FROM: BRUCE HOUGHTON  27/552/844/TOR                                           
Phone  (416) 448-5701     Tie 778-5701                                         
Subject: Gold Thickness Requirements for Tabs                                  
Jedic spec for Gold Tab SIMMS is minimum of 30 micro inches of hard            
plated gold over minimum (I think - I am not at work) 70 micro inches          
in nickel.                                                                     
There are companies using electoless nickel/immersion gold (5 micro            
inches) on SIMMS.  THe don't meet spec.  Life expectancy / reliability         
is unknown.  WIth the proce of SIMMS, I personally want parts that             
meet spec.  These SIMMS plug into Gold plated connectors.                      
                                                                               
There is also a tin/lead spec for SIMMS that are plugged into                  
connectors with tin/lead plating.  That spec calls for 200 microinches         
of tin/lead over 70 microinches of nickel, as a physical and                   
intermetalic growth barrier.  Again, there are companies that are              
applying solder over bare copper.                                              
                                                                               
Gold tab cards and tin/lead SIMMs should not be mixed in their                 
connectors.  If Gold tab SIMMS are plugged into tin/lead connectors,           
a high resistance intermetalic layer will grow between the gold and            
tin/lead and cause noise problems and failures.  The same is true              
with tin/lead tab SIMMS in Gold connectors.  Again, some companies             
and computer stores are mixing parts.                                          
                                                                               
Bruce Houghton                                                                 
Staff Engineer, Celestica, Inc.                                                
Internet:  [log in to unmask]                                              
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