Isola I-Tera MT40 RF microwave offers four Dk grades (3.38–3.75) and Df 0.0028–0.0035 in a single FR-4-compatible system — the only Isola RF material with multiple Dk options. Complete guide: Dk selection for SWaP/miniaturization, W-band stability, vs Astra MT77 and Rogers, hybrid build strategy, and PIM performance.

Primary keyword: Isola I-Tera MT40 RF microwave | ~2,800 words

Most RF and microwave PCB material selection conversations start with Dk and Df — pick the lowest available Df that your fabrication economics can support, specify the matching Dk, and design the circuit geometry around those numbers. That framing works well when your primary constraint is insertion loss. But a significant class of RF and microwave designs is not primarily insertion-loss-constrained — it’s size, weight, and power (SWaP) constrained, or mixed-signal constrained, or budget constrained in ways that make the cost premium of the lowest-Df materials hard to justify.

Isola I-Tera MT40 RF microwave laminate occupies a unique position in the microwave PCB material landscape precisely because it offers what no other Isola material does: a choice of four Dk grades — 3.38, 3.45, 3.60, and 3.75 — within a single qualified material system, with Df ranging from 0.0028 to 0.0035. That Dk flexibility means the same material family can minimize circuit area through higher Dk selection, match specific impedance targets with constrained trace geometry, or optimize for the widest available trace widths, all without changing the resin system, lamination process, or supplier. It’s a design tool that’s underutilized because most engineers select RF laminates by Dk/Df performance alone without considering what multiple Dk options within a single material system enables.

This guide specifically addresses the RF and microwave variant of I-Tera MT40, explains why the Dk selection matters in practice, and covers the specifications, construction options, applications, and competitive context from the viewpoint of an engineer who needs to make a real material selection decision.

Understanding the I-Tera MT40 RF/MW Variant vs the HSD Variant

Before getting into the RF/MW-specific details, it’s important to clarify the two I-Tera MT40 variants because the spec sheets and product pages can create confusion.

I-Tera MT40 exists in two forms that share the same name but serve different primary purposes. The standard I-Tera MT40 (HSD) is optimized for high-speed digital multilayer designs, available in 2 to 24 mil laminate thicknesses, and nominally characterized at Dk 3.45 / Df 0.0031. The RF/MW variant is specifically characterized and constructed for radio frequency and microwave circuit designs, available in heavier laminate constructions (10, 20, 30, 60 mil), and offered in four Dk grades.

I-Tera MT40 RF microwave laminate materials exhibit exceptional electrical properties which are very stable over a broad frequency and temperature range. They feature a dielectric constant (Dk) that is stable between -40°C and +140°C up to W-band frequencies. The Df ranges from 0.0028 to 0.0035 depending on the specific Dk grade — the lower-Dk grades (3.38) deliver the lower Df (0.0028), and the higher-Dk grades (3.75) carry the higher Df (0.0035).

Both variants share Tg 215°C (DSC), Td 360°C, T260 >60 minutes, T288 >60 minutes, FR-4 process compatibility, and no special through-hole treatments. For this guide, all specifications and application guidance refer to the RF/MW variant unless explicitly noted otherwise.

Isola I-Tera MT40 RF/MW Complete Specifications

The Four Dk Grades and Their Df Values

Dk Grade	Typical Dk (10 GHz, z-axis)	Typical Df (10 GHz)	Primary Application Driver
3.38	3.38	~0.0028	Lowest Df; widest traces for given impedance
3.45	3.45	~0.0031	Balanced performance; standard choice
3.60	3.60	~0.0033	Circuit size reduction; moderate SWaP
3.75	3.75	~0.0035	Maximum miniaturization; tightest SWaP

The relationship between Dk and Df within I-Tera MT40 RF/MW is intentional. The higher Dk grades use more glass reinforcement relative to resin content — glass has higher Dk than the resin, so more glass pulls the composite Dk up. That same glass-rich composition introduces slightly more dielectric loss. The tradeoff is Dk controllable by design within a 10% range, with Df varying by approximately 25% across the full range. Whether that tradeoff is favorable depends entirely on what is driving your circuit architecture.

