ITEQ IT-998G: Halogen-Free Super Ultra-Low Loss for Next-Gen Data Centers

The architectural landscape of next-generation data centers is undergoing a violent, rapid evolution. Driven by the explosive growth of Generative AI, machine learning clusters, and high-performance computing (HPC), network backbones are aggressively migrating from 400G to 800G Ethernet, with 1.6T implementations already visible on the horizon. For hardware architects and printed circuit board (PCB) engineers, this transition has introduced a terrifying signal integrity cliff.

When dealing with 112 Gbps and 224 Gbps Pulse Amplitude Modulation 4-Level (PAM4) signaling, standard high-speed laminates simply collapse under the physics of microwave frequencies. To route these extreme signals across switch motherboards and AI accelerator trays, a new tier of material is mandatory. Enter ITEQ IT-998G, a halogen-free, super ultra-low loss PCB material specifically engineered to solve the brutal channel loss budgets of next-gen data centers.

In this comprehensive engineering guide, we will strip away the marketing jargon and dive deep into the material science, electrical performance, thermal reliability, and fabrication realities of the ITEQ IT-998G laminate. Whether you are designing a 32-layer 800G network switch or a dense AI GPU module, this article will equip you with the knowledge required to successfully integrate this material into your next high-speed stackup.

The Signal Integrity Physics of Next-Gen Data Centers

To truly appreciate the engineering behind ITEQ IT-998G, one must first understand the physics that are actively trying to destroy your data center signals.

In legacy systems utilizing Non-Return-to-Zero (NRZ) encoding, signal margins were relatively forgiving. However, 800G Ethernet relies on 112G PAM4 over eight lanes. PAM4 utilizes four distinct voltage levels to transmit two bits per symbol. While this effectively doubles the data rate within the same bandwidth, it catastrophically shrinks the vertical eye opening—drastically reducing the Signal-to-Noise Ratio (SNR).

The Nyquist frequency for a 112G PAM4 signal sits at exactly 28 GHz. At 28 GHz, PCB traces cease to act like standard electrical wires and behave as lossy, dispersive microwave transmission lines.

The Dual Threat: Conductor Loss and Dielectric Loss

At 28 GHz, insertion loss (the total attenuation of the signal as it travels from transmitter to receiver) is primarily driven by two factors:

Conductor Loss (Skin Effect): High-frequency current does not travel through the core of the copper trace; it travels strictly along the outermost “skin.” If the copper foil has a rough profile to adhere to the resin, the signal must travel up and down the microscopic “teeth” of the copper, increasing the effective distance and the resistance.

Dielectric Loss (Dissipation Factor): As the electromagnetic wave propagates through the PCB substrate, the oscillating electric field causes the dipoles within the resin molecules to flip back and forth. This molecular friction converts RF energy directly into heat. The higher the Dissipation Factor (Df), the more energy is lost to the substrate.

The IEEE 802.3ck specification for 100G/lane connectivity demands an extremely tight insertion loss budget. For a Very Short Reach (VSR) channel inside a switch chassis, the ball-to-ball loss limit is roughly 16 dB at 28 GHz. If your laminate consumes 1.5 dB per inch, routing a simple 8-inch trace will consume 12 dB of your budget, leaving practically zero margin for vias, BGA breakouts, optical module connectors, and standard manufacturing variations. This is exactly where the super ultra-low loss properties of ITEQ IT-998G become architecturally necessary.

Demystifying ITEQ IT-998G: Core Characteristics

ITEQ IT-998G is not just an iterative update; it is a fundamental reformulation of the resin and glass matrix designed to rival pure PTFE (Teflon) microwave materials, but with the manufacturability of a traditional thermoset resin. The “G” designation signifies its “Green” or halogen-free chemical composition.

Halogen-Free Chemistry Without Compromise

Historically, PCB engineers viewed “halogen-free” (HF) materials with a degree of skepticism for ultra-high-speed applications. Traditional FR-4 relies on brominated flame retardants (like TBBPA) to achieve a UL94 V-0 flammability rating. When regulatory bodies like the EU (via RoHS and REACH) began pushing to eliminate halogens—due to the highly toxic, corrosive, and carcinogenic dioxin gases they release during combustion or recycling—chemical companies had to find alternatives.

Early halogen-free laminates used phosphorus or nitrogen-based reactive flame retardants. While safer for the environment, these early HF formulations were notoriously brittle, absorbed more moisture, and often suffered from inferior Dk/Df properties compared to their brominated counterparts.

ITEQ IT-998G shatters this historical compromise. By utilizing an advanced, proprietary polyphenylene ether (PPE) and hydrocarbon resin blend with novel phosphorus-based curing agents, IT-998G achieves a strictly halogen-free status (compliant with IPC/JEDEC J-STD-709) while simultaneously delivering better thermal and electrical performance than legacy brominated ultra-low loss systems.

