One of my customer's is interested in feedback from other companies 
     regarding incoming inspection as follows:  Any responses would be most 
     appreciated and will be sent to them.  
     
     
     1)  What would a normal telecommunications industry AQL and sampling 
     plan be for a company that has contractual obligations to meet 
     Bellcore's TR-NWT-000078 and that uses IPC-A-600, class 2, as an 
     inspection criteria for printed wiring boards?  This company also 
     wishes to use a reduced labor sampling plan.
     
     2)  Example:  Items being inspected at Incoming Inspection are printed 
     wiring boards. They are inspected to Bellcore TR'78 and IPC-A-600, 
     class 2.  The company inspection methodology is that a single 
     manufacturing process defect found on one board out of the sample 
     group (e.g. qty. 9) will cause the entire lot of boards (e.g. qty. 
     5,000) to be rejected.  Is this proper taking into consideration that 
     there can be hundreds of electrical nets per board and the defect 
     (say, a circuit width reduction of 80%) has occurred to only one of 
     the 9 sample boards' circuit runs?  If rejecting the lot based upon 
     finding this one defect on one sample board is too stringent, what 
     would be more reasonable?  How many defects of a particular kind 
     should be found across the samples before the defect can be considered 
     a seriously systemic process issue?  Is there a statistical way of 
     determining this?
     
     
     Carrie Lawn
     HADCO Corporation

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