Study On Manufacturability And Reliability Technology Of Embedded Passive Pcb Based On Fr4 Substrate Series

With rapid development of electronic technology, more and more passive components are used in electronic products. The trend of miniaturization and multi-functional electronic products are facing greater challenges. Embedded Passives PCB (EPPCB) is one of the key technologies for promoting performance and integration density of electronic products. According to ITRS, the growing demands of miniaturization, increased functionality, better performance and low cost for microelectronic products and packaging have been the driving force for new and unique solutions in system integration, such as system-in-package (SiP).By removing these discrete passive components from the PCB surface and embedding them into the inner layers of PCB, EPPCB technology can not only reduce the size and weight of the electronic products, but can also have many other benefits such as increased reliability, improved electrical performance and reduced cost. Specifically, due to their simplified structure and lack of solder joints, EPPCB tend to have considerably less parasitic inductance and potential higher reliability than surface-mount passives components. In this paper, aiming at the demand of high process compatibility, good manufacturability and high reliability of EPPCB, the key technologies of EPPCB are further studied.Firstly, the manufacturing process of EPPCB is further investigated, which including the manufacturing processes of embedded resistors and capacitors, laser trimmed of embedded resistors and formation micro via of embedded capacitors. The Design for Manufacturability (DFM) of EPPCB is study based on the above processes. The DFM analysis method of EPPCB is proposed,so that the DFM rules of embedded passives integrate into the DFM analysis of traditional PCB. In addition, the definition and compilation of DFM rules of EPPCB are presented in detail.Secondly, finite element method is used to study the process of embedded capacitor based on element birth and death technology and viscoelastic theory. The application of element birth and death technology in ANSYS software is introduced based on related theories and mathematical principles. The generalized Maxwell model is applied to describe the viscoelastic behavior of embedded capacitor, and the constitutive equations of generalized Maxwell model are obtained to calculate the viscoelastic deformation of embedded capacitor. The finite element model of central type and marginal type embedded capacitor are developed and employed to simulate the process of embedded passives with the application of element birth and death technology. The results of simulation process represent that the deformation of marginal type embedded capacitor is lower than central type. So the process reliability of marginal type is higher than central type. Then the residual stress field of process simulation is the initial stress field of the subsequent finite element analysis. The reliability of embedded capacitor is studied by coupling residual stress with accelerated thermal cycling. By comparing to experimental results, the simulation results show that the micro-via in the lateral substrate has been obvious deformed, and the stress concentration is found in the micro-vias, which will result in signal integrity problems and other reliability problems. In the subsequent uncoupling analysis, an assumption made for the finite element analysis is that there is not residual stress in the embedded substrate. The results of uncoupling analysis are not accord with practice and results of coupling analysis. So in the study of process and thermo-mechanical reliability, residual stress of embedded process must be considered.Finally, thermal design for an electronic product is developed based on EPPCB technology. The flow velocity and temperature distribution of system level simulation model are obtained based on Icepak software. And then the zoom-in method is used to develop the board level sub-model. So the boundary conditions of system level model are applied to the board level sub-model. According to two different layout schemes of embedded passives, thermal simulation analysis is also made based on Icepak software. Through comparing and analysis, the scheme of thermal design which meets the design requirements is obtained.