IMO,
Either the solder profile is not hot enough or the Pd -Au coating was porous
and did not prevent nickel oxides from forming. 
If there was adequate coating to protect the nickel I think the flux in the
paste would have resulted in solder fillets with normal appearance. 
R596 is pretty aggressive.
The little skips in the nickel might, if the parts were old, produced some
voids not dewetting on the scale depicted. 

Guy

-----Original Message-----
From: TechNet [mailto:[log in to unmask]] On Behalf Of Mumtaz Bora
Sent: Tuesday, January 12, 2010 5:56 PM
To: [log in to unmask]
Subject: [TN] NiPdGold Plating Soldering Issues

Hello Technetters,
 
 
We have some SC70 packages with NiPd gold plating that have wetting
issues .
Customer is using Kester R596L tinlead water soluble solder paste
conducting  eutectic reflow at 227C peak and have wetting issues.(first
3 images in PowerPoint).
We have checked plating thickness with our supplier and it meets spec.
EDX did not show any contamination, oxides etc. JEDEC solderability test
passed. 
 
X-section shows some areas of missing nickel or gaps in coverage of base
copper. I need the experts to look at the images and comment if this
could be the root cause of poor wetting and non-wetting.
 
I have forwarded the PowerPoint to Steven Gregory to post on his
website.
 
Your feedback will be much appreciated.
 
Thank-you

Mumtaz Bora

Senior Quality Engineer

Peregrine Semiconductor

9380 Carroll Park Drive

San Diego, CA 92121

858-795-0112-direct

858-731-9499 -fax

[log in to unmask]


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