Issue link: https://iconnect007.uberflip.com/i/1073397
52 FLEX007 MAGAZINE I JANUARY 2019 Circuit Outline with Dimensions and Datum Features The physical outline of the finished circuit needs to be accurately documented to define the periphery of the flex circuit material rela- tive to the circuitry itself. The outline data is used to: • Directly singulate the circuits from a panel by soft tooling via numerically- controlled routing machines, cutting blades, lasers, or water jet cutters • Create hard tooling including steel-rule die-punch tools and/or Class A tool-and- die punch set technology The datum features are important reference points to facilitate measurement of the cir- cuit features, especially the outline. It is best if datum features are called out based on the part's internal physical features rather than its external features. This allows inspectors to base their measurements on real features rather than imaginary points outside the part. Multiple datum features are recommended if space allows. Multiple datum features are also important because flexible materials are dimensionally less stable than rigid materials used for cir- cuits. Features on flexible circuits, especially those of larger size, often move relative to each other, and the circuit may shrink or grow dur- ing processing making predicting the precise Figure 2: Example of an eight-layer rigid-flex stackup. Figure 3. Coverlayer openings.