Estimated reading time: 9 minutes

An Inside Look: 3D AOI of Electronic Assemblies Seminar

In an informative presentation on image capture and modelling technologies used in 3D AOI, Sean Langbridge from CyberOptics gave a more in-depth explanation of phase measurement profilometry, which was widely used for accurate and repeatable measurements in 3D solder paste inspection systems, although component height was a potential limitation in 3D AOI SMT applications. Multi-view 3D sensors gave improved capability; the example he showed consisted of four 3D sensors, with a single projector and a 2D camera. Five images were acquired simultaneously and merged together by parallel processing, using 3D fusing algorithms and reflection-suppression techniques to produce high-precision 3D images with sub-micron resolution at production line speeds.

Langbridge reviewed current image-analysis technologies. Algorithm-based systems were generally complicated to programme. They relied on libraries of pre-defined inspection tasks, and tuning these libraries to understand process variation was very time consuming. Statistical appearance modelling was a knowledge based technology that learned from examples and adopted a single analysis technique for all inspections tasks, giving a simple intuitive approach to SMT inspection. Useful inspection could be achieved within five to 10 PCBs and because the user did not have to anticipate defects, undesirable variation was detected. Autonomous image interpretation was an advanced modelling technique based on appearance modelling, designed to support low volume production and to operate with minimum supervision, with the ability to predict variability from a single sample.

Doug Jones from TRI Innovation reported the results of an assessment of the capability of a 2D + 3D AOI system to inspect 0201 chip components based on 03015 chip analysis. The system evaluated used a top camera with multi-angle red, green, blue, plus white lighting for clear illumination of component features, with four separate lighting phases for improved detection of component bodies, marking and solder, and dual laser modules for shadow-free 3D inspection and true 3D profile measurement including board warpage. Blue lasers enabled a high dynamic range whilst maintaining high inspection speed. Feature analysis and comparison were by algorithms analysing visible reflected light, enabling shape, colour, gradient, and location inspection, combined with image-based techniques.

Page 2 of 4

• < Previous Page
• Next Page >