Super Ultra-Low Dielectric Loss

The defining metric of ITEQ IT-998G is its Dissipation Factor (Df). At 28 GHz, the material boasts a Df of approximately 0.001.

To provide context, standard FR-4 has a Df of ~0.020, and mid-tier high-speed materials hover around 0.005. By dropping the Df to 0.001, IT-998G prevents the substrate from absorbing the electromagnetic energy of 112G signals. When paired with ultra-smooth copper, the raw insertion loss of IT-998G drops to an astonishing ~0.73 dB/inch at 28 GHz. This enables hardware architects to route signals across massive 19-inch 1RU switch motherboards without being forced into utilizing expensive optical flyover cables for every single node.

Extreme Dk Flatness and Phase Stability

The Dielectric Constant (Dk) dictates the propagation velocity of the signal. ITEQ IT-998G features a Dk of approximately 3.0 at 28 GHz.

While a low Dk is excellent for increasing signal speed, the most critical factor for PAM4 signaling is Dk flatness. If a material’s Dk varies drastically across frequencies, the lower-frequency components of a digital pulse will travel at a different speed than the high-frequency harmonics. This phenomenon, known as phase dispersion, causes the signal to smear across the time domain, resulting in massive deterministic jitter and completely closed eye diagrams at the receiver. IT-998G provides a remarkably flat Dk response from 1 GHz all the way up to millimeter-wave frequencies, preserving the sharp, fast rise-times required by next-gen ASIC transmitters.

Technical Specifications: ITEQ IT-998G Material Data

When defining your PCB stackup in tools like Altium, Cadence, or Mentor, precise material data is required for 3D electromagnetic field solvers (like Ansys HFSS). Below is a typical performance table for ITEQ IT-998G based on industry evaluations.

Technical Parameter	Test Condition / Frequency	Typical Value	Unit	Engineering Significance
Dielectric Constant (Dk)	28 GHz (53% Resin)	~3.0	–	Low Dk increases signal velocity; flat curve prevents phase dispersion and jitter.
Dissipation Factor (Df)	28 GHz (53% Resin)	~0.001	–	Super ultra-low loss tangent minimizes dielectric signal attenuation.
Insertion Loss (IL)	28 GHz (Grounded Coplanar)	~0.73	dB/inch	Critical for meeting IEEE 802.3ck 16dB ball-to-ball 112G channel budgets.
Glass Transition (Tg)	DMA	> 200	°C	Ensures extreme thermal stability during lead-free assembly and AI workloads.
Decomposition Temp (Td)	TGA (5% weight loss)	> 400	°C	High survivability during multiple reflow cycles and complex HDI rework.
Z-Axis CTE	50°C to 260°C	2.5 – 2.9	%	Unmatched via reliability; prevents barrel cracking and pad cratering in thick boards.
Moisture Absorption	IPC-TM-650 2.6.2.1	< 0.1	%	Prevents Dk shifting in humid environments and reduces the risk of explosive delamination.
Halogen-Free	IPC/JEDEC J-STD-709	Pass	–	Environmentally compliant for global data center deployments.

Thermal Management and Extreme Reliability

Signal integrity is only half the equation in next-gen data centers; thermal integrity is the silent killer. A modern AI accelerator tray featuring multiple interconnected GPUs and NVSwitches consumes kilowatts of power. The ASICs sit directly on the PCB, acting as concentrated thermal point-sources that routinely push local board temperatures above 100°C.

Beating the Heat with High Tg and Td

If a PCB material’s Glass Transition Temperature (Tg) is too low, the ambient heat of the data center server will cause the resin to soften, dramatically increasing its Coefficient of Thermal Expansion (CTE). ITEQ IT-998G utilizes an advanced resin matrix that achieves a Tg exceeding 200°C (measured via Dynamic Mechanical Analysis, DMA) and a Decomposition Temperature (Td) greater than 400°C.

This means that even under the continuous thermal stress of a 24/7 AI workload, the physical dimensions of the board remain locked in place. The exceptionally low Z-axis CTE (roughly 2.5% expansion from 50°C to 260°C) is a lifesaver for PCB reliability engineers. As the board is subjected to the 260°C peak temperatures of lead-free RoHS reflow ovens—often multiple times for double-sided surface mount assemblies—the substrate will not excessively expand in the Z-axis. This prevents the mechanical rupturing of plated through-holes (PTH) and safeguards the integrity of microscopic blind and buried HDI vias.

