ITEQ PCB Laminate Dk & Df Comparison Chart: The Engineering Deep Dive

In high-speed digital and RF design, the “standard FR-4” mindset is a liability. As we push toward 112G PAM4 signaling and 5G millimeter-wave frequencies, the PCB substrate is no longer just a structural base—it is a critical, frequency-dependent component. For a hardware engineer, the ITEQ Dk Df comparison is the first step in managing signal integrity, impedance control, and insertion loss budgets.

ITEQ has positioned itself as a global leader by providing a roadmap from cost-effective high-Tg materials to ultra-low-loss substrates that rival PTFE performance. This guide provides a comprehensive technical breakdown of the ITEQ product line, categorized by loss class and application, to help you navigate the “Dk/Df Paradox” in your next multilayer stackup.

Understanding the Physics: Dk and Df in High-Speed Design

Before diving into the charts, we must define the parameters that dictate your link budget.

Dielectric Constant (Dk or $\epsilon_r$)

The Dielectric Constant measures the ability of the material to store electrical energy. In a PCB, Dk dictates the propagation velocity ($v_p$) of the signal and the characteristic impedance of the transmission lines. A lower Dk allows for faster signals and thinner traces for a given impedance, which is vital for miniaturized HDI designs.

Dissipation Factor (Df or $\tan \delta$)

The Dissipation Factor measures the amount of signal energy lost as heat within the dielectric. As frequencies climb into the gigahertz range, molecular friction in the resin system becomes the dominant source of attenuation. If your Df is too high, your eye diagram will close before the signal reaches the receiver.

ITEQ Product Line Classification by Loss Tier

ITEQ segments its materials into distinct tiers based on their Df at 10 GHz. This allows engineers to “right-size” their material choice—avoiding the cost of over-specification while ensuring the board meets the insertion loss requirements.

Standard and Mid-Loss Tier (DDR3, PCIe Gen 3)

These materials are the “workhorses” of the industry. They are optimized for thermal reliability and cost rather than raw signal speed.

Material	Tg (DSC)	Dk @ 10GHz	Df @ 10GHz	Key Application
IT-150	$150^{\circ}C$	4.30	0.0160	Industrial / Consumer
IT-180A	$175^{\circ}C$	4.20	0.0150	High-Reliability Servers
IT-170G	$175^{\circ}C$	4.10	0.0140	Halogen-Free General

Low-Loss and Very Low-Loss Tier (5G Sub-6, PCIe Gen 4/5)

This tier introduces modified PPE (Polyphenylene Ether) resin systems. These materials are essential for 25G NRZ and 56G PAM4 signaling where Dk stability over frequency is paramount.

Material	Tg (DSC)	Dk @ 10GHz	Df @ 10GHz	Key Application
IT-150DA	$180^{\circ}C$	3.65	0.0065	5G / Automotive Radar
IT-968	$185^{\circ}C$	3.70	0.0050	100G Networking
IT-200LK	$200^{\circ}C$	3.90	0.0110	High-Temp Power / RF

Ultra-Low Loss and Extreme Low-Loss (800G, 112G PAM4)

For the most demanding AI clusters and backbone switches, ITEQ offers the “Special Edition” (SE) and ultra-low loss (ULL) series. These materials utilize Low-Dk glass weaves and advanced hydrocarbon-modified resins.

Material	Tg (DSC)	Dk @ 10GHz	Df @ 10GHz	Key Application
IT-988GSE	$190^{\circ}C$	3.25	0.0023	AI Servers / 400G+
IT-88GMW	$170^{\circ}C$	2.98	0.0012	77GHz Radar / 5G mmWave
IT-998G	$190^{\circ}C$	3.10	0.0015	800G Switch Backplanes

Advanced Material Selection: The “Dk Stability” Factor

A single Dk value at 10 GHz is rarely enough for a modern broadband simulation. We must look at how Dk behaves across the spectrum.

