20-25 micron are excessive.. normally, you form intermetallic layers, you
stop the dissolution somewhat, unless, the plating quality is poor (porous
or high current density).  my guess.
 jk
> My apologies for answering your question with a question, but how do you
> know the reduction is 20-25 microns?  I presume a measurement before the
> floats is not possible.  I'm interested to see what the experts have to
> say. Louis Hart
>
> -----Original Message-----
> From: TechNet [mailto:[log in to unmask]] On Behalf Of Nagaraj U
> Sent: Tuesday, August 19, 2014 1:59 AM
> To: [log in to unmask]
> Subject: [TN] Query on Copper dissolution
>
> Hi All,
>
> We have a few customers asking for 6x solder float at 288°C, 10 seconds
> (IPC-TM-650, 2.6.8, Condition A). After completion of 6x solder float
> (using SnPb 63/37 solder) we typically see reduction of Copper in PTH (due
> to copper dissolution) in the range of 20 to 25µm. The reduction in Cu
> thickness is maximum at the PTH knee area.
>
> Can I have some inputs if this level of copper dissolution is normal?
> If it is not normal, how do we reduce this?
>
> Thanks in advance!
>
> Best Regards,
> U.Nagaraj
> MICROPACK, India.
> [Logo]<http://www.micro-pack.com>
>
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