If you’ve been designing PCBs for any length of time, you’ve likely encountered Isola materials on specification sheets, fab house material lists, or stackup recommendations from signal integrity engineers. But choosing the right Isola PCB laminate isn’t just about picking a name from a dropdown menu—it requires understanding what makes each material tick and how it matches your design requirements.
I’ve spent years working with various Isola PCB materials across everything from consumer electronics to aerospace applications. This guide distills that experience into practical advice you can actually use when selecting materials for your next project.
What is Isola PCB?
An Isola PCB refers to any printed circuit board fabricated using laminate and prepreg materials manufactured by Isola Group. Founded over 100 years ago, Isola has become one of the most trusted names in high-performance PCB substrates, with manufacturing facilities across North America, Europe, and Asia.
What sets Isola PCB materials apart from generic FR-4 is their consistency and engineered performance characteristics. While standard FR-4 might give you a dielectric constant somewhere between 4.2 and 4.8 depending on who manufactured it, Isola materials come with tightly controlled specifications that signal integrity engineers actually trust.
Isola specializes in copper-clad laminates (CCL) and prepreg materials—the fundamental building blocks of multilayer PCBs. These aren’t just generic glass-reinforced epoxy; they’re formulated with proprietary resin systems designed for specific performance requirements like low loss, high thermal reliability, or lead-free assembly compatibility.
| Material | Dk | Df | Tg (°C) | Application |
|---|---|---|---|---|
| FR408 | 3.70 | 0.0120 | 180 | High Reliability |
| IS410 | 4.00 | 0.0180 | 170 | Multilayer |
| Astra MT77 | 3.00 | 0.0017 | 200 | RF/Microwave |
| I-Tera MT40 | 3.45 | 0.0031 | 200 | High Speed |
| I-Speed | 3.63 | 0.0085 | 185 | Low Loss |
Understanding Isola PCB Building Blocks
Before diving into specific materials, let’s establish what we’re actually working with when we specify Isola PCB substrates.
Copper-Clad Laminates (CCL)
Copper-clad laminate is the foundation of any PCB. It consists of a cured prepreg core sandwiched between thin copper foil layers on each side. The lamination process involves compressing copper and prepreg plies together under precisely controlled heat, pressure, and vacuum conditions.
The quality of this lamination directly affects your PCB’s electrical performance, dimensional stability, and long-term reliability. Isola’s CCL products undergo rigorous quality testing that goes beyond standard IPC requirements.
Prepreg Materials
Prepreg—short for “pre-impregnated”—is the fiberglass fabric infused with partially cured resin that bonds laminate layers together during PCB fabrication. The resin system is what gives each Isola material its unique thermal, electrical, and mechanical properties.
Common Isola prepreg styles include 1080 (0.08mm thickness, ~64.5% resin content), 2116 (0.12mm, ~54% resin content), and 7628 (0.2mm, ~47% resin content). These different glass weaves and resin percentages allow fabricators to hit specific stackup thicknesses and impedance targets.
Isola PCB Material Categories
Isola organizes their laminate portfolio into categories based on primary application. Understanding these categories helps narrow down your material search before getting into specific products.
Standard FR-4 Laminates
These materials provide reliable performance for general-purpose applications where extreme speed or thermal demands don’t exist. They offer excellent processability with standard PCB fabrication equipment.
High-Speed Digital Laminates
Designed for multi-gigabit data transmission, these materials feature low dielectric loss and stable electrical properties across frequency. Products like I-Speed, I-Tera MT40, and Tachyon 100G fall into this category.
RF/Microwave Laminates
For applications above 3 GHz, these ultra-low-loss materials provide the controlled dielectric constant and minimal signal degradation that RF designs demand. Astra MT77, IS680, and IS680 AG serve this market.
Thermally Robust Laminates
When lead-free assembly, multiple reflow cycles, or high ambient temperatures are concerns, these high-Tg materials maintain their integrity under thermal stress. The 370HR and FR408HR are workhorses in this category.
