Flexible PCB Fabrication Capability
PCBELEC manufactures flexible printed circuits for compact, lightweight and bendable electronic designs, from single-sided and double-sided flex boards to selected multilayer flexible constructions. This page summarizes our flexible PCB fabrication capability, including supported materials, structural options, routing and drilling ranges, coverlay and stiffener solutions, impedance-related requirements and quotation-ready engineering considerations.
Use this capability page to review what can be manufactured, what conditions may require engineering evaluation, and what file details help speed up DFM review from prototype through production. For projects that combine rigid and flexible sections in one integrated build, a rigid-flex process path should be reviewed separately.
Flexible PCB Manufacturing Overview
This overview highlights the main flexible PCB fabrication ranges currently presented on this capability page, helping engineering and sourcing teams quickly assess whether a project fits the available manufacturing window before moving into detailed stack-up, routing, drilling and RFQ review.
1–16 Layers
Flexible PCB builds currently listed on this page cover single-sided, double-sided and selected multilayer flex constructions.
DuPont PI / Shengyi PI
Polyimide-based flexible laminates are listed as the primary substrate system for the fabrication capability shown here.
Single, Double & Multilayer Flex
Different board formats are supported with separate size and thickness windows depending on whether the construction is single-sided, double-sided or multilayer.
Down to 0.05 mm
Minimum board thickness for single-sided flex is listed at 0.05 mm ±0.02 mm, while finished thickness depends on layer count and final construction.
Down to 0.045 / 0.045 mm
The page shows multiple line-width and spacing windows depending on copper thickness, layer count and flex stack-up conditions.
Min Hole 0.10 mm
Published capability data also includes annular ring, PTH pad, blind via and capture pad values for more detailed fabrication review.
PI / PET Coverlay + Stiffener
Coverlay options and stiffener support are included, with stiffener notes currently limited to applicable PI and FR4 substrate-related builds.
OSP, HASL, ENIG & More
Surface finish options, air-gap capability and impedance-related support are listed as part of the current flexible PCB fabrication offering.
Detailed Flexible PCB Capabilities
The following table reorganizes the currently published flexible PCB capability data into a clearer engineering format. This first section focuses on stack-up scope, laminate choices, size limits and thickness windows before moving on to routing, drilling, vias, coverlay and finish details in the next tables.
Stack-up, Materials and Size Windows
Use this group to confirm whether the project fits the currently listed flex construction range before reviewing finer routing and drilling constraints.
| Capability Item | Category / Build Type | Published Range | Engineering Notes |
|---|---|---|---|
| Layer count | Flexible PCB constructions | 1–16 layers | Covers single-sided, double-sided and selected multilayer flexible PCB builds listed on the current capability page. |
| Laminate | Base material | DuPont PI / Shengyi PI | Polyimide-based laminate systems are shown as the primary flexible substrate options for the published fabrication capability. |
| Maximum PCB size | Single-sided flexible PCB | 480 × 4000 mm | Long-format flex builds should still be reviewed against handling, panelization and application requirements. |
| Maximum PCB size | Double-sided flexible PCB | 480 × 1800 mm | Final manufacturability may vary with copper weight, thickness target and structural reinforcement details. |
| Maximum PCB size | Multilayer flexible PCB | 236 × 600 mm | Multilayer flex size range is narrower than single-sided and double-sided formats because of stack-up complexity and process stability. |
| Minimum board thickness | Single-sided flexible PCB | 0.05 mm ± 0.02 mm | Minimum thickness values should be read together with copper selection, coverlay build and end-use bending requirements. |
| Minimum board thickness | Double-sided flexible PCB | 0.08 mm ± 0.02 mm | Practical thickness windows may change when reinforcement, shielding or special surface finish requirements are added. |
| Minimum board thickness | Multilayer flexible PCB | As per Gerber | Multilayer flex thickness is design-dependent and should be reviewed from the actual stack-up files rather than assumed from a generic nominal value. |
| Finished board thickness | 1–6 layer flex builds | 0.05–0.6 mm | This published range covers finished thickness windows for common lower-layer-count flex constructions currently shown on the page. |
| Finished board thickness | 8-layer flex build | 1.6 mm | Higher-layer-count builds should always be assessed together with stack-up intent, copper distribution and final rigidity expectations. |
| Panelization size | Manufacturing panel | 250 × 510 mm | Panel strategy should still be coordinated with part outline, process rails, breakaway needs and assembly handling requirements. |
Routing, Drilling and Via Features
This table summarizes the published routing, drilling and interconnection data for flexible PCB fabrication, including trace and space limits, drilled features, plated holes, blind vias and related dimensional tolerances.
