The sintering behavior of LTCC (low temperature cofired ceramics) chip couplers was investigated in relation with Ag diffusion at the interface of glass ceramic substrate-Ag electrode. Sintering temperature was in the range of 825$^{circ}C$-975$^{circ}C$. The commercial green sheet and silver electrode were used. Below 875$^{circ}C$ the diffusion of the Ag ion into the substrate and the penetration of glassy phases into the electrode occurred due to an increase of fluidity. Thus the lectrode line was severely deformed and damaged. At 975$^{circ}C$ the transformation of crystalline phases into glassy phases and the melting of the Ag electrode resulted in the diffusion of the considerable amount of Ag ions.