Pb-free resistor for Pb-free LTCC system

There exist various stresses generated by the affects of the internal wiring in LTCC (Multi Layered Low Temperature Firable Ceramic Circuit Board). Because of these stresses, thick film resistor formed on the surface layer drifts after resistor trimming and this is an obstruction for the high density design. Authors performed the FEM (Finite Element Method) for the analysis of the stress and found that significantly lower thermal coefficient of expansion (TCE) of resistor than LTCC is effective to the resistance drifts. Based on the analysis results, highly reliable Pb-free low thermal expansion resistor for high density LTCC was developed. Using low thermal expansion of SiO2-B2O3-K2O as main glass, the wettability with glass is secured by coated K2O on the conductive material of RuO2. It was successfully achieved to satisfy both low thermal expansion and electric properties. The developed resistor is fired in the same temperature as the conventional resistors at 850 degreesC. The highly reliable Pb-free LTCC system is established by using this resistor.