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PCBD-June2017

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64 The PCB Design Magazine • June 2017 by Dave Becker ALL FLEX FLEXIBLE CIRCUITS LLC CAD for Flexible Circuits ALL ABOUT FLEX To define and subsequently fabricate a flexi- ble circuit, a set of electronic documents known as CAD files must be created. These files contain all the data needed for each software-controlled machine to perform its required process step. The type of data a circuit supplier receives from a customer can vary widely. In some cases, the files contain a complete set of data to manufac- ture a one-up part. In other cases the customer may only provide a print or net list and request the fabrication house to provide a quotation for the design layout by creating the data needed to define the part number. In most of these cases, a CAD file is created and sent to the customer for review and approval. CAD engineers take a CAD file that defines a single part and panelize the data by creating a nested pattern repeated across the panel. Re- verse nesting and off-angle part placement may optimize material utilization, which is a con- stant cost concern. But this optimization needs to be balanced by ease of stiffener placement and component assembly. Part of the panelization process considers how to best apply manufacturing tolerance cor- rections such as artwork scaling as a compensa- tion for material dimensional changes resulting from etching, copper plating and coverlay lami- nation. Material thickness, percent etched and material types all contribute to determining fi- nal dimensions. These interactions combine to make initial estimates more art than science. Refinements occur as empirical data is gathered on individual part numbers. The CAD data is used to create all the elec- tronic files needed for the programmable equip- ment that fabricates the part as well as the phys- ical tooling. A few examples include:

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