Popular Isola PCB Materials: Detailed Specifications
Here’s where we get into the specifics that actually matter for your design decisions. The table below summarizes key properties, followed by deeper dives into each material.
| Material | Dk @ 10GHz | Df @ 10GHz | Tg (°C) | Td (°C) | Best Application |
|---|---|---|---|---|---|
| 370HR | 4.04 | 0.021 | 180 | 340 | High-reliability, lead-free |
| FR408HR | 3.68 | 0.0092 | 190 | 360 | Mid-loss, thermal performance |
| I-Speed | 3.63 | 0.006 | 185 | 340 | 10-25 Gbps digital |
| I-Tera MT40 | 3.45 | 0.0031 | 200 | 360 | High-speed, multiple Dk options |
| Tachyon 100G | 3.02 | 0.0021 | 215 | 360 | 100 Gbps+ data center |
| Astra MT77 | 3.00 | 0.0017 | 200 | 360 | RF/mmWave, automotive radar |
| IS680 | 3.00 | 0.0028 | 200 | 360 | General RF/microwave |
| TerraGreen | 3.45 | 0.0031 | 200 | 360 | Halogen-free, low-loss |
Isola 370HR: The Industry Standard
If there’s one Isola PCB material that deserves the title of “industry workhorse,” it’s 370HR. This high-performance FR-4 has been deployed in thousands of designs across virtually every market segment.
What makes 370HR special is its combination of thermal reliability, CAF (Conductive Anodic Filament) resistance, and ease of processing. With a Tg of 180°C and Td of 340°C, it handles lead-free assembly without issues. The low Z-axis CTE (coefficient of thermal expansion) means your plated through-holes stay intact through multiple thermal cycles.
The 370HR uses spread weave glass in both directions, which helps reduce fiber weave effects in high-speed designs—though for truly critical signal integrity applications, you’ll want to look at the lower-loss options below.
Best for: General high-reliability applications, automotive body electronics, industrial controls, military systems requiring proven reliability.
Isola FR408HR: The Mid-Loss Performer
FR408HR occupies the sweet spot between standard FR-4 and premium low-loss materials. With Dk of 3.68 and Df of 0.0092 at 10 GHz, it offers meaningfully better electrical performance than 370HR while remaining compatible with standard FR-4 processing.
The 190°C Tg and 360°C Td make it extremely robust for lead-free assembly. It’s rated for 6x 260°C reflow cycles, which gives you plenty of margin for rework scenarios.
I’ve used FR408HR extensively for designs running 5-10 Gbps where 370HR’s higher loss would start causing eye diagram concerns, but where specifying Tachyon or I-Tera would be overkill for the application.
Best for: Telecom equipment, datacom switches up to 25 Gbps, designs where you need better signal integrity than FR-4 without premium material costs.
Isola I-Speed: Bridging Standard and Premium
I-Speed is Isola’s entry point into genuine low-loss territory. The Df of 0.006 at 10 GHz represents a significant improvement over FR408HR while maintaining FR-4 process compatibility.
This material works well for designs in the 10-25 Gbps range where you’re starting to see loss budgets get tight. It’s also popular for backplanes and high-layer-count boards where cumulative losses through longer trace lengths become significant.
Best for: Networking equipment, server backplanes, storage systems running NVMe or SAS interfaces.
Isola I-Tera MT40: Flexible Performance
I-Tera MT40 is unique in offering multiple Dk options—3.38, 3.45, 3.60, and 3.75—all measured at 10 GHz through the z-axis. This flexibility is incredibly useful when you’re trying to match impedances in hybrid designs or optimize trace widths for specific layer constraints.
The Df of 0.0031 at 10 GHz puts it firmly in low-loss territory. Combined with a 200°C Tg and excellent thermal compatibility with materials like Astra MT77 and Tachyon 100G, I-Tera MT40 is often the material of choice for complex hybrid builds.
Best for: Hybrid RF/digital designs, applications requiring impedance matching flexibility, 5G infrastructure, high-speed networking.
Isola Tachyon 100G: Ultra-High-Speed Champion
When your signals are running at 100 Gbps and beyond, Tachyon 100G delivers the performance you need. With Dk of 3.02 and Df of 0.0021 at 10 GHz, this material enables longer channel reaches and cleaner eye diagrams than anything else in the standard FR-4 processing family.
