Thanks, Victor.
I saw the same  with unsufficient paste .
The article also recommends increase of solde paste volume whenever possible
for warpage compensation.
I think Henry did not mention what defects he found due to second reflow.
Gaby
----- Original Message -----
From: <[log in to unmask]>
To: <[log in to unmask]>; <[log in to unmask]>
Sent: Wednesday, June 26, 2002 10:33 PM
Subject: RE: [TN] Reflow on Wave.


> Gaby,
>    In a previous life, IBM, I saw a similar type BGA defect on several
cross
> section.   The x-ray revealed irregular shape bumps.   Temp. parameters
were
> characterized, etc.  The works.   After all the dust settled it came to be
a
> plugged stencil on the PCB side.   Insufficient solder paste/flux to
reflow
> the bump to the PCB pad.   This clue came about after several samples
> exhibited the same anomaly, PCBA date code dependant.   Others vendors of
> the same product line and technology did not exhibit this type of defect.
> The stencil was found to be restricted.
>
> Food for thought.
>
> Victor,
>
> -----Original Message-----
> From: Gaby Bogdan [mailto:[log in to unmask]]
> Sent: Wednesday, June 26, 2002 2:55 PM
> To: [log in to unmask]
> Subject: Re: [TN] Reflow on Wave.
>
>
> Maybe this article will help.
> http://www.alphametals.com/products/solder_solutions/pdf/pillowhead.pdf>
> Gaby
>
> ----- Original Message -----
> From: "Henry Rekers" <[log in to unmask]>
> To: <[log in to unmask]>
> Sent: Wednesday, June 26, 2002 4:07 PM
> Subject: [TN] Reflow on Wave.
>
>
> > Does anybody have any suggestions on avoiding reflow of a 357 ball bga
on
> > the wave?  I'm dealing with a 6 layer board and I've kept the preheat as
> low
> > as possible.  Kapton tape doesn't seem to help.  Has anybody tried any
> > custom manufactured sheilding?
> >
> > Thanks.
> >
> > Henry J. Rekers
> > Manufacturing Engineer.
> >
>
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