Fatigue Life Evaluation and Test Method for Representative Printed Circuit Board

Different from the strength design method, the environmental design method is traditionally used for instruments and equipment, which relies more on the idea of statistical probability, and the failure mode and failure mechanism are not clear. With the development of computational mechanics and measurement methods, the modeling technology and measurement technology for the complex system of instruments and equipment have made great progress. The strength based design method has been applied in the development of instruments and equipment, such as the life evaluation method based on failure physics. In this paper, with the help of analytical method and finite element simulation numerical method, the stress analysis and life evaluation of typical instrument structure are carried out. Based on the equilibrium equation, geometric equation, constitutive equation and deformation compatibility equation of mechanics, the thermal stress on the solder joint is obtained, and the structural life is evaluated according to the S-N curve. The stress analysis of various packaging forms of shell under temperature cycling load is carried out by using the finite element method. There are some problems in the optical measurement method, such as the micro deformation image is difficult to collect, the micro speckle with high contrast and high adhesion is difficult to make, and the reflection of hemispherical solder joint is difficult to suppress. The micro DIC device suitable for micro thermal deformation measurement and the manufacturing technology of anti reflective micro speckle are developed. By making high contrast anti reflective micro speckle in the test area, the micro DIC test system combined with micro lens is used to measure the micro scale deformation near the solder joint of PCB, and the correctness and accuracy of the calculation model are verified. two kinds of commonly used fatigue life models are listed, and the fatigue life of typical packaged circuit board under thermal environment is evaluated. The above analysis method is verified by the means of test and inspection. Finally, master the fatigue life assessment and test verification technology of typical instrument structure under thermal environment. Realize the ability to carry out life assessment and test verification of typical instruments and equipment in thermal environment.