![]() Parts too close to the PCB board edge are at risk of being damaged during first or second side assembly processing without an SMT carrier. Pay attention to the edge step thickness whenever a carrier is designed. Many “odd-shaped” PC board layouts are not easily conveyed through SMT process equipment and carriers provide solid edge step features making smooth conveyance a non-issue. Ask the tooling provider to explain how they design and fabricate carrier fiducials to be robust and easily seen with your process equipment. Reflow carriers can provide the required or additional fiducials needed to achieve optimum stencil registration and SMD placement accuracy. Productivity is obviously improved as the quantity increases, but stencil-to-PCB alignment is reduced exponentially with each image added. Proceed with caution when deciding the number of images to place into one carrier. PCB boards are oftentimes received in a de-paneled condition and the reflow carrier is the only solution to conveying and processing the SMT assembly. Printing smaller images after de-paneling operations can improve yields when fine pitch devices are present. Improved Stencil Alignment after De-paneling Tension or pressure against these tapered pins is generated by utilizing flush-mounted “pushers” with varying spring K-factors (dependent upon PCB board thickness and stack-up characteristics) helping to maintain printed board flatness throughout the entire process. Utilizing tapered tooling pins located in the tooling holes of the circuit board (plated or non-plated), a wedge effect is created to secure the printed board to the PCB pocket during solder paste screen print, pick and place, and reflow processes. Threaded inserts may be utilized to secure the PCB board to the carrier within the reflow process. ![]() The specific design features chosen for a given SMT pallet are critical to minimizing warpage. SMT carriers prove to be really essential when processing thinner substrates, but quite often prove beneficial with substrates that are considered “thick”. Providing mechanical support throughout the entire SMT line (top and bottom assembly) can reduce warpage of rigid PCBs, rigid-flex boards and flex circuits that can significantly reduce yields. There is a short of items to consider when reviewing the advantages of reflow carriers and the design elements that are important. Whenever reflow carriers are being considered and/or evaluated, take the time necessary to remind yourself of the benefits of using an carrier and how you would want it designed. Oftentimes only mechanical support is considered when deciding to use of reflow carriers, but there are many purposes and advantages. This tool is not new to the electronic manufacturing industry, and it’s a proven part of designing a robust PCB assembly process. ![]() Reflow carrier is often an essential part of achieving consistent, highest quality success with new product introduction (NPI) or high-volume PCB assembly runs. Sometimes, rigid board assembly may or may not requires reflow carrier, but if you are working with flex PCB assembly, your SMT assembly absolutely requires it.
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