Impedance-Specified Bare PCB Manufacturing
Controlled Impedance PCB Fabrication
Bare PCBs manufactured to your specified impedance targets, materials and stackup requirements. PCBELEC reviews the construction and finished conductor geometry, with coupon coverage, TDR verification and reports defined for the order.
Send your board files, stackup and impedance table to sales@pcbelec.com
- Impedance Modes Single-Ended & Differential
- Manufacturing Preparation Stackup & Geometry Review
- Order-Defined Verification Coupons, TDR & Records
Targets, Structures & Order-Defined Verification
Controlled Impedance PCB Capabilities
PCBELEC supports impedance-specified multilayer PCB fabrication for high-speed and RF designs. Define the target, structure and tolerance together with the material and manufacturing stackup.
- Common Target Examples 50 / 75 / 90 / 100 Ω Assign the required value to each identified single-ended or differential structure.
- Typical Impedance Tolerance ±10% Define the actual acceptance window for the specified structure with the order.
- Verification Options Coupon & TDR Identify coverage, measurement requirements and records before manufacturing release.
Manufacturing Scope and Required Definition
Swipe horizontally to view the full capability table.
| Requirement | Service Scope / Reference | Define with Your Order |
|---|---|---|
| Impedance mode | Single-ended and differential. | Identify the mode and target for each controlled structure; do not use an unqualified impedance number alone. |
| Target impedance | Common examples include 50 Ω and 75 Ω single-ended, and 90 Ω or 100 Ω differential. | Use the target required by your design or interface specification. Other targets are reviewed with the construction. |
| Tolerance | Typical impedance tolerance ±10%. | State the tolerance for each structure. Submit tighter requirements for engineering review rather than assuming one tolerance applies to every build. |
| Transmission-line cross-section | Microstrip, stripline and specified coplanar structures. | Identify signal layers, reference conductors, dielectric dimensions and relevant line widths or gaps. |
| Materials and stackup | FR-4, specified RF laminates and suitable hybrid constructions. | Provide the grade or material requirements, layer order, copper and dielectric construction. |
| Geometry review | Manufacturing-focused stackup and conductor review. | Distinguish fixed dimensions from permitted adjustments. Identify changes requiring customer approval. |
| Impedance verification | Coupon and TDR verification as defined for the order. | Specify structure coverage, test requirements, sampling and requested reports. |
| Order stages | Prototypes, small batches and production orders. | State quantity, revision, schedule and the requirements to carry into repeat builds. |
Target impedance, tolerance and measured result are different quantities. For example, 50 Ω ±10% gives a 45–55 Ω acceptance window; 100 Ω ±10% gives 90–110 Ω. The order defines the applicable verification and acceptance basis.
RF Materials and Hybrid Constructions
For boards using dedicated RF laminates or mixed RF / FR-4 construction, review the material and bonding requirements alongside the impedance structures. Our RF and microwave PCB fabrication service provides the related manufacturing context.
Copper Requirements by Layer
Specify starting foil and required finished conductor copper on the relevant layers. Use our PCB copper thickness reference to distinguish nominal weight conversion from finished acceptance requirements.
Cross-Sections, Reference Conductors & Manufacturing Variables
Impedance Structures and Stackup Factors
Controlled impedance depends on the finished transmission-line construction. Identify the cross-section and impedance mode separately, then define the conductor, dielectric and reference geometry together.
Microstrip
A surface signal conductor referenced to a plane beneath the dielectric. Define the finished conductor and dielectric dimensions, including mask coverage where applicable.
Stripline
An internal conductor between reference planes. Identify dielectric distances on both sides and whether the construction is symmetric or asymmetric.
Grounded Coplanar
A signal conductor with adjacent reference copper and an underlying plane. Specify the coplanar gaps separately from differential pair spacing.
- Signal conductor
- Reference conductor
- Dielectric
Simplified cross-sections, not to scale. These are not layout templates. Solder mask, surface finish and interconnections are omitted.
What Affects Controlled Impedance?
Finished Conductor Geometry
Trace width, copper thickness, etched profile and relevant gaps affect the transmission-line structure. Specify the required finished geometry rather than relying only on nominal artwork dimensions.
