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PCB-Sept2017

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50 The PCB Magazine • September 2017 "Pay no attention to the man behind the curtain." This famous quote from The Wizard of Oz conjures up the image of Dorothy, the Tin Man, the Cowardly Lion and the Scarecrow discovering that the great Wiz- ard of Oz isn't as grand or as magical as he seems. He is in fact just a guy operating a bunch of controls behind the green curtain. Today, references to "the man behind the cur- tain" imply someone making decisions and making things hap- pen behind the scenes. Process engineering at EMS companies and PCB fabricators could be considered "the man behind the cur- tain." I recently spoke with Holly Olsen from Electronic Systems Inc. about the fact that customers rarely tour their PCB fabricators or EMS suppliers to learn the processes and challenges behind building this cus- tom engineered product. Without these visits, knowledge of some of the behind-the-scenes decisions that are made day in and day out to help en- sure the best yields are easy to overlook. Holly and I thought it would be in- teresting to touch on a few of the key processes and decisions that are made behind the scenes and are often invisible to the customer. Panelization The deliverable is an assembled printed circuit board. But throughout processing at both the EMS provider and the PCB fabricator, product is man- ufactured in larger panels and then broken down to the final product. Most EMS providers prefer to specify their own panelization. This al- lows them to determine fiducial size and location, tooling holes and break- off points that best suit their unique process and equipment needs. The size of the board, components that overhang the edge of the board, and board shape and thickness all play a part in the design of the ideal pan- el for processing. Similarly, the deliverable to the EMS company is an array of parts for their further processing. During the PCB fab process, the size of the manufacturing panel and the placement of parts, or arrays with- in the manufacturing panel is one factor that is adjusted depend- The Man Behind the Curtain FEATURE COLUMN: FLEX TALK by Tara Dunn OMNI PCB 50 The PCB Magazine • September 2017

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