Crystallization and annealing effects of sputtered tin alloy films on electromagnetic interference shielding

Sn, Al and Cu not only possess electromagnetic interference (EMI) shield efficiency, but also have acceptable costs. In this study, sputtered Sn-Al thin films and Sn-Cu thin films were used to investigate the effect of the crystallization mechanism and film thickness on the electromagnetic interference (EMI) characteristics. The results show that Sn-xAl film increased the electromagnetic interference (EMI) shielding after annealing. For as-sputtered Sn-xCu films with higher Cu atomic concentration, the low frequency EMI shielding could not be improved. After annealing, the Sn-Cu thin film with lower Cu content possessed excellent EMI shielding at lower frequencies, but had an inverse tendency at higher frequencies. For both the Sn-xAl and Sn-xCu thin films after crystallization treatment, the sputtered films had higher electrical conductivity, however the EMI shielding was not enhanced significantly.

Research highlights▶ Sn, Al and Cu possess EMI shield efficiency and can be used to make Sn based alloying thin films for EMI applications. ▶ Sn alloying film must be an advanced method for EMI shielding. ▶ Due to the large number of IMCs and lower content of β-Sn, the higher frequency EMI shielding of the annealed Sn-Cu thin films deteriorated. ▶ The Sn-Al films had rich-Sn phases and rich Al phases in the matrix which were able to promote the EMI shielding.