CAF Resistance for Dense Pin-Outs

The ASICs powering 800G networks feature massive BGA packages with pin pitches shrinking to 0.8mm or 0.6mm. This forces PCB designers to place laser-drilled microvias dangerously close to one another. Under the influence of continuous voltage bias and ambient humidity, copper ions can migrate along the microscopic interface between the fiberglass weave and the resin system, causing a short circuit known as a Conductive Anodic Filament (CAF).

Because ITEQ IT-998G is engineered with highly optimized silane coupling agents that create an impenetrable bond between the low-loss resin and the glass bundles, it acts as a fortress against moisture ingress. It easily passes the industry’s most stringent hundreds-of-hours CAF testing protocols, ensuring long-term field reliability for mission-critical hyperscale infrastructure.

PCB Fabrication: Engineering Guidelines for IT-998G

Specifying a super ultra-low loss material is simple; manufacturing a 30-layer backplane with it is an intricate art form. ITEQ IT-998G is designed to be highly processable compared to pure PTFE microwave boards, but it still requires a top-tier fabrication partner.

Optimizing Copper Foils and Adhesion

To fully realize the 0.001 Df of IT-998G, you cannot use standard RTF (Reverse Treated Foil) copper. You must specify Hyper Very Low Profile (H-VLP) or rolled annealed copper. Because the skin depth of a 28 GHz signal is less than 0.4 micrometers, any surface roughness exceeding 1.0 micrometer (Rz) will aggressively drive up insertion loss.

However, smooth copper creates a manufacturing paradox: it is inherently difficult to bond smooth metal to a smooth substrate. The ITEQ IT-998G resin system features a unique chemical adhesion mechanism that bonds securely to H-VLP copper without requiring severe mechanical roughening. Still, PCB designers must be acutely aware that trace peel strength is mathematically lower on these systems than on standard FR-4. Designing adequate anti-pad clearances and robust thermal reliefs is mandatory to prevent pads from lifting during BGA rework.

Lamination, Laser Drilling, and Desmear

Data center motherboards frequently utilize sequential lamination and Any-Layer HDI (High-Density Interconnect) to break out the massive pin counts of 25.6T and 51.2T switch ASICs. ITEQ IT-998G exhibits predictable and uniform resin flow during the high-pressure press cycles, allowing fabricators to maintain ultra-tight registration tolerances across 30+ layers.

When fabricating HDI microvias, the ablation rate of the IT-998G PPE resin is vastly different from traditional epoxy. Fabricators must carefully tune their UV and CO2 laser parameters. Following drilling, the desmear process (typically utilizing plasma rather than aggressive permanganate baths) must be perfectly balanced. Over-desmearing can chemically attack the advanced low-loss resin, causing wedge voids behind the via plating, while under-desmearing will result in catastrophic via separation during thermal cycling.

Stackup and Routing Strategies

As a PCB engineer, utilizing ITEQ IT-998G requires implementing specific high-speed routing methodologies.

Defeating the Fiber Weave Effect

At 28 GHz, the physical gaps between the fiberglass yarns within the prepreg and core materials are large enough to disrupt the signal. If the positive trace of a 100-ohm differential pair routes over a dense glass knuckle (which has a higher Dk) and the negative trace routes over a resin-rich window (which has a lower Dk), the two signals will travel at slightly different speeds. This introduces glass weave skew, destroying the phase relationship of the PAM4 signal.

To mitigate this on IT-998G stackups, engineers must explicitly specify “spread glass” styles—such as 1067, 1078, or 1086 weaves. Spread glass mechanically flattens the yarn, creating a homogenous Dk environment. Additionally, routing your critical 112G lanes off-axis (e.g., at a 10-degree or 15-degree angle relative to the X/Y weave of the board) guarantees that both traces average out the Dk variations equally.

Via-in-Pad Plated Over (VIPPO)

The parasitic capacitance and stub resonance of standard through-hole vias will destroy an 800G signal. Plating and back-drilling are absolute requirements, but for the densest BGA fields, VIPPO is standard practice. Vias are drilled directly into the surface mount pads, filled with epoxy, and plated flat. Because IT-998G has an extremely low Z-axis CTE, it prevents the underlying via barrel from expanding and cracking the surface copper cap during the 260°C reflow process, effectively eliminating pad cratering.

Competitive Landscape: ITEQ IT-998G vs. Alternatives

The high-speed materials market is fiercely contested. When evaluating ITEQ IT-998G, it is often benchmarked against other elite “super ultra-low loss” laminates.

