Hi Fabien - the high phos SEM reading you are finding may just be due to
the fact that phos is not soluble in tin or lead so it isn't incorporated
into the solder joint microstructure as a coherent phase. I recommend you
have a microsection conducted on one of the failed solder joints or
adjacent solder joints. One of the tell tale signs of 'black pad' is hyper
corrosion of the nickel plating layer which can be observed in a
microsection.
Dave Hillman
Rockwell Collins
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Fabien Guizelin <[log in to unmask]>
Sent by: TechNet <[log in to unmask]>
10/17/2011 11:30 PM
Please respond to
TechNet E-Mail Forum <[log in to unmask]>; Please respond to
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Subject
Re: [TN] High Phosphorous content on ENIG PCB
Bob,
Thanks for the prompt support. Some more info :
On failed PWA, the communication between SDRAM and FLASH stops at -20oC.
The units boots and hang or just refuses to boot. Once temperature
reaches back -10oC, the unit operates again.
Dye&pry showed potential poor joints on the balls but nothing conclusive.
We conducted EDX on both failed PWA and fresh PCB. Both showed P-content
0.5% above IPC specs.
Black-pad originates from high Phosphorous content. But, how severe is
10.4%wt P-content ?
Regards,
Fabien
From: Bob METCALF [mailto:[log in to unmask]]
Sent: Tuesday, October 18, 2011 10:07
To: TechNet E-Mail Forum; Fabien Guizelin
Cc: [log in to unmask]
Subject: Re: [TN] High Phosphorous content on ENIG PCB
Fabien,
It would be helpful to understand the nature of the failure. You mention
it was a low temp failure. I don't understand what the failure is. Could
you please expand on this? As far as the P content being slightly about
10%, assuming it is a mid to high phos nickel, I wouldn't expect a
problem, but not knowing what has failed it would be difficult to
speculate.
Regards,
Bob Metcalf
Western Regional Manager
Atotech USA Inc
1750 Overview Drive
Rock Hill, South Carolina 29730 USA
Mobile: 714-334-7667
e-mail: [log in to unmask]
Internet: www.atotech.com<http://www.atotech.com/>
Managing Director: Kuldip Johal
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From: Fabien Guizelin <[log in to unmask]>
To: <[log in to unmask]>
Date: 10/17/2011 05:42 PM
Subject: [TN] High Phosphorous content on ENIG PCB
Sent by: TechNet <[log in to unmask]>
________________________________
Hi all,
I am facing a PWA failure at low temperature. An EDX analysis revealed a
P-content of 10.4%wt which is outside the IPC-4552 1.2.1 specifications
(7-10%). The PCB has an ENIG finish.
Could I be facing black-pad ?
How severe is the 0.4%wt additional Phosphorous content ?
Regards,
Fabien
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