Trends in the Industry
Apart from the vision technology itself, to which we will turn our attention shortly, there are a number of discernible trends in the industry which have a strong bearing of the possible success of vision companies and on the vision techniques which will need to be deployed to achieve the required functionality and to remain competitive.
These include the increasing demand for solder paste inspection to be integrated in the screening process (as a control function, rather than a QA function), the need for 3-D solder joint inspection, and the very stong demand for statistical process control functionality in all measurement systems. In addition, there is a trend toward compliance with the SECS/GEM. (Semiconductor Equipment Communications Standard Generic Equipment Model) CIM standard interfacing protocol. But, perhaps most problematic of all, there are the trends in PCB component packaging and assembly themselves. At present, fine-pitch gull-wing surface-mount devices (SMD) are prevalent. However, bump grid array, ball grid array, and flip-chip components are becoming more and more common. Inevitably, visual inspection will have to track the introduction of these new manufacturing technology with the consequent need to integrate non-visible light imaging techniques with visible-light inspection to provide a completely integrated inspection system.
In addition to the introduction of new robust vision techniques to solve emerging inspection and control problems, there is a strong trend in the industry for the deployment of vision to effect in-line process monitoring and control in the manufacture of PCBs. As a consequence, machine vision systems increasingly have to be able to achieve demonstrated accuracy, repeatability, and reproducability performances with strict industry-standard statistical process control parameters. In turn, this creates an urgent need for the adoption of acceptable benchmarking, characterization, and testing strategies for industrial machine vision.
Key Technologies for the Future Development of Machine Vision in the PCB Industry
In the previous sections, we noted that the electronics industry itself is evolving, with new PCB assembly and component packaging technologies being introduced. Consequently, it is difficult to predict what will be the required vision technologies in, say, three years time. However, one fact is clear: the industry continues to increased component densities and to increase pin-counts. Bearing in mind the trend toward in- line process control, we can make one reliable prediction: that very high-resolution image aquisition allied to very fast processing and analysis will be mandatory. Typically, both high-resolution line-scan and area-scan sensors will be needed and, increasingly, the use of colour image processing will be necessary. Furthermore, one can expect systems to exhibit a 1Gflop and 1Gbyte capability in order to deal with these speed and data requirments.
The increasing emphasis on pre- and post-reflow inspection of solder integrity will necessitate robust 3-D metrology (providing local object-centred measurements rather than viewer-centred range measurements) with a typical accuracy of 1 in 500. There will also be a requirement for reliable characterization and comparison of local shape of objects with complex geometry and reflectance properties.
One can also anticipate that the existing standard vision techniques, such as edge detection, segmentation, blob analysis, feature extraction (using, inter alia, 1-D and 2- D, grey-scale and gradient signatures), and classification, will remain key to the success of PCB applications. What will undoubtedly change, however, is that these techiques will have to exhibit demonstrated performances according to some benchmarking and characterization standard.
Moving away from the image processing and image analysis techniques to the equally important production and mechanical engineering factors, the availability and deployment of fast and accurate mechanical stages, with controllable illumination heads, is, and will continue to be, a critical aspect of successful systems.
Achieving Success in Commercial Machine Vision
Since this report is concerned with the competitiveness of industries which exploit vision technology as well as the scientific and engineering development of machine vision, it may be appropriate to spend a short amount of time to consider the critical success factors governing commercial and industrial success in the deployment of machine vision in the electronics industry. These factors are derived from the experience of a PCB inspection company which, over the last ten years, has successfully developed from being a university-based research group through a national R&D centre to being a highly-competitive company trading both in Europe and the USA and selling in to most of the major multinationals. Consequently, this section should be of interest both to RTD funding agencies, those responsible for technolgy transfer, and to vision companies themselves.
Unsurprisingly, there are two classes of success factors: those concerned with the underlying technology which enables machine vision to be deployed successfully to solve specific application problems and those concerned with the creation and support of a successful commercial venture. It may not gladden the hearts of the vision engineers and scientists, but the key message to emerge from their experience - and the experience of other companies in industrial machine vision - is that standard (and ageing) techniques are still the mainstay of successful systems but, perhaps more importantly and more remarkable, image acquisition, processing, and analysis itself accounts only for some 5% of a complete machine vision system; the remaining 95% derives from a mixture of mechanical and production engineering, targetted marketing, organizational and business management, and effective procurement strategies, such as outsourcing. |
