Am I using the correct temperature to desolder a chop - Page 1
Forum section: electronics / beginners

author: ke1ko
author_rank: Newbie
timestamp: July 06, 2019, 02:52:04 pm
content: I have a T862++ BGA rework station. I'm trying to remove a GPU from an xbox 360.I have set the tray temperature to 180, and the IR lamp to 240.When i start, the flux i've applied starts to bubble but that's it.I'm not sure where i'm going wrong. Do i have to raise the temperature higher that 240? I tried 260 but even that was ineffective.Can anyone point me in the right direction?

author: janoc
author_rank: Super Contributor
timestamp: July 06, 2019, 03:56:02 pm
content: Quote from: ke1ko on July 06, 2019, 02:52:04 pmNo experience with that rework station but lead-free solder is only starting to melt at around 220 C. You aren't heating the solder balls directly plus that chip is large, so a higher temperature is likely needed - 240 should be enough, though.What you need to do is to preheat the board first - that means you let the board actually sit with the tray heat on only for some time to bring it to temperature, do not apply top heat right away! Only then apply the heat from the top for a short time to melt the solder and pop the chip off.Also make sure that the chip isn't glued to the board - some BGAs are! That has to be removed first.

author: ke1ko
author_rank: Newbie
timestamp: July 19, 2019, 11:10:21 pm
content: i've tried heating the bottom of the chip up, using the plate. The temperature of the chip does not seem to go beyond 70 degrees.Even when i use the main desoldering lamp, still nothing happens.Could my BGA rework station not be powerful enough?

author: janoc
author_rank: Super Contributor
timestamp: July 20, 2019, 11:17:35 am
content: Quote from: ke1ko on July 19, 2019, 11:10:21 pmIt is either defective or you are using it wrong. Here is a guy removing a fairly substantial BGA chip with it:

author: Deus
author_rank: Contributor
timestamp: July 21, 2019, 04:29:37 pm
content: The BGA lift in that video is a FAIL !!!He might have gotten the BGA off, but at least the PCB is knackered and most likely the BGA too.Look at the blister pointed out by the arrow on the included pic.I suspect there's even more damage on the pcb but hard to see due low quality.It's alos not the way to remove them as you can knock off or move components around it.

author: Deus
author_rank: Contributor
timestamp: July 21, 2019, 04:53:17 pm
content: Quote from: ke1ko on July 19, 2019, 11:10:21 pmSorry to say, but it's indeed not powerful enough.It might be usable on small pcbs same size or only a bit larger as the bottom heater. But even then...For BGA rework the bottom heater is important, should cover the whole, or a very large part, of the pcb.Especially with lead free multi layer pcbs with lots of copper in it. They suck away the heat.You could try with very long preheat steps going up very slowly if you have enough pcbs to destroy to create a usable work flow..But tbh... I wouldn't spend much time on it. (In that video posted by janoc the PCB and probably BGA was/were destroyed for sure).Control and repeatability is important. Might not always be exact the same but you have to be able to get +/- the same performance/result everytime.If you really have a need for this, get yourself a decent BGA rework station with programmable profiles capable of things like included pic.Yours might have even more problems then you already have on the BGA on that pic as it has a metal heat spreader on it.On the left arrow tip you see the chip before lifting/after soldering back again.On the right one the cleaned and reballed BGA with the cleaned BGA area of the pcb above it.The graph shows the used lead free profile.

author: janoc
author_rank: Super Contributor
timestamp: July 21, 2019, 06:51:35 pm
content: Quote from: Deus on July 21, 2019, 04:29:37 pmQuite possibly, I didn't check the video in detail. It was only to show the OP that it is, indeed, possible to lift a largish BGA with this station. However, I think this gadget is more targeted at the various street phone repair shops where chips are much smaller than someone wanting to replace GPUs.

author: Deus
author_rank: Contributor
timestamp: July 22, 2019, 08:27:20 am
content: Quote from: janoc on July 21, 2019, 06:51:35 pmIf it popcorns/delaminates most of the BGA's/PCB's reworking with it sounds more "impossibleto lift a largish BGA with this station".At least if you buy it for rework as in repair...Pretty good to see on the posted pic.

author: janoc
author_rank: Super Contributor
timestamp: July 22, 2019, 09:47:24 am
content: Quote from: Deus on July 22, 2019, 08:27:20 amSure, but given that OP's solder likely wasn't even melting (either because of a wrong setting or the board was conducting the heat away too quickly) that's a bit besides the point.You will find a lot of videos like this one that uses that station on a large BGA (an ATI GPU) without popcorning anything:or this one:But both of them have also protected the rest of the board with foil, to make sure the IR goes only where it should go.So I would say that stationiscapable of doing it, given that people are expressly buying it for "reballing" and "reflowing" GPUs (let's not go into the debate how BS that kind of "repair" is).The small size of the preheater is a problem, so I wouldn't want to use this for GPUs and similarly sized chips, but at the very least it should be possible to desolder a knackered chip with it without destroying the board (if the chip doesn't survive you don't care as it was defective anyway).

author: Deus
author_rank: Contributor
timestamp: July 22, 2019, 01:17:28 pm
content: @janoc:In the first video he's doing an MXM videocard, which is smaller than the bottom heater, so full bottom preheat. Even on that one it struggles but lift might've been ok.The 2nd video uses a hot air heat gun as top heater,nottheIR lamp. It's also in his comment:"As most of you know, the T-862 is a pretty cheap machine on Ebay these days. The trouble is it won't get hot enough to do the bigger jobs so I decided to experiment. I took apart a heat gun and took the gubbings out of the T-862 so I had the best of both worlds!""With Ease"... If you see him pulling on that BGA with tweezers... Should come off like butter...People in the past starting out with T862 or T870 (slightly larger preheater) using it for larger pcb's/bga's might've had few successes but too much fails switching to something more usable pretty quick.Quote from: janoc on July 22, 2019, 09:47:24 amYou've probably seen the "bullshit" video too?Ok, there were, still might, BGAs that had/have internal defects, like 8xxx and 9xxx that had problems with bumps. nVidia made the wrong choice back then.Many failing BGAs are fine and do only have a solder problem.Prefer reballing over getting "new" chips. With a reball it's not a fake sanded/re-lasered re-printed whatever chip.(If it's still the original on the pcb and not abused by oven, hot air, hair drayer, paint stripper, stove etc or DIY seen it on youtube attempts.)If you can't buy new or used/recovered/refurbished BGAs, reballing is sometimes the only option to get it working again.