The 215°C Tg is the highest among Isola’s high-speed digital materials, providing exceptional thermal margin. Its CTE characteristics closely match Astra MT77, making hybrid constructions straightforward.
Data center operators and hyperscalers have driven significant adoption of Tachyon 100G for 400G Ethernet switches and next-generation AI/ML accelerator boards.
Best for: Data center switches, 100G/400G Ethernet, AI accelerators, high-performance computing, anywhere loss budgets are extremely tight.
Isola Astra MT77: RF and Millimeter-Wave Excellence
Astra MT77 represents Isola’s answer to traditional ceramic-filled PTFE materials—but with FR-4 process compatibility. The ultra-low Df of 0.0017 at 10 GHz, combined with Dk stability from -40°C to +140°C through W-band frequencies (75-110 GHz), makes it ideal for the most demanding RF applications.
What really sets Astra MT77 apart is its dimensional stability and consistent electrical performance across temperature extremes. Automotive radar systems operating at 77 GHz rely heavily on this material, as do 5G mmWave base stations and phased array antennas.
The FR-4 process compatibility means you avoid the handling headaches and cost premiums associated with PTFE materials while getting comparable electrical performance.
Best for: Automotive radar (77 GHz), 5G mmWave, aerospace communications, satellite systems, any application above 10 GHz requiring excellent Dk stability.
Isola IS680 and IS680 AG: General RF Solutions
IS680 provides reliable RF performance for applications that don’t require the extreme specifications of Astra MT77. With Dk of 3.0 and Df of 0.0028, it’s suitable for most RF designs below 20 GHz.
The IS680 AG variant adds enhanced characteristics for antenna applications, offering Dk of 2.80 and Df of 0.0013—making it an excellent choice for RF front-end modules and antenna arrays.
Best for: General RF/microwave circuits, wireless infrastructure, antenna feed networks.
Isola TerraGreen: Halogen-Free Performance
Environmental regulations increasingly require halogen-free materials in consumer electronics. TerraGreen provides low-loss performance (Dk 3.45, Df 0.0031 at 10 GHz) while meeting halogen-free requirements.
The TerraGreen 400G variant pushes performance even further, with Dk of 3.05 and Df of 0.0018 at 10 GHz—suitable for ultra-high-speed digital circuits requiring halogen-free compliance.
Best for: Consumer electronics requiring environmental compliance, European markets with halogen restrictions, designs requiring both performance and environmental certification.
How to Select the Right Isola PCB Material
Material selection shouldn’t start with picking a product name. It should start with understanding your design requirements, then matching those requirements to material properties.
Signal Speed and Loss Budget
The most common selection driver is signal speed. Here’s a practical guideline:
| Data Rate | Recommended Materials |
|---|---|
| Under 5 Gbps | 370HR, FR408HR |
| 5-10 Gbps | FR408HR, I-Speed |
| 10-25 Gbps | I-Speed, I-Tera MT40 |
| 25-56 Gbps | I-Tera MT40, Tachyon 100G |
| 100 Gbps+ | Tachyon 100G |
| RF under 10 GHz | IS680, I-Tera MT40 |
| RF 10-40 GHz | Astra MT77, IS680 AG |
| RF 40-110 GHz | Astra MT77 |
Run your signal integrity simulations with actual trace lengths and determine what loss level you can tolerate. Over-specifying material drives up costs without adding value.
Thermal Requirements
Consider your assembly process and operating environment:
- Standard lead-free assembly: 370HR, FR408HR, or any material with Tg > 170°C and Td > 300°C
- Multiple reflow cycles or rework: FR408HR (rated 6x 260°C reflow)
- High ambient temperature operation: Materials with Tg well above your maximum operating temperature
- Extreme thermal cycling: IS550H for automotive power electronics, polyimide (P95/P96) for extreme temperature ranges
HDI and High-Layer-Count Considerations
For HDI (High Density Interconnect) boards and designs with many layers, you need materials with excellent CAF resistance, low Z-axis CTE, and good lamination characteristics. The 370HR and FR408HR have extensive track records in sequential lamination designs.
High-speed HDI applications often benefit from I-Tera MT40’s multiple Dk options, which help achieve target impedances with constrained trace geometries.
