Study On Reliability Modeling And Test Technology For CNC PCB

Printed circuit board (PCB) is the main support of the electronic components and the provider of the electrical connection. Its reliability determines the quality and reliability of the electronic products. With the development of modern science and technology, PCB tends to develop towards higher reliability, higher density and smaller hole. However, for the PCB with high reliability and long life, how to assess the quality in acceptable time in engineering is also a lack of appropriate theoretical basis and method. Based on the National Science and Technology major projects, this dissertation mainly carries on a systemic research on the law of changing property of CNC PCB, reliability test technology, reliability modeling, statistical analysis and reliability assessment under the combined action of applied voltage, conductor spacing, temperature and humidity. This study is of great significance in theory and practical applications. The main contributions and conclusions of this dissertation are summarized as follows:By analyzing the failure of physical/chemical, it shows ECM is the main reason for insulation failure of PCB, which helps to realize reliability modeling and reliability test method. And based on performance parameters analysis, CNC PCB failure criterion is proposed, which provides a basis for reliability test and reliability analysis. Then the life distribution of CNC PCB is provided. It lays a basis for the reliability evaluation of CNC PCB.According to the defects of the existing humidity models for threshold, a humidity model reflecting the effects of the conductor spacing and bias is provided. Then a double stress accelerated life test is conducted, and the parameter estimation and model verification are carried out. The results show that the model well described the effect of bias stress and conductor spacing on the humidity threshold of CNC PCB. It provides reference for reliability design and environmental safety.Based on the failure analysis of CNC PCB, the accelerated model of CNC PCB is built under the action of temperature and conductor spacing. Then the double stress accelerated life test is conducted and the statistical inferences are carried on. The results show that the failure life distribution of CNC PCB is Weibull distribution, and the accelerated model well describes double stress on PCB and life feature.In the condition that the relationship model between ECM time and conductor spacing, and bias voltage has not been studied at home and abroad. Through the ECM failure mechanism analysis, a relationship model, which can effectively quantify the effect of conductor spacing and applied voltage on characteristic life of CNC PCB, is proposed under high temperature, high voltage bias and high humidity circumstance. Based on the accelerated degradation test data, the reliability statistical model of CNC PCB in multi-stress acceleration degradation test is established. Finally, CNC PCB multi-stress accelerated degradation test is conductor, and a verification of the reliability statistical model is carried on. The results show that the accelerated statistical model of CNC PCBs is correct and reasonable.In the background to improve the reliability of CNC system and its components, aiming at evaluating and protecting the reliability of CNC PCB, this dissertation studies the performance degradation rules of PCBs. Then the reliability statistical model of CNC PCB is built. The research results are meaningful for the application of reliability prediction and reliability growth of PCB.