Automatic PCB Inspection Systems

There are more than 50 process steps required to fabricate a printed circuit board (PCB). To ensure quality, human operators simply inspect the work visually against prescribed standards. The decisions made by this labor intensive, and therefore costly, procedure often also involve subjective judgements. Automatic inspection systems remove the subjective aspects and provide fast, quantitative dimensional assessments. Machine vision may answer the manufacturing industry\u27s need to improve product quality and increase productivity. The major limitation of existing inspection systems is that all the algorithms need a special hardware platform to achieve the desired real-time speeds. This makes the systems extremely expensive. Any improvements in speeding up the computation process algorithmically could reduce the cost of these systems drastically. However, they remain a better option than increasingly error prone, and slow manual human inspectio

An investigation of the influence of 3d printing defects on the tensile performance of ABS material

Recently, the popularity of 3d printing for industrial and consumer use has spread across many different sectors. For this reason, quality assurance of 3d printed parts is becoming increasingly important. The extrusion and layer-by-layer deposition of a polymer filament on the print bed can introduce defects such as pores and voids into the internal structure of 3d printed parts. The relation between 3d printing defects and tensile performance of 3d printed samples is studied in this paper. The study considers tensile specimens of acrylonitrile butadiene styrene (ABS) that were 3d printed by varying the infill strategy and percentage to simulate different levels of strength for the part. Before the tensile tests, the ABS samples were inspected by X-ray tomography to identify the presence of internal voids generated by the 3d printing process. For each sample, data and statistics about the internal defects were used for determining a relation with the tensile test results. The local deformation of the sample and the position of the final fracture were observed using a digital camera and digital image correlation (DIC). In most cases, the experimental results confirmed the matching between the presence of internal voids and the areas of high deformation. However, the position of the specimen fracture did not always coincide with the largest defects. Nevertheless, this study highlights the importance of non-destructive inspection in quality assurance of 3d printed parts when in-situ monitoring of the 3d printing process is not applied. Copyright (C) 2022 Elsevier Ltd. All rights reserved. Selection and peer-review under responsibility of the scientific committee of the Third International Conference on Aspects of Materials Science and Engineering

Nondestructive evaluation of 3d printed, extruded, and natural polymer structures using terahertz spectroscopy and imaging

Terahertz (THz) spectroscopy and imaging are considered for the nondestructive evaluation (NDE) of various three-dimensional (3D) printed, extruded, and natural polymer structures. THz radiation is the prime candidate for many NDE challenges due to the added benefits of safety, increased contrast and depth resolution, and optical characteristic visualization when compared to other techniques. THz imaging, using a wide bandwidth pulse-based system, can evaluate the external and internal structure of most nonconductive and nonpolar materials without any permanent effects. NDE images can be created based on THz pulse attributes or a material’s spectroscopic characteristics such as refractive index, attenuation coefficient, or the level birefringence present within. The evaluation processes for polyethylene gas pipes and amber specimens lack efficient and accurate NDE techniques while 3D printed polymer structures currently have no standardized NDE methods. The primary focus of this research is to determine and evaluate the use of THz spectroscopy and imaging as a NDE technique for a variety of polymers extruded mechanically and naturally. Results indicate the refractive indices, attenuation coefficients, and level of birefringence of several 3D printing filaments including copolyester (CPE), nylon, polycarbonate (PC), polylactic acid (PLA), and polypropylene (PP) may change depending on the printing parameters. THz spectroscopy is used to measure relative permittivity of printed ceramic samples with various sintering temperatures. THz imaging proves to be a successful method to diagnose print head misalignment in ceramic nanoparticle jetting printing processes. Proper diagnosis of surface level defects on polyethylene (PE) gas pipelines is achieved along with preliminary joint fault imaging and 3D visualization by creating an interactive detailed map of surface level defects. THz NDE imaging, combined with tailored refractive index matching materials, can construct tomographic images and 3D reconstructions of multi-million-year-old amber. Visual and THz birefringence images are created to determine stress direction within extruded PE and amber. These results suggest that THz spectroscopy and imaging have multiple confirmed uses in the NDE of polymer structures, both mechanically and naturally fabricated

