It was determined that the reflow profile was not long
enough for this chip to reach full reflow.
Experiments filming the double drop showed that with
the higher speed chip, reflow of the balls took longer
and was not as uniform as with other BGAs (same
component package, same ball composition).  Even
though all documentation from the vendor states that
there isn't any differences between the two, we saw a
marked difference with respect to heat transfer.  How
'bout you?  Any solution to your woes?

Regards,
Lisa
--- "Ingemar Hernefjord (EMW)"
<[log in to unmask]> wrote:
> Lisa, what about your BGA disaster? Was there a
> happy end?
> Ingemar
>
> -----Original Message-----
> From: Lisa Anderson [mailto:[log in to unmask]]
> Sent: den 18 januari 2001 14:06
> To: [log in to unmask]
> Subject: [TN] PGBA Cold solder joints
>
>
> Good morning to all!  Question for those with
> experience in the BGA arena .. lately, we have
> noticed
> cold solder joints on the outermost row of balls of
> a
> 357 Motorola PBGA package.  The problem is not found
> at any testing stage since the ball and reflowed
> paste
> are making sufficient contact; it shows up later
> after, what is assumed, oxidation forms.  At
> present,
> we are suspecting 1) coplanarity issues, 2)
> activation
> of the flux too early in the reflow soak stage, 3)
> cupping ("potato chipping") of the device as it is
> processed through the reflow oven.  Has anyone out
> there experienced this problem?  TIF file attached
> for
> viewing pleasure.
>
> Many thanks in advance for your help,
>
> Lisa Anderson
>
> Note: if file can not be viewed, send me a note.
>
> __________________________________________________
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