Printed Circuit Design & Fab - June 2008 - (Page 37)

DFA ing and processing capabilities. These advances account for one of the more important aspects in the accuracy of today’s AOI machines. An advanced feature is the capability of AOI machine to be able to check and detect shorts, especially those hidden under an IC. Inspecting and catching a simple open circuit using an AOI inspection is relatively an easy task, but an improvement in existing AOI machines would be the ability to find the hard to find opens, which may require more powerful algorithms and techniques. The alternative to AOI is human visual inspection, which is not acceptable in light of the growing complexity and reduced component sizes used on PCBs. For effective human PCB inspection, technicians typically must have 10 to 15 years experience visually inspecting PCBs, but regardless of experience, while progressing through the workday, an inspector will become tired and less efficient. As this occurs, carelessness can lead to an increasing number of board defects. That’s why advanced AOI is a “must” to provide OEM customers with the ultimate reliability in the inspection of their highly complex PCBs. pcd&f FiGurE 3. Current AOI systems feature two cameras at the top and bottom and one each on two opposite sides. tion, increasing detection sensitivity and accuracy of the system. But what’s missing and should be incorporated into future developments is a “grey test.” This feature measures the brightness level on the tip of an SMT pad to detect a defective condition, such as an incorrect amount of solder. This problem area could be improved by the use of different and perhaps better illumination sources. Finally, a good AOI machine has at least six cameras to inspect the top, bottom, right, left, front and back areas of a board, as shown in FiGurE 3. The quality of cameras has come a long way from those in the past, and are more powerful with considerably higher image captur- Zulki khan is president and founder of Nexlogic Technologies and can be reached at zk@nexlogic.com. MILLION GHz* * When tested with lab optimized and unrealistic PCB routings. My connectors are good to a My connectors are good to a BILLION GHz* TRILLION GHz* * When tested without thinking about the PCB Break-Out Region at all. My connectors are good to a My connectors are good to a GHz* * When tested with Final Inch® certiﬁed Break-Out Region PCB designs. 9 * When tested with lab optimized manufacturing processes and exotic materials. Samtec Final Inch® Break Out Region (BOR) PCB design recommendations that save design, development and validation time and resources and predict real-world performance expectations in real-world signal integrity applications. www.ﬁnalinch.com fina JUNE 2008 ® linch.com printEd circuit dESign & fAB 37 http://www.finalinch.com http://www.finalinch.com

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Printed Circuit Design & Fab - June 2008 Contents Our Line Market Watch Around the World Happenings ROI Tip Jar Interconnect Strategies Final Finish Forum DFA/DFT Signal Integrity From the Field DFA Fab Basics Drill Off the Shelf Marketplace Ad Index BGA Bulletin

Printed Circuit Design & Fab - June 2008

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