Jamie t wrote in message
...
N_Cook wrote:
Removed in good order for re-use that is . No specialised tools
available
and I'm not going out to buy any for a once in a year job. I have a few
ideas but have never had to do it in earnest before. There is about 0.05
mm
clearance space between the balls under the chip and about 5 x 5mm in
size.
A few minor SM can be removed from the opposite face of the board,
multilayer and about 1mm thick


If you're trying to save the chip.. fab a small chimney to fit the
outer edges to be used to direct the heat on the bottom side. Use a
hot air gun, timer and suction cup puller on the top side..

Knowing the time it takes to heat the solder for proper removal will
help for installing it later on.

For installation, I've cleaned the surface, used solder paste to
tack down the chip. Put the chimney back on and heat up the under side
while pushing down to reflow the joints. The paste helps in rejoining
the joints of course.

I wouldn't recommend doing this on a regular bases but has worked for
me when I didn't have the proper tools at hand..

Btw. I do have a home made ported hot air fixture I made to remove
chips with under body legs. It blows the air on all four sides
horizontal under the chip. The heater element was a little tricky!




Some ideas there. This is a glass? chip web cam CCD , having a go at making
an "endoscope" so just a matter of freeing the CCD. Will not re-use BGA but
individual wires soldered between with some sort of ground plane.
I was thinking of kevlar fibres pushed under in X and Y sense formed into
loops over some cotton wool pad that can be soaked in freezer spray.
Mask off around the underside of the board and blast with hot air while
tugging at the kevlar "strops"