Managing Materials for RF PCB Toolbox

When to Use

• Creating dielectric substrates for transmission lines, filters, couplers, or custom pcbComponent designs
• Selecting metals (Copper, Gold, etc.) for realistic conductor loss modeling
• Building multi-layer dielectric stacks for stripline or embedded designs
• Choosing frequency-dependent dispersion models (DjordjevicSarkar) for wideband accuracy
• Looking up catalog material properties or adding custom materials

When NOT to Use

• Building the PCB layer structure itself — use matlab-assemble-pcb-layout
• Running EM analysis after materials are defined — use matlab-analyze-em
• Designing transmission lines that happen to need substrates — use matlab-design-pcb-txline (it references this skill for material details)
• Importing material properties from an existing board file — use matlab-read-pcb-layout

Typical Workflow

1. This skill: Define substrate, conductor, and stackup — typically the first step in any RF PCB design
2. After: Any design skill (matlab-design-pcb-filter, matlab-design-pcb-txline, matlab-assemble-pcb-layout, matlab-model-via) — pass materials to the component

Quick Reference

Creating Dielectrics

The dielectric object defines substrate properties. Create from the built-in catalog or specify custom parameters.

From Catalog

sub = dielectric("FR4");
sub = dielectric("Teflon");
sub = dielectric("RO4730JXR");
sub = dielectric("TMM10");

To see every name in the catalog:

dc = DielectricCatalog;
disp(dc.Materials)

Available catalog names (R2026a): Air, FR4, Teflon, Foam, Polystyrene, Plexiglas, Fused quartz, E glass, RO4725JXR, RO4730JXR, TMM3, TMM4, TMM6, TMM10, TMM10i, Taconic RF-35. Add custom materials with add(dc, ...) if your material is not listed.

Custom Properties

sub = dielectric(Name="Rogers4350B", EpsilonR=3.66, LossTangent=0.0037, Thickness=0.508e-3);

Key Properties

Browsing the Catalog

dc = DielectricCatalog;
open(dc)               % Opens interactive catalog viewer
disp(dc.Materials)     % List all materials as a table
s = find(dc, "FR4");   % Returns struct with Name, Relative_Permittivity, Loss_Tangent, Frequency, Comments

Creating Metals

The metal object defines conductor properties.

From Catalog

cond = metal("Copper");       % Conductivity=5.96e7, Thickness=35.56e-6 (1 oz)
cond = metal("Aluminium");    % Conductivity=3.77e7, Thickness=762e-6
cond = metal("Gold");         % Conductivity=4.11e7, Thickness=0.2e-6

Available catalog metals (R2026a): PEC, Copper, Aluminium, Gold, Silver, Zinc, Tungsten, Lead, Iron, Steel, Brass.

Custom Properties

cond = metal(Name="ThickCopper", Conductivity=5.8e7, Thickness=70e-6);

Browsing the Catalog

mc = MetalCatalog;
open(mc)                    % Opens interactive catalog viewer
disp(mc.Materials)          % List all metals as a table
s = find(mc, "Aluminium");  % Returns struct with Name, Conductivity, Thickness, Units, Comments

Assigning to Components

mline = microstripLine;
mline.Conductor = metal("Copper");

Multi-Layer Substrates

Many RF PCB components support multi-layer dielectric stacks. Pass multiple material names or use vector properties.

Shorthand Syntax (catalog names)

sub = dielectric("FR4", "Teflon");
sub.Thickness = [0.0016 0.0008];

Explicit Multi-Layer

sub = dielectric(Name={"FR4","Foam","FR4"}, ...
    EpsilonR=[4.4 1.05 4.4], ...
    LossTangent=[0.02 0.001 0.02], ...
    Thickness=[0.4e-3 0.8e-3 0.4e-3]);

Important: Use a cell array {...} for Name, not a string array [...]. String array concatenation (["FR4","Foam"]) produces a single string "FR4Foam", not a multi-element array.

Assigning to Components

balun = balunMarchand;
balun.Height = 0.0016;
balun.Substrate = sub;
show(balun);

Multi-layer substrates are supported by all catalog components that have a Substrate or Height property (transmission lines, filters, couplers, splitters, etc.).

