Low-temperature sintering and thermal-aging reliability of nano-silver joints on cyanate ester composite substrates

Direct nano-silver sintering on cyanate ester composite substrates provides a promising route for integrating power chips with lightweight, thermally stable, and low-dielectric polymer composites. In this study, power chips were directly bonded onto fiber-reinforced cyanate ester composite substrates by low-temperature nano-silver sintering. Ag particles coalesced on the composite surface and formed a mechanically bonded heterogeneous interface. The joint achieved a maximum shear strength of 11.5 MPa, while the sintered Ag layer exhibited a porosity of 10.1% after sintering at 15 MPa for 15 min, while the porosity decreased to 6.5% at 20 MPa. After high-temperature aging for 600 h, the shear strength remained at 9.3 MPa, respresenting a decrease of only approximately 19%. The failure mode progressively shifted from separation at the Ag/composite interface to cracking and delamination within the composite substrate. These results demonstrate the feasibility of low-temperature nano-silver bonding on non-metallized cyanate ester composites and identify substrate thermal degradation as the principal limitation on long-term joint reliability.