Re: BGA Assembly

[Dimiter Popoff <tgi_earth@yahoo.com>]

Anthony Moulds,

>Does anyone in the UK know of a company that can successfully
>handle the assembly of fine-pitch BGA devices (FBGA680) in small
>volumes? So far I've drawn a blank!

Well I am not in the UK but right now I am struggling with my first
board which has 3 normal pitch (1.27) BGAs. The mistake I made
with the first soldering attempt was that I fixed the chips to
the board by glueing their corners to the board (using UV-hardening
glue); the result was that the solder balls did never
touch the pads, surface tension was > gravity impact.
I removed the glue and put just limiting feet at each corner (I used
pieces of enammeled wire); then back into the oven again.
This time it worked - though, as I discovered later, I still had
several non-contact pads ( I am still chasing one of them, one
of the 3 BGA chips still does not work OK).
Fortunately, I had routed the board with a hole (drilled 0.3mm)
at each pad; repairing the bad ones turned out possible (but not easy,
as one would expect). It amounted to a very hot soldering iron
and a piece of 0.15mm copper wire (taken from a coax cable shield);
with a drop of solder I could eventually melt all through the hole
and reach to the the BGA ball. The wire was necessary to punch
through the surface tension barrier, just solder did not always work.

Now while this is not the address of a company which would do
small quantities for you I hope it may be useful during your
prototyping. Good luck!

Dimiter

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Dimiter Popoff
Transgalactic Instruments, Gourko Str. 25 b, 1000 Sofia, Bulgaria
http://transgalactic.freeyellow.com
Email: tgi@bulnet.bg, tgi_earth@yahoo.com
Phone: 00359/2/9923340, 00359/2/9805997, Fax: 00359/2/9540384