appeared in the polyscope 10/2012
This inspection system has been specially developed for the testing of initial samples, small series, prototypes and for setup control. It offers the user a great time advantage combined with an increase in quality and productivity. Automatic optical test systems - AOI - are primarily suitable for use with large lot sizes. The high acquisition costs, combined with the great teaching effort, pay off for this purpose.
The automatic detection depends on the quality and quantity of the “learned”. After the creation of a test program, good quality "pseudo errors" have to be entered, so that the automatic detection can improve learning. Experience shows that depending on the total number of components per board, the threshold for the economy of the AOI is 100 boards. As a rule, an AOI only really and reliably checks automatically and economically from 100 boards.
Manual inspection: magnifying glass or microscope are the tools
However, many of the optical inspection tasks do not fall within the scope of the AOI. With an initial sample test or with a small series of far less than 100 boards, the teaching effort of the automatic systems is very high. In the absence of alternatives, the assemblies are usually checked manually in such cases. If necessary armed with a magnifying glass or a microscope, one checks the existence, polarity and orientation of the components from memory or in comparison to a good sample or the layout plan.
In addition to a good memory, the test personnel need a high degree of concentration on the course of the inspection. Locating and checking targeted components also takes time to find the components on the board. As a result, there is still an uncertainty in the quality, as tiredness of the inspector increases the susceptibility to errors and there is no traceability of the visual inspection.
Man is the best "visual inspector"
The inspection system combines the competence of the inspector with an automatically guided and traceable inspection procedure. Nevertheless, the human being as an evaluating body is an important component. Thanks to the experience gained and the possibilities to react competently to unexpected situations, the inspector is superior to an automatic system without any «inspection program», especially for variable test tasks. The inspection system therefore supports manual visual inspection by transferring processes that can be automated to the computer.
Finding the components on the test object or preparing all the necessary information such as design, polarity, part number, etc. are the basis for the expert's assessment. The test personnel can be guided through the inspection automatically so that no component is forgotten. The inspection is also continuously recorded. The optical inspection with the test system thus optimally supports the processes and ensures the quality of the products and the cost-effectiveness of the test task.
The inspection system in detail
The inspection system consists of a hardware component and the inspection software EFA-Inspection. The photo station EFA-Picture-Touch is a good «all-rounder», which is designed for fast pictures with changing board sizes in the SMD and THT area. The scan solution EFA-Scan300 is particularly suitable for large boards with many small SMD components.
The software is at the heart of the inspection solution. Designed in accordance with the current program design, it offers the simplest, intuitive operation with the greatest possible variability. A project with coordinate data can be set up within a few minutes. It is not necessary to prepare the data beforehand - the inspection system understands over 200 different image and data formats. The software can also be used to quickly and easily merge coordinate lists and BOM files. The coordinate data can be easily linked to the layout plan.
System is optimized for small series
Other functions include variant management, the calculation of the coordinate data for use or even working without coordinate data based on a good sample. The test system could be specially optimized for small series inspections, so that recurring set-up and sequence functions run automatically. All the user has to do is take another picture of the next test object - and can inspect the assembly seconds later.
So that the test personnel can make an inspection decision quickly and safely, all necessary information can be displayed in an optimized manner. For example, the assembly plan can be shown on the picture of the device under test. Or the assessment is based on an alternating image display between the examinee and the golden board. Errors immediately catch the eye as a movement. Through the software-optimized, automatic alignment of the two images against each other, this alternating image is incredibly quiet, and the differences alone move.
Versatile use of the system with simple operation
The basis of the software concept for the inspection system is to create an intuitive system that allows even inexperienced computer users quick access. At the same time, however, a wide range of different test scenarios and variants can also be supported. The test system thus adapts to the existing inspection process of a company and can optimally support it.
True to this principle, you can choose one of a total of six inspection types depending on the test task involved. This covers both the classic initial sample inspection and an inspection according to image segments or according to selected areas. The inspection itself is carried out automatically and ensures that all relevant components or image sections can be displayed for inspection. The inspection results can be saved. These can also be documented permanently using a report or an Excel file. The software solution is a "living" system that has arisen directly from the diverse wishes.