Can we call it 'Black Pudding' instead, as it is a mess of obscure
ingredients?
Inge
----- Original Message -----
From: "Wenger, George M." <[log in to unmask]>
To: <[log in to unmask]>
Sent: Friday, November 21, 2008 10:47 AM
Subject: Re: [TN] black pad
That is how a lot of the confusion around (I hate t
Peter,
That is how a lot of the confusion around (I hate the name but I need to
use it here) Black Pad started. Creep fatigue cracking, brittle
fracture, etc. are recognized failure modes or mechanisms, "Black Pad","
Black Line Nickel", etc. are not names of recognized failure modes.
They are names of what people see when they look at a failure. They
are short cute names that people like to repeat but they don't help to
describe what the failure is or what caused it. All I know about "Black
Pad" is that it happens with ENIG, it's a low level problem that follows
Murphy's Law (i.e., it happens when you least expect it and usually and
an inappropriate time), it might be caused by a high P content at the
interface, it might be caused by "weak" electroless nickel, it might be
caused by cavitation and attack at grain boundaries, it might be cause
by too much gold plating attaching the under lying nickel, it might be
caused by board shops not controlling the ENIG process properly, etc.
There are just too many "might". The data that has been generated by
many over the last couple of years certainly shows that control of the
plating chemistry is a key to reducing the occurrences of "Black Pad"
failures and the number of occurrences has certainly decreased but the
failures certainly have not been eliminated. Many of the ENIG failures
I've seen over the years are fractures at an interface. Vladimir would
certainly not agree with calling all ENIG failures "Black Pad" and I'd
agree with him. I'd much rather refer to the ENIG failures as "ENIG
Interface Failures" rather than "Black Pad" but that will never happen
because "Black Pad" is a cute and short 8 letter name that can even be
shorted to two ("BP"). It takes 23 key strokes to type "ENIG Interface
failures".
Sorry for the long answer but it's Friday and I had an exhausting week.
Regards,
George
George M. Wenger
Andrew Wireless Solutions
Senior Principle FMA/Reliability Engineer
40 Technology Drive, Warren, NJ 07059
(908) 546-4531 (Office) (732) 309-8964 (cell)
[log in to unmask]
-----Original Message-----
From: TechNet [mailto:[log in to unmask]] On Behalf Of Pete Houwen
Sent: Friday, November 21, 2008 12:54 PM
To: [log in to unmask]
Subject: Re: [TN] black pad
not to step in a place I don't beloing, between werner and Vladimir, but
how
about "dark line defect" instead of "black pad"?
Similar phenomenon for a different reason.
We went through this a while ago, wondering why suddenly boards from a
very
good ENiG supplier were looking like black pad, all that P on top of the
pad.
Changing reflow profiles to reduce TAL and max temp, reducing rework
cycles
made it all go away. All that extra time at temperature just continued
the
Ni/Sn reaction, leaving P behind. Quantities of Ni in the Sn tipped us
off that
we weren't starting out with black pad, but we were ending up with it.
I do get why people don't like ENiG, but we've done very well with it by
making
sure we use good suppliers.
Pete
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