Complete Guide to Isola PCB Materials: Every Product Explained (2025)

In the high-stakes world of PCB engineering, the laminate is the foundation upon which every other design decision is built. If the substrate fails, the most brilliant circuit design in the world becomes electronic scrap. For over a century, Isola Group has been at the forefront of laminate technology, evolving from basic phenolic resins to the sophisticated, high-speed, and thermally robust materials we rely on today.

As we move through 2025, the demand for Isola PCB materials is driven by three massive industry shifts: the transition to 800V automotive architectures, the rollout of 6G-ready RF infrastructure, and the move toward 224G PAM4 data rates in AI-driven data centers. Choosing the right Isola grade is no longer just about Tg (Glass Transition Temperature); it’s about Dk stability, Z-axis CTE, and CAF resistance.

This technical guide provides a deep dive into the entire Isola portfolio. We will categorize these materials by application—from the industry-standard 370HR to the ultra-low-loss Astra MT77—giving you the engineering data needed to optimize your next stack-up.

The Isola Advantage: Why Engineers Specify These Materials

When you’re drafting a fabrication note, you aren’t just looking for “FR-4.” You’re looking for a predictable resin system that won’t delaminate during a 260°C lead-free reflow or suffer from via-barrel cracking after 1,000 thermal cycles.

Isola’s reputation is built on consistency. Their proprietary resin chemistries are designed to be “fabricator-friendly,” meaning they don’t require exotic plasma desmear or specialized lamination cycles that drive up bare-board costs. Whether you are designing a 4-layer industrial controller or a 32-layer backplane, there is an Isola substrate engineered for that specific stress profile.

1. High-Reliability and Standard FR-4 Materials

For the vast majority of multilayer designs, thermal reliability is the primary concern. These materials are the “workhorses” of the electronics industry, used in everything from medical devices to aerospace avionics.

Isola 370HR: The Industry Benchmark

If there is one material every PCB engineer should know, it is Isola 370HR. It is a high-performance, 180°C Tg FR-4 system that has largely replaced standard FR-4 in high-reliability applications.

Key Strength: Exceptional CAF (Conductive Anodic Filament) resistance and a low Z-axis CTE (2.8%).

Best For: Heavy copper designs, sequential lamination (HDI), and lead-free assembly.

Isola 185HR: The AOI-Optimized Workhorse

Very similar to 370HR in terms of thermal specs (180°C Tg), the 185HR system is uniquely formulated to be UV-blocking and laser-fluorescing.

Key Strength: Superior performance during Automated Optical Inspection (AOI) and precise solder mask registration.

Best For: High-volume automotive and industrial boards where manufacturing yield is a critical KPI.

Isola IS400: The Cost-Effective Mid-Tg Choice

Not every board needs a 180°C Tg. The IS400 offers a 150°C Tg, providing a thermal “safety net” for lead-free soldering at a lower price point than the HR series.

Best For: Consumer electronics and white goods that require RoHS compliance without the premium cost of high-Tg substrates.

Material	Tg (°C)	Td (°C)	Dk @ 1GHz	Df @ 1GHz	Primary Benefit
370HR	180	340	4.04	0.021	Best-in-class reliability
185HR	180	340	4.01	0.020	AOI & yield optimization
IS400	150	330	4.00	0.022	Cost-effective mid-Tg

2. High-Speed Digital (HSD) and Low-Loss Materials

As data rates climb toward 112G and 224G, the “loss tangent” (Df) becomes the most critical metric. Standard FR-4 absorbs too much signal energy, turning high-speed pulses into heat. Isola’s HSD portfolio is designed to minimize this insertion loss.

Isola TerraGreen and TerraGreen 400G

TerraGreen is Isola’s answer to the need for halogen-free, ultra-low-loss materials. The 400G version is specifically engineered for the 400Gbps (and 800Gbps) networking era.

Key Strength: Extremely low Df (0.0018) and high thermal stability.

Best For: Data center switches, high-speed routers, and AI accelerators.

Isola I-Tera MT40

The MT40 is a “very low loss” laminate that serves as a bridge between high-end digital and RF. It maintains a stable Dk across a massive temperature range.

Best For: 5G infrastructure, power amplifiers, and high-speed digital designs requiring 20GHz+ performance.

Isola Tachyon 100G

Tachyon 100G is designed for the absolute limit of digital speeds. It features very low Dk and Df, identical to many PTFE-based materials but with the ease of FR-4 processing.

Key Strength: Virtually identical Dk/Df properties to Rogers 4350B but in a thermoset resin system.

3. RF, Microwave, and Millimeter-Wave Materials

At RF frequencies (24GHz to 77GHz+), the physical weave of the fiberglass can cause phase skew. Isola’s RF materials often utilize “spread glass” and highly filled resins to ensure a homogeneous dielectric constant.

