The Mechanism And Simulation Of Ingress Of Dust To The Mobile Communication Equipments

The reliability of electronic equipments depends on the structure of electric system, the performance of electrical components and the changes of surrounding environments, including interferences of electromagnetic field, temperature and operational manners of users. One of the most important factors influencing the reliability is environment. According to statistics,52% of failures on the electronic products were caused by environment effects, among which 40% were by temperature, 27% by vibration,19% by humidity and the rest 14% were by dust and salt-fog. Considering that the dust density is very high in China, it makes great senses to study the mechanism of ingress of dust when assessing the reliability of electronic equipments.Factors like structure and environments will affect the ingress of dust to the electrical equipments. According to the past studies of environments'effects to dust ingress, electromagnetic field and temperature field have less influence on the ingress and can be ignored, while the structure of interface has more effects. So this subject uses mobile phones on behalf of mobile communication equipments and divides into three parts to research the ingress ability of dust of different mobile phones'structures.The first part designs the experiment facility. Because acceleration of ingress of dust is needed in the experiment, specific facilities are necessary. According to the relevant criterions, the dust-box experiment facility is designed. The second part is to do experiments. To find out the suitable parameter of dust-box, experiments are operated to test the three environmental factors including the wide speed, time and density of dust. Besides, different experiments are also operated according to different numbers and structures of interfaces to acquire suitable parameters. The third part is the simulation study on this basis. According to the corresponding parameters, the finite element analysis software Ansys are used to do simulation.In summary, comparisons of experiment and simulation are done and the results appear basically similar at the circumstance of smooth interface of PCB board. And it comes to a conclusion that the dust in mobile phones will improve with the increase of speed, time, concentration, number and size of entrance, the decrease of number of exit and middle position of interface. Then the factors like the density of dust, number and size of interfaces, structure and the smoothness of PCB board of the mobile phone, have more influence on ingress of the dust while factors like time and position have fewer effects. By comparison and analysis, the results indicate that when designing the mobile communications equipments, it is possible to combine the finite element method with the experimental method to assess the reliability of the product.