Reactive cold sintering of dense barium sulfate ceramics for high-reliability chip packaging in integrated circuits

Reactive cold sintering (RCS) is an innovative ceramic consolidation technique that combines a low-temperature reaction with the cold sintering process . In this work, equimolar (CH 3 COO) 2 Ba and (NH 4 ) 2 SO 4 were homogeneously mixed to obtain a reactive activator abbreviated as RA and then added to barium sulfate (BaSO 4 ) powder obtaining BaSO 4 – x wt%RA ( x = 5, 7.5, 10, 12.5, and 15). Dense (>96 % theoretical) BaSO 4 ceramics were successfully fabricated via RCS of BaSO 4 – x wt%RA at 200℃ with a constantly applied pressure of 250 MPa. The Woolfrey-Bannister method provided quantitative insights into the activation energy , indicating that RA effectively reduced the energy required for densification . The Vickers hardness (1.76 GPa) and coefficient of thermal expansion (CTE, 18.8 ppm/°C) of the RCSed BaSO 4 ceramics were comparable to the high-temperature (850 °C) sintered counterparts. Moreover, finite element analyses confirmed the high CTE value of the RCSed BaSO 4 ceramics holds great promise for high-reliability chip packaging applications.