Isola Astra MT77

Astra MT77 is the flagship for the automotive radar and 5G mmWave markets. It offers an ultra-low Df (0.0017) that remains stable up to 100 GHz.

Best For: 77 GHz ADAS (Advanced Driver Assistance Systems) and satellite communications.

Isola I-Tera MT40 (RF Grade)

While mentioned in HSD, the RF-grade MT40 is frequently used in hybrid stack-ups. You can laminate MT40 RF layers onto a 370HR core to save money while keeping the RF signals on the low-loss outer layers.

Material	Dk @ 10GHz	Df @ 10GHz	Tg (°C)	Process	Ideal Application
Astra MT77	3.00	0.0017	200	FR-4 Like	77GHz Radar / 5G mmWave
Tachyon 100G	3.02	0.0021	200	FR-4 Like	100G/400G Ethernet
I-Tera MT40	3.45	0.0031	200	FR-4 Like	5G Base Stations

4. Extreme Environment: Polyimide Materials

When the ambient temperature stays above 200°C, epoxy resins fail. For the most demanding aerospace, defense, and down-hole oil drilling applications, Isola offers a robust polyimide line.

Isola P95 and P96 (Core) / P25 and P26 (Prepreg)

These are high-temperature polyimide materials with a Tg of 260°C.

P95/P25: The standard high-temp version, rated UL 94 HB.

P96/P26: The flame-retardant version, rated UL 94 V-0.

Best For: Jet engine sensors, geothermal drilling, and semiconductor burn-in boards.

5. Automotive Electrification: The IS550H

One of the newest and most exciting Isola PCB materials is the IS550H. As EVs move to 800V systems, the risk of high-voltage arcing and CAF failure is extreme.

Key Strength: Passes 2,000 hours of 1,500V CAF testing and offers a high thermal conductivity (0.70 W/mK).

Best For: On-board chargers (OBC), DC/DC converters, and battery management systems (BMS).

6. Specialty Bonding: No-Flow and Low-Flow Prepregs

If you are designing a rigid-flex board or bonding a heat sink into a cavity, you cannot use standard prepreg. High-flow resin will bleed onto the flex arm or foul the thermal interface.

Isola FR406N and P25N

These are “No-Flow” versions of the FR406 and P95 resin systems. They bond layers together without the resin liquefying and running across the board.

Best For: Rigid-flex interfaces, cavity boards, and busbar bonding.

Stack-Up Design: Mixing Isola Materials (Hybrids)

One of the best ways to optimize cost is through a hybrid stack-up. You don’t always need an entire board made of Astra MT77.

By using Astra MT77 for the top and bottom signal layers (where the RF travels) and using 370HR for the inner ground and power planes, you get the performance of a high-end RF board at a fraction of the price. Isola materials are specifically engineered to have compatible lamination cycles to make these hybrid builds possible.

For a deep dive into how to source and fabricate these complex stack-ups, visit the ISOLA PCB resource center.

Useful Resources for PCB Engineers

Isola Technical Library: Access the full datasheets for every material mentioned here.

IPC-4101 Standards: Most Isola materials are governed by specific IPC slash sheets (e.g., /98, /101, /126).

Field Solver Integration: Use tools like Polar Speedstack or Simberian to import Isola Dk/Df tables directly for impedance modeling.

Fabrication Capability Database: Check the ISOLA PCB database to verify which fabricators carry stock of specialty materials like MT77 or P96.

5 Frequently Asked Questions (FAQs) About Isola PCB Materials

1. Can I swap 370HR for standard FR-4 without changing my layout?

Generally, yes, but you must check your impedance. 370HR has a slightly different Dk than commodity FR-4. If you have tight impedance tolerances, you may need to adjust trace widths by a fraction of a mil to maintain your 50-ohm or 90-ohm targets.

2. Why is Astra MT77 so popular for automotive radar?

It’s all about the Df and the glass. Astra MT77 has an ultra-low dissipation factor and uses spread glass to ensure that the 77 GHz signal doesn’t “see” the fiberglass weave, which would otherwise cause phase errors in the radar’s detection.

3. What is the shelf life of Isola prepreg?

Typically, prepreg must be stored in a cool, dry environment (<5°C). Under these conditions, the shelf life is usually 6 months. If stored at room temperature, it can degrade in as little as a few days, leading to poor lamination.

4. Are Isola materials lead-free compatible?

Almost all modern Isola materials (370HR, 185HR, I-Tera, Astra, etc.) are designed for lead-free assembly, meaning they can survive multiple 260°C reflow cycles without delaminating.

5. How do I choose between I-Tera MT40 and Tachyon 100G?

If you are designing for RF/Microwave (Antennas), MT40 is often the better choice. If you are designing for ultra-high-speed digital (400G networking), Tachyon 100G is optimized specifically for signal integrity and low skew.