Tek LCD screen failure

Which I acknowledged for finding a failed PART. This is NOT a case of a failed part. What part of that do you not understand?

When one is looking for a failed part. And don't get me wrong, intermittent behavior IS a failure mode.

Using it to locate mechanical connectivity issues is ludicrous, at best.

Firing freeze spray UNDER a BGA is ridiculous behavior, at best.

When you fire it under a BGA, you will very likely ALWAYS see a difference in circuit behavior. If you cannot see that fact, you have no business being a tech, or attempting to call yourself one.

Also, ANY lab that has an RH below 30% is an ESD hazard, and an ESD event waiting to happen... on a daily basis.

Any lab with an RH above 30%, the recommended value, BTW, WILL condensate water on parts that have been shot with freeze spray.

It is basic physics 101, son. No sauna required. No goddamned freeze spray required either.

Jeez what got stuck up this guy's butt? I'm not a tech, nor do I call myself one, I'm a hobbyist doing this stuff for myself with a very good record of fixing things others have given up on.

Removing the crossposting..

You don't spray anything *under* a BGA, just a quick shot on top does the trick. Ludicrous it may be, but I've been using it for years and it works. The contraction from the temperature change can cause a much more local effect than prodding at a board with mechanical pressure, which can sometimes distort the whole area of the board, while with the freeze spray I'm able to narrow it down very easily. I don't care if it's the "right" way, I just care that it works for me, and that it does. It's just one more tool at my disposal and if it helps me solve the problem, great, if not, well in the decade or so since I discovered it, I've yet to have it make anything worse.

"James Sweet" wrote in news:pE9Vi.191$gl1.79@trndny09:

I prefer to squirt the spray on a Q-tip and put that on the suspect part. I've seen people get into trouble using freeze spray directly,get led down a false path.

--
Jim Yanik
jyanik
at
kua.net

"James Sweet" wrote in news:8IeVi.4547$8R1.585@trndny02:

If you have a bad solder joint under a BGA,how do you "fix" it?

--
Jim Yanik
jyanik
at
kua.net

If one makes it spray slowly, one can fill a small cap with it, like a mini dewar. vessel. Then, you can dip the Q-tip and soak away heat on suspected parts all day long.

Still, these methods are not very good toward connectorization issues.

Generally you don't, but you know to stop screwing around looking for the problem elsewhere.

It may be possible to fix with a heat gun as a last ditch effort, but that really could do further damage.

I've had some success reflowing BGAs that have fractured or poor solder joints around their perimeter using a Hako 850 and a small nozzle which allows me to concentrate the air just where it's needed.

JW wrote in news: snipped-for-privacy@4ax.com:

it seems that the only reliable way would be to remove the BGA chip and somehow put new solder balls and flux on all the PCB pads,then reinstall the BGA and reflow using a preheat hot plate and hot air gun. Never tried it,though.

--
Jim Yanik
jyanik
at
kua.net

[...]

I don't think I'd attempt it but:

I doubt it'd be economically feasible for the devices we use. When we have a BGA that has failed solder joints and it can't be fixed with the Hako, we send it out to have the chip replaced.