| Capability Item | Condition / Build Type | Published Range | Engineering Notes |
|---|---|---|---|
| Minimum trace / space | 1/3 oz copper, 1–6 layer | 0.076 / 0.076 mm | Published values vary by copper thickness and layer count, so the applicable window should be selected with the final stack-up. |
| Minimum trace / space | 1/3 oz copper, 8 layer | 0.05 / 0.05 mm | Finer routing on higher-layer builds should still be checked against yield, copper distribution and registration requirements. |
| Minimum trace / space | 1/2 oz copper, 1–6 layer | 0.076 / 0.076 mm | Trace and space capability is influenced by copper weight, etching control and structure stability. |
| Minimum trace / space | 1/2 oz copper, 8 layer | 0.06 / 0.06 mm | Higher routing density may require tighter process control and should not be treated as a blanket value for all designs. |
| Minimum trace / space | 1 oz copper, 1–6 layer | 0.10 / 0.10 mm | Heavier copper typically increases routing constraints and should be reviewed with both current-carrying and manufacturability requirements. |
| Minimum trace / space | 1 oz copper, 8 layer | 0.065 / 0.065 mm | The published value indicates an advanced routing window, but final application still depends on stack-up feasibility. |
| Minimum line width / line spacing | General published minimum | 0.045 / 0.045 mm | This value appears separately on the source page and should be read as a best-case routing capability rather than the default standard for every construction. |
| Minimum annular ring | General plated-hole design | 4 mil | Final annular ring selection should still consider registration, drill tolerance and reliability margin in flex constructions. |
| Minimum hole size | General published minimum | 0.10 mm | This is the smallest stated hole value on the page and should be interpreted alongside the CNC drilling data listed below. |
| Minimum drilled hole | 1–6 layer, CNC | 0.20 mm (8 mil) | The page lists this as the CNC drilling value for common lower-layer-count builds. |
| Minimum drilled hole | 8 layer, CNC | 0.15 mm | Higher-layer builds may use different drilling constraints because of stack-up depth and registration requirements. |
| Minimum PTH size | General plated through-hole | 0.10 mm | This value should be coordinated with pad size, annular ring and finished-hole tolerance expectations. |
| Minimum PTH pad size | General plated-hole pad | 0.20 mm | Pad diameter must be matched with drill size and annular ring rather than selected in isolation. |
| Minimum blind via diameter | Blind via feature | 0.075 mm | Blind via feasibility depends on build-up structure, dielectric thickness and process route. |
| Minimum capture pad size | Blind via / interconnect feature | 0.175 mm | Capture pad dimensions should be checked with via geometry, registration and manufacturing tolerance. |
| Minimum solder mask bridge | Mask / isolation feature | 0.065 mm | On flex circuits, mask-related values should be reviewed together with coverlay and opening design intent. |
| Coverlay registration tolerance | Coverlay alignment | 0.10 mm | Coverlay registration is especially important near pads, bend zones and reinforcement transitions. |
| PTH hole size tolerance | Finished plated holes | ±0.038 mm | Hole tolerance should be evaluated with fit requirements, connector interfaces and final function. |
| Contour tolerance | Outline routing / profile | ±0.05 mm | Contour tolerance matters most when the flex outline interfaces with housings, slots or precision assembly features. |
| Outside dimensional tolerance | General / precision mold | ±0.07 mm / ±0.05 mm | The source page lists two tolerance levels, indicating different dimensional control windows depending on tooling method. |
| Minimum slot hole width | Machined slot feature | 0.50 mm | Slot features should be coordinated with overall contour design, reinforcement and component interface needs. |
| Pitch tolerance | Precision pattern / feature pitch | ±0.03 mm | Pitch control is especially relevant for finer interconnects and connector-related flex layouts. |
Coverlay, Surface Finish and Special Technologies
This table groups the currently published flexible PCB data related to coverlay protection, surface finish options, selected reliability indicators and special-process features.
