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World of Industries 3/2020

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World of Industries 3/2020

Smart laser sensors

Smart laser sensors inspect finest details AUTIOMATION When manufacturing circuit boards (PCB), extremely high precision and high production speeds are required. Therefore, smart displacement sensors from Micro-Epsilon are used in pick-and-place machines. They perform reliable quality monitoring in the micrometer range and they are compact, precise, fast and digital. Whether it is smartphones, medical devices or machine tools – almost all electrical devices have a PCB. However, these devices are getting smaller, more efficient and faster whereas the development cycles are becoming increasingly shorter. This also means that the boards have to become significantly more powerful by using highly integrated components. Miniaturization of switches and individual components as well as ever increasing packing density are essential elements to fulfill the required performance. In order to ensure that current in the form of electrical energy signals or as information signals easily flows through the components, exact positioning of electronic components is crucial. With PCB manufacturing, these must not only be in the right place but also on the Author: Erich Winkler, Product Management Laser Triangulation Sensors, Micro-Epsilon Messtechnik GmbH & Co. KG, Ortenburg, Germany right level in order to properly connect them. For smooth function, the components must not be tilted. High requirements for the measuring system Sensors inspecting the position of highly-integrated components in the line must overcome a series of challenges. Primarily, these are high speed because of the highly dynamic production process, a small diameter of the focus due to extremely small components, and high spatial resolution due to minimal displacement changes that have to be detected. The smart optoNCDT 1420 laser triangulation sensors from Micro-Epsilon are designed for high-tech applications. These laser sensors measure without contact and do not affect the PCB or the highly-sensitive components. The non-contact measuring procedure enables the laser sensors to acquire and process the measurement values very quickly. Designed for dynamic processes In quality control of PCB production, the sensors are placed in such a way that they measure the PCB from above. A traversing system guides them over the PCBs and its highly-integrated components. With a measuring rate up to 4 kHz, they detect dynamic processes directly in the production line. The sensor’s compactness at just 46 × 30 mm and its integrated controller allow it to be integrated in restricted installation spaces. The smallest possible diameter of the light spot is just 45 × 40 µm, which enables high precision measurements on fine pins as the light spot can be sharply projected onto them. 18 WORLD OF INDUSTRIES 2020

The sensor measures on permanently changing surfaces Another essential prerequisite for reliable measurements on PCBs is a measuring procedure that can measure different materials, from plastics to metals, which is why the laser triangulation principle is the right choice. Therefore, laser sensors from Micro-Epsilon provide the innovative Active Surface Compensation feature. Particularly with a PCB, the sensor measures on permanently changing surfaces from matt black to shiny and reflecting targets, as well as from bright to dark. The ASC ensures that the exposure time adapts to the conditions presented by the respective measurement object. To determine the measurement values, the laser sensor projects a red laser point at a wavelength of 670 nm onto the target. The laser light is back-scattered in a certain reflection angle to hit the optical system of a CMOS line. With quickly changing objects from bright to dark, only a small amount of light would reach the receiving matrix without Active Surface Compensation. In contrast, the intensity would be too high when quickly changing from dark surfaces to shiny objects. In both cases, the result would be inaccurate or even useless. Therefore, the Micro-Epsilon sensor regulates the exposure time via the Active Surface Compensation and also the intensity of the light emitted during the measurement task in such a way that the reflection on the CMOS line is in the perfect range. Then the sensor calculates the distance values with micron accuracy via the three-point relationship between the laser diode, the measuring position on the object and the depiction on the CCD line. The values determined can be fed in as analog or digital output signal into the plant and machinery control system. Measuring scribe lines on PCB panels Another application in PCB manufacture is the scribing of predetermined breaking points into the panels for depaneling. A PCB consists of several panels or smaller PCBs which go through the production as one large PCB. This kind of bundling is necessary for production reasons since it simplifies board assembly. The scribe lines are about 400 µm wide. The scribe lines of PCB panels must be measured exactly. Here, the optoNCDT 1420 laser sensor is also used due its unique combination of speed and precision combined with an extremely compact design for this application. An optimal combination of functional properties Using modern sensors such as the optoNCDT 1420 laser triangulation sensor from Micro-Epsilon ensures quality improvements while reducing waste and saving money. The smart laser sensor reliably measures displacement, distance and position with a repeatability from 0.5 µm. Its extremely small measurement spot detects even the smallest of components such as pins on PCBs with high The smart optoNCDT 1x20 displacement sensors are specially designed for the high requirements placed by Industry 4.0 accuracy. With more than 4000 measurement values per second, this sensor is designed for highly dynamic processes such as those found in the electronics industry or in additive manufacturing. Its small design and the integrated controller enable easy integration into machines and systems even when installation space is low. The intelligent surface control balances the fluctuating intensity of the light reflected during the measurement process when color or brightness change rapidly. The intuitive web interface allows the user to operate the sensor. It offers predefined set ups for different measurement tasks. Furthermore, up to eight user-specific settings can be stored and exported. The video signal display, signal peak selection and a freely adjustable signal averaging enable the optimization of measurement tasks. The characteristics that the optoNCDT 1420 combines is as unique as its design, which received the Red Dot Design Award. Photos: Micro-Epsilon 01 Also the scribe lines of the PCB panels must be measured precisely – the smart laser sensor is ideally suited to this application due to its combination of speed and precision with a compact design WORLD OF INDUSTRIES 2020 19


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