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Which AOI method is best?

martys

#6489

Which AOI method is best? | 7 May, 2001

Which AOI imaging method is best for the post-solder stage- 2D or 3D?

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Eyal

#6491

Which AOI method is best? | 7 May, 2001

3D imaging refers to the acquisition of images from multiple perspectives using, preferably, multiple sources of illumination, while 2D imaging refers to the acquisition of an image from one perspective.

An AOI system with 3D imaging is able to acquire detailed multi-dimensional information regarding the properties of the elements that are mounted on the PCB as the basis for inspection.

The benefits inherent in 3D AOI for electronics assembly lines are most pronounced at the post-solder inspection stage where the topography of the components on the board may cause part of the components and their joints to be hidden from view using a single perspective. For example - a solder joint of a J-lead is mostly hidden from top-view when a single 2D top camera is used. With 3D multiple perspective imaging, an angled camera will see it. Even if 2D imaging is used from an angled perspective, part of the joints and part of the components will be still be hidden.

Using a 3D imaging method that acquires images from multiple perspectives enables the extraction of the 3D properties of each image element in order to enhance classification with reduced false alarms. If a board element is hidden from one perspective, another perspective will capture it and will cross reference to it. When the 3D AOI system�s algorithms have to judge, for example, the quality of the solder joint, the data extracted from one image can be matched and verified against the data from another perspective.

Overall, the data extracted from the multiple perspectives by employing multiple illumination sources better represents (or models) the real 3D properties of the elements on the board.

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tomgervascio

#6550

Which AOI method is best? | 10 May, 2001

It sounds like 3D imaging is much better at fault detection for partially visible leads like SOJ packages. Can any of the 2D systems actually do a solderjoint inspection on the outer rows of BGAs or is the angle too acute to accurately look at these. Is there a trade off in cycle times for a 3D versus 2D systems. I assume that 3D system would also need multiple cameras and lighting as well as more powerful processing/algorithms. How do most systems handle variations in part or PCB colorations. Suppose the board vendor changes soldermask or the cap vendors has variations in part coloration.

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Solder Paste Inspection