Full Electrical and Thermal Properties

Property	Typical Value	Test Method / Notes
Dk (3.38 grade) @ 10 GHz	3.38	IPC-TM-650 2.5.5.5 / z-axis
Dk (3.45 grade) @ 10 GHz	3.45	IPC-TM-650 2.5.5.5 / z-axis
Dk (3.60 grade) @ 10 GHz	3.60	IPC-TM-650 2.5.5.5 / z-axis
Dk (3.75 grade) @ 10 GHz	3.75	IPC-TM-650 2.5.5.5 / z-axis
Df range @ 10 GHz	0.0028–0.0035	Varies by Dk grade
Dk thermal stability	-40°C to +140°C	W-band frequencies
Glass Transition Temp (Tg) — DSC	215°C	Rev E update (long-term data)
Glass Transition Temp (Tg) — TMA	210°C
Glass Transition Temp (Tg) — DMA	230°C
Decomposition Temp (Td)	360°C	TGA, 5% weight loss
T260	>60 minutes	IPC-TM-650 2.4.24.1
T288	>60 minutes	IPC-TM-650 2.4.24.1
Z-Axis CTE (50–260°C, total)	~2.8%	TMA
X/Y-Axis CTE (pre-Tg)	~14 ppm/°C	TMA
Moisture Absorption	0.1%	IPC-TM-650
UL Flammability	V-0	UL 94, File E41625
IPC Classification	IPC-4103/17
RoHS	Compliant

Standard Product Availability (RF/MW Variant)

Parameter	Available Options
Laminate thickness	10, 20, 30, 60 mil (0.25, 0.51, 0.76, 1.50 mm)
Standard copper foil	HTE Grade 3
Low-profile copper foil	HVLP (VLP2) ≤2.5 µm Rz JIS (1 oz and below standard)
Alternate copper foil	RTF (Reverse Treat Foil)
Special foil	Embedded resistor foil
Copper weight	½, 1, 2 oz (18, 35, 70 µm)
Available Dk grades	3.38, 3.45, 3.60, 3.75

The heavier laminate thickness options (10–60 mil) reflect the substrate thickness requirements of microwave circuit design. A 50 Ω microstrip line on a 60 mil (1.5 mm) substrate at Dk 3.45 is approximately 110 mils wide — the thick substrate is appropriate for power amplifier circuits, low-noise amplifier modules, and antenna feed networks where the physical width of the trace is needed for the transmission line current-handling capacity or for connector launch geometry. The 10 mil option serves fine-line microwave circuits where compact geometry and close-spaced transmission lines are the design requirement.

The Core Unique Attribute: Why Four Dk Options Matter for RF Circuit Design

The higher Dk values enable miniaturization of circuit structures for a given frequency or wavelength, in support of reduced circuit size, weight, and power in military and aerospace applications. This statement from Isola’s own communications about I-Tera MT40 at IMS 2023 identifies the key engineering principle.

The Physics of Dk and Circuit Miniaturization

The physical dimensions of microwave circuit elements — quarter-wave stubs, half-wave resonators, patch antenna elements, Wilkinson power splitters, and all other wavelength-dependent structures — are proportional to the guided wavelength in the substrate. The guided wavelength is shorter than the free-space wavelength by a factor related to the effective dielectric constant: a higher Dk substrate shrinks the guided wavelength and therefore shrinks all wavelength-dependent structures proportionally.

For a patch antenna operating at 10 GHz on a Dk 3.00 substrate (Astra MT77), the patch element is approximately 8.2 mm long. On a Dk 3.75 substrate (I-Tera MT40 at its highest grade), the same antenna shrinks to approximately 7.3 mm — roughly an 11% linear reduction. For a phased array with 256 antenna elements on a constrained board area, that 11% per-element reduction is a 21% reduction in array footprint area. At the board-level integration density of modern active electronically scanned arrays (AESAs) and 5G Massive MIMO panels, that is meaningful space savings.

For military airborne and spaceborne systems where volume, mass, and thermal dissipation per unit area are the binding constraints, designers seeking higher Dk values to enable miniaturization of circuit structures for a given frequency or wavelength can look at I-Tera MT40 RF/MW as a technically justified choice that no single-Dk material can substitute for without significant circuit redesign.

The Trace Width Control Argument for Dk 3.38

The argument runs in the opposite direction for Dk 3.38. A lower Dk requires a wider trace for the same impedance target. In a process environment where minimum feature size is 4 mil (100 µm), a Dk 3.45 substrate at 10 mil thickness produces 50 Ω microstrip at approximately 9 mils wide — close to the process floor. Shifting to Dk 3.38 widens that trace to approximately 9.5 mils, providing more process margin in the etching step. For designs with tight yield requirements on controlled impedance, selecting the lowest available Dk grade provides wider traces that are easier to etch accurately and have better tolerance to minor over-etch.

