Impedance Calculation For PDN Structure On Package Level

The packaging industry comes into a new era with the development of science and technology,and the working frequency of the IC in the chip and the performance requirements of the system are getting higher and higher.The volume of the package is getting smaller and smaller,and the form is getting more and more to accommodate the transmission of higher frequency signals.When the frequency of the signal through the package increases to a certain extent,the reduction in package size will have a greater impact on the signal.In order to analyze these effects,the package needs to be modeled.The modeling of the package is divided into thermal modeling and electrical modeling.Thermal modeling focuses on the thermal stability of the package,while the electrical modeling primarily analyzes the effect of the package on its internal signal or power supply.In recent years,with the further reduction of the package size,and the further increased of the operating frequency in IC,the internal electrical performance of the package has become the focus of packaging research,and the PDN research in package is the key of package modeling.However,the research on the packaging-level PDN is not common in current.We need to model and calculate the impedance of the packaging-level PDN,and study the impact of it throughout the system from the impedance curve to analyze the performance of the packaging-level PDN.Base on this key point,this paper makes a simple modeling of the packaging-level PDN,and estimate its impedance roughly,and then in the form of human-computer interace,the fast operation of the network impedance of the packaging-level PDN is realized.The basic unit models of the package-level PDN are bonding wires,power ground planes,vias,and solder balls.In this paper,these basic unit models will be modeled to calculate the partial impedance.For the bonding wire,this paper equivalents it with Multi-section ?-type equivalent circuit or T-type equivalent circuit.A number of bonding wires are equivalent to a circuit model similar to a small number of bond-equivalent models,and then through the empirical formula and data statistics to extract the circuit parameters of the components,finally,calculate the impedance of the bonding wire equivalent circuit according to the circuit and parameters.For power ground planes and vias,this paper models them together.The concrete method is to model the rectangular or isosceles right angle triangular power/ground planes of regular shape by the resonator theory;and then connect thesepower/ground planes which are formed by regular shapes to the irregular shape of the power/ground plane by virtual port connection method,and obtain the equivalent resonator model of irregular shape of the power/ground plane according to matrix operations;finally,connect the equivalent circuit model of the via to the corresponding port on the power/ground plane resonator model,and get the resonator model of any shape of the power/ground plane with vias by matrix parallel calculation eventually.The solder ball is a bridge between the package and the printed circuit board,it has a small size,therefore,it is equivalent to an inductive form simply when modeling the solder balls in this topic,and the inductance value is calculated from the empirical formula of inductance calculation in bonding wire modeling.The actual complex encapsulation structure is simplified in these modeling methods,thereby it can greatly reduce the time of modeling,estimate the impedance of the packaging-level PDN quickly.Finally,the impedance calculation of package-level PDN is concise and clear performance by the PDN rapid modeling tool,making the package simulation before produce more convenient.