Effect of flux quantity on Sn-Pb and Pb-free BGA solder shear strength

The global movement to eradicate Pb from electronic assemblies has made it necessary to manufacture Pb-free packages. While the industry has identified potential Pb-free alternatives, much work still needs to be done in the component and board level reliability. Ball Grid Array (BGA) packages are commonly used in the electronics industry today. Flux deposition is a standard step in the BGA sphere-attach process and requires precise since it plays a critical role in the formation of the BGA solder joint. Flux measurement is difficult as it is clear or amber colored, thus making it invisible to standard optics techniques. The patent pending Ultraviolet Fluorescence Intensity Mapping (UV-FIM) technique is used in this research effort for flux measurement. BGA spheres are attached using different quantities of flux. A correlation is made between the solder joint shear strength and the flux quantity for Sn-Pb and Pb-free (96.5Sn-3.5Ag, 95.5Sn-4Ag-0.5Cu) BGA solder joints.