Well, it may be not that straight forward calculation. We know that there are 2 of them - Cu6Sn5 (which forms first) and Cu3Sn and each one has its own activation energy.
Regards,
Vladimir
Vladimir Igoshev, Ph. D.
Senior Materials Researcher
Research in Motion
451 Phillip St.
Waterloo, ON, N2L 3X2
Voice: (+1) 519-888-7465, ext. 5283
Fax: (+1) 519-886-0863
E-mail: [log in to unmask]
-----Original Message-----
From: TechNet [mailto:[log in to unmask]]On Behalf Of Guenter Grossmann
Sent: Friday, April 15, 2005 5:34 AM
To: [log in to unmask]
Subject: [TN] Antw: Re: [TN] ENIG - no more problems? / Sn plating
Phil, John
I looked a bit in good ol' Klein Wassink and found his formula for the
growth of intermetallic compounds on Cu surfaces:
d=10^3(exp(-5*10^3/T)t^1/2
d= Thickness of IMC in um
T= Temperature in K
t= time in sec.
The equation can easily be solved for t. Gives a nice Excel spreadsheet
where the time for a given temperature can be estimated a layer of Sn of
a certain thickness needs to be transformed to IMC and will thus make
problems in soldering. Gives interesting results when Sn 0.8um is
compared with 1.2um thickness.
Guenter
EMPA
Swiss Federal Laboratories for Materials Testing and Research
Centre for Reliability
Guenter Grossmann, Senior Engineer
8600 Duebendorf
Switzerland
Phone: xx41 1 823 4279
Fax : xx41 1 823 4054
mail: [log in to unmask]
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