Hi Bob -
     
     I would advocate NOT relating specific conditioning recipes to 
     specific times for at least solderability type conditions. The IPC 
     solderability committee used to equate 16 hours of steam aging as one 
     year of shelf life but after the EIA/IPC round robin and several 
     independent testing investigations it was shown that the oxide created 
     with steam aging does not represent the oxide conditions of solder 
     after a year on the factory shelf. IPC TR 462 (accelerated aging and 
     solderability)  technical report is a good compilation of many 
     "recipes" that the industry has tried. The steam aging recipe is one 
     conditioning method to see how robust a finish is but it doesn't 
     equate directly to use conditions. I think we will find the same 
     "problem" will occur on the humidity testing type recipes. Many people 
     who conduct SIR testing do not try to equate the SIR recipe to a 
     specific amount of time, only that for the conditions tested, the 
     materials they were investigating were robust enough to not cause CAF 
     or corrosion problems and therefore give the tester some amount of 
     comfort zone in some use environments. The IPC SM 785 Table is very 
     good but also has several caveats on how to view the time factors. It 
     will very interesting to see the kind of responses you receive. The 
     IPC solderability committees would be very interested on any data that 
     could be used to improve the specs.
     
     
     Dave Hillman
     Rockwell Collins
     [log in to unmask]


______________________________ Reply Separator _________________________________
Subject: Reliability Testing
Author:  [log in to unmask] at ccmgw1
Date:    1/2/97 3:12 AM


What does accelerated testing mean in terms of time ?
     
Take for example 16h at 155oC for Solderability it is accepted to = 1 year
     
The IPC SM 785 Table one provides temperature cycling conditions but does it 
provide an indication on the equivalent in days and years. 
     
What do the following tests relate to in days, years etc.
     
7 days 85%RH 85oC = ?
     
21 days 85%RH 85oC = ?
     
21 days 40oC 95%RH = ?
     
Temperature cycling -55 to 125oC = ?
     
A listing of the suggested test conditions and what they are considered to 
equate too will be mailed to the IPC forum. 
     
     
Bob Willis
Process Engineering Consultant
Electronic Presentation Services
2 Fourth Avenue, Chelmsford, Essex CM1 4HA. England. 
Tel: (44) 01245 351502
Fax: (44) 01245 496123
Home Page: http://ourworld.compuserve.com/homepages/Bwillis 
Email: [log in to unmask]
     
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