| Printed circuit board(PCB) is a kind of important carrier unit for electronic products function. The environmental worthiness of electronic products and electronic systems are highly depended on the performance of PCBs. Environmental worthiness is one of the most important quality property of products, which reflect the ability of the products to function normally or not to be damaged in any kind of environment in the total life cycle when they are exposed to some kinds of environments, and endure environmental effect they may meet.The tropic ocean environment has some features like high temperature with high humidity, high salt fog concentration of the atmosphere, and the fungus grow actively. High temperature and high humidity(damp heat), salt fog and fungus environment may cause significant problems like corrosion and aging to PCBs. To ensure the PCB components to function well and keep them exposed directly from those severe environments, conformal coating is commonly used, by spreading a kind of organic material on the surface of PCBs. Therefore, it is an important work to study on the environmental worthiness of these protective coating process and technology, in order to ensure these electronic equipments and systems used on ships which may work on the sea frequently to function well and with high reliability.In this paper, five kinds of typical PCB protective coatings and processes are used to conduct research work, environment test methods are formulated, testing and test result analyzing work are conducted too. Based on the test result, some suggestions are made to improve the protective process technology to enhance their tropical ocean environmental worthiness, and verification test are carried out by using re-produced PCB test specimens enhanced. The main work and achievement are generalized as follows.1.Due to the present situation of no test methods can be used to assess the tropical ocean environmental worthiness of PCB, in this paper, we make comprehensive analysis about the South C hina sea environment, which is typical tropical ocean environment, and its primary environment condition as well as its effect; Moreover, request of manufacturing standard PC B test specimens, and performance of parameters with their test methods were researched. Based on the work summarized above, the environmental worthiness test methods for PC B protective coating and process are carried out.2.Laboratory environmental test and 18 months XiSha tropical ocean environmental atmospheric exposing test are conducted, sensitive performance parameters of PC B specimens are periodically tested. By study on the the results of performance parameters changing regulation of PC B specimens, we found that under test condition of laboratory, salt fog is the conclusive factor that curse the PCB specimens corrosion and make performance deterioration, compared to damp heat and fungus factor. Under Xisha atmospheric exposing environment, all the PCB specimens performance parameters reduced to extremely worse situation after 18 month test.3.Some suggestions are proposed to enhance the tropical ocean environmental worthiness of PCB protective process, and these suggestions were taken by the manufacturer, new PCB specimens were produced, then verifying test were conducted to these new specimens. The test result shows that these new protective process has excellent performance under the same test condition of laboratory test, the visual evaluation and electric performance were all in perfect state, which means these suggestions are practically useful. |
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