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Process Control Strategies for EMS Assemblers Continued from page 62
many hidden joints, mostly as a result of BGA and QFN style pack- ages that are in widespread use. These parts absolutely cannot be inspected by the human eye or AOI cameras. The only way to properly monitor these components to identify process variation (solder voiding), monitor solder formation trends, and screen for solder-related defects (bridging, opens/head in pillow, insufficient and excess solder) is by using X-ray inspection.
Manual X-Ray. X-ray equipment is not just a
defense against defects such as opens or shorts before a board ships. Its greater purpose is used in process setup and development. In this case, x-ray examination of the solder joints provides a complete understanding of the interaction of the oven profile, the solder paste and its position on
the pad; it provides a firm under- standing of the solder profile. Measuring solder voids is a good example of gaining process knowl- edge about the interaction of the
oven and the paste/flux chemistry. 2D X-ray, while basic, can pro-
vide an EMS provider with 80 per- cent of the critical information regarding the process. The top-down views (2D) provide detail of the solder profile. Small EMS com- panies can benefit greatly by deploying a basic system to help them attain better process con- trol as well as to screen potential defects before the product ships. FocalSpot’s MiniV is a good example of an inexpensive 2D system which can provide quick and useful information to adjust the process and catch defects before they go out the door. For more advanced process
MiniV is an inexpensive 2D system which can provide useful information quickly.
development, solder defect screening such as head-in-pillow defects as well as failure analysis of boards that do not pass ICT, function test or perhaps returned product, a system which provides
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Oblique X-ray In spection such as FocalSpot’s Verifier Series can reveal further information, although 100 percent detail is still far away. Oblique viewing either by moving the PCB in 2 directions (tilt and rotate) or by moving the imaging train around the stationary PCB, the view of the solder joint can be seen in a 3D per- spective. This is made possible by instruments in the FocalSpot Semi- Automated Insight Series, which can determine solder shape, BGA com- pression, and fillet angles — all are more visible using Oblique viewing.
Post Reflow X-ray Critical Class III devices and
densely populated double-sided PCB assemblies require a major step up in x-ray equipment technology to effec- tively monitor these assemblies and screen for defects. One of FocalSpot’s partner companies, Matrix Technol - ogies GmbH (Munich, Germany), offers a line of high-speed dual mode inspection systems. For double-sided assemblies, the machine’s ability to view slices of overlapping joints allows the PCB to be fully tested. The
The many hidden solder joints on today’s PCB assemblies absolutely can- not be adequately inspect- ed by the human eye or AOI cameras.
Matrix X3 Series AXI x-ray system provides full handling, traceability, and advanced real time solder joint measurement and defect detection capability.
Final Visual Inspection Once the board is completely
built — including mounting of thru- hole assembly parts and connectors — the board will undergo a final visual inspection process and/or functional test prior to shipment. Most EMS providers, however, do not have func- tional test equipment necessary to test the product before its packaged and leaves the facility. A simple tool to use on the production floor is a Digital Scanner to provide a compari- son between a Reference board (or Golden Sample) and the boards built. Such a tool performs a digital scan and permanently stores an image of the entire card for permanent storage and traceability. This can be useful later, since once the board leaves the facility, it is gone forever, unless it’s returned as a result of the OEM find- ing a problem with it. Using FocalSpot’s FA Comparator, the oper- ator is able to see two simultaneous images of the PCB, the board under inspection and its reference board. Today, when operators are visually inspecting a board under a microscope they are only looking at one board, while trying to remember what is sup- posed to be where. That’s pretty hard to do for multiple hours a day. By deploying a host of practical
inspection technologies EMS pro - viders can improve their yields, bot- tom lines and enjoy stronger cus- tomer satisfaction. Contact: FocalSpot, Inc.,
9915 Businesspark Ave., Ste. A, San Diego, CA 92131. % 858-536-5050 fax: 858-536-5054 E-mail:
sales@focalspot.com Web:
www.focalspot.com r
See at IPC/APEX Booth #3009.
VOCs VO VOCs VOCs VOCs
s VOCs VOCs VOCs s VOCs VOCs VOCs
Cs VOCs VOCs VOCs Cs VOCs VOCs VOCs Cs VOCs VOCs VOCs
OCs VOCs VOCs VOCs OCs VOCs VOCs VOCs OCs VOCs VOCs VOCs VOCs VOCs VOC VOC
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