Lead-free solder joints are the most widely used interconnects in electronic packaging industries.  Usually solder joints in most of the electronic devices are exposed to an environment where variation of temperature exists, which indicates cyclic thermal loading to be a very common type of external loading. Moreover, due to difference in the coefficient of thermal expansion (CTE) among dissimilar contact materials, shear stress develops in junctions under thermal loading, which significantly deteriorates the overall reliability. Hence, characterization of lead-free solder materials under cyclic thermal loading is essential to predict the performance and deformation behavior of joints in practical applications. A significant portion of the studies in this field are concerned with thermal loading of lead-free solder interconnects, each of which has a very small diameter, in sub-millimeter range.  Although the solder balls have very small dimensions, most of the analyses considered them as a bulk material with homogeneous and isotropic properties.  However, with the decrease of specimen dimensions, size effects and material directionality play a significant role in deformation mechanisms.  Since a very few grains exist in a small specimen, individual grain properties play a vital role on overall material response.  Therefore, modeling from the grain structure and orientation point of view could be an effective and more accurate way to predict solder joint deformation behavior under thermal loading.

 

  In this study, the effect of grain size and orientation of SAC305 is investigated for predicting anisotropic behavior of solder joints under cyclic thermal load.  A simplified three-dimensional model of beach-ball configuration solder joint was generated and simulated using ABAQUS finite element (FE) software. Experimentally obtained directional properties such as elastic modulus and thermal conductivity were assigned to the computational geometry to create material anisotropy.  The effects of material anisotropy were studied for varying grain size specimens, as well as for specimens with varying grain orientation.  Finally, a comparison was established between the simulation predictions and the experimental results obtained from cyclic thermal test on SAC305 solder balls.


Deformation Behavior Sac305 Solder Joints With Multiple Grains

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

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

InterPACK2020 - Virtual Conference

Supporting the need among researchers worldwide for additional online and multimedia content, ASME now offers the ASME Conference Video Collection. This platform will collect and provide long-term access to conference presentation videos, encompassing all technology areas within ASME's technical conference and events program. About 30,000-40,000 engineers across all mechanical engineering and related disciplines participate in ASME conferences each year. This includes authors of approximately 6,000 to 8,000 technical papers published by ASME, the majority of whom also submit video presentations for our virtual conferences. The video collection will be available as an add-on to existing product packages or as a separate subscription.