Silver@Expanded Microspheres/Silicone Conductive Composites with Ultra-low Compression Stress for Electromagnetic Interference Shielding in Electronic Packaging

Silicone conductive composites are the ideal materials for electromagnetic interference (EMI) shielding in electronic packages because of their excellent sealing properties, chemical inertness, and mechanical durability. Notably, chips and other miniature electronic components with limited pressure-bearing capacity often require soft conductive composites with low compressive stress and high electromagnetic shielding performance. However, conventional silicone conductive composites still face significant challenges in balancing compressibility and electromagnetic shielding performance as the conductive filler content increases. Here, a composite with ultra-low compression stress and excellent EMI shielding properties was successfully prepared by incorporating silver-plated expanded microspheres (Ag@EM) into a silicone substrate, followed by a heat curing process. In particular, the lightweight Ag@EM conductive filler possess low density (0.14 g/cm
³
). Compared to conventional polymer conductive composites filled with hard fillers (Ag@hollow glass microspheres), the Ag@EM/silicone composites with Ag@EM loading of 15.5 wt% show ultra-low compression stress of only 0.22 MPa at 50% of compressive strain and high EMI SE of 60 dB at thickness of 1 mm. Significantly, the Ag@EM/silicone composites has a maximum shielding effectiveness of 71 dB at the edge in near-field (NF) shielding tests due to its low compressive stress, good sealing and excellent shielding properties. This work suggests that the Ag@EM/silicone composites with ultra-low compression stress, outstanding EMI and NF shielding performance, verifying the potential of the Ag@EM/silicone composites for electronic devices.