This paper reports observations of defects in laminated eight layers of a glass-ceramic composite system fabricated by a standard low temperature co-fired ceramic (LTCC) technology. The layers were laminated at 3000 psi and 70 °C for 10 minutes and were fired at 850 °C for 15 minutes. Material characterizations of the green compact and fired substrate were carried out on density, surface roughness and microstructure. The crack and warpage of the substrate were related to the microstructure and densification process of the system. It was found that the presence of these defects could be due to a mismatch of the sintering kinetics of the glass-ceramic composite system and silver conductor materials which lead to the development of stresses which act on both materials. The detailed microscopic observation of the internal and surface defects is explained.