Modeling And Impedance Calculation For PDN On QFP Package Level

Among the modern electronic packaging structure,Quad Flat Package(QFP)is one of the most common types of packaging,and is widely utilized in contemporary high-speed and high-frequency circuits.Due to the complexity of the QFP package structure,its design has many problems such as long electromagnetic simulation time,many iteration cycles and high design cost.In order to solve these problems,it is necessary for the QFP package to be pre-simulated.that is to say,we need to predict initially the key parasitic parameters of it,and to give a reasonable design scheme within a certain error range before the QFP package structure is not designed.So this topic takes the QFP package type as the research object,models and analyzes the power distribution network of QFP package,and finally realizes the pre-simulation of QFP package.The main research contents are as follows:1.This thesis proposes a simplified model method for the actual model layout and the irregular shape of the QFP package.Based on this,the overall equivalent circuit model for the QFP package is built.The simplified method is as follows: Firstly,the QFP package is cut into two parts,the bonding wires and the Pin,and then equivalently modeled separately.Wherein,for the bonding wire portion,the lines are homogenized and equivalently arranged by determining the bandwidth,length,arrangement structure,number and radius of the bonding wire,and they are equivalent to a parallel metal round bar coplanar Line structure.For the Pin part,it has a homogenization process by determining the length,spacing,height,number and cross section of the Pin,and it is equivalent to a parallel microstrip line structure.Secondly,the bonding wire and the Pin establish the equivalent circuit model by using the multi-section RLC series-parallel structure.Finally,this thesis cascades two-port equivalent circuit model of the two parts,and builds the overall equivalent circuit model of the QFP packaging level.2.In the process of modeling QFP package power distribution network,it is difficult to extract parasitic parameters of bonding wires(coplanar lines)and Pin(microstrip lines)due to the coupling effect.So this topic designs a corresponding algorithm from the engineering point of view,which can be used to quickly extract the parasitic parameters of single or multiple coplanar lines and microstrip lines.First of all,for the inductance parameters of the coplanar line,it is necessary to calculate the self-inductance of eachcoplanar line and the mutual inductance between each two coplanar lines by empirical formula,to form an inductance matrix,and then to extract the total inductance of the coplanar line by the inductance matrix formula derived in this subject.Secondly,for the capacitance parameter of the coplanar lines,we take the SPICE capacitance matrix of unit length extracted as the basis,and calculate the total parasitic capacitance of the coplanar lines according to its number and length.Finally,for the inductance and capacitance parameters of microstrip lines,the core idea is to determine the minimum element and the fitting formula,and then to calculate the total parasitic parameters according to their respective rules of thumb.The algorithm proposed in this thesis has been verified,and the parasitic parameters of the bonding lines and the Pin can be obtained quickly within the range of error expectation.3.Finally,based on the GUI platform of MATLAB software,a rapid modeling tool for the QFP package is designed.This tool can quickly calculate the parasitic parameters and the impedance curves of the QFP package,and obtain intuitive and clear results,which makes the pre-simulation of the QFP package easier and faster.The modeling methods and tools in this thesis can effectively shorten the design cycle of products,improve the yield and profit of enterprises,and reduce the design cost of products.Therefore,this thesis has a wide range of engineering application value.