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32 SMT Magazine • March 2017 In most cases, depending on PCB size and how they are panelized, any PCB that is thinner than 0.032" requires a pallet for the assembly process. This will help to ensure that the board doesn't bend or get damaged during manufac- turing. Pallet design is critical to appropriately support a flex assembly, and it's important to identify a supplier who understands the nuanc- es of flex circuit behavior in different machines. At Saline Lectronics, the manufacturing and engineering teams work closely with hard- ware vendors to design the ideal pallet for each specific flex assembly. In the case of double-sid- ed flex circuits, Lectronics' process engineers build the perfect pallet to accommodate top and bottom configurations. This can be tricky depending on the differences between the two sides, but a single pallet design is far more cost effective. Since flex circuits are so easily manipulated and extremely light, it can sometimes be diffi- cult to ensure that they remain flat on the pal- let. If the flex PCBA doesn't stay flat and fully supported under the component pads, the air cushion under the flex can act like a trampoline and cause components to bounce off during the placement process. To avoid this from happen- ing, Lectronics' specifies a certain material that holds the flex circuit flat during the assembly process to guarantee that components are being placed appropriately. "Pallets are the most important thing for flex circuit assembly," said Jason Sciberras, man- ufacturing manager at Lectronics. "Flex circuits are completely manufacturable if done right— design is right, panelization is right, and tool- ing is right. We've manufactured high-volume, complex rigid-flex assemblies with micro-BGAs, QFNs, and 0201s at 31,000 units per week. With the right support structure, it's easy to do." Pallets also help to ensure that the flex as- sembly is presented to the machines at a consis- Figure 2: Dylan Stringer, SMT operator, verifies the solder paste inspection results on a DEK Horizon 03iX SPI machine. SUPPORTIVE TOOLING: THE MAGIC INGREDIENT FOR FLEX CIRCUIT ASSEMBLY