Dielectrics in pcbComponent

When building custom structures with pcbComponent, dielectrics appear as layers in the Layers cell array:

pcb = pcbComponent;
substrate = dielectric("RO4730JXR");
substrate.Thickness = 1.52e-3;
ground = traceRectangular(Length=20e-3, Width=10e-3);

pcb.BoardThickness = substrate.Thickness;
pcb.Layers = {signalTrace, substrate, ground};

For multi-dielectric pcbComponent stacks (5-layer):

sub1 = dielectric(Name="FR4", EpsilonR=4.4, LossTangent=0.02, Thickness=0.8e-3);
sub2 = dielectric(Name="FR4", EpsilonR=4.4, LossTangent=0.02, Thickness=0.8e-3);

pcb.BoardThickness = sub1.Thickness + sub2.Thickness;
pcb.Layers = {topTrace, sub1, groundPlane, sub2, bottomTrace};

Frequency-Dependent Loss Models

For accurate wideband modeling, specify a reference frequency for the loss tangent:

sub = dielectric(Name="FR4", EpsilonR=4.4, LossTangent=0.02, ...
    Thickness=1.6e-3, Frequency=1e9);

When Frequency is specified, the FrequencyModel property automatically becomes 'DjordjevicSarkar'. This causal model extrapolates permittivity and loss tangent across the analysis bandwidth, ensuring physically consistent results. Without Frequency, the model uses 'Constant' (frequency-independent).

Available dispersion models:

• "Constant" -- (default) frequency-independent permittivity and loss tangent
• "DjordjevicSarkar" -- wideband causal model, best for PCB substrates
• "MeanDjordjevicSarkar" -- averaged version of DjordjevicSarkar
• "TableDriven" -- user-supplied frequency-dependent data from vendor datasheets

Frequency Model Selection Guide

Querying Dispersion-Aware Properties

Use getMaterialProperties() to calculate permittivity and loss tangent at specific frequencies, accounting for the active dispersion model:

sub = dielectric("FR4");
sub.FrequencyModel = "DjordjevicSarkar";
sub.Frequency = 1e9;

% Get properties across a frequency sweep
freq = linspace(1e8, 10e9, 100);
[epsr, tand, f] = getMaterialProperties(sub, freq);

% Plot frequency-dependent permittivity
plot(f/1e9, epsr);
xlabel("Frequency (GHz)"); ylabel("\epsilon_r");
title("FR4 Permittivity (DjordjevicSarkar)");

Common Material Parameters

Dielectric Catalog Values (R2026a)

Materials not in catalog that must be created manually:

sub = dielectric(Name="RO4003C", EpsilonR=3.38, LossTangent=0.0027, Thickness=0.508e-3);
sub = dielectric(Name="RO4350B", EpsilonR=3.66, LossTangent=0.0037, Thickness=0.508e-3);

Metal Catalog Values (R2026a)

Pitfalls

1. Set BoardThickness before Layers: pcbComponent.BoardThickness must equal the sum of all dielectric thicknesses. Always assign BoardThickness before Layers — reversing the order triggers a warning and silently overwrites dielectric thicknesses.

1. Default conductor is PEC: If you don't assign a Conductor, components use perfect electric conductor (lossless). Always assign metal("Copper") for realistic loss modeling.

1. Most Rogers materials not in catalog: Only RO4725JXR and RO4730JXR are in DielectricCatalog. Common substrates like RO4003C, RO4350B, and RO3003 must be created manually from datasheet values. Calling dielectric("RO4003C") will error.

1. Multi-layer Thickness must match element count: When using vector Thickness, the number of elements must equal the number of names/EpsilonR values. Mismatched lengths throw an error.

1. Units are always SI: Thickness in meters (not mm or mils). A 1.6 mm board is 1.6e-3, not 1.6.

1. FrequencyModel can be set post-design. After design() creates a component with a default constant dielectric, you can switch to DjordjevicSarkar: obj.Substrate.FrequencyModel = 'DjordjevicSarkar'; obj.Substrate.Frequency = 1e9;. This is useful when the design step doesn't accept frequency-dependent substrates.

1. Named catalog dielectrics are single-layer: dielectric("FR4") creates a 1-layer object with fixed catalog properties. For multi-layer pcbComponent stacks, create separate unnamed dielectric objects with explicit EpsilonR, LossTangent, and scalar Thickness for each layer. Do NOT use a named catalog entry when you need to control per-layer thickness in a Layers cell array.

1. Dielectric layer count for `viaSingleEnded`: When building a multi-layer substrate for viaSingleEnded, the number of dielectric layers must equal N-1 where N is the number of conductive layers in the stackup (e.g., Signal=[1 5], Ground=[3 7] → 4 metal layers → 3 dielectric layers). When using the viaSingleEnded(N) constructor, soldermask layers are added automatically — see matlab-model-via Pitfall #17 for exact requirements. All dielectric property arrays (Name, EpsilonR, LossTangent, Thickness, Frequency) must match in size.

Related Skills

• matlab-assemble-pcb-layout — Using materials in custom pcbComponent structures
• matlab-analyze-em — How material properties affect solver accuracy
• matlab-design-pcb-txline — Substrate selection for impedance control

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