ITEQ IT-988G vs. Isola I-Speed: The Definitive Ultra-Low Loss PCB Comparison

In the high-stakes arena of 100G and 400G networking, the printed circuit board (PCB) is no longer just a structural base—it is a critical, frequency-dependent component. As data rates push toward 56 Gbps and 112 Gbps PAM4, signal integrity (SI) engineers are forced to move beyond standard High-Tg FR-4 into the world of ultra-low loss (ULL) laminates.

Two of the most prominent contenders in this space are ITEQ IT-988G and Isola I-Speed. While both are marketed as high-performance solutions for high-speed digital (HSD) applications, they serve slightly different niches in the loss-budget spectrum. ITEQ’s IT-988G (particularly the SE variant) is often positioned for the bleeding edge of data center switches, while Isola’s I-Speed is the “bridge” material designed to offer superior bandwidth while maintaining a familiar FR-4 processing window.

This engineering deep-dive compares IT-988G vs. I-Speed to help you determine which material fits your specific insertion loss budget and thermal reliability requirements.

The Engineering Logic: Why Ultra-Low Loss?

To appreciate the difference between these materials, we must understand the “Loss Tangent” or Dissipation Factor ($Df$). In a typical high-speed channel, signal energy is lost through two primary mechanisms: conductor loss (skin effect) and dielectric loss. At frequencies above 10 GHz, dielectric loss becomes the dominant enemy.

Standard FR-4 has a $Df$ of ~0.020. Mid-loss materials like Isola 370HR sit at ~0.016. Ultra-low loss materials like IT-988G and I-Speed push this value below 0.006, drastically extending the viable reach of high-speed differential pairs.

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ITEQ IT-988G: The 400G Powerhouse

ITEQ IT-988G is a halogen-free, ultra-low loss material engineered specifically for the 100G and 400G switch markets. It utilizes an advanced resin technology that offers exceptionally low dielectric constant ($Dk$) and $Df$ stability across a wide frequency range.

Key Features of IT-988G

Extreme Low Loss: With a $Df$ as low as 0.0014 (in the SE variant), it is designed for 56G and 112G PAM4 signaling.

High Thermal Reliability: A $Tg$ of 190°C (DSC) and $Td$ of 405°C make it one of the most thermally robust laminates available.

CAF Resistance: Excellent Conductive Anodic Filament (CAF) resistance, essential for high-density interconnect (HDI) designs with tight via pitches.

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Isola I-Speed: The Bandwidth Bridge

Isola I-Speed is a high-performance FR-4 resin system designed to offer 25% more electrical bandwidth than competitive products in the high-speed digital space. It is engineered to provide a “best of both worlds” scenario: significantly lower loss than standard High-Tg materials while being “FR-4 process compatible” for the fabricator.

Key Features of I-Speed

Enhanced Bandwidth: Targeted at 25 Gbps to 56 Gbps NRZ/PAM4 applications.

Processing Simplicity: It is intentionally designed to be the closest high-speed material to conventional FR-4 processing, reducing fabrication risk.

Thermal Stability: A $Tg$ of 180°C and improved Z-axis expansion (15% better than competitive products) ensure via reliability in high-layer-count boards.

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Technical Specifications: IT-988G vs. I-Speed

When evaluating these materials, the datasheet values (typically tested at 10 GHz) are the primary constraints for your 3D electromagnetic field solvers (like Ansys HFSS).

Table 1: Side-by-Side Material Properties

Property	Test Method	ITEQ IT-988G (E-Glass)	Isola I-Speed (E-Glass)
Glass Transition (Tg)	DSC	190°C	180°C
Decomposition (Td)	TGA	405°C	360°C
Dk @ 10 GHz	Bereskin Stripline	3.63	3.63
Df @ 10 GHz	Bereskin Stripline	0.0029	0.0060
Z-Axis CTE (Pre-Tg)	TMA	58 ppm/°C	45 ppm/°C
Z-Axis CTE (Total 50-260°C)	TMA	2.95%	2.50%
Moisture Absorption	IPC-TM-650	0.31%	0.06%
Thermal Conductivity	ASTM E1952	~0.45 W/m·K	0.40 W/m·K

The “Special Edition” Factor: IT-988G SE

For ultra-high-speed designs (112G), ITEQ offers the IT-988G SE. This variant uses Low-Dk glass to push the $Dk$ down to 3.24 and the $Df$ to an incredible 0.0014. In this configuration, ITEQ significantly outperforms the standard Isola I-Speed in terms of raw insertion loss.

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Signal Integrity Analysis: Insertion Loss and Skew

Insertion Loss Comparison

In a long-reach (LR) channel, the difference between a $Df$ of 0.006 (I-Speed) and 0.0029 (IT-988G) is massive.