| Capability Item | Condition / Build Type | Published Range | Engineering Notes |
|---|---|---|---|
| Air gap capability | Flexible circuit construction | Yes | Air-gap structures should always be confirmed from the actual design intent, stack-up and mechanical use case. |
| Solder mask color | Standard color options | Green, White, Blue, Black, Red, Yellow | Color availability may still depend on process combination, order type and special finish requirements. |
| Solder-stop coating / coverlay | Protective film options | PI and PET film | Coverlay selection affects flexibility, pad opening control and long-term reliability in bendable circuits. |
| Salt spray tolerance experiment | Published test reference | 24 hours | This value is best treated as a listed reference condition rather than a blanket field-life guarantee. |
| Bending resistance | FPC finished products | More than 30 times | Bending life depends heavily on bend radius, conductor layout, copper type, material selection and whether the design is static or dynamic. |
| Silkscreen color | Legend marking options | White, Black, Yellow | Final silkscreen selection may be limited by surface color contrast, coverlay color and marking clarity. |
| Gold finger pitch tolerance | Adhesive FCCL | ±0.05 mm | Connector-edge dimensional control should be checked together with finish type, contact geometry and final insertion requirements. |
| Gold finger pitch tolerance | Adhesiveless FCCL | ±0.03 mm | The tighter published value suggests better pitch control under adhesiveless constructions where dimensional stability is improved. |
| Surface finish | OSP | Available | OSP is listed as one of the current finish options for flexible PCB fabrication. |
| Surface finish | HASL | Available | Finish selection should still be matched to coplanarity, assembly method and flex structure requirements. |
| Surface finish | ENIG | Ni: 2–6 um / Au: 0.025–0.05 um | ENIG is listed with separate nickel and gold thickness windows for finish specification review. |
| Surface finish | Flash Gold | Ni: 2–8 um / Au: 0.025–0.15 um | Flash gold data is published separately and should be selected according to contact, bonding or other end-use needs. |
| Surface finish | Immersion Tin | Tin: 0.5–1 um | Tin-based finish choice should be reviewed against storage, assembly sequence and final reliability expectations. |
| Surface finish | Plating Tin | Tin: 1–10 um | Published thickness data indicates a broader tin-plating window than immersion tin. |
| Impedance-related capability | Differential impedance tolerance | ±6% | The source page lists this value separately under impedance tolerance and it should be read together with stack-up and trace-geometry control. |
| Special technology | Peelable solder mask | Available | Peelable protection is listed as a special process option for selected build requirements. |
| Special technology | Gold fingers | Available | Gold finger support is published separately from the general finish list and is typically tied to connector-edge applications. |
| Special technology | Stiffener | Only for PI / FR4 substrate | This condition is explicitly stated on the source page and should be preserved in the capability summary. |
| Special technology | Impedance control | ±10% | This appears under the special-technologies section and is best interpreted as a broader controlled-impedance capability statement alongside the tighter differential-impedance value listed separately. |
| Special technology | Rigid-flex PCB related build | Available for separate review | Projects that integrate rigid and flexible sections in one build should be reviewed through the dedicated rigid-flex capability path rather than treated as a standard flex-only board. |
Construction Options for Flex Circuits
Flexible PCB projects do not all use the same structure. Depending on routing density, bend requirements, assembly method and mechanical space, the most suitable construction may be a single-sided flex circuit, a double-sided flex PCB, a multilayer flex design or a reinforced build that should be reviewed as a rigid-flex or stiffener-supported structure.
Single-Sided Flex PCB
Single-sided flexible PCB is the simplest flex construction, using one conductive copper layer on a flexible substrate such as polyimide, usually protected by a coverlay layer. It is commonly selected when the design needs low profile, lower structural complexity and efficient routing on one conductor layer.
This construction is often suitable for compact interconnects, lightweight electronics and simpler bendable circuits where the signal count remains moderate and the mechanical path is clear.
