Circuits Assembly - August 2008 - (Page 32)

Cover Story is 0.0008" (0.020 mm) higher than the dark blue region just southeast of it. The extent of bow in the whole BGA package can be seen by comparing the lowest point (dark blue) with the highest point (pale green near southeast corner): The difference is 0.0017" (0.043 mm). The “spike” is therefore about half as high as the highest points on the upwardly bowed edges of the BGA. Differences in elevation can be seen more easily by using the data to make a 3-D image that permits controlled exaggeration of the differences in elevation. The 3-D topographic image also can be rotated and tilted to provide a desired perspective. Figure 3 is the 3-D image of the plastic BGA package. The overall bowing of the package is very conspicuous in this image, and the surface “spike” caused by the void at the epoxy-die interface is clearly visible, and is enlarged in the inset. The color map at right shows the highest region is the red-brown region at the right end of the BGA. Figure 4 is the optical image and Figure 5 the surface topography of a printed circuit board measuring 1.989" by 3.038". The wide range of colors shows the board is warped, most likely in response to heat. When heat is sufficient to warp a board, it may also cause internal delaminations among the board’s innerlayers. Depending on the board structure and thickness, internal board delaminations may be visible in depthof-interest acoustic images. The Best of Our Industry is Coming In this surface topography image, white areas Together for You — are the components whose tops are outside of One Show … One Place! the level being imaged. The highest regions (shortest time-of-flight) are the red-to-black areas along the left edge. The lowest regions are the magenta portions along the top edge. The difference in elevation between the highest and lowest points is approximately 0.020". Differences in elevation are more pronounced in the 3-D image (Figure 6). GET INTERCONNECTED IPC Midwest gave me a great chance to meet new people from wellknown companies across the industry. We had a great exchange of ideas about the machines, products and processes we use daily.. Steve Black, Borisch Manufacturing, Grand Rapids, Michigan If you need to see electronics assembly or PCB equipment, you need to be at this show! DESIGN PRINTED CIRCUIT BOARDS ELECTRONICS ASSEMBLY TM Figure 6. 3-D surface mapping of the PWB. Keep up with global changes in technology, standards and customer expectations. TEST Sunday–Thursday, September 21–25, 2008 Renaissance Schaumburg Hotel & Convention Center Schaumburg, Ill www.IPCMidwestShow.org The new combination of the two methods – acoustic surface flatness measurement and acoustic imaging of internal features – creates a direct link between these two sources of data. By itself, measuring surface topography may reveal a location that needs in-depth imaging for a potential anomaly. Made simultaneously, the two methods reveal not only the anomaly, but the extent of 3-D distortion the anomaly has caused. n Tom Adams is a consultant at Sonoscan Inc. (sonoscan. com). circuitsassembly.com 32 Circuits Assembly AUGUST 2008 http://www.IPCMidwestShow.org http://www.IPCMidwestShow.org http://sonoscan.com http://sonoscan.com http://circuitsassembly.com

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Circuits Assembly - August 2008 Contents Caveat Lector Industry News Market Watch Talking Heads Screen Printing Better Manufacturing Auditing a Fabricatior Cutting Machine Programming Time Simultaneous Acoustic Imaging and Surface Mapping Tech Tips Soldering Test and Inspection Process Doctor Pb-Free Lessons Learned Getting Lean Component Advances Product Spotlight Ad Index Assembly Insider Techincal Abstracts

Circuits Assembly - August 2008

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