Isola I-Speed is ideal for 10G to 28G NRZ designs or short-reach 56G PAM4 where cost-to-performance ratio is critical.

ITEQ IT-988G is the mandatory choice for long-reach 56G or 112G PAM4 designs where the total channel loss budget (often ~30-35 dB) is the primary constraint.

Glass Weave Effect and Skew

High-speed differential pairs are susceptible to skew caused by the fiberglass weave.

I-Speed is available with “Square Weave” and mechanically spread glass styles to mitigate skew.

IT-988G is frequently specified with Low-Dk glass (SE version) which not only lowers loss but also provides a more homogenous dielectric constant, further reducing intra-pair skew without requiring zig-zag routing.

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Thermal Reliability: Z-Axis Expansion and HDI

For high-layer-count (HLC) boards (24 to 32+ layers), the Z-axis Coefficient of Thermal Expansion (CTE) is the silent killer. During reflow, if the resin expands significantly more than the copper plating in the holes, the result is via barrel cracking.

Isola I-Speed has a very impressive Z-axis CTE profile (2.5% total expansion). This makes it exceptionally reliable for thick backplanes.

ITEQ IT-988G offers higher absolute thermal resistance ($Td$ of 405°C vs 360°C), meaning it can survive more intense reflow cycles and rework sessions without delaminating.

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Fabricator Perspective: Yield and Processability

A high-performance material is only useful if it can be manufactured with high yields.

I-Speed Advantage: Isola has engineered I-Speed to be “FR-4 process compatible.” It doesn’t require the exotic plasma desmear or specialized drilling bits that some other ultra-low loss materials demand. This often leads to higher yields and lower fabrication costs at standard board houses.

IT-988G Advantage: As a halogen-free material, IT-988G is more environmentally friendly and is a “Green” solution. ITEQ has optimized the resin flow for HDI structures, making it a favorite for advanced 400G switch motherboards that utilize complex Any-Layer HDI.

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Strategic Selection: Which One Should You Choose?

Use Isola I-Speed If:

You are upgrading from a Mid-loss (Df ~0.010) material and need a significant bandwidth boost (up to 25/56 Gbps).

Your design requires a 24+ layer backplane where via reliability and Z-axis expansion are the primary risks.

You need a material that is widely available in both North American and European fab shops with standard FR-4 processing.

Use ITEQ IT-988G (or SE) If:

You are designing for 56G or 112G PAM4 signaling and every 0.1 dB of insertion loss matters.

Your project has strict “Green” or Halogen-Free requirements.

You are building advanced 400G networking equipment with complex HDI and sequential lamination.

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Essential Resources for Hardware Engineers

To simulate these materials accurately, do not rely on generic “market values.” Use the official technical data:

ITEQ IT-988G Official Datasheet: Download PDF

Isola I-Speed Official Product Page: Visit Isola Group

Laminate Procurement & Stackup Support: For hardware teams looking to bridge the gap between design and physical production, exploring specialized ITEQ PCB manufacturing partners can help synchronize material procurement with engineering requirements.

Signal Integrity Journal: Peer-reviewed articles on 112G PAM4 channel modeling and laminate selection.

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Frequently Asked Questions (FAQs)

1. Is ITEQ IT-988G a direct equivalent to Isola I-Speed?

No. While they occupy similar high-speed digital markets, IT-988G (especially the SE variant) is an Ultra-Low Loss material ($Df$ ~0.002-0.003), whereas I-Speed is generally considered a Low-Loss material ($Df$ ~0.006). IT-988G offers significantly lower insertion loss.

2. Can I use I-Speed for 112G PAM4 designs?

For short-reach (VSR) or chip-to-module (C2M) interfaces, I-Speed can be used. However, for medium or long-reach channels, the insertion loss of I-Speed is usually too high for 112G signaling budgets.

3. What is the benefit of Halogen-Free in IT-988G?

Beyond environmental compliance, halogen-free resin systems often offer better thermal stability ($Td$) and moisture resistance, which improves the CAF reliability of the board in harsh data center environments.

4. Why is Isola I-Speed easier for fabricators to process?

Isola designed the chemistry of I-Speed to mimic standard FR-4 epoxy behavior. This means fabricators don’t have to adjust their drilling speeds or desmear chemistries as drastically as they do for some specialized high-speed resin systems.

5. How does moisture absorption affect these materials?

Moisture has a high dielectric constant. If a board absorbs moisture, its $Dk$ shifts, causing impedance mismatches. I-Speed has an exceptionally low moisture absorption rate (0.06%), providing superior impedance stability in humid environments.