Hybrid Material Builds
Modern high-performance designs often combine different materials within the same stackup—for example, using Astra MT77 for RF layers and Tachyon 100G for high-speed digital layers.
Isola specifically designs materials like Tachyon 100G and Astra MT77 to be thermally compatible for hybrid builds. Their similar CTE characteristics prevent warpage and delamination issues that plague mismatched material combinations.
Isola PCB Design Best Practices
Beyond material selection, here are engineering practices that get the most out of Isola PCB materials.
Use Actual Dk/Df Values for Simulations
Datasheet values are typical, not guaranteed. For accurate signal integrity analysis, use the Dk/Df tables specific to your construction rather than marketing datasheet values. Isola provides detailed Dk/Df tables for each material showing values at multiple frequencies and for various constructions (core and prepreg combinations).
Build margin into your design for Dk variations (±5-10% is common), thickness tolerances, and etch factors.
Account for Glass Weave Effects
In high-speed designs, the glass weave pattern can cause impedance variations and timing skew. Isola’s 370HR uses spread weave glass to minimize these effects, but for critical applications, consider rotating traces 5-10° relative to the glass weave or using materials specifically designed to mitigate fiber weave effects.
Follow Isola Fabrication Guidelines
Each Isola PCB material has specific processing parameters for optimal results. Ensure your fabricator follows Isola’s recommendations for lamination profiles, drilling parameters, and plating processes. This is especially important for the higher-performance materials like Tachyon 100G and Astra MT77.
Use IsoStack for Stackup Design
Isola provides the IsoStack tool for designing and validating PCB stackups. It helps visualize how different material combinations affect overall board thickness, impedance, and manufacturability. Using this tool early in your design process prevents surprises during fabrication.
Isola PCB Applications by Industry
Different industries have different priorities when selecting Isola PCB materials. Here’s what typically works in each sector.
Telecommunications and 5G
5G infrastructure demands both high-speed digital performance for baseband processing and excellent RF characteristics for radio units. Hybrid builds using I-Tera MT40 or Tachyon 100G for digital sections and Astra MT77 for RF sections are common.
Automotive Electronics
Automotive spans a wide range from infotainment (370HR provides proven reliability) to ADAS radar at 77 GHz (Astra MT77 is purpose-built for this) to EV power electronics facing extreme thermal cycling (IS550H handles continuous temperatures up to 175°C).
Aerospace and Defense
Mission-critical applications demand proven reliability and often require extended temperature ranges. The 370HR and FR408HR have extensive qualification histories. For extreme temperatures, polyimide materials like P95/P96 may be necessary. RF radar systems benefit from Astra MT77’s stability through millimeter-wave frequencies.
Data Centers and High-Performance Computing
The push to 400G Ethernet and beyond drives adoption of Tachyon 100G. AI/ML accelerator boards with multiple high-speed interfaces also benefit from this ultra-low-loss material.
Medical and Industrial Equipment
These sectors typically prioritize reliability and longevity over cutting-edge speed. The 370HR offers the proven reliability these applications require at reasonable cost. For applications requiring very long service life, IS550H provides enhanced thermal endurance.
Quality Certifications for Isola PCB Materials
When specifying Isola PCB materials, verify the quality certifications relevant to your application:
| Certification | Description | Typical Applications |
|---|---|---|
| ISO 9001 | Quality management system | All applications |
| IATF 16949 | Automotive quality standard | Automotive electronics |
| AS9100 | Aerospace quality standard | Aerospace, defense |
| UL Recognition | Safety certification | All commercial applications |
| IPC-4101 | Laminate qualification | PCB fabrication validation |
| RoHS/REACH | Environmental compliance | European markets, consumer products |
Isola materials generally exceed industry qualification requirements through their own rigorous internal testing before product release.
Isola PCB vs. Competitor Materials
Engineers often ask how Isola PCB materials compare to alternatives from Rogers, Panasonic Megtron, or Nelco. Here’s my practical take based on real-world project experience.
Isola vs. Rogers
Rogers dominates the traditional PTFE-based RF market with materials like RO4003C and RT/Duroid. However, PTFE materials require specialized processing—different drill bits, lower processing temperatures, and careful handling to prevent delamination.
