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The market for rigid PCBs is estimated to be about 10x the market size for flexible printed circuits (FPCs). As a result, the equipment infrastructure is driven primarily by the needs of the rigid board market. This is true of both equipment used to fabricate the circuitry (image, etch, copper plate, AOI, etc.) and equipment used for component assembly (wave solder and SMT assembly).
Flexible circuits are often sold in multiple-up panels or arrays to facilitate the assembly of SMT components. Coordination between the desires of the assembly supplier and the fabricator can have a significant effect on costs based on material/panel utilization. Fabrication panels are generally larger (12”x24” and 18”x24” are common sizes in the U.S.) than assembly panels. Assembly panel sizes should be efficient subsets of fabrication panel sizes to optimize material utilization. The math for determining parts per panel becomes a bit more complicated since fabrication panels will have a “keep out” border around the perimeter of the panel for tooling holes, fiducials, and test coupons.
In addition to considerations for material utilization based on circuit fabrication panel sizes, the quantity of circuits on a given panel size will be a function of several other variables. These variables include: size of the circuit, components to be populated, registration requirements, and assembly equipment capability. Multiple fiducials per panel may slow SMT placement rate, but this tradeoff is often trumped by the yield improvement and/or rework avoided.
Editor's Note: This article originally appeared in the May 2016 issue of SMT Magazine.