Impedance Controlled PCB
Impedance Control
Within ±8%. Verified.
Precision-controlled impedance for high-speed digital, RF, and mixed-signal designs. TDR tested. Full measurement report included with every shipment.
How Controlled Impedance Works
The characteristic impedance a trace presents to a high-speed signal is set by geometry, not by the copper alone. On a controlled impedance PCB, three variables dominate: the trace width, the dielectric height separating the trace from its reference plane, and the substrate's dielectric constant (Dk). Widen the trace or shrink the dielectric and impedance drops; increase the dielectric height or Dk and it rises. We solve for that geometry against your target, then verify the finished board by TDR — which is why our controlled impedance boards hold ±8% single-ended and differential, and ±10% for GCPW.
Microstrip
A signal trace routed on an outer layer over a single reference plane, with the trace exposed to air on top. Microstrip is the simplest controlled-impedance geometry — impedance is tuned almost entirely by trace width and the dielectric height to the plane beneath it. Common for 50Ω single-ended routing.
Stripline
An inner-layer trace sandwiched between two reference planes, fully embedded in dielectric. Stripline gives tighter field confinement and better noise immunity than microstrip, so it suits dense differential pairs like DDR and PCIe — at the cost of a symmetric stackup and careful control of both dielectric heights.
Coplanar Waveguide (CPW)
A trace flanked by coplanar ground pours, usually with a ground plane below (GCPW). The gap to the side grounds becomes a primary tuning variable alongside trace width, giving low-loss, well-behaved impedance for RF and mmWave designs up to 77GHz. We hold ±10% on GCPW.
Not sure which geometry your stackup calls for, or what trace width hits your target? See the impedance and trace-width parameters on our PCB capabilities page, or send your targets to our engineers for a stackup calculation.
Impedance Control Capabilities
Every parameter verified, every board tested.
Single-Ended
±8% tolerance
50Ω standard. Custom values 25-120Ω. Microstrip and stripline configurations.
Differential Pair
±8% tolerance
90Ω, 100Ω standard. Custom values available. Edge-coupled and broadside-coupled.
Coplanar Waveguide
±10% tolerance
GCPW with ground plane. For RF and high-frequency applications up to 77GHz.
TDR Testing
100% tested
Time Domain Reflectometry measurement on every impedance-controlled board. No sampling.
Test Coupon Design
Per IPC-2141
Impedance test coupons placed on panel edge. Designed to match your actual trace geometry.
Measurement Report
Every order
Full TDR measurement report included with shipment. Coupon retained for 6 months.
Verified, Not Just Calculated
Many manufacturers offer "impedance control" but only simulate the stackup and hope production matches. We test every single board with calibrated TDR equipment.
Your impedance test report shows actual measured values against target — not theoretical calculations. If a board fails the ±8% window, it doesn't ship.
For critical applications requiring ±5% tolerance, contact our engineering team to discuss enhanced process control options.
Stackup Design Assistance
Not sure about your stackup? Our engineers can calculate trace widths, spacing, and dielectric requirements to hit your target impedance. Free for confirmed orders.
Supported Configurations
Common impedance targets and materials we work with daily.
| Application | Impedance | Material |
|---|---|---|
| USB 2.0 / 3.0 | 90Ω differential | FR-4 TG150+ |
| PCIe Gen4/5 | 85Ω differential | Low-loss FR-4 / Megtron |
| DDR4 / DDR5 | 40-50Ω single / 80-100Ω diff | FR-4 TG170 |
| Ethernet 10G+ | 100Ω differential | FR-4 or low-loss |
| RF (50Ω system) | 50Ω single-ended | Rogers RO4350B |
| LVDS | 100Ω differential | FR-4 TG150+ |
| MIPI CSI/DSI | 85-100Ω differential | FR-4 standard |
| mmWave 28-77GHz | 50Ω GCPW | Rogers / PTFE |
Sample Impedance Test Report
Every order ships with a report like this.
FAQs
Impedance Control Questions
What tolerance can you achieve?
±8% standard on all impedance-controlled boards. ±10% for GCPW. Enhanced ±5% available for critical applications — contact engineering to discuss.
Do you test every board or just samples?
Every single board with impedance requirements is TDR tested. No statistical sampling. If it has impedance requirements, it gets measured.
Can you help calculate my stackup?
Yes. Send us your impedance targets and we will calculate trace width/spacing for your stackup. This is free for confirmed orders, or available as a standalone service.
What if my design needs both 50Ω and 100Ω?
Multiple impedance targets on one board are standard. We design test coupons for each unique impedance and verify all targets independently.
Is there extra cost for impedance control?
Impedance control adds a modest premium (typically 10-20%) to cover test coupon area and TDR measurement time. The exact cost is included in your instant quote.
Need impedance-controlled boards?
Specify your impedance targets in the quote form. TDR test report included with every order.