Russell,
 
Sounds as if you might have more than one issue here.
 
Regarding the dull solder joints:  How does the gold thickness of the May and October batches compare?  (Note: use measurements taken after the May boards were scrubbed)  The treatments given to your gold bath could increase plating efficiency and/or alter the surface finish of the nickel.  Gold plating is usually so thin that it mirrors the surface of the underlying nickel.  If the October batch is thicker, your customer may be seeing a gold/solder alloy.  I don't know the concentration where the appearance changes (seems like 30 microinches is a magic number), but gold embrittlement could be an issue.
 
Regarding the inability to recognize fiducials:  Scrubbed gold has a different surface texture that plated gold.  Even though they appear shiny, the different textures can fool the cameras.  An eraser could "fix" the problem until the cameras are adjusted for the new surface condition.
 
Just a quick note: black pad is not associated with electrolytic plating.
 
Hope this helped.
 
Don Vischulis


-----Original Message-----
From: TechNet [mailto:[log in to unmask]]On Behalf Of Russell Burdick
Sent: Thursday, November 14, 2002 4:04 PM
To: [log in to unmask]
Subject: [TN] gold solderaility


Hello everyone!

I could use some help concerning soldering to gold.

Problem:
A customer of ours has given feedback to our salespeople that hard gold
boards we made in May 2002 were much better to solder to than what we sent
in October 2002. Biggest difference was stated as the newest boards have
fiducials that auto pick and place equipment can't read because under the
lights they look "black". Under normal shop lights both boards look bright
and shiney(sp?).

Also, the customer commented that on the boards with "black" unreadable
fiducials had solderjoints that looked very dull.

Known manufacturing/processing differences between months of May and October
(aka, confessions of a process engineer):
Prior to August 2002, dull plated gold boards were scrubbed to improve
appearances. After August 2002 no scrubbing needed when a carbon treat and
proper wetters were performed/maintained in nickel and gold baths.


Any and all comments are greatly appreciated.





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