A study on epoxy/BaTiO/sub 3/ embedded capacitor pastes for organic substrates

In this work, embedded capacitor pastes (ECPs) with various BaTiO ₃ (BTO) powder contents were formulated and screen-printed on PCBs to fabricate capacitors. Material properties of ECPs such as rheology, curing behavior and dielectric constant were investigated. Using optimized ECPs, embedded capacitors were fabricated for reliability tests such as thermal cycling test and high temperature/humidity test. ECP resin had curing process while temperature changed from 130degC to 220degC. All ECPs had sufficiently low viscosities at a shear rate of 100 sec^-1 to be screen printed. The dielectric constant of cured ECP increased up to 60 at 70 vol%, and dielectric loss was about 0.023 for all ECPs regardless of BTO volume content. For the reliability test, ECPs with 50, 60, and 70 vol% BTO powder contents were selected, and embedded capacitors were fabricated. Thermal cycling test with a temperature range from --55degC to 125degC for 1000 cycles and high temperature/humidity test with 85degC/85RH% condition for 1000 hours were performed. After thermal cycling test, capacitance decreased about 5~10%, but dielectric loss was not changed. After 85degC/85RH% test, capacitance and dielectric loss increased about 20%. Capacitance changes after thermal cycling test was presumably due to high temperature exposure above T_g and water absorption to polymer matrix