Manufacturer	Material Series	Dk (@ 28 GHz)	Df (@ 28 GHz)	Target Application & Key Traits
ITEQ	IT-998G	~3.0	~0.001	800G, AI Servers; Halogen-Free, Excellent multi-layer processability.
ITEQ	IT-988G SE	~3.24	~0.0014	100G/400G Networks; Low Dk glass, highly stable.
Panasonic	Megtron 8	~3.0	~0.001	AI clusters, 800G switches; Industry benchmark, excellent thermal robustness.
Rogers	RO1200	~3.05	~0.0017	RF/Microwave, High-Speed Digital; PTFE-like electricals, very low loss.
TUC	TU-883	~3.1	~0.0015	Telecommunications, High-layer count servers; Strong CAF resistance.

While materials like Megtron 8 and RO1200 offer spectacular performance, ITEQ IT-998G is frequently chosen due to its aggressive combination of strictly halogen-free compliance, flawless 30+ layer press compatibility, and highly competitive global supply chain availability.

Applications in Next-Gen Architecture

ITEQ IT-998G was designed with specific endpoints in mind:

AI and Machine Learning Accelerator Trays: Compute platforms such as NVIDIA’s massive multi-GPU NVLink ecosystems require uncompromised bandwidth. The HDI structures connecting these chips rely on the ultra-low insertion loss of IT-998G to push massive data payloads without excessive heat generation.

800G / 1.6T Ethernet Switch Motherboards: To achieve 25.6T and 51.2T total switching capacities, the routing from the central ASIC to the front panel OSFP or QSFP-DD cages must be mathematically flawless. IT-998G easily supports these heavy, high-layer-count chassis.

Automotive Radar and 6G Telecommunications: As frequency allocations push into the millimeter-wave spectrum (77 GHz for ADAS radar, and >100 GHz for 6G research), the flat Dk and extremely low Df of this material are ideal for Antenna-in-Package (AiP) and massive MIMO backplanes.

Useful Resources and Databases for PCB Designers

Designing with super ultra-low loss materials requires cross-referencing datasheets with empirical industry data. Below are vital resources for hardware architects and PCB designers:

IEEE 802.3ck Task Force Public Archives: Access the raw presentation data and insertion loss simulations (C2M channel budgets) that led to the ratification of 100G/lane standards. You will frequently find ITEQ materials cited in these models.

IPC-4101 Specification Database: Review the specific “slash sheets” that govern halogen-free, high-Tg, low-loss materials to ensure your fabrication notes are strictly compliant with international standards.

Material and Stackup Support: For official datasheets, precise 3D field solver models, simulation parameters, and to locate qualified PCB fabricators who can reliably press high-layer-count halogen-free designs, access specialized laminate databases. You can explore ITEQ PCB resources to synchronize your material procurement with your engineering stackup requirements.

Signal Integrity Journal: A phenomenal resource for peer-reviewed articles regarding copper roughness modeling (Huray vs. Hammerstad models) and mitigating the fiber weave effect.

Frequently Asked Questions (FAQs)

1. What makes ITEQ IT-998G different from standard FR-4?

Standard FR-4 uses an epoxy resin with a high dissipation factor (Df ~0.020) that absorbs and ruins high-speed signals. IT-998G uses an advanced PPE/hydrocarbon blend with a super ultra-low Df (~0.001) that allows 112G PAM4 signals to travel long distances with minimal loss. Furthermore, IT-998G is halogen-free and possesses a vastly superior Glass Transition Temperature (Tg >200°C).

2. Why is a “Halogen-Free” (HF) PCB material important?

Halogens, specifically bromine and chlorine used in legacy flame retardants, produce highly toxic and corrosive dioxins when burned or improperly recycled. Halogen-free materials like IT-998G replace these with safer phosphorus or nitrogen compounds, allowing technology companies to comply with strict global environmental regulations (RoHS, REACH) without sacrificing electrical performance.

3. What type of copper foil is required for ITEQ IT-998G?

To achieve its incredibly low insertion loss (approx. 0.73 dB/inch at 28 GHz), IT-998G must be laminated with Hyper Very Low Profile (H-VLP) or rolled annealed copper. Standard profile copper creates severe skin-effect losses at 28 GHz, entirely negating the benefits of the ultra-low loss resin.

4. Can ITEQ IT-998G be used in high-layer-count (30+ layers) designs?

Absolutely. Unlike pure PTFE (Teflon) materials which are incredibly difficult to laminate and suffer from dimensional instability, IT-998G was engineered specifically for thick, high-layer-count switch motherboards and backplanes. It flows predictably during lamination, allowing fabricators to maintain precise via-to-pad registration.

5. How does IT-998G combat the fiber weave effect in high-speed routing?

While the material itself has a fantastic Dk, PCB engineers must still specify “spread glass” (such as 1067 or 1086 styles) when defining the IT-998G prepregs in their stackup. Spread glass ensures the Dk is homogenous beneath the differential pairs, preventing glass weave skew and maintaining the phase integrity of the 112G PAM4 signals.