For applications above 40 GHz or requiring Dk below 2.5, Rogers PTFE materials remain the gold standard. But for automotive radar at 77 GHz, 5G mmWave, and most RF applications up to W-band, Astra MT77 delivers comparable electrical performance with FR-4 processing compatibility. This translates to shorter lead times, more fabricator options, and typically 20-40% lower costs.
Isola vs. Panasonic Megtron
Panasonic’s Megtron series (particularly Megtron 6 and Megtron 7) competes directly with Isola’s high-speed digital materials. Both product lines offer excellent electrical performance for multi-gigabit applications.
From a practical standpoint, Megtron materials tend to have better availability in Asian supply chains, while Isola materials are often more readily available from North American and European fabricators. Performance-wise, they’re quite comparable—material selection often comes down to your fabricator’s experience and material stocking.
Isola vs. Nelco
Nelco materials, now part of Park Aerospace, offer similar high-performance options to Isola. In my experience, Nelco materials have slightly better thermal and mechanical performance in some cases, particularly for demanding aerospace applications.
However, Isola’s broader product portfolio and global manufacturing footprint often provide better availability and more competitive pricing. For most commercial applications, both vendors deliver comparable results.
Cost Considerations for Isola PCB Materials
Material cost matters, but it’s rarely the deciding factor for performance-critical designs. Here’s how material costs typically stack up:
| Material Category | Relative Cost | When to Accept Higher Cost |
|---|---|---|
| Standard FR-4 | 1x (baseline) | Basic applications only |
| 370HR | 1.2-1.5x | When reliability matters |
| FR408HR | 1.5-2x | 5-10 Gbps, thermal concerns |
| I-Speed | 2-2.5x | 10-25 Gbps applications |
| I-Tera MT40 | 2.5-3x | High-speed, hybrid builds |
| Tachyon 100G | 3-4x | 100 Gbps+, data centers |
| Astra MT77 | 3-5x | RF above 10 GHz |
Remember that material cost is typically 15-30% of total PCB cost. Saving 20% on material might only reduce your total cost by 3-6%—not worth compromising signal integrity or reliability for most applications.
The real cost savings come from selecting the right material the first time. A board spin caused by inadequate material performance costs far more than the premium for better material.
Understanding Isola PCB Material Properties
To make informed material decisions, you need to understand what the key specifications actually mean for your design.
Dielectric Constant (Dk)
The dielectric constant determines trace impedance for a given geometry. Lower Dk means wider traces for the same impedance, which can ease routing in dense designs. Higher Dk enables narrower traces and smaller structures, useful for miniaturization.
Isola materials typically range from Dk 3.0 (Astra MT77) to Dk 4.4 (IS410). For most high-speed digital designs, a Dk around 3.0-3.7 provides good balance between trace width and loss performance.
Equally important is Dk stability across temperature and frequency. Materials like Astra MT77 maintain consistent Dk from -40°C to +140°C through W-band frequencies—critical for RF designs where impedance drift causes performance degradation.
Dissipation Factor (Df)
The dissipation factor directly relates to signal loss in your traces. Lower Df means less energy lost as heat, enabling longer traces and better signal integrity. This is the primary differentiator between standard and premium materials.
As a rule of thumb, Df below 0.01 is considered low-loss for most high-speed digital applications. Ultra-low-loss materials like Tachyon 100G (Df 0.0021) and Astra MT77 (Df 0.0017) become necessary when loss budgets are extremely tight—such as 100 Gbps channels or mmWave RF designs.
Glass Transition Temperature (Tg)
Tg is the temperature at which the laminate transitions from rigid to rubbery. Above Tg, the material’s CTE increases dramatically, and mechanical properties degrade. For lead-free assembly with peak reflow temperatures around 260°C, you need Tg well above your maximum process temperature.
Most Isola PCB materials offer Tg from 180°C to 215°C, providing adequate margin for lead-free assembly. The higher Tg materials like Tachyon 100G (215°C) are especially valuable when multiple reflow cycles or rework is anticipated.
Decomposition Temperature (Td)
Td indicates when the material begins to chemically break down. This is your absolute upper limit—exceed it and the laminate will degrade permanently. Isola materials typically range from 340°C to 360°C Td, well above normal processing temperatures.
