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With the launch of the new Flex007 section in Design007 Magazine, we asked David Wiens, product marketing manager with Mentor, a Siemens Business, to tell us about their tools’ flex and rigid-flex design capabilities. As David explains, today’s higher-end design software tools are optimized for flex design, making workarounds a thing of the past.
Andy Shaughnessy: What are your customers’ biggest challenges in designing rigid-flex?
David Wiens: Engineering teams have designed advanced rigid-flex products for years using a series of workarounds to their EDA tools, often verifying with paper dolls. Rigid-flex designs require advanced stackup constructs (e.g., multiple outlines, each with its own stackup, and new materials). There are also additional rules that need to be applied, including bend/fold control with collision clearances, curve routing with arcs and teardrops, hatched plane fill shapes, component placement limits in flex areas, and fabrication rules around board stiffeners and coverlays. The workarounds naturally take longer to implement and often result in errors because the design must be checked manually. This can lead to a non-optimized product because once something is designed, nobody wants to go back and make ECOs. Some errors, such as copper micro-cracks, create long-term product reliability issues. Manufacturing is also a challenge. Design teams must align with their manufacturer to understand the costs of different rigid-flex structures—costs can go up quickly—and optimize the hand-off from design to manufacturing.
Shaughnessy: Tell us about the rigid-flex design capabilities in the latest versions of Mentor’s tools.
Wiens: Our solution supports flex, rigid, or rigid-flex with a common set of functionality. Native support for flex/rigid-flex extends across the flow, from initial stackup definition through design validation and manufacturing outputs, eliminating time-consuming workarounds.
It starts with an independent stackup for each rigid or flex element; these can easily be modified or overlapped. This approach limits the board outline and stackup modifications necessary when the shape of the board changes. With flex stackups, there are additional materials and layer types to model, such as cover layers, stiffeners, and adhesives. These materials are intelligent and are understood at design verification as well as the hand-off to manufacturing. Control of where bends occur is critical, so a bend area object defines the location, radius, angle, and origin. Attributes also define placement, routing (e.g., via utilization, trace corners, trace width changes, etc.) and plane metal (e.g., hatch/cross-hatch) rules in the area.
For place and route, each rigid-flex area has its own external/internal layers, so parts can be placed on any external layer (including flex regions and/or in cavities) with appropriate pads and openings automatically handled. During routing, true arcs are utilized to minimize stress fractures in flex regions, and they adhere to the constraint-driven, correct-by-design methodology for which we’re known. Curved teardrops are automatically generated and maintained dynamically. Due to the automation throughout layout, design changes are easy and safe.
To read this entire interview, which appeared in the July 2019 issue of Design007 Magazine, click here.