Paymon,

To fill some of the details; what is the finish plating of the board, what is the solder being used and what is the flux being used?

This will help.  In the past there has been discussion about immersion tin oxidizing during an initial heat cycle (SMT) and then not being able to solder the PTH parts.

Phil

-----Original Message-----
From: TechNet [mailto:[log in to unmask]] On Behalf Of Paymon Sani
Sent: Thursday, October 09, 2008 9:57 AM
To: [log in to unmask]
Subject: [TN] PCB pad non-wetting issues

Hello All,



We are experiencing a pad non-wetting issue for the though-hole
component pads ONLY! The PCB goes through few heat cycles with top and
bottom side assembly during at SMT process and then through-hole
assembly at wave process. The problem is found at Wave process. The Pb
solder does not wet to the through-hole component pads on the solder
side only! An SEM/EDS evaluation revealed high concentration of P in the
Nickel and Nickel/Tin intermetalic layer of 11% to 21%. I would like to
ask anyone if they have experienced a similar defect in the past. What
is the Root Cause?



Thank you in advance,

Paymon


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