On May 8, 2011, at 07:49 AM, V G wrote:

> Would I need to reflow it in my toaster? Or can I use my hot air
> rework station and blow hot air at it?
>=20
> Then there's the problem with alignment...
> =97=20

I've done quite a bit of amateur BGA rework with large pin count chips usin=
g an inexpensive hot-air station and a skillet.  Approximately 180 x 0.6mm =
balls.  A stencil for placing the balls is absolutely required.  In my expe=
rience, the difficult part is removing and cleaning the board/chip.  Obviou=
sly, that wouldn't be a part of what you intend to do, so yield would be be=
tter.  Any board that I've ruined has always been ruined in the removal ste=
p.

If I was to do a one off board as you're trying to do, I'd have at least on=
e extra PCB made.  Depending on the cost of the FPGA, I might order a backu=
p of the chip as well.

As for alignment, that was my biggest concern starting out.  It turns out t=
hat alignment is very easy. As long as it is close and the heat from the gu=
n is even (i.e. all the solder balls melt at the same time), it will self a=
lign.  It's very cool to watch.

While it can definitely be done by hand, I'd still put considerable effort =
into finding a pre-assembled board that fit my requirements before I tried =
to roll my own.

- Nate


--=20
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