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
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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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