F and 675 F. (Your station is reading degrees Fahrenheit, not Celsius. It can't get to 790 C.)

[mariushm]

Liquid or gel flux on the component pads, optionally heat the board from the other side with a hot air gun or even a hair dryer, add solder to the pads ... your iron should probably be at around 380-400c ... 450c is rarely needed.  If you have a conical tip, change the tip to something with more contact area.

 

If you still have a hard time, get a low melt solder for example https://www.digikey.com/en/products/detail/chip-quik-inc/SMD3SWLT-047-1OZ/13625136 (this one has no flux inside, so extra flux would be required)  or https://www.digikey.com/en/products/detail/chip-quik-inc/SMDSWLT-040-10G/9836741 ( with flux )  or  paste in syringe like https://www.digikey.com/en/products/detail/chip-quik-inc/TS391LT/7802220

 

 

[FlyingPotato_is_taken]

350°C (whatever this is in F), high thermal mass tip and preheating the PCB.

[Heats with Nvidia]

Also make sure the tip is properly tinned. If it doesn`t wet with the solder you have, clean it properly and try again. Of this doesn`t work, you need a new tip. Also th temperature is way too high and you most probably burned the surface of your tip, so it needs to be replaced. Also like said above, don`t use the standard conical tip, but something with as much surface area and thermal mass as you can get.

 

Oh and by the way, if you want to solder more in the future and make your life easier, the Pinecil, TS101 and so on are a real upgrade to your current Hakko.