Comparing Isola I-Tera MT40 RF/MW to Key RF PCB Materials

RF/Microwave Laminate Comparison Table

Material	Manufacturer	Dk (10 GHz)	Df (10 GHz)	FR-4 Process	Multiple Dk Options	Tg
I-Tera MT40 RF/MW	Isola	3.38–3.75	0.0028–0.0035	Yes	Yes (4 options)	215°C
Astra MT77	Isola	3.00	0.0017	Yes	No (single Dk)	200°C
Tachyon 100G	Isola	3.02	0.0021	Yes	No (single Dk)	215°C
TerraGreen 400G (RF/MW)	Isola	~3.07	~0.0018	Yes	No (single Dk)	200°C
Rogers RO4350B	Rogers	3.48	0.0037	No	No	>280°C
Rogers RO3003	Rogers	3.00	0.0010	No (PTFE)	No	—
Rogers RO4003C	Rogers	3.55	0.0027	No	No	>280°C
Megtron 6	Panasonic	3.60	0.0037	Yes	No	185°C

The direct competitor for I-Tera MT40 RF/MW in the FR-4-compatible low-loss microwave space is Rogers RO4003C (Dk 3.55, Df 0.0027). I-Tera MT40 at Dk 3.60 / Df 0.0033 sits close to Rogers RO4350B (Dk 3.48, Df 0.0037) on dielectric constant while offering better Df. The principal differentiator of I-Tera MT40 RF/MW is the Dk flexibility — neither Rogers RO4003C nor RO4350B offers multiple Dk grades within the same material system. An I-Tera MT40 design at Dk 3.45 and a Dk 3.75 design use the same fabricator qualifications, the same process parameters, and the same thermal material properties; a Rogers design at Dk 3.45 (RO4350B) and one at Dk 3.00 (Astra MT77) are entirely different material systems with different process requirements.

I-Tera MT40 RF/MW vs Astra MT77: Complementary, Not Competitive

RF engineers sometimes frame Astra MT77 and I-Tera MT40 RF/MW as competing alternatives. They are more accurately complementary materials within the Isola portfolio. Astra MT77 at Dk 3.00 and Df 0.0017 is the ultra-low-loss choice for applications where every fraction of a dB at W-band matters and where wider traces are acceptable or desirable. I-Tera MT40 RF/MW at Dk 3.38–3.75 and Df 0.0028–0.0035 is the choice when Dk flexibility is needed for circuit miniaturization or impedance matching constraints, when the operating frequency is below W-band, or when the application tolerates slightly higher Df in exchange for the Dk control that no single-Dk material provides.

Another circuit material well matched to Astra MT77 in CTE is I-Tera MT40 RF/MW, with a slightly higher Dk of 3.45 at 10 GHz but also with very low loss. Both have the qualities needed for many emerging mmWave circuit applications. The shared CTE characteristics between Astra MT77 and I-Tera MT40 are explicitly designed to enable hybrid multilayer builds where the two materials coexist in the same stack-up — RF layers using Astra MT77 for minimum loss at W-band, digital interconnect layers or mixed-frequency RF layers using I-Tera MT40 RF/MW for the frequency range and circuit geometry flexibility it provides.

Processing I-Tera MT40 RF/MW: What Makes It FR-4-Compatible

I-Tera MT40 does not require any special through-hole treatments commonly needed when processing PTFE-based laminate materials. This is the sentence that separates it from a large class of microwave laminates in the market and opens it to essentially the entire global high-performance PCB shop network.

For microwave PCB design engineers who have dealt with PTFE substrate manufacturing constraints, the freedom from sodium naphthalide etch or plasma chamber activation is a substantial operational benefit. But there are specific processing disciplines that distinguish I-Tera MT40 RF/MW from commodity FR-4.

The lamination cure cycle targets 60 minutes at 200°C cure temperature — consistent with the Isola high-performance thermoset family. Multiple lamination cycles are supported, enabling sequential lamination constructions. The Tg of 215°C DSC provides margin above standard SAC305 assembly peak temperatures, and T260 >60 minutes / T288 >60 minutes means aggressive lead-free assembly profiles won’t delaminate the board.

For drilling, use lower chiploads and cutting speeds than standard FR-4. I-Tera MT40 RF/MW’s resin system is optimized for low dielectric loss, which produces a slightly harder cured polymer than standard FR-4 epoxy. This affects drill bit wear rate and hole wall quality if FR-4 parameters are used without adjustment.

