Dan,
Just to throw my 2 cents in....we found that with solder paste we get much
better coverage of the PWB pad with solder, resulting in a more consistent
solder connection. With just flux we were getting a small percentage of the
connections with a thin solder contact to the pad. Although percentage was
small, it was frequent enough on a large ball count to reduce our rework
yields. Paste also helps to cancel any co-planarity problems.
Jim Kittel
-----Original Message-----
From: d. terstegge [mailto:[log in to unmask]]
Sent: Monday, February 05, 2001 9:56 AM
To: [log in to unmask]
Subject: Re: [TN] BGA REWORK
Hi Robert,
Are there any data that support your statement ? If you calculate the
amount of solder from the solderpaste and compare this with the volume of a
ball, you'll see that about 90% of the solder joint's volume comes from the
ball. 10 percent more or less of total solder volume shouldn't make out the
difference between a short and a long product life.
Kind regards,
Daan Terstegge
SMT Centre
Thales Communications
Unclassified mail
Personal Website: http://www.smtinfo.net
>>> "Furrow, Robert Gordon (Bob)" <[log in to unmask]> 02/05 4:27 pm >>>
Trevor,
I think it will depend on the expected useful life of the repair. If you are
looking at short life product with eutectic solder balls, and coplanarity is
not an issue, then using just flux should not be an issue. If you require
long term reliability then in most cases paste is preferable.
Thanks,
Robert Furrow
New Product Engineering
Lucent Technologies
978-960-3224 [log in to unmask]
> -----Original Message-----
> From: Trevor Goddard [SMTP:[log in to unmask]]
> Sent: Monday, February 05, 2001 9:44 AM
> To: [log in to unmask]
> Subject: [TN] BGA REWORK
>
> Hi all.
> I have a question about reworing BGAs. Do you have to reprint the solder
> paste before placing the component or can you lay down some flux and rely
> on
> the solder balls of the BGA?
> Thanks in advance
>
> Trevor Goddard,
> SMT Supervisor
> XLTEK
> (905) 829-5300 x 348
> [log in to unmask] <mailto:[log in to unmask]>
>
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