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mike[_22_] mike[_22_] is offline
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Default reflowing BGA with a hot air gun?

On 2/10/2018 2:03 PM, Gareth Magennis wrote:
It's worth a go if the laptop is scrap otherwise.

Chances of success are extremely slim though.


The success stories you see on Youtube are either fake, or the tiny
percentage of these repairs that lasted long enough to make the video.



Gareth.







wrote in message ...

I have a laptop that is acting really weird. It's an older ASUS,
probably ten or twelve years old. It was plugged in, closed, sitting
on a table. It worked fine a few days before the problems started. The
display keeps shaking. The machine takes forever to boot up. And then
acts weird. But if I push down hard on the lower left side of the
machine it works fine. As long as the pressure is kept up and in just
the right area.
I spoke to my son about this problem because he knows more about
this kind of thing than I do. He said it sounded like a video card
problem that he and some of his computer whiz friends have run into.
Apparently the video processor can get too hot and the BGA under it
can start to debond.
He has a hot air rework tool and he said I might be able to reflow
the chip. Is this something that a rank amateur can likely do?
Eric


I experimented with it on a laptop video chip.

I built a box with a square hole in the top. Put in air baffles
to point airflow at the hole.
Stuck a variable paint stripper in the side of the box.

Cleaned the area under the chip with repeated applications
of simple green, alcohol, water and lots of air. Dried it overnight
in a hot box at about 120F.
Used liquid flux designed for reflow repair under the chip.

Put thermocouples on the board and spaced it above the hole.

Adjusted the paint stripper to ramp the temperature of the bottom
of the board to just below the melting point of solder.
Aimed a temperature controlled air flow designed to desolder chips
at the unmasked area around the chip on the topside.
Heated the top of the chip to above the melting temperature
of solder. Used topside thermocouples, but today would probably
try a thermal imager.
Fixed the intermittent video problem.

Elated with my success, I tried another.
I had been using paper towels for insulation under the aluminum foil
topside mask. Got careless and set the paper towels on fire.
Putting out the fire jostled the board and some chips fell off
the backside. EPIC fail!

over the next year...
Third try fixed another laptop.

Fourth try didn't help that laptop.
Fifth try didn't help that laptop.

Laptops got so cheap at garage sales that reflowing
one wasn't worth trying.

YMMV