Discoloration mechanism of silver-filled adhesive used for packaging solder joint

Owing to the trend of the miniaturization and high density, conductive adhesive is regarded as the new promising kind of electronic packaging and bonding materials. Reliability of adhesives has been one of the key issues in practical applications. A phenomenon occurred on packaging solder joint of silver-filled adhesive, which declined the normal performance and reliability of phase shifter, was presented in this paper. Base on unusual discoloration (turning black) of adhesives on solders, scanning electron microscope (SEM) and electron probe energy disperse spectroscopy (EDS) were carried out on the microstructure and micro-area composition analysis. The discoloration mechanism was found through comparing the composition of the normal solder with the discolored. Discoloration mechanism and potential effect on reliability were evaluated. The study in this case is of great significance in applications.