Analysis And Design Of Thermal Performance And Thermal Fatigue For E-series Electronic Packaging Products

An exposed pad package, namely E-series package which has a large area ofexposed pad at the center of the bottom of package, is directly welded to the PCBboard using the solder. Heat produced by the chip mostly conducts to PCB boardthrough the solder, and finally to the air. So this kind of package has very goodthermal performance. However, due to the presence of a large area exposed pad, themechanical performance of the package declines. Therefore, thermal performance andmechanical reliability analysis for E-series products becomes an important studysubject in the R&D of products, especially the appearance of some advanced packageforms with small size, low cost, including single or dual-row quad flat no lead package(QFN), very quad flat no lead package (VQFN), area array quad flat no lead package(AAQFN), flip chip quad flat no lead package (FCQFN) and so on. At present theresearch of thermal performance and mechanical reliability analysis for theseadvanced E-series packages is quite few, the influence of material properties,geometrical structure and environmental conditions on thermal p erformance andmechanical reliability of these advanced E-series packages are studied even less.The content of researches basically includes the following two aspects:(1)thermal analysis for exposed pad packages.(2) fatigue life analysis for exposed padpackages. The model used was dual-row QFN package.Design of experiment based on the numerical simulation technology was used toresearch thermal performance and fatigue reliability of the dual-row QFN package,and to design the optimal combination of factors. First of all, ANSYS numericalsimulation software was used to analyze thermal performance and fatigue life of thedual-row QFN packages, and the single factor method was used to study the influencefrom the geometry, material properties and temperature load on dual-row QFNpackage. And then the design of experiment method was used to do factorcombination design, to find the best parameter combination.Orthogonal technological experiment based on the numerical simulation is usedto obtain some factors influencing thermal performance and fatigue life reliability ofproducts and to get the optimal parameter combination of factors. That makes usimprove both thermal performance and fatigue life reliability of packages in researchstage of products which plays an important role in research and design phase of newproducts.