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August 2014

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Subject:
From:
Victor Hernandez <[log in to unmask]>
Reply To:
TechNet E-Mail Forum <[log in to unmask]>, [log in to unmask]
Date:
Tue, 19 Aug 2014 09:43:48 -0500
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Usually the IMC formation thickness on post solder, Time Zero, is from 2 - 5 microns and 5 - 10 on post 6x for LF solder PTHs and BGAs.   Of course not copper dissolution on ENIG surface.   The thicker the IMC the interface becomes brittle.

Victor,

-----Original Message-----
From: TechNet [mailto:[log in to unmask]] On Behalf Of Louis Hart
Sent: Tuesday, August 19, 2014 9:28 AM
To: [log in to unmask]
Subject: Re: [TN] Query on Copper dissolution

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.
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