Ribbon cable
The Belden 9R280 datasheet specifies 28 AWG, 7x36 tinned-copper conductors on 1.27 mm pitch in a 0.914 mm body. A ground-signal-ground group is nominally 105 ohm.
WebAssembly Port of the Open Source MMTL Solver
A high-accuracy field solver for PCB and transmission-line cross-sections that runs locally in your browser.
What Web-MMTL Is
MMTL was developed from Mayo Clinic transmission-line research beginning in the 1980s and was publicly released under the GPL in 2004. It is a 2-D/2.5-D field solver for trace impedance, propagation, crosstalk, and conductor coupling.
It uses a boundary-element and method-of-moments field solution. It's as accurate as expensive commercial tools like Polar SI9000e.
Arbitrary Geometry and Dielectric Regions
Web-MMTL is much more accurate than formula-based impedance calculators. It models the cross-section that is actually being manufactured as a 2D field.
- Mixed and stacked core, prepreg, resin, solder-mask, coating, and air-adjacent dielectric regions
- A pure-resin region across, above, or beside a trace
- Asymmetric stripline with different materials or distances above and below the conductor
- Rectangular, etched-trapezoid, or circular conductors
- Multiple signal and ground conductors with coupling and modal impedance results
Free-form Examples
This solver supports free-form geometries. These examples use that flexibility to calculate cable impedance from physical dimensions and dielectric properties.
Open the free-form stackup editor
Cat5e twisted pair
The Belden 1583ANS datasheet specifies 24 AWG solid copper, a 0.89 mm PE-insulated diameter, and 100 ohm nominal impedance.
JLCPCB Dielectric Support
This tool has JLCPCB-specific material support, including construction/thickness-dependent dielectric-constant references and frequency-dependent dielectric-loss models. JLCPCB currently uses Nan Ya NP-155F for 4-8-layer impedance calculations and Shengyi S1000-2M for 10-layer and higher constructions.
Example JLCPCB Four-Layer Stackups
Click a diagram to open a trace tuned to 50 Ω with standard copper selections: 1 oz outside and 0.5 oz inside. These examples use nominal copper thicknesses and a 0.5 mil total etch reduction; the calculator solves them automatically.
JLC04161H-3313
1.56 mm finished thickness, +/- 10%. Uses 0.0994 mm 3313 RC57 prepreg above and below a 1.265 mm core.
JLC04161H-7628
1.59 mm finished thickness, +/- 10%. Uses 0.2104 mm 7628 RC49 prepreg above and below a 1.065 mm core.