Yes, Opens not shorts. My error.
You all are correct! Thank you for the responses.
It looks like we may be cooling too quickly after reflow, and this is
causing stress to the PCB and/or BGA. Is there any difference to cooling
rates when dealing with SAC405 (or any other Pb Free alloy)?
Many thanks,
Danielle L. Casha
-----Original Message-----
From: Lester Subrattee [SMTP:[log in to unmask]]
Sent: Friday, March 31, 2006 3:58 PM
To: [log in to unmask]
Subject: RE: Brittle Interfacial fractures of SAC405 BGAs on ENIG PCBs
Lot's of industry data and recommendations against using ENIG for BGAs pads
subject to impact stresses.
Could be brittle interfacial, black pad, poor wetting to begin with.
Is the fracture occurring after drop tests or during normal processing ?
Larger BGAs if not processed properly or if they aren't supposed to be
processed at high temps will show significant warpage and stress the
joints.
Be sure that the problem is properly diagnosed as brittle interfacial
failure and not the result of processing issues.
Why is the ICT finding shorts ?
Brittle interfacial fractures aside, with ENIG there are always more things
that can go wrong from the PCB manufacturer side and the assembly side.
LS
-----Original Message-----
From: Danielle Casha [mailto:[log in to unmask]]
Sent: Friday, March 31, 2006 3:31 PM
To: [log in to unmask]
Subject: Brittle Interfacial fractures of SAC405 BGAs on ENIG PCBs
Hello All,
We are currently experiencing fractures with a SAC alloy BGA (I/O 529) on
an ENIG surface PCB. ICT is finding shorts at locations on the outer rim of
the BGA.
We sent a sample out to the lab, and with cross sectioning, they were able
to determine a fracture along the nickel/SAC intermetallic. I have heard
of problems with ENIG before, especially with Pb free alloys.
Has anyone else dealt with this before, and if so, how were you able to
overcome this?
All opinions/suggestions would be greatly appreciated.
Thank you,
Danielle L. Casha
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