Sunny Prospects – EckelmannAs energy prices continue to rise, the call for regenerative energy sources is growing louder. One of the fastest growing sectors among them is photovoltaics, in other words the generation of electric power from solar energy. Rapid technological progress has contributed to the fact that a widespread use of solar thermal systems is becoming increasingly affordable. Government funded projects, such as the German "100,000 Roofs" program, additionally stimulate the solar market. The key criterion in the use of solar modules is their efficiency factor. To achieve maximum power output, high demands are placed on the quality of each wafer produced for solar cells. The German company ECKELMANN AG meets this challenge with a newly developed wafer inspection system. High-resolution Gigabit Ethernet cameras from IDS and a powerful image processing application form the backbone of this system.
The Image Processing and Intralogistics department at ECKELMANN is currently developing a new test and inspection station for a customer who wants to equip several wafer production lines with the system. The production lines have a throughput of 3,600 wafers per hour. This leaves the station just about a second to not only inspect a wafer for flaws, chipping and edge defects, but also to measure the wafer's surface area and the angle of each chamfered corner. When the test and inspection station will be finished, more than two man-years of development work will have gone into camera control and image processing. "The trickiest thing has been to get the necessary accuracy at that fast throughput rate," summarizes Jan Helmerichs, one of the software developers in charge of the project. The work paid off: With the combination of a large field of view paired with high measurement accuracy and a fast throughput time of 0.8 sec, the German company estimates to have taken the lead over competitors.
In the new wafer inspection station, the camera is installed in a metal housing that is open at the bottom and has built-in lighting. During production, a rotary table positions the sawn silicon wafers below the camera for in-line inspection. The camera takes two successive images, each with different lighting. First the wafers are examined in red LED backlight to make through-cracks visible. While the camera takes the second image, the analysis software based on MVTec's HALCON is already segmenting the first image using grayscale operators. As image capture and analysis can be performed in parallel, this solution saves valuable time. The second image is taken using incident white light. Impurities and defects on the surface as well as non-throughgoing cracks contrast clearly under the diffuse LED lighting. This image is also used for measuring the wafer size and the chamfers at the corners.
The corporate philosophy is to flexibly customize standard components to the individual customer's needs. Consequently, the cameras have to not only meet the technical specifications, but yet another essential requirement: easy integration and expandability. Here is where the uEye demonstrates true excellence through the software development kit (SDK) that ships with every camera. The uEye SDK provides a ready-to-go interface for the HALCON software library that is used in the wafer inspection system. This greatly facilitates integrating the camera with the analysis program and ensures that all important functions are available. Besides interfaces for ActiveX, DirectShow and various libraries, the uEye SDK also features a direct programming interface (API) for accessing the driver in C++, C# and VB, for example. More than 20 ready-to-run sample applications complete with source code make it easy to get started with camera programming. Another major advantage is that all cameras of the uEye series use the same SDK, no matter whether they are USB or GigE based. Therefore no programming is necessary in order to switch to a different camera model. And that is an essential aspect in a future-oriented technology like photovoltaics, where it is important to be well prepared for any future requirements.
Author: Daniel Seiler, IDS Imaging Development Systems GmbH
ECKELMANN AG is an MVTec Certified Integration Partner