Dk vs. Frequency

Many standard materials exhibit “dispersion,” where the Dk drops significantly as frequency increases. This causes different frequency components of a digital pulse to travel at different speeds, leading to ISI (Inter-Symbol Interference). High-performance ITEQ materials like IT-988GSE are engineered for a “flat” Dk curve, ensuring signal timing remains pristine from DC to 50 GHz.

Glass Weave Effect and Skew

In high-speed differential pairs, the physical weave of the fiberglass can cause “intra-pair skew.” If one trace of the pair sits over a glass knuckle and the other over a resin-rich area, they see different Dk values.

ITEQ Solution: Most ULL materials in the ITEQ PCB lineup support “Spread Glass” (styles 1067, 1078, etc.). These spread the glass bundles to create a more homogenous Dk environment, effectively eliminating skew without requiring zig-zag routing.

Thermal Reliability: The Z-Axis CTE Paradox

For high-layer-count (HLC) boards (24 to 50 layers), the Z-axis Coefficient of Thermal Expansion (CTE) is as critical as the Df. If the board expands too much vertically during lead-free reflow ($260^{\circ}C$), the copper plating in the via barrels will crack.

IT-180A: Exceptional Z-axis expansion of 2.7% (total 50-260°C).

IT-988GSE: Designed for AI server backplanes with a low Z-CTE of ~2.6%.

By matching a low-loss resin with a low-CTE glass system, ITEQ allows for 30+ layer boards that can survive multiple rework cycles—a requirement for expensive data center hardware.

Sourcing and Engineering Resources

To move from a comparison chart to a physical stackup, use the following technical databases:

ITEQ Official Online Stackup Tool: The primary resource for identifying exact Dk values based on specific resin content (RC%).

IPC-4101/102 & /103: Sectional design standards for high-frequency base materials.

Signal Integrity Journal: Peer-reviewed data on VNA-based material characterization for ITEQ laminates.

Stackup Consulting: For real-time material availability and factory-specific stackup verification, consult ITEQ PCB specialized resources.

Frequently Asked Questions (FAQs)

1. Why does Dk vary with resin content (RC%)?

The “Effective Dk” of a laminate is a composite of the glass Dk (typically ~6.1 for E-glass) and the resin Dk (typically ~3.0 for low-loss resins). A higher resin content (RC%) will lower the overall Dk of the laminate.

2. Is IT-988GSE a direct equivalent to Panasonic Megtron 6?

In terms of Df classification, yes. They are both ultra-low loss PPE-based materials. However, their Dk values differ slightly, so a stackup recalculation is mandatory when switching between them to maintain impedance targets.

3. What copper foil should I pair with IT-88GMW?

For mmWave frequencies (24GHz+), you must use HVLP (Hyper Very Low Profile) copper. Standard profile copper has a surface roughness that will dominate your insertion loss budget, effectively nullifying the benefits of the ultra-low-loss dielectric.

4. How does moisture absorption affect Dk and Df?

Water has a Dk of ~80. If a material absorbs moisture, its Dk will spike and its Df will increase. ITEQ materials for high-speed design maintain moisture absorption below 0.15% to ensure impedance stability in humid environments.

5. Can I use standard IT-180A for 10G Ethernet?

For short traces (under 4 inches), IT-180A might pass. However, for 10G and 25G over longer reaches, the higher loss tangent (0.015) will consume your loss budget quickly. Moving to IT-968 or IT-150DA is recommended for 10G+ applications.

Summary for the Hardware Architect

Selecting the right ITEQ laminate is a balancing act. If you are designing for AI compute, the focus is on IT-988GSE for its ultra-low Df and thermal robustness. If you are building 5G mmWave antennas, the low Dk and Df of IT-88GMW are non-negotiable. For General Industrial designs, the reliability and cost-effectiveness of IT-180A remain the gold standard.

By utilizing the ITEQ Dk Df comparison data effectively, you can build a PCB that is not only electrically transparent but also mechanically resilient through the life of the product.