Sol-gel derived Pd-SiO2 catalyst for high-adhesion metallization of silicone rubber

초록

The metallization of silicone rubber remains challenging because of its low surface energy (approximately 20 mN/m) and chemical inertness. This paper reports a method for metallizing silicone rubber surfaces using a sol-gel derived Pd-SiO2 catalyst layer. Palladium (Pd) nanoparticles (5-10 nm) were nucleated and stably dispersed within a silica sol matrix via sonochemical synthesis. The catalyst layer was applied to alkali-pretreated silicone rubber by dip-coating, and thermal curing at 120 degrees C induced covalent Si-O-Si bond formation. Electroless nickel-boron (Ni-B), electroplated copper (Cu), and electroless tin (Sn) deposition produced uniform multilayer coatings with thicknesses of 840 nm, 3.3 mu m, and 490 nm, respectively. Cross-sectional focused ion beam analysis demonstrated stable interfacial adhesion with no delamination or detachment at the boundaries between the silicone rubber substrate, Pd-SiO2 catalyst layer, and Sn/Cu/Ni-B plating layers. The metallized samples achieved the highest adhesion rating (ISO 2409 Grade 0) and a solder joint strength of 0.79 kgf, indicating suitability for electronic components. Furthermore, the metallized gaskets demonstrated excellent dynamic reliability, maintaining stable electrical resistance (<0.1 Omega) and no delamination after 10,000 cyclic compression tests. The developed process produced conductive silicone gaskets, exhibiting strong potential for ground gasket applications.

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