Whisker growth behaviors in POSS-silanol modified Sn3.0Ag0.5Cu composite solders

As an ideal modifier, the cage-type polyhedral oligomeric silsesquioxane (POSS)-silanol creates a strong bonding with the solder without agglomeration. It has been shown that the addition of POSS-silanol improves both the mechanical performance and the solder's resistance to electromigration. This study further examined the effect of the addition of POSS-silanol on whisker growth in a Sn3.0Ag0.5Cu (SAC305) solder. The whisker growth was studied for pure SAC305 and SAC305 modified with POSS-silanol under isothermal aging and thermal cycling conditions. The results indicate that the added POSS-silanol not only reinforces the solder joint, but also inhibits whisker formation under both thermal aging and thermal cycling conditions. POSS-silanol can therefore be considered a promising modifier material which enhances the reliability of solders. During the thermal aging process, the added POSS-silanol was found to inhibit the interdiffusion of Sn and Cu atoms at the interface region, thereby preventing the formation of Cu6Sn5 but promoting the conversion of Cu6Sn5 into Cu3Sn. During the thermal cycling process, the added POSS-silanol significantly inhibited whisker formation and the deformation of the interface by stiffening the solder matrix and decreasing the driving force for whisker formation.