Desoldering - soldering BGA chip close plastic mini fpc connectors ?

[corrize]

Hello, I need your advise please ? I need to remove and replace the BGA black chip with fpc connectors around. The PCB is small, from camera.

There is no plastic component directly under, on the other face, (only fuse and oscillator I can remove if they are sensitives to heat), but there is a lot of very small smd components I don't want to desolder by mistake.

I have :
- hot air, and a ll stuff around
- true kapton tape
- 140 and 180 degree soldering paste
- bismuth
- little hot plate 250 degree max
- the new BGA chip with probably lead free solder balls

The best way is by bottom ? How to be sure hot air dont push away the components on the bottom please ?

[Aliencomputres]

heloo,
use aluminium tape or kapton to isolate/desolder fpc connectors .

[corrize]

I never tried to desolder with connectors so close. I tried with connectors around, with kapton on it, and direct hot air, and after the connector was a little rounded… I'm scared.

Ok thx, I like this way : desolder connectors first. Because the new chip with leed free balls could be long to solder and with high temp. I guess it's better to solder with hot air by the top.

The way I see :
1 - desolder connectors by bottom, help with 140 solder paste on connectors : that could decrease hot air temp needed (360 degree ?) and help to keep the other components in place ?
2 – increase hot air temp (400 ?) to direct desolder BGA and resolder new one.
3 – resolder connectors with 180 solder paste, with hot air by bottom (360 degree ?) That could help to no reflow the chip and other components around ?

It is the best way for you ? (If I burn connectors, I could never found new ones)

[CapLeaker]

2 more options: If you replace that chip anyway, you can also dill or dremel the lid away, then unsolder the rest with a regular soldering iron. Or you replace the connector and the IC.
I think preheat is key, cover the connector with aluminum tape, then just a short hot blast on the IC to take it off.

[mateusassuncao]

It's not difficult!
Use aluminum tape or kapton to isolate as my friend Aliencomputres said!
Use a little solder flux on the BGA.
With the FPCs well insulated, you can use the air station at 380º without any problems!
But apply the heat on top of the BGA, in seconds it will "swim" on the board!
Remember to fix the board well, to remove the chip!
Then clean it well, remove the old solder, with desoldering mesh, flux on it, and you can install the new BGA without any problems!
Good luck!!!

[Joe24]

Preheating from bottom will help by reducing the amount of top heat you need, and therefore shortening the time with the air station. Opinions vary, but I like to get the board temperature up around 100-110°C using bottom preheat. Measure the actual board temperature with a probe or IR gun. Then as the others say, shield the components you don't want to melt, and then remove the chip with hot air.

I prefer a piece of aluminum tape doubled on itself. Leave an air gap between sensitive parts and the heat-shielding, if you can. And be conscious of the direction your air gun is pointing; angle it a bit so it's blowing away from the sensitive components.

You shouldn't have problems with components falling off the other side of the board. Board itself spreads top-heat out enough that the bottom of board shouldn't hit melting temperature.

[Unspun01]

While I would normally pre-heat from beneath and apply hot-air from top, this approach is likely to damage the delicate FPC connectors.

On the other hand, I have de-soldered such a BGA chip with nearby delicate plastic connectors by applying hot air directly from underneath the board with lots of flux on the BGA from above. I would try 400C hot air wand as-is without any nozzles. Using nozzles will only limit the amount of air and heat and you will need to spend much more time trying to de-solder.

This technique is also useful to replace individual LEDs on LCD/LED TV backlight strips where physical soldering or hot-air directed at the LED will destroy the LED itself.

If you are worried about desoldering bottom components, you should be careful to support the board well so it does not move, and apply air from distance of about 1 inch or 3 cm. Just do not contact the bottom of the board with the hot air wand. And don't have crazy high flow-rate of air. Gentle air-flow rate is sufficient to provide the heat.