Thermo-mechanical reliability of embedded capacitors

The ever growing physical and functional integration need in the field of electronic on-board systems led to develop new printed circuit board (PCB) integration technologies. One of the latest consists in embedded passive components within the thickness of the board. Resistors, capacitors and inductors are built within the printed circuit board in the form of laminate layers instead of packaging being soldered on the surface of the board. This technology involves reconsidering reliability aspects regarding the integration of components in printed circuit boards. This work features numerical assessment of embedded capacitors in terms of thermo-mechanical reliability and electrical functionality. A printed circuit board model with different substrates and capacitor materials has been represented and submitted to reflow temperature profile. Different sizes of embedded capacitors are numerically tested in order to determine the influence of thermal conditions on component´s electrical values. First of all, a short bibliographical synthesis on numerical simulation of embedded capacitors has been performed. Under curing temperature profile a trend corresponding to a decrease of the component´s capacitance value is observed in literature. This decreasing value could be the effect of thermal deformation. Numerical simulations based on finite element analyses have been performed to investigate reliability models of embedded capacitors under thermal loading conditions. A printed circuit board with embedded capacitors has been modelled in three dimensions. Appropriate material properties have been applied to the embedded capacitor model. Thermal loading conditions have been applied to the simulated printed circuit board. The thermo-mechanical analyses developed allowed obtaining the deformation of capacitor´s electrodes and dielectric material. An electrical analyse will be then achieved to determine the change in capacitance value. Results pointed out that electrical para- eters evolution of components had a strong link with the substrate material of the printed circuit board and with the dielectric material from the capacitor itself. This study has been done in the frame of PCB² project, funding by French government (FUI project).