Electrical and mechanical modeling of embedded capacitors

Integral passives have many advantages, such as: improving packaging efficiency and electrical performance, reducing the use of print wire board (PWB) real estate, eliminating assembly to board, minimizing solder joint failure and enhanced reliability. The objective of this research is to reduce the size and enhance the performance of a multi-chip-module (MCM) used in aerospace accelerometers and gyroscopes by incorporating all the discrete components into the low-cost printed wiring board MCM substrate. To achieve this goal, we intend to use the low temperature process to incorporate decoupling capacitors directly into the substrate during the PWB manufacturing process. Computer simulation and modeling of embedded capacitors were carried out to predict the capacitance range, fabrication tolerance, the interference between adjacent capacitors and the effects of via, etc. The commercial finite element software ANSYS was used for the modeling work, which includes electric and thermomechanical analyses of embedded capacitor with/without via, the interference between two adjacent capacitors. Attention was given to the effects of different dielectric constants and geometry of the embedded capacitors. FEM model provides a good picture about the distribution, electric performance and tolerance of capacitors for the design and manufacture process.