A number of PCB defects, though having passed successfully the defect identification procedure, can potentially grow into critical defects under the influence of various external and (or) internal influences. The complex nature of the development of defects leading to PCB failures demands developing and updating the data measuring systems not only for detection but also for the prediction of future development of PCB defects considering the external influences. To solve this problem, it is necessary to analyse the models of defect development, which will allow predicting the defect growth and working out the mathematical models for their studies.
The study uses the methods of system analysis, theory of mathematical and imitation modelling, analysis of technological systems. The article presents four models for determining the theoretical stress concentration factor for several types of common defects, considering the strength loss of PCB elements. For each model the evaluation of parameters determining its quality is also given. The formulas are given that link the geometry of defects and the stress concentration factor, corresponding to four types of defects. These formulas are necessary for determining the number of cycles and time to failure, fatigue strength coefficient.
The chosen models for determining the values of the stress concentration factor can be used as a database for identifying PCB defects. The proposed models are used for software implementation of the optical image inspection systems.
With the aim to compare methods for counting the number of lines of a raster matrix, intersecting a round mark image, and a number of pixels belonging to this image for measuring its radius, a numerical simulation is carried out in the present article. It is proved that the application of the method for counting the number of pixels belonging to the image of the round mark allows obtaining more than 30 times gain in the accuracy of this image radius measurement using the same equipment. The formulas proposed in the article are used for software implementation of non-contact vibration measurement systems.