Non-destructive evaluation of 3D printed materials using air-coupled ultrasonic technique

open3D printing for prototyping and component production has grown increasingly popular in recent years due to the improvement of available printers and cost reductions. One of the most widely used technologies is FDM (Fused Deposition Modelling), which involves depositing filaments of polymeric material in overlapping layers by extruding it from a heated nozzle. This has increased the demand for characterisation of these objects to verify their proper quality. Due to the non-use of a coupling agent, this technique allows for faster analysis and is an excellent alternative to traditional immersion or contact methods. This work, therefore, aims to apply and evaluate the effectiveness of the innovative non-destructive analysis technique of air-coupled ultrasound by applying it to this type of component. Various samples differing in size, filling density, infill pattern and induced defects were 3D printed, and excited with ultrasound probes by evaluating their effect on ultrasonic propagation in the samples

ARMD Workshop on Materials and Methods for Rapid Manufacturing for Commercial and Urban Aviation

This report documents the goals, organization and outcomes of the NASA Aeronautics Research Mission Directorates (ARMD) Materials and Methods for Rapid Manufacturing for Commercial and Urban Aviation Workshop. The workshop began with a series of plenary presentations by leaders in the field of structures and materials, followed by concurrent symposia focused on forecasting the future of various technologies related to rapid manufacturing of metallic materials and polymeric matrix composites, referred to herein as composites. Shortly after the workshop, questionnaires were sent to key workshop participants from the aerospace industry with requests to rank the importance of a series of potential investment areas identified during the workshop. Outcomes from the workshop and subsequent questionnaires are being used as guidance for NASA investments in this important technology area

Computer Vision Inspection And Classification On Printed Circuit Boards For Flux Defects

The manual inspection of Printed Circuit Boards (PCB) is labor intensive and slow down the production line. During the assembly process, the defective PCBs with flux defects if not detected and remove, it can create corrosion and cause harmful effects on the board itself. As such, an automated inspection system is very much needed to overcome the aforementioned problems in PCB production line. The main objective of this work is to develop a real-time machine vision system for quality assessment of PCBs by detecting defectives PCBs. The proposed system should be able to detect flux defect on PCB board during the re-flow process and achieve good accuracy of the PCB quality checking. The proposed system is named as An Automatic Inspection System for Printed Circuit Boards (AIS-PCB), involves design and fabrication of a total automation control system involving the use of mechanical PCB loader/un-loader, robotic pneumatic system handler with vacuum cap and a vision inspection station that makes a decision either to accept or reject. The decision making part involves classifier training of PCB images. Prior to ANN training, the images need to be processed by the image processing and feature extraction. The image processing system is based on pattern matching and color image analysis techniques. The shape of the PCB pins is analyzed by using pattern matching technique to detect the PCB flux defect area. After that, the color analysis of the flux defect on a PCB boards are processed based on their red color pixel percentage in Red, Green and Blue (RGB) model. The red color filter band mean value of histogram is measured and compared to the value threshold to determine the occurrence of flux defect on the PCBs. The texture of the PCB flux defect can also be extracted based on line detection of the gradient field PCB images and feature indexing by using Radon transform-based approach. The feed-forward back-propagation (FFBP) model is used as classifier to classify the product quality of the PCBs via a learning concept. A number of trainings using the FFBP are performed for the classifier to learn and match the targets. The learned classifier, when tested on the PCBs from a factory’s production line, achieves a grading accuracy of coefficient of efficiency (COE) greater than 95%. As such, it can be concluded that the developed AIS-PCB system has shown promising results by successfully classifying flux defects in PCBs through visual information and facilitates automatic inspection, thereby aiding humans in conducting rapid inspections

Automated visual inspection for the quality control of pad printing

Pad printing is used to decorate consumer goods largely because of its unique ability to apply graphics to doubly curved surfaces. The Intelpadrint project was conceived to develop a better understanding of the process and new printing pads, inks and printers. The thesis deals primarily with the research of a printer control system including machine vision. At present printing is manually controlled. Operator knowledge was gathered for use by an expert system to control the process. A novel local corner- matching algorithm was conceived to effect image segmentation, and neuro-fuzzy techniques were used to recognise patterns in printing errors. Non-linear Finite Element Analysis of the rubber printing-pad led to a method for pre-distorting artwork so that it would print undistorted on a curved product. A flexible, more automated printer was developed that achieves a higher printing rate. Ultraviolet-cured inks with improved printability were developed. The image normalisation/ error-signalling stage in inspection was proven in isolation, as was the pattern recognition system