The silver diffusion behavior in the low-temperature cofired ceramic ( LTCC) comprising of borosilicate glass and alumina was investigated in this work. Transmission electron microscope ( TEM) analysis revealed that silver ions diffused into LTCC materials through the glass phase. The addition of copper oxide in the LTCC materials can suppress the silver diffusion during the sintering process because of the enhanced crystallization of borosilicate glass, which leads to the quick increase in glass viscosity and retards the silver diffusion. Thermal dynamic analysis confirmed that the diffusion coefficient of silver in the copper- oxide-modified LTCC materials was largely reduced.