Dielectric Thickness
Define the dielectric separating the signal and its reference conductors. Pressed dielectric thickness is not the same as overall finished board thickness.
Material and Copper Definition
Identify the laminate and applicable Dk basis with the copper configuration. For dedicated RF constructions, the RF PCB material guide explains the related selection factors.
Reference and Stackup Configuration
Layer order, reference planes, nearby copper and mask coverage form part of the structure. Record the applicable construction instead of using one impedance assumption across unrelated layers.
A target such as “100 Ω differential” starts the specification but does not complete it. Identify the relevant layers, construction, tolerance and permitted adjustments so the manufacturing definition can be reviewed and released.
Impedance Table & Fabrication Notes
How to Specify Impedance Requirements
Identify each controlled structure in an impedance table linked to the released stackup. Include the mode, target, tolerance, layer references and the rules governing geometry or construction changes.
Example Impedance Table: Adapt to Your Design
Scroll horizontally where needed to view all specification columns.
| Structure ID | Mode / Cross-Section | Target / Tolerance | Signal / Reference Layers | Finished Width | Defined Gaps | Change Rule | Verification / Records |
|---|---|---|---|---|---|---|---|
| SE-01 | Single-ended microstrip. |
50 Ω ±10% |
Signal: L1. Reference: L2. | Specify the dimension or identify it as open for review. | No coplanar reference in this example. State other relevant clearances separately. | Define whether width or dielectric changes may be proposed. | State coupon coverage, TDR and report requirements. |
| DIFF-01 | Edge-coupled differential stripline. |
100 Ω ±10% |
Signal: L3. References: L2 and L4. | Specify each conductor's required finished width or review basis. | State pair edge-to-edge gap and its tolerance; identify any other controlled spacing. | Define width and pair-gap approval requirements. | Specify differential measurement and required acceptance records. |
Illustrative entries only, not an approved stackup or recommended geometry. Layer IDs and impedance targets are examples. Add your actual dimensions or identify open items for engineering review, then confirm the released definition before fabrication.
Finished Width
State the intended finished conductor dimension and acceptance basis. Where the cross-section profile is controlled, distinguish the relevant width definitions rather than assuming artwork width is the finished result.
Differential Pair Gap
Define whether spacing means edge-to-edge gap or center-to-center pitch. Identify any requirement to hold pitch, gap or another relationship fixed during manufacturing review.
Coplanar Reference Gap
Define the lateral distance from the signal conductor to adjacent reference copper. Keep it separate from the differential pair gap and unrelated copper clearances.
Need a More Detailed Specification Guide?
Our guide to specifying controlled impedance requirements explains the target, stackup, documentation and verification information to prepare.
Include the Matching Production Files
Submit the impedance table with the artwork, drill data, stackup and drawing. Follow the PCB manufacturing file requirements and identify one consistent design revision.
Design Constraints, Approval & Process Execution
Stackup Review and Manufacturing Control
PCBELEC reviews impedance requirements with the proposed stackup and finished geometry. Identify fixed design constraints and permitted adjustments so manufacturing preparation follows an agreed construction rather than unrecorded assumptions.
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Review Basis 01
Target Fixed, Construction Open for Review
The required impedance and tolerance are defined, while selected material, dielectric or conductor dimensions remain open for manufacturing proposals.
State the electrical, mechanical and cost constraints that limit the proposal. Confirm the resulting stackup and geometry before release.
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Review Basis 02
Material or Stackup Partly Fixed
A specified grade, board thickness or dielectric construction must be retained, while certain conductor dimensions may be reviewed.
Identify exactly which values are controlled and the approval rule for proposed width, gap or construction changes.
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Review Basis 03
Material and Geometry Fixed
The design specifies both the construction and critical dimensions alongside an impedance requirement. Review their consistency before production preparation.
If the supplied requirements conflict, resolve the specification with the customer. Do not silently change controlled design features.
From Review to a Controlled Manufacturing Release
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01 / Review
Align Files and Requirements
Match the impedance table to the artwork, material specification and stackup. Identify missing layer references, ambiguous gaps and conflicting drawing notes.
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02 / Confirm
Approve the Construction
Record agreed materials, dielectric dimensions, finished conductor requirements and permitted changes. Define coupon coverage and acceptance needs with the production requirements.
