Re: [oc] Multi-layer PCB boards

[Victor the Cleaner <jonathan@canuck.com>]

On Tue, Nov 20, 2001 at 10:59:48AM -0500, Lior Shtram wrote:
> 
> What did you have in mind for assembly? You know that mounting a 456BGA 
> in your garage workshop will also probably not work...

I'm not sure I agree on that point.  

(Note that to date I've stuck to QFP parts for a number of reasons, but 
 expect to start working with BGAs soon, so this is based on informed 
 speculation rather than experience.)

The word I've gotten from our CM is that BGAs are actually *easier* to mount
(by pick+place, I must qualify) because the nature of the contact array tends
to exert a higher self-centering force upon the part during solder reflow.
Given that the pin spacing is reasonably high (eg 1mm), I don't think it's
beyond reason to think that this can be done by hand without advanced gear.

I've got a rework station called a "Hart" blower that directs hot air to 
both the top and bottom surfaces of the board.  It's crude, but it *was* 
designed for BGA work.  This is something that could be easily approximated 
with a couple of mounted and modified Master heat guns, and I think with care 
acceptable results could be obtained.

Of course, the *real* problem isn't the soldering, it's inspection in the 
event that things don't work properly.  Although it's pretty easy to do, I 
do not recommend homebrew X-ray.

Jonathan

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