Total vision proficiency increases bonding quality

Citation

(2005), "Total vision proficiency increases bonding quality", Assembly Automation, Vol. 25 No. 2. https://doi.org/10.1108/aa.2005.03325baf.003

Total vision proficiency increases bonding quality

Total vision proficiency increases bonding quality

Keywords: Machine vision, Assembly, Electronics industry

In the microcosm of bonding technology, many image processing problems are intensified and multiplied. To ensure precise bonding, the minute dimensions of the chips require strong magnification in image capturing and high-quality imaging systems must fulfil specific requirements. In comparison with normal image processing, the problem issues of illumination, contrast, distortion or depth of focus are intensified. The contrast qualities of the chips, of their coated surfaces, patterns and textures, may exhibit great dissimilarities due to material related properties. With these small- sized chips, minute tilting can for example have a considerable effect on the quality of the image with regard to contrast.

The highest demands are imposed upon the image processing systems used in this critical production technology and Dr Ing. Farhad Farassat, Managing Director of F&K Delvotec Bondtechnik GmbH in Munich explained, “We have to work with a fiftyfold magnification and the precision and process safety of the image processing system are extremely important to us”.

The decision to use integrated machine vision from Cognex was primarily based on the reliable vision tools and the high-precision results of the vision algorithms down to the sub- pixel region. It was also necessary to be able to handle the very short cycle times safely. The main task of image processing in machines for die- and wire-bonders is the exact determination of the position of the chips together with their patterns, edges, circles and drill holes. The Framegrabbers from the MVS-family from Cognex could be embedded in the UNIX real time processing of the machines.

Using the powerful PatMax^® vision software package, this geometry- oriented vision software is clearly different from that of the other competitors. With these patented methods, characteristics such as contours with low contrast can be identified a great deal faster, far more accurately and with greater reliability. On the basis of a partial contour, PatMax will for example, immediately recognise where to find further features despite distortion, displacement, or covering. It is no longer necessary to conduct a linear analysis of the complete plotted image. This simplifies the identification of features, and it makes the vision-system very fast, flexible and reliable.

Delvotec is achieving a measuring accuracy of 1/50th of a pixel by using PatMax and cycle times from 30 to 50ms for the complete process from searching to result are mastered. Regarding exact positioning, pattern quality and the reference pattern, the value of 1mm is attained, which is an important contribution to process quality. Different illuminations are necessary in the machines, corresponding with the parts to be manufactured and all the lighting systems, such as red, blue, or white light, lateral light and incident light have to be guided directly with the image processing system. This is also accomplished using PatMax.

Corresponding with the excellent results, the latest fifth generation F&K Delvotec machines are being equipped with PatMax and the high-performance hardware from the MVS 8000 family. The new bonder-series 64/66000 G5 can process thin wires of 17μm, as well as thick wires of up to 600μm diameter on one single machine. The speedy replacement of the bonding head allows maximum flexibility and cost-savings in a very broad field of applications. Furthermore, the bonding quality is also increased. In the processing of 17μm thin wire, this means for example, that only minimal gaps of 2- 3μm can be achieved between the bonded wires.

Approved partnership

The PC-based vision systems from Cognex have been integrated at Delvotec since 1996. During that time, around 2,000 machines have been equipped with both Cognex hardware and software and more than two-thirds of those machines went to non- European markets. All new machines are being fitted with the efficient vision- package PatMax, which not only allows very convenient programming of complex requirements thanks to the graphically supported user-interface, but it also allows access to the precise localisation of objects, even under very difficult conditions (Plate 3).

Plate 3 The newest 5th generation bonding machines 64/60000 G5 are also being equipped with the hardware and software from Cognex. Here the powerful features of PatMax^® have proven themselves

For further information visit Cognex web site: www.cognex.co.uk