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03 / Manufacture
Control the Relevant Features
Prepare lamination, imaging, etching and plating around the released construction. Apply process compensation to achieve the agreed finished characteristics.
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04 / Verify
Use the Agreed Acceptance Basis
Complete the specified checks and impedance verification. Associate requested results with the relevant structure and order reference, and review discrepancies against the agreed requirements.
Review the Full Material Definition
Similar nominal Dk values do not automatically make laminates interchangeable. For dedicated RF constructions, use the RF and high-frequency material guide to identify the properties and construction requirements relevant to the design.
Manufacturing Compensation Is Not a Layout Redesign
Process compensation aims to produce the agreed finished structure. Changes to controlled routing geometry, reference features or stackup follow the defined approval rules; they are not automatic authority to redesign the customer's signal path.
Representative Structures & Defined Acceptance
Impedance Coupons, TDR and Reports
Connect the impedance table to a defined verification plan. PCBELEC provides coupon and TDR verification according to the agreed order requirements, with structure coverage and requested records identified before fabrication.
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01 / Represent
Match the Coupon to the Construction
A coupon represents a specified transmission-line structure using the relevant layer, dielectric and conductor construction in the manufacturing panel.
Define Coverage Identify the structures and layer combinations to be represented, together with sampling and order references.
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02 / Measure
Use the Correct Mode and Test Region
TDR evaluates the impedance response of the test structure. Match the measurement mode to the requirement and define how launch and end effects are excluded.
Define the Method State the relevant test conditions, evaluation region and result statistic or acceptance rule where controlled.
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03 / Record
Relate Results to the Order
Compare the measured result with the specified target and tolerance. Associate requested records with the tested coupon, structure and manufacturing reference.
Define Deliverables Request the required summary, waveform, report format and traceability information with the quotation package.
For additional background, see how TDR and coupons verify controlled impedance . The order still defines the applicable test coverage and acceptance requirements.
Keep the Verification Scopes Separate
Swipe horizontally to view the complete comparison.
| Verification | What It Addresses | What It Does Not Establish by Itself |
|---|---|---|
| Continuity and isolation | Intended bare-board connections and separation between nets. | Characteristic impedance, insertion loss or complete channel performance. |
| Coupon TDR verification | The tested structure's impedance against the agreed evaluation and acceptance requirements. | Every feature on the finished PCB, connector launch or full signal path. |
| Channel or RF performance evaluation | Separately specified behavior of the defined path under its test conditions. | Automatic qualification from a coupon impedance pass result alone. |
Agree Sampling and Acceptance Before Release
Identify whether verification applies to first articles, selected panels or another agreed sampling basis. Define how results are associated with the shipment and how discrepancies are reviewed.
Include Other Bare-Board Requirements
Impedance verification forms part of the order's bare PCB testing and inspection scope. Specify additional dimensional, material or cross-section records separately where they are required.
Engineering Samples to Repeat Orders
Prototype and Production Consistency
PCBELEC supports impedance-controlled prototype, small-batch and production builds. Carry the approved construction, geometry and verification requirements forward so each order has an identifiable manufacturing basis.
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01 / Prototype
Establish the Initial Build Definition
Release the impedance table with the selected stackup, material and conductor requirements. Define the sample-stage coupon and TDR scope needed for your evaluation.
Keep IdentifiableDesign revision, approved construction, structure IDs and requested records.
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02 / Pilot and Small Batch
Incorporate Approved Changes
Move the selected design into a limited manufacturing run. Update the artwork, stackup and impedance table together when prototype evaluation leads to changes.
Keep IdentifiableUpdated revision, change summary, material approvals and verification coverage.
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03 / Production and Reorders
Manufacture Against the Released Requirements
Reference the approved part and construction for repeat orders. Identify changes to material, geometry or acceptance requirements before the next manufacturing release.
Keep IdentifiableOrder reference, production revision, agreed sampling and shipment documentation.
Planning a Pilot or Limited Run?
Our low-volume PCB fabrication service supports small-batch orders using the released design and manufacturing requirements. Include quantity and the intended evaluation stage with the inquiry.
