It sound like you're assuming that "Champagne voids" ar
Richard,
It sound like you're assuming that "Champagne voids" are "Kirkendahl
voids". That may be an incorrect assumption. I've seen "Champagne
voids" in optical micrographs of cross sectioned solder joints but the
only images I seen of "Kirkendahl voids" have been high magnification
SEM images.
Regards,
George
George M. Wenger
Senior Principle FMA / Reliability Engineer
CommScope / Andrew Wireless Solutions
40 Technology Drive, Warren, NJ 07059 (908) 546-4531
[log in to unmask]
-----Original Message-----
From: TechNet [mailto:[log in to unmask]] On Behalf Of Stadem, Richard D.
Sent: Tuesday, January 29, 2008 2:31 PM
To: [log in to unmask]
Subject: Re: [TN] Microvoids immersion silver
Werner and Don.
I was always under the impression that Kirkendahl voiding was a result
of the noble metal's (in this case, silver) nucleation through the SJ. I
always thought that this was a time-variable migration. I understand how
all of the process variables described in Werner's response will affect
or support the eventual void formation, but I would not expect Gaby to
find anything in microsections taken immediately after soldering. Would
it not make more sense to thermally cycle the SJs in order to facilitate
the nucleation prior to microsectioning?
-----Original Message-----
From: TechNet [mailto:[log in to unmask]] On Behalf Of Werner Engelmaier /*
Sent: Tuesday, January 29, 2008 12:35 PM
To: [log in to unmask]
Subject: Re: [TN] Microvoids immersion silver
Hi Gaby,
I take it what you are seeing are 'champagne voids.'
Voids like these are 'encouraged by rough topography copper, excessive
Ag thickness, some solder paste choices and rapid cool-down after
reflow. But as Donald Cullen says in his comprehensive paper, it
"requires the "Perfect Storm"
of a rather contrived combination of parameters" to produce planar
micro-voiding.
Well Gaby, now you know it-you are "Perfect." ;-)
Werner
**************
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