When the silver finish is subjected to thermal cycle - silkscreen cure,
stamping, touch-up etc, the silver will tend to yellow.  Increasing the
nitric acid concentration in the silver bath will minimize this - also
caused from the bath age as the nitric becomes weak.  



Jeffrey Bush
Director, Quality Assurance and Technical Support

                          76 Technology Drive - POB 1890
                             Brattleboro, Vermont 05302-1890
                                Tel. 802.257.4571.21 Fax. 802.257.0011
                                    [log in to unmask]
                              http://www.vtcircuits.com	



-----Original Message-----
From: Richard Kraszewski [mailto:[log in to unmask]] 
Sent: Wednesday, June 16, 2004 10:13 AM
To: [log in to unmask]
Subject: [TN] Yellow Discoloration of Immersion Silver Boards


We are seeing yellow discoloration of Immersion Silver Boards right out
of the package from our board house.  They seem to solder fine, however
this is causing some concern with our customer.  I suspect that it could
be a thin film of  silver bromide or silver carbonate both which are
yellow powders.
 
Any one seen this before?
 
What is it?
 
How does the board house remedy this situation?
 
Any associated concerns or other bits of wisdom?
 
I would truly appreciate any input.
 

Rich Kraszewski 

Advanced Manufacturing Engineer - KEDS

Phone:  260.925.8919

 

 

 

 

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