Rigid Flex PCB Design Rules Guaranteeing Reliable Products (2)

In-design inter-layer checks could lower errors that could be presented during the design process, consisting of the complying with areas:.

– Mask-to-pad, metal-to-coverlay, coverlay-to-pad.
– Gap/overlap between mask layers.
– Edge-to-edge space in areas such as the bend line to the part, via-to-bend line, and stiffener-to-bend location.
– Bend line/area to stiffener, pin and via, component.- Gold mask-to-coverlay, stiffener adhesive-to-stiffener, and pin-to-coverlay.
– Minimum overlap, such as when 2 geometries overlay by a minimum or more (e.g., solder mask overlay right into the transition zone).

Typical Rules for Compound Layouts

Mechanical restrictions.

Rigid flex PCB drive additional policies when the flex circuit is folded up or bent inside an enclosure. Generally, the mechanical engineer provides the bend line, bend radius and bend location to the PCB developer. With contemporary EDMD (IDX) user interface, this information can be automatically imported into the PCB design devices. These bend locations need developers to:.

– Prevent putting pads also near the bend area to stop peeling.
– Do not position vias or pins too close to stiffeners, to avoid shorting.
– Do not overlap bend areas with stiffeners, to stay clear of peeling.
– Prevent positioning vias in bend areas to prevent fracturing the substratum gradually.

Mechanical engineers define the limits for areas– rigid, flex, rigid– where the number of layers and therefore densities are different in each zone. However, they require added details regarding layer structures and density for the areas, layers above top and below bottom to precisely model the thickness of the last PCB assembly, and to perform collision checks before handing the design to PCB manufacturing. Examples of such layers consist of paste mask, coverlay, stiffeners, external copper, and other materials that impact general elevation, thickness, and bend efficiency.

Inter-layer checks.

For sophisticated flex and rigid flex PCB layouts, PCB developers should abide by brand-new design standards from the producers. These brand-new layers and surface finishes need detailed in-design inter-layer checks of nonconductive layers in rigid flex PCBs.With an accurate image, developers could execute a lot more exact DRCs, receive better feedback, and provide better data to the MCAD tool for fabrication. Not having these checks expands the design cycle. In-design inter-layer checks give a correct-by-construction method that stays clear of unnecessary design versions and, sometimes, expensive prototype develops. Tools supplying a photographic view of the stack-ups based upon various substrates allow designers to visualize the layout stack-up intent as it is being defined.


Routing on flex wiring usually calls for arcs within the paths. Most of the geometry on the flex portion, consisting of board overview, teardrops and routing, calls for arcs and tapered shifts. Group routing features should lug a group of webs (bus) across the flex, while easily locking to the contour of the flex/board rundown. PCB designers obtain modifications each day; including an added trace to a routed set of nets need to not force rerouting of the entire bus. Shifts in line sizes require tapering and all pad/via entry/exits be tear-dropped to reduce stress and anxiety at the solder joints. A lot of PCB design devices support push-and-shove routing, yet these abilities currently need to sustain push-and-shove with arcs in the traces.

As the intricacy of a flex or rigid flex PCB increases, the quantity of time a developer spends boosts as a result of manual checks. Today’s CAD tools should provide a means for developers to leverage new PCB fabrication methods without prolonging design time. The breadth and depth of in-design checks needs to cover 30 or more new flex and surface coating layers. Customers should likewise have the ability to integrate their own layers for the tool to check, so they do not have to wait for device updates.

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