Paving the way for 3D AOI inspection

Author : Altus Group

03 November 2016

Koh Young and Altus first worked together in the SPI field 10 years ago, when 3D measurement of solder paste deposits were very much new technology.

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The systems were developed to a very high degree of sophistication allowing measurement of size, shape and volume of deposits, spotting trends before they reached a point where the solder deposit was outside the manufacturing process widow and led to failures, after reflow. 

Closed loop process control with the screen printers all but eliminated process related problems emanating from the critical screen printing process. This is of considerable importance with the ever decreasing size of components. 

While many customers felt that 2D AOI was “good enough” for their commercial application, with the ever increasing interest in 3D AOI technology, they also felt the need to benchmark the technology and were happy to participate in demonstrations of full evaluations. 

Metrology-based inspection provides repeatable results, false calls which frequently led to escapes are mitigated substantially by basing the inspection process on measurement.
Programming time and tuning times are also reduced significantly, the process of program creation is based on accurate measurements rather than subjective calls by the programmer on variable images.

3D AOI improves the measurement accuracy by providing true measurement of features and detecting features like “lifted leads” or slight changes in “co-planarity”. This enables the detection of process drift and allows correction of potential problems before they end up as expensive value added boards having to be scrapped.

Measurement accuracy is increasingly important within the electronic assembly industry with the ever decreasing geometry of components used in modern electronic assembles and the need to offer 100% reliable and traceable processes for critical applications, such as automotive, aerospace, telecoms, but is increasingly important to all manufacturers as they strive to improve reliability of electronic assemblies.

The development of 3D AOI inspection has led to a step change in product quality. Greater visibility of problem areas with the ability to measure features monitor process changes and take corrective action before the line starts producing failures.

Without this, process changes, such as screen print deposition go unnoticed, Boards are assembled and may pass 2D inspection, but with insufficient solder paste in some areas the joints may be prone to early life failure. In the worst case, they may pass functional test and be used in an assembly which end in in a critical part.

For example, the world’s leading car manufacturers do not want ABS modules causing brake failures in the field, where recalls and litigation cost could run to millions, so will insist on the sub-contractors making such parts from them to use SPI and AOI systems, which have been qualified after exhaustive testing. This sets the course of action to other users who do not have the same resources, but can follow this lead.

3D in-line Inspection AOI systems are able to run at production speeds, provide full fault capture, close loop feedback and real time data and full traceability to management.

Koh Young produced and launched the first full 3D metrology based Automatic Optical Inspection (AOI) system called Zenith. This development of 3D AOI systems utilised the same technology and allowed a level of inspection and measurement from the AOI systems which simply was not possible from the traditional 2D AOI systems which are still in use in many areas. 

Altus provides technical sales, applications and service support, which dovetails well with the philosophy of Koh Young, providing well-matched synergy between manufacturer and representative. This provides a very broad range of knowledge and skills. Altus is currently supporting more than 300 SPI systems in the Altus/Danutek Group regions of the UK, Hungary and Romania, and since the recent introduction of Koh Young’s 3D AOI system, more than 40 of these units also. 

Koh Young’s implementation of multi frequency Moiré technology allows the Zenith machines to inspect and make quantitative measurement of all components in three dimensions. This technology provides a strong technical lead and systems are manufactured to a high quality at cost effective prices, which meet the needs of the SME sector through to very high volume manufacturers operating multiple high speed manufacturing lines, 24/7, where downtime is unacceptable. Users are also able to select the resolution they need for their application, or to provide closed loop communications with upstream and downstream equipment.

Koh Young’s latest AOI development is the Zenith 9 Way, for the volume OEM or CEM manufacturer. It complements the existing Zenith 8 Way and Zenith LiTE offerings. 

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