2 years ago

Automation Technologies 3/2015

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Automation Technologies 3/2015


MACHINE VISION A 3 rd dimension to automated optical inspection The development of increasingly smaller components and integrated circuits requires both highly precise production processes and new, innovative methods of quality assurance. This includes the use of highresolution 3D line scan cameras. Company name: Chromasens GmbH Headquarters: Konstanz, Germany Employees: 55, Germany Products: Image capturing and processing systems About The reliability of integrated circuits in real application environments depends on the quality of the components, connections, and contacts which are used. This especially applies when connection technologies, such as wire bonds, are used with which the connections of an integrated circuit are connected to the electrical connections by means of extremely thin wires. High technological complexity The inspection of wire bonds normally consists of combined mechanical, electrical, and optical inspection. There are a series of defects which cannot be identified in the scope of a mechanical and electrical inspection, like the control of the height of the bonds, the assurance of sufficient spacing between the wire connections, recognition of detachment at contact points, discovery of missing connections, or dangerous contact points due to crossing bonds. In addition, the use of contact-based methods for quality inspection entails the risk of electrostatic and physical damage. On the other hand, optical 2D or 3D inspections prevent inadvertent damage and enable the inspection of additional components in the area around the connections, such as the solder quality. The use of optical inspection processes in the quality control is of high technological complexity. Traditional 2D visualisations only provide a top view of the wire AUTOMATION TECHNOLOGIES 3/2015

MACHINE VISION connection and are not sufficient for the extraction of 3D data. For example, visual microscopes used for the 2D inspection were supplemented with X-ray sensors or laser projection methods for the purpose of a three-dimensional image capture. 2D and 3D combined The latest generation of stereoscopic image capture systems offer clear advantage of combining the 2D and 3D visualisations in one camera. The 3DPixa color line scanning camera developed by the image processing specialist Chromasens is one of the most capable systems currently on the market. It is based on the stereo principle, whereas two images are captured from the same object. The system has an optical resolution of 5μm for 2D color visualisations, and 1μm for 3D image capture. This high resolution is the basic requirement for the inspection of wire bonds having a thickness of less than 1 mm. A further requirement for determining the exact condition of the bonds is optimal lighting. Lighting methods such as homogeneous LED white lighting contribute to producing high-quality 3D results. With the 3DPixa, 2D and 3D visualisations are individually captured by a single sensor, therefore requiring only a single light source. This technology is also independent of the lighting angle and lighting type, which greatly simplifies the design of AOI systems. Since the 3DPixa is a line scan camera, and not an area scan camera, it offers extremely fast image capture. A segment with great potential for line scan cameras is the automated printed circuit board inspection (Automated Optical Inspection) of unpopulated and populated PCBs. In this process, the correct assembly and connection of nearly all mounted electronic components, such as SMDs, IC chips, resistors, capacitors, and LEDs, are checked. Based on the line scan technology, the printed circuit board inspections can be conducted significantly faster than the previously used Moire projection method. The scanning speed further depends on the image size or height range. Longest line sensor on the machine vision market The measurements of critical components, such as the circuit path thickness or the integrity of bonding contacts, can be performed with 3D visualisation. Defective applications of solder, foreign particles, or possible incorrect positioning of components are also detected automatically. Laser markings are also identifiable integrated dark field lighting. In addition the color visualisation helps in fast recognition of production errors. The 3DPixa is suitable for PCBs with components of different heights. It enables a maximum scan speed of 1,360cm 2 /s with an optical resolution of 30 μm at a consistent height resolution of 5 μm. If higher resolutions are needed, such as 5 μm optical resolution with a 1μm height resolution, the scan speed is reduced to 35 cm 2 /s. This high-speed inspection is made possible by the intelligent GPUs (Graphics Processor Units) which assure real-time processing. A unique feature of the 3DPixa is its sensor. Being the longest sensor on the market is an advantage when it comes to line scan systems. The 3DPixa achieves high throughput not only through high speed; but also through high scanning widths. At a lateral resolution of 5 μm, a scanning width of 35 mm is possible. This is at least 3 times higher than any other 3D system on the machine vision market. Photographs : fotolia teaser 01 High-Resolution 2D image of Wire Bonds 02 3D point cloud of Wire Bonds AUTOMATION TECHNOLOGIES 3/2015


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