Reliability of chip on glass module fabricated with direct printing method

To investigate the effect of the sintering temperature on the electrical properties of a chip on glass (COG) module, a screen-printed conductive circuit was sintered at various temperatures, viz. 150, 200, 250 and 300 °C for 30 min. An anisotropic conductive film (ACF) is a suitable bonding material for the interconnection between a device and printed circuit, because of the conductive particles within it. We expected that the conductive particles in the ACF would provide a good electrical connection and reliability in our study. The electrical properties of the printed Ag circuits improved with increasing sintering temperature. The conductive particles in the ACF were well deformed in between the Au bumps and printed Ag pads after the bonding process. The resistances of the interconnections drastically decreased with increasing sintering temperature. Also, the temperature–humidity reliability of the ACF was investigated by measuring the resistance after the temperature–humidity test (THT) at 85 °C and 85% relative humidity. After the THT, the resistance shows a tendency to decrease when sintered below 200 °C, whereas it increases when sintered over 250 °C. The increase in the resistance due to the effect of surface oxidation is negligible.

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► We investigated the feasibility of using printing methods to fabricate the COG module.
► We successfully fabricated the COG module using direct printing method and adhesive bonding method.
► We studied the hydro-thermal reliability of COG module fabricated by direct printing and adhesive bonding method.