Electrical and mechanical modeling of embedded capacitors

Integral passives have many advantages, such as improving packaging efficiency and electrical performance, reducing the use of 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 multichip module (MCM) used in aerospace accelerometers and gyroscopes by incorporating all the discrete components into the low-cost PWB 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, interference between adjacent capacitors and the effects of vias, etc. ANSYS commercial finite element software was used for the modeling work, which includes electric and thermomechanical analyses of embedded capacitors with/without vias, and the interference between two adjacent capacitors. Attention was paid to the effects of different embedded capacitor dielectric constants and geometries. The FEM model provides a good picture of the distribution, electric performance and tolerance of capacitors for the design and manufacturing processes.