Research Of Gold Bonding Wire Model For Power Amplifier Miniaturization

With the development of integrated circuits in recent years,electronic packaging has become indispensable in the application of device miniaturization,functionalization and integration manufacturing.Although there are many advanced forms of connection such as flip chip and wafer level package,wire bonding technology has become the mainstream form of device chip connection after years of development,with lower cost and more reliable process.Gold wire,with its stable chemical properties,good ductility and excellent solderability,accounts for the highest proportion of lead bonding in high-end electronic products.As the operating frequency of the system increases to GHz,the gold bond wire is no longer a simple transmission line,but exhibits RF characteristics in a variety of ways.The prediction of parasitic parameters caused by parasitic effect and the establishment of an accurate equivalent circuit model of gold bonding wire have become the research hotspots.Aiming at the precise modeling of the gold bonding wire,this paper studies as follows:Firstly,the research history of gold bonding wire modeling is reviewed,which reflects the significance of gold bonding wire modeling.Secondly,the geometric model of gold bonding wire was established by HFSS.The influence of different Flat area length,wire diameter,span,arch height and substrate thickness on transmission characteristics in 1-6GHz was simulated.It is found that when the thickness of the substrate and the diameter of gold wire are constant,the transmission loss of the gold bonding wire is positively correlated with the parameters which have great influence on the total length of gold wire by the span and the height of arch.The Flat area length,which has little effect on the wire bus length,is nonlinear.Therefore,the line parameters under each type are normalized to the total length.Then,a test system of gold wire bond line including vector network analyzer,test fixture and automatic test algorithm is designed to test a large number of gold bonding wire test pieces.At the same time,a set of calibration parts is designed based on TRL calibration principle,which is used for de-embedding calibration of test data.In establishing a single wire bonding line ? type equivalent circuit model of process,test the commonly used three kinds of wire diameter(1 mil,1.5 mil,2 mil)under different wire parameters of the eight kinds of linetypes,and the test data was embedded in the calibration and extract the equivalent circuit parameters.In 1-2GHz,2-3GHz,3-4GHz and 4-6GHz frequency bands,the least square method in data fitting technology was used to model the parameters of each equivalent circuit and the wire bus length.Then the model was compared with the measured data.In addition,on the basis of single gold bonding wire test board,eight types of parallel double wire test board with 150um-800 um spacing were designed and tested.After analyzing and simplifying the classical formula of double gold wire mutual inductance,the fitting formula of double wire mutual inductance varies with total length and double wire spacing is proposed.By using the fitting formula and the mutual inductance extracted from the test data of the test board,the mathematical model of the mutual inductance of parallel double gold wire bond lines was established,and the equivalent circuit modeling of double gold wire was completed.And based on Python,a double gold wire fast modeling tool is designed and a GUI interface is built.Two miniaturized power amplifier operating at 3-4GHz are designed by using the modeling tool.The two miniaturized power amplifier use different gold wire linetypes to connect the die with the matching circuit.The test results show that the equivalent circuit model of gold bonding wire designed in this paper can be used to guide the pre-simulation of circuit design,and has an important value in use.Finally,based on the concept of partial inductance,a 3D model of unparallel double wires with different linetypes is established.The mutual inductance extraction method of double gold wire under this condition is studied and the modeling of double gold wire is extended.