Preparing Repeat Production?
For PCB production orders , identify the approved revision, delivery schedule and any change from earlier builds. A previous prototype result does not automatically approve a later construction change.
Impedance-Specified Bare PCB Manufacturing Inquiry
Request a Controlled Impedance PCB Quote
Send your board files, stackup and impedance requirements for engineering review and quotation. Identify the controlled structures, permitted adjustments and verification needs so the manufacturing scope can be defined together.
Include with Your Inquiry
- Fabrication Files Artwork, drill data, board outline, fabrication drawing and design revision.
- Impedance Table Structure IDs, modes, targets, tolerances and signal / reference layers.
- Material & Stackup Material requirements, dielectric construction, copper by layer and finished board thickness.
- Geometry & Approval Rules Finished widths, defined gaps, fixed design features and permitted adjustments.
- Verification & Records Coupon coverage, TDR requirements, sampling, acceptance criteria and requested reports.
- Quantity & Delivery Required quantity, delivery date, destination and previous order reference, where applicable.
Use the impedance table example to organize the electrical requirements. Check the PCB manufacturing file requirements for the supporting production data.
Send Your Impedance-Controlled PCB Requirements
Complete the form below and attach the available files. If your impedance table is included in the drawing or archive, reference it rather than re-entering every structure.
Upload your fabrication files, stackup and impedance table. You may also email the package to sales@pcbelec.com.
Targets, Stackups & Acceptance Questions
Controlled Impedance PCB FAQ
Answers to common questions about impedance targets, manufacturing adjustments, coupon verification and order requirements.
Preparing a quotation package? Include the impedance table and identify the design features that must remain fixed.
View the Quotation ChecklistWhat is a controlled impedance PCB?
A controlled impedance PCB is manufactured with specified transmission-line structures designed to meet target characteristic impedance values within agreed tolerances.
The manufacturing definition connects conductor geometry, dielectric construction, material properties and reference conductors. It is not simply a DC resistance requirement.
When does a PCB need impedance control?
Use the electrical design and interface requirements to identify which structures need controlled impedance. Typical examples include high-speed digital paths, differential links and RF transmission lines.
There is no single clock frequency that decides every case. Signal transition behavior, path length and the complete channel requirements also matter.
Is 100 Ω differential the same as two separate 50 Ω traces?
Not automatically. Differential impedance depends on the coupled pair and its reference construction, including conductor dimensions and separation.
For an identical, balanced pair, differential impedance is twice the odd-mode impedance. That is not the same as assuming two isolated 50 Ω lines form the required differential structure.
Can I provide target impedance without finalized trace dimensions?
Yes. Provide the targets, modes, tolerances and relevant layers with the available stackup and design files. Identify material, thickness or geometry constraints that must be preserved.
Mark open dimensions for manufacturing review. The resulting construction and required approvals are confirmed before production release.
What impedance tolerance can PCBELEC support?
The typical tolerance listed for this service is ±10%. Define the required tolerance separately for each controlled structure.
Submit tighter targets for engineering review with the material, stackup and geometry. The accepted order defines the final verification and acceptance requirements.
Do all orders automatically include coupon TDR testing and reports?
Coupon coverage, TDR verification and reports are defined with the order. Specify which structures require verification and what records must accompany the shipment.
Identify the sampling, test requirements and customer report format before fabrication. Do not assume identical coverage for every order.
Does a passing coupon prove the complete signal channel is compliant?
No. A coupon represents the defined manufacturing structure under its measurement conditions. It does not automatically verify every via, connector, transition or complete channel.
Insertion loss, RF performance and product-level interface qualification require their own defined evaluation scope.
Can you control impedance on Rogers or hybrid RF boards?
Yes. PCBELEC supports specified RF laminate and hybrid constructions with impedance requirements. Define the exact materials, bonding system, layer order and controlled structures.
See our RF and microwave PCB fabrication service for the related material and manufacturing scope.
Do you provide PCB layout or signal integrity design?
PCBELEC provides manufacturing-focused review of customer-supplied files, stackups and impedance requirements. The review addresses the construction and fabrication definition.
PCB layout, routing design and complete signal integrity analysis are separate from this bare-board manufacturing service.