Shrinkage matched cofireable thick film resistors for LTCC

One of the major advantages of low temperature cofired ceramic (LTCC) technology is the ability to integrate passive components such as resistors, capacitors and inductors into a monolithic package. Due to materials interaction during processing, it is challenging to develop cofirable resistor, capacitor and inductor materials. This paper describes the development of compatible thick film resistors for Ferro´s A6 tape system. The shrinkage behavior of the thick film resistors was matched to that of the tape material during firing. This shrinkage matching resulted in a distortion-free fired LTCC package with buried resistors. The resistor formulations were developed with sheet resistance in decade values starting from 10 Ω/□ up to 100 KΩ/□. The electrical properties of the resistors such as sheet resistance, TCR values, ESD stability and voltage handling were studied and found to be good. The microstructure development of the resistor during firing was studied using the scanning electron microscope (SEM). The electrical properties of the buried resistors such as sheet resistance, TCR, drift on ESD, and voltage handling capacity were studied for different buried levels of the resistor from the surface. The effect of firing time and temperatures and package design on the electrical properties of the resistors at different layers was also studied