Explore Single-Sided Flex PCBDouble-Sided Flex PCB
Double-sided flexible PCB uses conductive copper patterns on both sides of the flexible base film and connects them through plated holes where needed. This construction provides more routing freedom than a single-sided flex circuit while keeping the mechanical benefits of a flexible substrate.
It is typically used when signal density, interconnection count or layout constraints exceed the practical routing space of a one-layer flex circuit.
Explore Double-Sided Flex PCBMultilayer Flex PCB
Multilayer flexible PCB is used when a project needs additional conductor layers, denser interconnection or more complex signal organization than single-sided and double-sided constructions can provide. As layer count increases, size windows, thickness planning and process stability become more structure-dependent.
These builds should be reviewed with special attention to stack-up intent, layer distribution, drilling features, thickness control and the final mechanical use of the flex areas.
Explore Multilayer Flex PCB OptionsFlex with Stiffener or Rigid-Flex Review
Some projects need local reinforcement for assembly support, connector stability or controlled thickness in selected areas. In those cases, the build may still be a flexible PCB with stiffener support, provided the reinforced zones do not function as integrated rigid board sections.
When the design combines rigid and flexible sections into one integrated circuit structure, it should be evaluated as a rigid-flex PCB rather than a standard flex-only construction. That distinction helps define the correct fabrication path from the beginning.
Review Rigid-Flex PCB PathMaterials, Coverlay and Stiffener Notes
Flexible PCB manufacturability is shaped not only by routing and drilling limits, but also by the material system chosen for the flex areas. Base film, copper type, coverlay construction and local reinforcement all affect bend performance, thermal behavior, dimensional stability and the final assembly process.
Base Materials and Copper Choices
Polyimide is generally the preferred flexible PCB base material when the design needs stronger heat resistance, repeated flexing and better long-term reliability. PET may still be suitable for more cost-sensitive applications with lower thermal and mechanical demands.
Copper choice also matters in flex design. Rolled annealed copper is usually favored for repeated bending, while other copper options may be acceptable where flexing is limited and the structure is more static.
Read PI vs. PET GuideCoverlay and Protection Strategy
In flexible circuits, coverlay usually serves the protective role that solder mask serves on rigid boards, but it is often better suited to bending regions and moving flex areas. Proper coverlay choice and opening design can improve durability while still exposing pads for soldering and connection.
Flexible solder mask may still appear in selected areas or selected process routes, but coverlay is commonly preferred where the flex section must maintain mechanical endurance.
Read Coverlay vs. Solder MaskStiffener Selection
A stiffener is a localized reinforcement layer added to selected parts of a flexible circuit to improve mechanical support, connector stability, SMT handling or thickness control. The best stiffener material depends on the area being reinforced, the assembly process and the mechanical load applied during use.
FR4, polyimide and other stiffener materials should be selected according to whether the design needs rigidity for assembly, stress relief near connectors or support under component-bearing zones.
Read Stiffener Selection GuideWhen to Review as Rigid-Flex
A flexible PCB with local stiffeners is still a flex circuit when the reinforcement only supports selected functional areas and does not create integrated rigid board sections. This is common around connectors, SMT zones and insertion areas where local flatness or thickness is required.
If the project combines rigid and flexible sections into one integrated circuit architecture, it should be reviewed through the rigid-flex path instead of being treated as a standard flex board with added reinforcement.
Compare Stiffener vs. Rigid-FlexDesign and DFM Considerations
Flexible PCB fabrication capability should always be read together with design intent. A practical DFM review looks beyond nominal minimum values and checks how bend behavior, routing strategy, pad and via placement, coverlay definition, stiffener details and fabrication files work together in the actual flex construction.
Define Static and Dynamic Flex Areas Early
A reliable DFM review begins by clearly defining rigid areas, flex areas, bend direction and the expected bend radius before the build enters fabrication review. Static and dynamic flex zones should not be treated the same, because repeated bending requires much more conservative mechanical design than a circuit that is bent only once during installation.
Designs that do not document bending intent early often create avoidable risk in material choice, copper routing and thickness planning.