Permanganate desmear at standard high-performance epoxy parameters. No PTFE activation chemistry. No plasma chamber. Any shop running FR408HR, I-Tera MT40 HSD, or Tachyon 100G can process I-Tera MT40 RF/MW without capital equipment changes or chemistry additions.

All I-Tera MT40 glass is spread weave in both directions across all constructions. For RF circuits above 5 GHz where fiber weave effect can cause localized Dk variation in transmission lines, the spread weave construction provides the same mitigation as premium low-loss grades — without special requests.

PIM Sensitivity and Copper Foil Selection

I-Tera MT40 RF/MW datasheets include PIM (Passive Intermodulation) data because the material is used in antenna systems where PIM is a specification requirement. PIM values are influenced by copper foil treatment roughness. PIM values presented in the datasheet were achieved with VLP-2 copper foil. For RF designs at base station power levels where PIM certification is required (3GPP TS 25.466, for example), specifying HVLP (VLP2) ≤2.5 µm copper foil is the correct approach. For applications where PIM is not a specification concern, the standard HTE Grade 3 foil is cost-effective and provides good adhesion.

The embedded resistor foil option is available for I-Tera MT40 RF/MW — useful in compact RF filter and attenuator designs where surface-mount resistors add component height, lead inductance, and assembly complexity.

Target Applications for Isola I-Tera MT40 RF Microwave

The application space for Isola I-Tera MT40 RF microwave is defined by three co-occurring conditions: W-band or below operating frequency, FR-4-process-compatible fabrication economics, and a need for either Dk flexibility or PTFE-free process access.

Military and Aerospace Radar and EW Systems: Electronic warfare receivers, radar front-ends in the 6–40 GHz frequency range, and satellite communications payload RF boards where SWaP constraints drive the use of higher Dk grades (3.60, 3.75) to minimize substrate area. At IMS 2023, Isola explicitly positioned the higher Dk values of I-Tera MT40 RF/MW as enabling miniaturization of circuit structures in support of reduced circuit size, weight, and power in military and aerospace applications. Phased array feed networks, Butler matrix beam-forming networks, and corporate feed architectures all benefit from the circuit footprint reduction that Dk 3.60–3.75 provides relative to Dk 3.00–3.45 alternatives.

5G Sub-28 GHz Base Station RF Sections: Antenna feed networks for 5G NR sub-6 GHz and 24–28 GHz band base stations where halogen-free compliance is not required, the circuit frequency is within I-Tera MT40’s characterized range, and the PCB program economics benefit from FR-4 shop accessibility. While Astra MT77 is the better choice at W-band (77 GHz), I-Tera MT40 RF/MW covers the 5G mmWave frequency bands adequately with lower insertion loss than Rogers RO4350B and better Dk stability than epoxy FR-4 materials.

Automotive ADAS at Sub-77 GHz: Forward collision warning radar operating at 24 GHz, vehicle-to-everything (V2X) communications at 5.9 GHz, and LiDAR signal processing electronics where the automotive-grade temperature specification (-40°C to +140°C in the RF/MW variant) aligns directly with the application environment. I-Tera MT40 RF/MW’s two higher Dk grades support compact automotive radar antenna geometries within the constrained board areas of bumper-mounted radar modules.

Satellite Ground Terminal Receivers: LNB (Low Noise Block) downconverter circuits for Ku-band (12–18 GHz), Ka-band (26.5–40 GHz), and Q-band (33–50 GHz) satellite receive systems where the operating frequency is within I-Tera MT40’s characterized performance range and the lower Df grades (3.38 at Df 0.0028) are appropriate for the receive signal path.

RF Test Fixtures and Reference Standards: Calibration substrates, fixture interconnects, and calibration standards for vector network analyzers and spectrum analyzers where stable, documented Dk and Df properties are more important than achieving the lowest possible Df. I-Tera MT40 RF/MW’s multiple Dk grades make it possible to design fixture elements at specific impedance values for a given substrate thickness without requiring custom substrate thickness selection.

For fabrication and engineering support on RF/microwave PCBs using ISOLA PCB materials including I-Tera MT40 RF/MW, working with a fabricator who processes both standard high-performance epoxy and recognized microwave substrate materials is essential for achieving the tight impedance tolerances that RF circuit performance requires.

Dk Selection Guide for I-Tera MT40 RF/MW Applications

This is the section that most RF engineers need and few material guides provide: a practical decision tree for which Dk grade to specify.

