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|Influence of Different Solder Materials on the Location of the Most Damaged PBGA Solder Balls and on the Life Time Reduction Due to Assembling of a Mounted Printed Circuit Board in an Electronic Control Unit|
|Keywords: low cycle fatique of PBGA, solder joint reliability for SnPb and SnAgCu, system level experiment and simulation|
|PBGA with SnPb and SnAgCu solder joints were stressed with temperature cycles on board- and system-level. A significant influence of the different solder materials on the location of the most damaged PBGA solder balls has been observed in the experiment. The reason for this experimental finding was investigated and explained in the FE–simulation . The simulations of the PBGA has been done on the package-, board- and system-level (PCB within a metal housing). For the system level simulation a 2-step sub-model technique described in  has been used. This approach allows to consider the transient PCB deformation and the transient temperature field within the ECU-housing in the creep simulation of the PBGA solder joints. The creep results for both SnPb and SnAgCu solder joints from the board- and system-level simulation were compared. The calculated life time loss factor due to the ECU housing influence is different for PBGA with SnPb and SnAgCu solder joints. The simulation results were validated step by step by measurements and experiment: warpage of the unsoldered PBGA, temperature and mechanical strain on the mounted PCB, crack length evaluation of all PBGA solder joints.  Schafet,N., Lemm,C., Becker,U., Güttler,H., Schmidt,P. “Development of a submodel technique for the simulation of solder joint fatigue of electronic devices mounted within an assembled ECU.” Proceedings Eu-roSimE 2009, Delft, Netherlands, April 2009, pp. 253-260.|
|Natalja Schafet, Senior Expert for Thermo-Mechanical FE-Simulation
Robert Bosch GmbH
Schwieberdingen, Baden-Würtemberg 71701,