Conductive microsphere monolayers enabling highly conductive pressure-sensitive adhesive tapes for electromagnetic interference shielding

Conductive adhesive tape is one kind of electromagnetic interference (EMI) shielding materials for electronic packaging. However, the inferior conductivity of the pressure-sensitive adhesive (PSA) layer results in serious electromagnetic leakage at the conjunctions between the conductive tapes and target objects. Adding conductive fillers is a traditional method for highly conductive adhesive tapes. However, the content of conductive fillers is needed to reach the percolation threshold, which is usually as high as tens of percent. High-content fillers result in significant loss of adhesive property and high fabrication cost. Herein, we introduce a rational architecture of conductive microsphere monolayer (CMM) in the PSA layer. The CMM connects the top and bottom surfaces of the PSA layer and improves its conductivity in the z-direction. Importantly, low contents of conductive microspheres (≤5 % (mass fraction, w)) can achieve the target of conductivity improvement, but not result in the serious loss of the adhesive property. Therefore, the strategy of CMMs can balance the tradeoff between the conductivity and the adhesive property of conductive PSA tapes. Finally, we demonstrate the superior EMI shielding performance of as-made conductive adhesive tapes, indicating their potential applications as the advanced EMI shielding materials in the electronic packaging.