Lpc2000

> Of unity0724
> Sent: Tuesday, January 31, 2006 7:21 AM
> To: lpc2000@yahoogroups.com
> Subject: [lpc2000] Re: Philips LPC3180 - BGA loading Qs
> 
> --- In lpc2000@yahoogroups.com, Greg Deuerling <egads@f...> wrote:
> > I use a hot air re-work machine and it does a great job.  The
> > great things about BGA's are they are self centering.  They can be
> > off pad up to 60% and when the balls flow they will pull the
> > package into proper alignment.   For a big production run you want
> > to go to a place that does IR re-flow, but for the qnt we do here
> > our hot air machine work nicely.  It's not all that
> > hard!!!
> 
> We used hot air blower (600W SMT rework/desodlering tools) to solder
> BGA on prototype boards but could only get 20-30% successful rate.
> Difficult part would be chip blown completely out of PCB footprint.
> Self-centering does not always pull the chip back to proper alignment
> also.   Any special skill/experience to share??
> Regards

Special skill's?  Yes, lots of practice and the temperature and timing have
to be closely controlled.  I recently mounted 40 672pin PBGA's and had a
100% success rate.  Altera and Xilinx will usually give you 10 or so dummy
packages to practice on before you try to place that $1000 FPGA the 1st time
:)

Our system heats the PCB from the top and the bottom board.  We use a three
step process:

1) Pre-heat the PCB to 200C for a minute or so.

2) Next soak the PCB to just 20-30C under where the solder starts to flow
for 2 minutes.  Most 10 to 12 layer PCB's I use 230C.

3) Next hit the PCB with enough heat to flow the solder for 10-30 seconds.
Most 10 to 12 layer PCB's I use 300C for 10 seconds.  This is the real
trick, you only want to flow the solder for a very short time or the package
will lay down too flat and short out balls.

The air speed on the above steps is pretty slow.  I've had 0402 cap's that
were not held down by anything but solder paste and they did not blow away.

We use a Metcal/OKI BGA-3500 series re-work station.  Metcal does not make
the BGA-3500 any more, but I think the APR-5000 replaced it.

See: http://www.okinternational.com/product_advanced



Greg Deuerling
Fermi National Accelerator Laboratory
Feynman Computing Center, Room 370, MS 368
P.O.Box 500 Batavia, IL 60510
(630)840-4629     FAX  (630)840-8208
Electronic Systems Engineering Group
Work: egads@...