Re: gEDA-user: Cheap 4 layer manufacturer?

[Darrell Harmon <mail@xxxxxxxxxxxx>]

On Mon, Oct 10, 2005 at 10:48:56PM -0500, John Griessen wrote:
> What is it like hand assembling a BGA package?
> Seems like positioning would be hard to get right
> with no repeatable robot arm to move one thing away
> from the other and check alignment.  I've got a maybe customer
> for a stripped down wireless linux motherboard that
> might run into this kind of package on several parts.
> If that turns into a product, I will likely get some
> rights to make versions of it and do just like you are
> thinking  -- JIT cottage industriousness.
> 
> John G
> 

Surface tension does the alignment job. All that matters with
the initial placement is that the balls touch the pads. Once
the oven reaches about 185 Celcius, the BGAs can be seen moving
by surface tension to the centers of the pads. QFPs are more
critical to align due to the finer pitch. 

-- 
Darrell Harmon
http://dlharmon.com/dspcard
Credit card size DSP/FPGA board