Coefficient of Thermal Expansion (CTE)
CTE, particularly in the Z-axis, affects via reliability. Higher Z-axis CTE puts more stress on plated through-holes during thermal cycling. Materials like 370HR feature low Z-axis CTE (around 45 ppm/°C), contributing to excellent via reliability through thousands of thermal cycles.
Useful Resources for Isola PCB Design
Here are resources I regularly reference when working with Isola materials:
Official Isola Resources:
- Isola Product Datasheets – Complete specifications for all materials
- IsoStack Stackup Tool – Interactive stackup builder
- Dk/Df Tables – Detailed electrical properties by construction
Technical Papers:
- Isola’s technical papers on CAF resistance, high-speed material selection, and laminate manufacturing provide deeper insight into material behavior
IPC Standards:
- IPC-4101: Base Materials for Rigid and Multilayer Printed Boards
- IPC-TM-650: Test Methods Manual
Frequently Asked Questions About Isola PCB
What is the difference between Isola 370HR and FR408HR?
The primary difference is electrical performance. FR408HR offers lower dielectric loss (Df 0.0092 vs 0.021 at 10 GHz) and lower Dk (3.68 vs 4.04), making it better for high-speed digital applications. FR408HR also has higher Tg (190°C vs 180°C) and Td (360°C vs 340°C), providing superior thermal performance. Choose 370HR for general high-reliability applications where electrical performance isn’t critical; choose FR408HR when you need better signal integrity or more thermal margin.
Can I use Isola materials in hybrid stackups with different materials?
Yes, and Isola designs many products specifically for hybrid compatibility. Materials like Tachyon 100G and Astra MT77 share similar CTE characteristics, making them excellent partners for builds requiring both high-speed digital and RF performance. Always verify thermal compatibility with your fabricator and use IsoStack to model the stackup before committing to production.
How do I choose between I-Speed, I-Tera MT40, and Tachyon 100G?
It comes down to data rate and loss budget. I-Speed (Df 0.006) works well up to about 25 Gbps. I-Tera MT40 (Df 0.0031) handles higher speeds and offers multiple Dk options for impedance flexibility. Tachyon 100G (Df 0.0021) is optimized for 100 Gbps and beyond. Run your signal integrity simulations with actual trace lengths to determine what loss level you can tolerate for acceptable eye diagrams.
Is Astra MT77 a replacement for PTFE materials?
For many applications, yes. With Dk of 3.0 and Df of 0.0017 at 10 GHz—stable through W-band frequencies—Astra MT77 rivals ceramic-filled PTFE materials while processing like FR-4. This eliminates the handling difficulties, longer lead times, and higher costs associated with PTFE. However, for applications requiring Dk below 2.5 or very specific dielectric properties not available in Astra MT77, PTFE may still be necessary.
What should I consider when designing for lead-free assembly with Isola materials?
Ensure your selected material has sufficient thermal margin. Look for Tg above 170°C and Td above 300°C at minimum. Materials like 370HR (Tg 180°C), FR408HR (Tg 190°C), and the low-loss materials (Tg 185-215°C) all support lead-free assembly. FR408HR is specifically rated for 6x 260°C reflow cycles, making it suitable for designs that may require rework. Also consider Z-axis CTE—lower values reduce stress on plated through-holes during thermal cycling.
Conclusion
Selecting the right Isola PCB material isn’t complicated once you understand your requirements and how each material addresses them. Start with your signal speed and thermal requirements, match those to material categories, then fine-tune based on specific design constraints and budget.
For most applications, 370HR or FR408HR will serve you well. When signal speeds push above 10 Gbps, move to I-Speed or I-Tera MT40. For 100 Gbps applications, Tachyon 100G is the go-to choice. RF designs above 10 GHz benefit from Astra MT77’s exceptional stability.
The key is matching material to application—not over-specifying because a better material exists, and not under-specifying because you’re trying to save a few dollars on a high-performance design that needs proper materials to work reliably.
Whatever Isola PCB material you choose, work closely with your fabricator to ensure proper processing. The best material in the world won’t perform if it’s not fabricated correctly.