When to Choose Dk 3.38 (Df 0.0028)

Select the Dk 3.38 grade when: the insertion loss budget is primary and every tenth of a dB of Df matters; the operating frequency is in the range where Astra MT77 (Dk 3.00, Df 0.0017) is over-specified but you still need better loss than Dk 3.45 can deliver; or when the trace widths resulting from Dk 3.45 or higher are uncomfortably close to the fabricator’s minimum feature size. Dk 3.38 is the grade most competitive with Rogers RO4003C (Dk 3.55, Df 0.0027) — it provides better Df than RO4003C while being Dk-comparable.

When to Choose Dk 3.45 (Df 0.0031)

The Dk 3.45 grade is the standard choice and the most commonly available option. It matches the Dk of the I-Tera MT40 HSD variant, which means designs that start on the HSD variant and move to the RF/MW construction for different thickness options don’t need to recalculate controlled impedance. It also closely matches Rogers RO4350B (Dk 3.48) — enabling a material substitution path from RO4350B to I-Tera MT40 RF/MW at Dk 3.45 with minimal circuit redesign. This grade is appropriate for designs up to approximately 20 GHz where the Df of 0.0031 provides adequate insertion loss margin.

When to Choose Dk 3.60 (Df 0.0033)

The Dk 3.60 grade is the entry point for SWaP-driven miniaturization. At Dk 3.60 versus Dk 3.45, transmission line physical lengths for a given electrical length are approximately 3.2% shorter — not dramatic, but compounding across a complex circuit. For designs with many resonant elements, the aggregate footprint reduction is meaningful. Dk 3.60 also closely matches Panasonic Megtron 6 (Dk 3.60, Df 0.0037) — I-Tera MT40 RF/MW at Dk 3.60 provides better Df (0.0033 vs 0.0037) while being in the same Dk range, with FR-4 process compatibility on par with Megtron 6.

When to Choose Dk 3.75 (Df 0.0035)

The Dk 3.75 grade maximizes circuit miniaturization within the I-Tera MT40 RF/MW system. Wavelength-dependent structures are approximately 11% shorter compared to Dk 3.00 reference materials. For military airborne radar boards where volume and weight specifications are hard constraints, or for compact automotive radar modules with tight PCB form factors, Dk 3.75 enables circuit designs that Dk 3.45 or lower simply cannot achieve within the available board area. The Df of 0.0035 is the penalty — verify your insertion loss budget tolerates it before specifying Dk 3.75 on a loss-sensitive receive path.

Useful Resources and Data Downloads

Resource	Type	Link
I-Tera MT40 RF/MW Product Page	Isola product page	isola-group.com/i-tera-mt40-rfmw
I-Tera MT40 RF/MW Datasheet PDF	Official datasheet	isola-group.com (RF/MW PDF)
I-Tera MT40 HSD Product Page	HSD variant	isola-group.com/i-tera-mt40
I-Tera MT40 RF/MW Processing Guide	Fabrication guide	isola-group.com RF/MW Processing
Astra MT77 Product Page	Ultra-low-loss companion	isola-group.com/astra-mt77
Tachyon 100G Product Page	HSD hybrid partner	isola-group.com/tachyon-100g
IsoDesign Impedance Calculator	Online stack-up tool	isola-group.com/design-tools
Isola IMS 2023 Article — I-Tera MT40	Technical article	isola-group.com/ims-2023
IPC-4103/17 Specification	IPC Standard	ipc.org
UL Product iQ (File E41625)	UL Certification DB	iq.ul.com
EverythingRF I-Tera MT40 Page	Distributor/specs	everythingrf.com

Frequently Asked Questions About Isola I-Tera MT40 RF Microwave

1. What is the primary difference between I-Tera MT40 RF/MW and I-Tera MT40 HSD, and when should I choose each?

Both share the same resin system, Tg (215°C DSC), Td (360°C), and processing parameters. The differences are: the RF/MW variant is characterized across four Dk grades (3.38, 3.45, 3.60, 3.75) with Df 0.0028–0.0035, and is available in heavier laminate constructions (10, 20, 30, 60 mil) suited to microwave circuit substrate thicknesses. The HSD variant is nominally characterized at Dk 3.45 / Df 0.0031 and available in thinner laminates (2 to 24 mil) suited to multilayer digital stack-ups. Choose the RF/MW variant for any application where you need a specific Dk grade other than 3.45, require substrate thicknesses of 20+ mil, or are designing transmission line circuits where the Dk grade selection impacts circuit area. Choose the HSD variant for high-speed digital multilayer designs where the 2–12 mil core thickness options are needed.