Read Static vs. Dynamic BendingMatch Trace Routing to Flex Behavior
Routing capability on a flexible PCB is not only about the smallest trace and space value. Trace layout through bend areas, copper distribution and the selected copper type all influence whether the design will survive handling and long-term use.
For repeated bending, rolled annealed copper is typically preferred because of its better ductility, while more static applications may allow broader material choices.
Read Bend and Routing GuideReview Vias, Pads and Mechanical Features Together
A proper flex PCB DFM review should verify via and hole placement, drill-to-copper spacing, pad support, coverlay opening alignment and the relationship between mechanical features and bend zones. Features that are acceptable on a rigid board may create fatigue or registration risk if they are placed too close to flexing areas.
This is especially important on fine-pitch designs, connector zones and boards that combine thin flex sections with localized reinforcement.
Review Common Flex Design MistakesClarify Coverlay, Stiffener and Stack-up Details
Coverlay openings, stiffener outlines, adhesive strategy and total flex thickness should be defined clearly in the fabrication package. Missing or vague stack-up information can lead to misalignment, unsupported assembly zones or incorrect assumptions during engineering review.
Flex stack-up planning should also keep bend zones, symmetry, reinforcement transitions and final thickness control in view rather than treating them as separate issues.
Read Stack-up Optimization GuideSubmit Complete Files Before RFQ and Prototype Review
Flexible PCB quotation and DFM review are more efficient when the design package clearly includes material intent, bend-area definition, stack-up, thickness target, coverlay details, stiffener information, surface finish requirements and any impedance-related constraints. Incomplete files force the engineering review to guess the build intent, which slows quotation and increases the chance of avoidable revisions.
For prototype builds, complete documentation is even more valuable because it shortens the loop between design review, fabrication feedback and the next design iteration.
Review the Flex PCB DFM ChecklistInspection, Testing and Reliability
Flexible PCB capability is ultimately validated through inspection, electrical verification and reliability-focused review. The most effective quality control approach checks not only conductor continuity and dimensions, but also the mechanical and environmental conditions that influence long-term flex performance.
Visual and Dimensional Inspection
Flexible circuits require inspection of outline accuracy, hole and slot quality, pad registration, coverlay alignment and overall surface condition before shipment or assembly release. Dimensional verification becomes especially important when the flex must interface with connectors, housings, stiffeners or tightly controlled installation paths.
On thinner constructions, small dimensional shifts can have a larger functional impact than they would on a conventional rigid board.
Review Manufacturing File RequirementsElectrical Continuity and Prototype Verification
Prototype validation should confirm electrical continuity, basic functionality and manufacturability before the design moves toward volume production. PCBELEC’s broader prototype guidance emphasizes that complete files, test expectations and DFM review all help reduce iteration time and improve build accuracy.
For flex projects, early prototype feedback is particularly valuable because electrical success alone does not guarantee acceptable bend or assembly behavior.
Review Flex Prototype GuidanceBend and Mechanical Performance Checks
Flexible PCB reliability testing commonly includes bend cycle or dynamic flex testing, along with peel strength evaluation where mechanical durability must be verified. These checks are important because real-world reliability depends on how the material system, copper behavior, bend radius and reinforcement strategy perform under repeated use.
Bend-related validation is most critical when the flex area is part of the product’s regular movement rather than a one-time installation shape.
Review Flex Reliability TestsThermal and Environmental Qualification
Flexible PCB reliability methods also include thermal cycling, thermal shock, humidity and moisture-resistance evaluation when the application requires broader environmental confidence. These tests help determine whether the selected flex construction can maintain adhesion, electrical function and structural stability under changing operating conditions.
The need for these checks becomes more important in automotive, industrial, wearable and outdoor-use environments.
Explore Reliability Standards and MethodsHandling, Fixtures and Process Validation for Assembly
When flexible PCBs move into SMT or mixed assembly, quality control must also address flatness support, fixture design, handling methods, reflow profiling and inspection strategy. PCBELEC’s flex assembly guidance highlights the use of carriers or support fixtures, warpage checks, flex-specific AOI setup and controlled thermal profiling to avoid damage during processing.
