Fabrication of Soft Conductive Microspheres and Their Application in Electromagnetic Interference Shielding Sheets

Conductive fillers are one of the key factors to determine the conductive and shielding properties of conductive polymer composites. Herein, an emulsion polymerization method was used to prepare soft polydimethylsiloxane (PDMS) microspheres. And the soft conductive fillers of Ag coated PDMS microspheres (PDMS@Ag) were fabricated by electroless plating technique. The EMI shielding sheets were further fabricated by mixing the soft PDMS@Ag fillers with liquid silicone precursor and curing agent, followed by rolling and heat curing process. The compression ratio of the EMI sheets with 66 wt% of PDMS@Ag is 51.2% at 40 psi. Moreover, the EMI shielding sheets present a high EMI shielding effectiveness (SE) value of ~120 dB with 66 wt% of PDMS@Ag fillers. Our work proved that the soft conductive fillers present great advantages in compression and EMI shielding performances of the conductive polymer composites, which has promising potential in electronic packaging applications.