2. How does the Dk tolerance (±0.05 or ±0.07) affect RF circuit performance in practice?

I-Tera MT40 RF/MW carries a Dk tolerance of approximately ±0.05 around the nominal value for each grade (some older datasheets show ±0.07 on certain grades). For a 50 Ω microstrip line, a Dk variation of ±0.05 around Dk 3.45 translates to a controlled impedance variation of approximately ±0.7 Ω — well within ±5% impedance specification without lot-specific trace width adjustment. For the tightest impedance requirements, use the IsoStack tool or a field solver with the actual Dk from the Dk/Df table for your specific construction and resin content, not the nominal grade value.

3. Can I-Tera MT40 RF/MW be used in a hybrid stack-up with standard FR-4 for cost optimization?

Technically yes, but with caveats. I-Tera MT40 RF/MW’s Z-axis CTE is approximately 2.8% (50–260°C), while standard FR-4 like 370HR runs approximately 3.5–4.5%. That mismatch creates differential expansion stress at the material interface during lamination and thermal cycling. For non-critical applications or boards that don’t see extreme thermal cycling, hybrid builds with standard FR-4 can work. For programs requiring IPC Class 3 reliability or automotive-grade thermal cycling qualification, the preferred hybrid partners are materials with similar CTE values — specifically Astra MT77, Tachyon 100G, and the I-Tera MT40 HSD variant. Always verify your specific hybrid combination with your fabricator before committing to production panel design.

4. Does I-Tera MT40 RF/MW meet automotive-grade temperature specifications?

The RF/MW variant specifies Dk stability from -40°C to +140°C — this range is directly aligned with the automotive AEC-Q100 Grade 1 temperature specification (-40°C to +125°C) and the operating temperature range of ADAS radar modules. The 215°C DSC Tg provides substantial margin above the maximum rated operating temperature. For automotive-qualified designs, verify that the complete material system (core, prepreg, copper foil, surface finish) meets the specific automotive OEM’s material qualification requirements, which may include additional testing beyond IPC standards.

5. Why does I-Tera MT40 RF/MW offer PIM performance data in its datasheet, and when does it matter?

Passive Intermodulation (PIM) is relevant for RF systems that simultaneously transmit high power and receive weak signals on nearby frequencies — most importantly cellular base station antenna systems, where PIM products can fall directly in the receive band and degrade system sensitivity. The 3GPP standards for base station PIM certification require -153 dBc or better at 2×43 dBm test signals. PIM is influenced by copper foil surface roughness, mechanical connections, and material nonlinearities. I-Tera MT40 RF/MW includes PIM data (measured with VLP-2 copper foil) to support antenna substrate qualification for base station programs. If your application includes a PIM certification requirement, specify HVLP (VLP2) copper foil on I-Tera MT40 RF/MW and verify with your fabricator that the assembly process doesn’t introduce PIM-generating mechanical connections.

Engineering Conclusion: The Dk Selection Advantage

Isola I-Tera MT40 RF microwave earns its specification in RF and microwave designs through the combination of FR-4-compatible processing economics, W-band-stable electrical properties, and — most distinctively — four Dk grades within a single qualified material system. The last attribute is genuinely unique among FR-4-process-compatible RF laminates: no other Isola material and no direct Rogers competitor offers four Dk grades in the same system from Dk 3.38 to Dk 3.75.

The practical consequence for RF circuit engineers is a design tool that other laminates don’t provide. When SWaP constraints require miniaturizing antenna and circuit elements beyond what Dk 3.00–3.45 materials can support at a given substrate thickness, Dk 3.60 or Dk 3.75 delivers that miniaturization within the same material qualification. When trace width tolerancing on fine-feature circuits needs more process margin, Dk 3.38 widens the traces. When a design migrating from Rogers RO4350B needs a drop-in replacement with better Df and FR-4 processing, Dk 3.45 is the substitution path.

That Dk flexibility, combined with the material’s genuine Df performance (0.0028–0.0035 at 10 GHz), W-band stability, and no PTFE through-hole treatment required, makes I-Tera MT40 RF/MW the material of choice for RF and microwave designs where the fixed-Dk alternatives don’t serve all the design constraints simultaneously.

For fabrication and sourcing support for Isola RF and microwave PCB materials including I-Tera MT40 RF/MW, visit RayPCB’s ISOLA PCB resource page.