The development of a low cost non-destructive inspection system for plating quality assessment of plated-through holes in printed circuit boards : a thesis presented in partial fulfilment of the requirements for the degree of Master of Technology in Information Engineering at Massey University
The status of printed circuit board inspection is reviewed with special focus placed on the existing techniques of assessing plated-through hole quality. The need for developing a non-destructive method for plated-through hole inspection has been identified and is the major objective of this research. The results of the investigation into various methods that could lead to this objective are presented. This investigation has been concerned with the application of image processing techniques and the leakage light detection method. The hardware and software requirements for automatic visual inspection of stuffed board components are established initially using available equipment from the Department of Production Technology. Image processing techniques are found to be capable of discriminating copper-plated and unplated surfaces using the difference in reflectance between the surfaces. This suggests the possibility of applying such techniques to assess the quality of through-hole plating. The leakage light detection method can be implemented to assess the plating coverage of plated-through holes. A low cost inspection system demonstrating the principle of leakage light detection has been constructed. This system is particularly relevant to the small batch manufacturers in the printed circuit board industry. The performance of the demonstration system has illustrated the simplicity and reliability of the design. It is concluded that the leakage light detection technology offers a practical low cost solution for non-destructive plated-through hole inspection.