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Proceedings Paper

Inspection of microchip mounting tolerances by 3D vision
Author(s): Stefan Behler; Martin von Arx
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Paper Abstract

We have designed and tested a 3D vision system for measuring microchip surface heights relative to a substrate. The microchip is mounted with an adhesive to the substrate. The goal is to check the thickness of the adhesive layer between microchip and substrate before it is encapsuled by a plastic mold compound. This thickness has a significant influence on the reliability and electrical performance of the microchip. The system consists of one camera, a telecentric lens and three semi-transparent mirrors (beamsplitters). Reference patterns on the microchip and the substrate are imaged and illuminated from opposite 45° angles. This yields sets of coordinates which are used to extract the orientation of the chip relative to the substrate. We found that the vertical resolution of the system is greatly influenced by the setup of the image processing system. In principle, the reference patterns are identical for all chips and substrates of a production lot. Thus, the reference needs to be learned only once on a particular chip. With this setup we achieved a resolution of 2 micrometer. On the other hand, if the reference pattern is learned for each chip individually, we achieved a higher resolution of 1 micrometer. However, learning the pattern for each chip individually is time-consuming and may not be applicable for an on-line production inspection system with 2 - 3 chips per second.

Paper Details

Date Published: 25 February 2008
PDF: 8 pages
Proc. SPIE 6805, Three-Dimensional Image Capture and Applications 2008, 680504 (25 February 2008); doi: 10.1117/12.764830
Show Author Affiliations
Stefan Behler, Oerlikon Assembly Equipment (Switzerland)
Martin von Arx, Oerlikon Assembly Equipment (Switzerland)

Published in SPIE Proceedings Vol. 6805:
Three-Dimensional Image Capture and Applications 2008
Brian D. Corner; Masaaki Mochimaru; Robert Sitnik, Editor(s)

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