KiCad Flex PCB: Bend Regions, Drawings & Fabrication Outputs

KiCad can describe a flat flex design; the released drawing must describe its use

KiCad flex PCB design involves more than selecting a thin dielectric in Board Setup. The CAD files describe the flat electrical geometry, while the fabrication and assembly drawings explain flexible regions, stiffeners, coverlay, bend direction and the installed condition. A flat model that looks correct on screen does not establish bend life, local strain or compatibility with the intended assembly process.

Begin by defining whether the circuit bends once during installation, moves occasionally in service or undergoes repeated dynamic motion. Then agree the local construction and mechanical constraints with the fabricator. The material system, copper construction, layer arrangement and transitions affect the result. Do not turn a generic bend-radius rule into a guarantee for an unspecified stackup.

This page focuses on expressing those requirements in a KiCad-based release. The flex design and manufacturing guide owns the broader engineering decisions. The flex PCB manufacturing process explains how the construction is produced. Use both when the question extends beyond CAD representation.

Establish a region plan before routing

Sketch the circuit's flat outline and identify each functional region. Name flexible spans, bend zones, component areas, connectors and stiffened regions. Use stable region identifiers that can appear in the drawing, construction notes and engineering correspondence. A colored shape without a legend is easy to misinterpret when it becomes a monochrome print or a manufacturing plot.

Keep electrical copper layers distinct from explanatory drawing layers. A line that marks a bend axis is not automatically copper, a routed outline or a machining instruction. State its purpose in the legend and verify that it appears in the intended drawing export. Review the actual layer set rather than assuming every visible CAD object will be included in a fabrication package.

The region plan is also a useful review agenda. Ask which dimensions must be held, which materials are approved and which features need manufacturing compensation. Keep finished-product requirements separate from process adjustments. The fabricator should not need to guess whether a drawing value is a functional requirement or merely a preliminary designer assumption.

Describe local construction without overclaiming the CAD model

KiCad's board setup and layer controls help organize the electrical design and document a stackup. They do not by themselves validate a mechanically bent flexible assembly. If different regions have different finished constructions, supplement the project with a clearly labeled region table and cross-section drawings. Identify which information is represented natively and which remains in the released engineering documentation.

For a simple two-layer flex circuit, record the approved dielectric and copper construction, coverlay or other protective layers, adhesive where applicable, and any local stiffener. If a material name is not yet selected, mark that item as open rather than inventing a generic production stackup. Material substitutions can change electrical, mechanical and assembly behavior; review them as engineering changes.

Thickness values must carry a definition. The overall stiffened connector thickness is not necessarily the same quantity as the thickness through a bend zone. Likewise, a nominal film thickness does not include every layer in the finished laminate. A reviewer should be able to tell which layers are included in each dimension and where the measurement applies.

Refer to the official KiCad PCB editor documentation for the installed version's layer and board-setup behavior. Use the software to express the agreed design, then retain the region drawing as part of the release. Avoid describing a flat 3D preview as a flex simulation or a proof of repeated-bend reliability.

Prepare a bend-region drawing brief

Enter one CSV row per region with Region, Role, Thickness_mm and Radius_mm. The allowed roles are bend, flat and stiffener. Radius is required for bend rows and left blank for the other roles. This deliberately separates a local bend dimension from unrelated flat or stiffened portions of the circuit.

The worksheet reports the entered radius-to-thickness ratio for each bend region. It does not compare that ratio with a universal acceptance limit, calculate fatigue life or prescribe a safe radius. The value is useful as a dimensioned discussion point only when the radius definition, local layer construction, copper and movement conditions are understood. The illustrative example is not a recommended stackup.

Use the downloaded brief with your region drawing and the intended installed geometry. Include any unknown dimensions or material approvals in the accompanying enquiry. The worksheet does not alter KiCad files, transfer data to a contact form or perform a mechanical analysis. Direct engineering review remains available without completing it.

Route with the bend and the manufacturing route in mind

Discuss routing direction, conductor geometry and transitions with the fabricator using the actual construction and bend use. A route that is electrically convenient can place copper or a stress concentration in an unsuitable region. Components, holes, vias, pad transitions and stiffener boundaries all deserve deliberate placement relative to the moving or folded zone.

Do not replace a construction-specific review with a single internet distance rule. A one-time installation bend and a repeated dynamic application can require different decisions. Current carrying, impedance, shielding, mechanical constraints and available area can also compete. Record the design tradeoff rather than pretending that one layout pattern is universally preferred.

Use named keepouts and drawing annotations to communicate the agreed restrictions. After editing the layout, confirm that those restrictions still align with the region boundaries. A shifted outline or relocated connector can leave an old bend marker in a misleading position. Treat drawing consistency as part of the design check, not as cosmetic documentation added at the end.

Make the flat and installed views agree

The flat manufacturing view should define the cut outline, region boundaries, copper-layer intent and relevant dimensions. The installed view should show orientation, fold direction, mating interfaces and the radius or envelope that matters to the product. Identify the viewpoint so a top-view drawing is not mistaken for a folded underside view.

Include a cross-section for any region whose construction cannot be understood from the global stackup alone. Label the protective layers, copper, dielectric and stiffener with their actual functional roles. Clearly distinguish explanatory graphics from controlled dimensions. A polished illustration is useful only when the drawing references and notes remain unambiguous.

For a connector tail, state the contact-side orientation and the finished thickness relevant to the mating connector. Review any plating and insertion requirements against the exact connector specification. A flex tail can fit visually in a CAD model while having the wrong contact side, unsupported thickness or assembly orientation.

Export manufacturing data and explanatory drawings together

Fabrication layers, drill data where applicable, outline information and a fabrication drawing belong to one coherent revision. Inspect the exported files in a viewer and confirm that explanatory bend lines have not accidentally become machining features. Likewise, confirm that a coverlay or stiffener requirement has not disappeared because it existed only on an unexported user drawing layer.

The KiCad Gerber export guide covers the export operation. The PCB file-format guide helps distinguish manufacturing artwork from editable design files and assembly documentation. Specify what the supplier should manufacture rather than expecting a native CAD file to communicate every nonstandard requirement automatically.

For assembled flex circuits, the BOM and placement data describe only part of the job. Explain how the circuit is supported during printing, placement, reflow and inspection, and whether components are assembled before the final fold. The PCB Assembly service can review the assembly scope alongside the mechanical and fabrication information.

Use a representative prototype to test the installed requirement

A representative prototype can reveal handling, fit and movement issues that are difficult to infer from a flat drawing. Define what the prototype is meant to validate: installation fit, connector engagement, electrical behavior after folding, repeated movement under defined conditions, or another specific question. A successful visual fit does not automatically validate every service condition.

Record the tested construction, fixture, movement path and environmental conditions. If the production material, copper, thickness or mounting changes, review whether the earlier evidence still applies. Avoid treating all prototypes carrying the same project name as mechanically equivalent. The tested configuration and its limitations are part of the engineering record.

When asking RAYPCB for a manufacturing review, send the flat design, region drawing, intended use and unresolved questions together. This enables discussion of construction and process constraints before a quote becomes tied to an ambiguous stackup. State any customer-mandated material or acceptance requirements explicitly.

Questions about KiCad flex design