Electronics > Beginners

Am I using the correct temperature to desolder a chop

<< < (2/2)

Deus:

--- Quote from: ke1ko on July 19, 2019, 11:10:21 pm ---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?

--- End quote ---

Sorry 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.

janoc:

--- Quote from: Deus on July 21, 2019, 04:29:37 pm ---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.

--- End quote ---

Quite 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.

Deus:

--- Quote from: janoc on July 21, 2019, 06:51:35 pm ---
--- Quote from: Deus on July 21, 2019, 04:29:37 pm ---The BGA lift in that video is a FAIL !!!
--- End quote ---

Quite 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.

--- End quote ---

If it popcorns/delaminates most of the BGA's/PCB's reworking with it sounds more "impossible to 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.

janoc:

--- Quote from: Deus on July 22, 2019, 08:27:20 am ---
--- Quote from: janoc on July 21, 2019, 06:51:35 pm ---
--- Quote from: Deus on July 21, 2019, 04:29:37 pm ---The BGA lift in that video is a FAIL !!!
--- End quote ---

Quite 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.

--- End quote ---

If it popcorns/delaminates most of the BGA's/PCB's reworking with it sounds more "impossible to 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.

--- End quote ---

Sure, 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 station is capable 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).

Deus:
@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, not the IR 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 am ---"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)."
--- End quote ---
You'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.

Navigation

[0] Message Index

[*] Previous page

There was an error while thanking
Thanking...
Go to full version
Powered by SMFPacks Advanced Attachments Uploader Mod