This means that reliability review for flex circuits does not stop at bare-board fabrication; it should extend into how the board will be assembled, inspected and handled throughout production.
Review Flex Assembly ChallengesQuotation and Project Support
Once the flex construction, capability window and DFM requirements are clear, the next step is to submit a complete project package for engineering review. Accurate quotation and faster feedback depend on how clearly the design files, stack-up intent and manufacturing notes describe the real build requirement.
1. Prepare core manufacturing files
Submit Gerber files, NC drill data, stack-up details, fabrication drawings and any project-specific notes needed for flexible PCB review. These are the main inputs PCBELEC highlights for quotation and production evaluation.
2. Clarify flex-specific design intent
Include the planned layer count, material preference, thickness target, bend areas, coverlay requirements, stiffener locations, surface finish and impedance-related expectations wherever they apply. This reduces engineering assumptions and improves quote accuracy.
3. State prototype or production goals
If the project is for prototyping, design iteration or volume production, say so in the request. Prototype-focused builds often need faster feedback loops and tighter coordination around DFM review, while production builds may require broader reliability and process planning.
Flexible PCB Capabilities FAQ
These answers address common engineering and sourcing questions related to flexible PCB fabrication, including structure selection, bend design, material choice and project review readiness.
What types of flexible PCB constructions does PCBELEC support?
PCBELEC’s current flex-related content covers single-sided flexible PCB, double-sided flexible PCB, multilayer flexible PCB and rigid-flex PCB manufacturing paths. That means project review should begin by matching the design to the correct construction type rather than treating every bendable circuit as the same product category. [web:2][web:7][web:10]
How do I decide between a standard flex PCB and a rigid-flex PCB?
A flex PCB with local reinforcement can still be treated as a flexible circuit when the stiffener only supports selected areas such as connectors or SMT zones, but a design that integrates rigid and flexible sections into one combined circuit structure should be reviewed as rigid-flex. This distinction helps define the right fabrication path, stack-up logic and mechanical review from the beginning. [web:26][web:40]
What is the most important bend-related design information to define before quotation?
A practical DFM review for flexible PCBs should clearly define rigid areas, flex areas, bend direction and expected bend radius before fabrication review begins. PCBELEC’s flex design guidance also notes that bend radius, coverlay design, copper distribution and stiffener locations are key checks before release. [web:14][web:10][web:52]
When should I use PI instead of PET in a flexible PCB?
PI is generally the better choice when the design needs stronger heat resistance, repeated flexing and long-term reliability, while PET is more suitable for lower-cost applications with less demanding thermal and mechanical requirements. Material selection should be tied to the real use case rather than chosen only on raw material cost. [web:45]
Does a flexible PCB always use solder mask, or is coverlay preferred?
Coverlay performs a similar protective function to solder mask on rigid boards, but PCBELEC’s flex content explains that coverlay is often the preferred protection method for flexible regions because it is better suited to bending and mechanical endurance. Flexible solder mask may still be used in selected situations, but coverlay is commonly favored in active flex areas. [web:48][web:49][web:52]
What files should be prepared for a flex PCB quote or engineering review?
PCBELEC’s manufacturing file requirements highlight Gerber files, NC drill data, stack-up details, fabrication drawings and related project notes as key inputs for quotation and production review. For flex projects, it is also important to include bend intent, material preference, thickness targets, coverlay details, stiffener information and any impedance-related requirements that affect manufacturability. [web:50][web:52]
How is flexible PCB reliability usually evaluated?
PCBELEC’s reliability testing content identifies bend cycle or dynamic flex testing, peel strength testing, thermal cycling, thermal shock, and humidity or moisture-resistance testing as key evaluation methods. The right test scope depends on whether the circuit faces repeated motion, environmental stress or higher long-term stability requirements. [web:64]
Why is prototype validation especially important for flex PCB projects?
Prototype review is especially valuable on flex projects because electrical continuity alone does not confirm bend behavior, reinforcement suitability or assembly readiness. PCBELEC’s prototype and assembly guidance emphasizes early DFM review, complete files, fixture support, warpage control and process validation before a design moves into broader production. [web:63][web:8]