Electronic packages are frequently exposed to a thermal cycling environment in real life applications.  Particularly, the plastic ball grid array (PBGA) is one of the most widely used electronic package, and consists of various component materials, e.g. solder joint, silicon die, die attachment adhesive, mold compound, solder mask, etc.  All of these materials play a significant role on the reliability of the overall package.  Failure under creep deformation is one of the significant failure mode for electronic packages.  Hence, it is important to study their creep behavior and evolution under the thermal cycling environment.  These changes must be evaluated in order to understand and predict their failure behavior due to creep damage in operation.  In our previous study, evolution of mechanical properties of SAC305 solder joints in a PBGA package up to 250 thermal cycles was evaluated using the nanoindentation technique.  In this work, the nanoindentation technique was utilized to understand the evolution of creep behavior of the die attachment adhesive, silicon die, and solder mask material for various durations of thermal cycling.  Test specimens were first prepared by cross sectioning a PBGA package to reveal the different materials, followed by surface polishing to facilitate SEM imaging and nanoindentation testing.  After preparation, the package samples were thermally cycled from T = -40 to 125 ^o^C in an environmental chamber.  At various points in the cycling (e.g. after 0, 50, 100, 250 and 500 cycles), the package was taken out from the chamber, and nanoindentation was performed on above mentioned materials to obtain creep behavior at room temperature (25 ^o^C).  Creep strain rate as a function of applied stress was obtained and plotted for different cyclic durations.  From the nanoindentation test data, it was found that die attachment and solder mask materials showed initial reduction in creep strain rate due to increase in strength.  As expected, the silicon die material does not show any significant change during same duration of thermal cycling. 

 


Evolution of Creep Response of Various Materials Within Pbga Packages Exposed to Thermal Cycling Loading

Division / Sponsors: 
Electronic & Photonic Packaging Division (EPPD)

Paper Proceedings: https://asmedigitalcollection.asme.org/InterPACK/InterPACK2020/volume/84041

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