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Non-contact optical (visual) testing of electronic components

Non-contact optical (visual) testing of electronic components

Optical (visual) tests on small, complex components impose great demands on the tester. When the work is also carried out in a three-shift operating system, as happens at the Paragon AG Company in Suhl, Germany, a manufacturer of electronic components, the testing instruments must also satisfy special requirements regarding their ergonomic handling in addition to the technological demands. This is why eyepieceless viewing systems are used for visual testing by microscopy.

The high-tech company Paragon, founded in 1988, develops and manufactures system solutions for automotives, electronic solutions and buildings engineering through the symbiosis of electronics, mechanical engineering and software. The German sites are in Suhl, Heiden¬heim, St. Georgen and Cadolzburg, and the head office is in Delbrьck. The Suhl factory, which is the subject of the present report, focuses on products for in-car electronics. This starts with communications technology and goes all the way to the air quality sensors for air-conditioning systems. Paragon is, among other things, world market leader in the manufacture of air quality sensors for the automobile industry.

Thomas Gьnther from Paragon’s production management explains: “We manufacture here on automatic fabrication lines on which Vision Engineering’s instruments are also used for the visual monitoring. Firstly these optical inspection systems are used to check soldered joints in the SMD (surface-mounted device) area, and secondly they are also used to check modules and to repair them in the context of trouble-shooting. In addition they are also employed for the quality control of the mechanical connections in the context of the qualification of modules.”

Thus at Paragon the whole operation is a thorough visual checking. However, the test instruments also play their part in new developments. For example they are also used for process qualification steps and technological new starts, i.e. when a master component placement is made for a particular product, a 100% visual check is then carried out under the microscopic testing system.

About 15 optical inspection systems for visual testing are in use in the production facility at Paragon. The stations in the photo are also used for small repairs on the components.

Continuous use and ergonomics

The optical inspection systems that are used have been marketed in Germany by the English company Vision Engineering for more than 20 years and they differ significantly from classical microscopes. Marketing representative Walter Dirschl, who is responsible for supporting Paragon, explains that: “We regard ourselves as more than manufacturers of work equipments, i.e. the difference compared to classical microscopes lies in that fact that staff can work on these systems for prolonged periods, e.g. an entire shift as at Paragon. The user adopts an unconstrained body attitude and sitting position during the inspection work, as a result of which he/she does not suffer any neck and back problems and over-strained eyes or headaches.” Moreover, various lens systems were developed for electronics applications like those here in Suhl. For example a soldered joint can be viewed not only from above but all round from all sides. For Thomas Günther, the ability to inspect soldered joints in three dimensions and from all sides represents a great benefit. Technologically this is the decisive speciality of Vision Engineering’s test systems. In principle the microscopes are constructed like stereo microscopes. The only difference is that instead of the eyepieces, Vision Engineering has developed a “Projection Head”. Two beam paths are brought into this projection head. The latter then contains a disk on which about 3.5 to 4 million lenses are positioned by photo technology. Each of these lenses individually splits up the beam path and feeds it into the projection lens so it can be seen by the observer. This creates an optical image at a point where the microscopy can be carried out at a large working distance from the image. This is also a decisive advantage for spectacle wearers, because they can continue to wear them during the entire inspection work. For the same reason the instruments do not need any refraction adaptation either. This technology also completely eliminates the danger of infections caused by direct eye contact with the eyepiece by different persons.