Hi Werner,

 

I was expecting your reply. :-) The term by itself has been used for
quite a while and there is a good summary by Atotech on both phenomena
"Black Pad" and ""Brittle Fracture". Below is a summary I put down for a
paper"

 

Brittle fracture type of failure - a "razor-like" separation between
solder and the solder pad, has been known to the industry for quite a
few years. This type of failure is usually called "Brittle Fracture"
(BF). As BF is mainly observed in the joints of grid array components
(BGA, LGA) on ENIG finished boards, it is very often confused with a
completely different phenomenon known as "Black Pad". The confusion is
probably caused by the similar appearance of the fracture surfaces in
both cases. However, simple metallurgical cross-sectioning can easily
tell the phenomena apart. 

 

The most significant difference between "Brittle Fracture" and "Black
Pad" is that the solder joints, which might experience BF, are perfectly
healthy in "as-reflowed" condition and can bear a significant amount of
mechanical load. However, joints affected by "Black Pad" are not capable
of bearing virtually any mechanical load and the components can be
literally "blown off the board". The root cause of "Black Pad" is
believed to be in the ENIG process.

 

Regards,

 

Vladimir

 

________________________________

From: [log in to unmask] [mailto:[log in to unmask]] 
Sent: Tuesday, November 28, 2006 2:21 PM
To: Vladimir Igoshev; [log in to unmask]
Subject: Re: [TN] Ultimate PCB assembly books (and more)

 

Hi Vladimir,
A failure due to ENIG Black Pad is in fact a brittle interfacial
fracture. It is one of a number of root causes resulting in this failure
mode.
How do you define "Brittle Fracture" [with capital letters]?



Werner




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