Hi Werner,

 

I wish we had a definition of BP everyone agreed on :-) 

 

In the cases of BP I've been dealing with, I could virtually blow off
the components from the boards.

 

Regards,


Vladimir

 

________________________________

From: [log in to unmask] [mailto:[log in to unmask]] 
Sent: Thursday, June 19, 2008 2:34 AM
To: Igoshev, Vladimir; [log in to unmask]
Subject: Re: [TN] [LF] [TN] SN100 for Reflow Application

 

Hi Vladimir & Dean,
First, neither BP nor the PCB resin cohesion needs to be anywhere near
zero. Those SJ's can generate in excess of 10 MPa at the higher T's,
more at lower T's.
Second, I have seen ENIG layers with no P at all-the consequence was
'hyper-galvanic' corrosion [cavitation] with etched crevasses along the
Ni grain boundaries all the way down to the Cu with the Cu attacked. The
basic scenario is like Dean laid it out in his e-mail, except that the
growth of the Ni-IMC over time is very slow because of the very low
dissolution rate of Ni in Sn at operating T's. It may be more an issue
that sooner or later the loading conditions get severe enough to
overload the weak interface, or perhaps that there is some crack
propagation at that weak interface further weakening the attachment.
Werner




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