AbstractThe effects of the dielectric constant on the transmission characteristics of multilayer ceramic circuit boards were examined. Multilayer ceramic circuit boards were fabricated using various kinds of ceramic materials with different dielectric constants, and their characteristic impedances, crosstalk, and propagation delays were measured. Experimental results show that the lower the dielectric constant, the higher the characteristic impedance, with less crosstalk and propagation delay. Based on these results, lowering the dielectric constant of the board material is found to be essential for realizing higher‐density wiring, e.g., the reduction in the dielectric thickness and transmission line spacing in multilayer ceramic circuit board