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Combining 2D and 3D AOI Inspection Continued from previous page
Since true volumetric height
era is then used to capture the pat- tern of lines and any line distortions due to component(s) with heights greater than the PCB surface. Through phase-shift analysis, a 3D height map can be created, and the height can be measured on any point of this FOV. Finally, a color 2D image of this FOV can be applied to the height map to provide a realistic 3D rendered image. Digital projectors represent a
mature technology that has been in use since the early 1990s, and is now being used in a variety of applica- tions. The numerous technological advancements of digital projectors have allowed manufacturers to opti- mize the dynamic range projection capability. For example, through the control of appropriate software, the projectors can be digitally pro- grammed to project fringe patterns at multiple frequencies for greater inspection flexibility. As 3D inspection becomes more
widespread, the question arises whether 100 percent 3D inspection will be the most effective strategy for inspection, without the aid of 2D inspection. Many believe that this is not the case, and that 2D inspection still serves as a viable tool for compre- hensive inspection coverage on PCB assemblies. However, 2D inspec tion approaches have limitations, and that is where 3D inspection can shine.
2D Inspection One of the first advantages to
note when comparing 2D and 3D inspection approaches is the ease of programming 2D systems versus 3D systems.
information cannot be measured, 2D inspection systems are limited com- pared to 3D systems. The coplanarity of height-sensitive devices, such as BGA packages and leaded compo- nents, can be inspected in 2D using multi-angled colored lighting and side-angle cameras. However, these methods will be susceptible to an increase in false calls, a need for additional programming and cycle time, and possible escapes.
3D Inspection The primary advantage of 3D
inspection over 2D inspection is that it provides true volumetric height information. Coplanarity on lifted leads and other height-sensitive devices can be detected without diffi-
T
This 2D image uses YESTECH’s Fusion RGB, multi-angled colored lighting.
culty. Since height data can be meas- ured, AOI programmers can specify the precise height tolerance accept-
Page 61
able for a particular component. Using 3D inspection for coplanarity detection also provides a significant reduction in false calls versus the use of 2D inspection. However, there are also disad-
vantages of using 3D inspection sys- tems. 3D inspection approaches can- not check for printed part nomencla- ture, polarity marks, or color. Even with the use of multiple digital projec- tors, shadowing issues may still occur depending on circuit-board layout and the varying heights of adjacent com- ponents. Typically, additional pro- gramming steps are required to train components for inspection by a 3D system. The use of 3D inspection also results in increased cycle times, due to the extra time required by the pro-
Continued on page 65
Koh Young Technology, the global leader in patented true 3D AOI and SPI inspection systems, continues to develop best-in-class technology solutions to meet the emerging challenges of PCB design and assembly:
Koh Young’s Zenith 3D AOI inspection eliminates false calls, escapes, shadowing, specular problems, and helps you optimize your process;
aSPIre 2 from Koh Young America delivers 100% 3D Inspection of
2D side-angle image taken on Nordson YESTECH’s FX-940 AOI system.
Since 2D inspection approaches
have been around for many years, much time has been spent on the development of software interfaces and image processing to simplify the programming process. In addition, inspection cycle times are signifi- cantly faster since fewer 2D images are captured and processed. The camera, optics, and lighting used in a 2D system allows for inspection flex- ibility, where assemblies with small and tall components (i.e., SMT and through-hole assemblies) can be inspected at
the same time.
Inspection for printed nomenclature, polarity marks, and even color, can be trained and inspected easily in 2D. Multiple side-angle 2D cameras can also be used to inspect solder quality on J-Lead devices, and even part or polarity markings printed on the sides of through-hole compo- nents. Finally, the cost of a 2D sys- tem is lower in comparison to a simi- lar 3D system.
solder paste with unmatched speed and accuracy, for zero defect manufacturing goals;
The new KY8030-3 3D SPI system features a new hardware platform for greater robustness and reliability, plus the latest KY software platform, more powerful and with greater functionality, a true color display, and foreign material inspection.
Visit
www.Kohyoung.com Today to Learn More
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