Rogers RO4400/RO4400T Series Bondply: Complete Guide to Specs, Processing & Applications

When you’re designing multilayer RF boards or high-speed digital circuits, the bonding material you choose can make or break your project. I’ve worked with dozens of prepreg options over the years, and the RO4400/RO4400T Series Bondply from Rogers Corporation consistently stands out for high-frequency applications where signal integrity matters.

This guide covers everything you need to know about this bondply family—from electrical properties and processing parameters to real-world applications. Whether you’re evaluating materials for a new design or troubleshooting lamination issues, you’ll find practical information here that goes beyond what’s in the datasheet.

What Is RO4400/RO4400T Series Bondply?

The RO4400 series is a family of high-frequency thermoset prepregs designed specifically to complement RO4000 series laminates. Unlike standard FR-4 prepreg, these materials use a hydrocarbon/ceramic-based resin system that delivers significantly lower dielectric loss at microwave frequencies.

Rogers developed this bondply family to solve a common problem: how do you build reliable multilayer boards when your RF layers need high-performance materials but your power and ground layers don’t justify the cost? The answer is hybrid construction—and RO4400 bondply makes that possible with FR-4-compatible processing temperatures.

Key Product Variants in the RO4400 Family

The series includes four main grades, each targeting specific design requirements:

The “T” designation in RO4400T refers to spread glass reinforcement, which provides better thickness control and resin distribution—particularly useful when you’re stacking 8+ layers and need consistent dielectric spacing.

RO4400 vs RO4400T: Understanding the Difference

This is one of the most common questions I get from engineers new to Rogers materials. Here’s the straightforward answer:

RO4400 (standard grades) uses conventional woven glass reinforcement. The resin-to-glass ratio creates predictable flow characteristics during lamination, and these grades have been the workhorse of the industry for years.

RO4400T grades incorporate spread glass technology. The glass fibers are more uniformly distributed, reducing the “knuckle effect” you see in standard weaves. This matters when you’re working with:

• High multilayer count designs (10+ layers)
• Tight impedance tolerances requiring consistent dielectric thickness
• Applications where surface roughness affects insertion loss

For most 4-6 layer designs, RO4450F handles the job perfectly. Once you’re dealing with 8+ layers or tight thickness budgets, RO4450T becomes worth the premium.

Technical Specifications: RO4400 Series Bondply Properties

Let me break down the specs that actually matter for your design decisions.

Electrical Properties

That Df of 0.004 is where these materials really shine. Compare that to standard FR-4 prepreg at 0.02-0.025, and you’re looking at roughly 5-6x lower dielectric loss. At 10 GHz, that difference translates directly to better signal integrity.

Thermal Properties

The high Tg (>280°C for RO4450F) is crucial if you’re doing sequential lamination. Fully cured RO4400 bondply can handle multiple lamination cycles without degradation—something that trips up engineers who don’t realize their material choice limits their fabrication options.

Mechanical Properties

Available Thicknesses

Thickness tolerance runs ±0.0006″ based on Rogers’ lamination parameters. Your actual results depend on how planar your inner layers are—heavily etched patterns with significant copper variation will see more thickness deviation.

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Compatible Laminates for Multilayer Stackups

One of the main advantages of RO4400 bondply is its compatibility with the broader RO4000 family. You can build hybrid constructions using:

• RO4003C — Dk 3.38, the economy option for less critical RF layers
• RO4350B — Dk 3.48, the industry standard for RF/microwave
• RO4835/RO4835T — Higher Tg version with improved oxidation resistance
• RO4360G2 — Dk 6.15, matches RO4460G2 bondply for high-Dk designs
• RO4000 LoPro — Low-profile copper for reduced conductor loss

The beauty of this system is that you can also combine RO4400 bondply with low-flow FR-4 prepreg in a single bond cycle. This lets you use Rogers PCB materials only where you need them (RF signal layers) while keeping costs down on power distribution and mounting layers.

Example Stackup Configuration

Here’s a typical 6-layer hybrid design I’ve used for radar front-ends:

This approach puts high-performance materials where they matter and keeps fabrication cost reasonable.

Processing Guidelines for RO4400 Series Bondply

Getting consistent results with RO4400 requires attention to detail during fabrication. Here’s what works based on Rogers’ guidelines and practical experience.

Storage and Handling

Never store bondply under vacuum—it changes the resin distribution. Use a first-in-first-out inventory system to prevent using expired material.

Lamination Parameters

This is where most fabrication problems originate. The RO4400 resin system reaches minimum viscosity between 100°C and 120°C (210°F-250°F). Spending adequate time in this temperature window is critical for proper fill.

Recommended Lamination Profile:

Challenging Designs (heavy copper, opposing planes): Increase pressure to 650-750 PSI and extend the low-viscosity dwell time.

Inner Layer Preparation

• Surface Treatment: Oxide treatment is required for proper adhesion. Reduced black oxide, brown oxide, or additive/subtractive alternatives all work.
• Pre-bake: Bake inner layers for 15-30 minutes at 115-125°C immediately before layup.
• Dielectric Surfaces: Do not mechanically or chemically alter etched dielectric surfaces before bonding.

Copper Fill Capability

Each ply of RO4450F or RO4460G2 bondply can fill up to 0.0018″ (45 μm) of total copper thickness—whether that copper is on one side or split between both sides of the adhesive layer.

For designs exceeding this fill requirement:

• Add additional bondply plies
• Use vertically offset (non-stacking) copper dot patterns in flow/venting areas
• Ensure proper venting around panel perimeter

Applications for RO4400/RO4400T Series Bondply

The combination of low loss, thermal stability, and CAF resistance makes RO4400 bondply suitable for demanding applications across multiple industries.

RF and Microwave Communications

This is the primary application space. RO4400 bondply enables multilayer construction for:

• Base station antennas and power amplifiers
• Point-to-point microwave links
• Satellite communication terminals
• Low-noise amplifiers (LNAs) and frequency converters

The low Df (0.004) minimizes insertion loss through via transitions between layers—a critical factor when your signal path crosses multiple planes.

5G Infrastructure and Devices

5G networks operating in FR1 (sub-6 GHz) and FR2 (mmWave) bands demand consistent dielectric properties. RO4400 bondply provides:

• Stable Dk across temperature variations
• Low-loss signal transmission for mmWave frequencies
• Compatibility with high-density via structures

Automotive Radar Systems

77 GHz automotive radar modules for ADAS (Advanced Driver Assistance Systems) benefit from:

• Tight Dk tolerance for consistent antenna performance
• Low z-axis CTE for plated through-hole reliability during thermal cycling
• CAF resistance for humid operating environments

Military and Aerospace

Defense applications leverage the material’s compliance with stringent reliability requirements:

• Sequential lamination capability for complex multilayer builds
• Lead-free process compatibility
• UL 94 V-0 flame rating
• MIL-PRF-55342 Class 1M compatible constructions

High-Speed Digital

While primarily an RF material, RO4400 bondply also serves high-speed digital designs where signal integrity matters:

• Backplane interconnects running at 25+ Gbps
• High-performance computing systems
• Network switching equipment

Benefits of Using RO4400 Series Bondply

Let me summarize why this material family deserves consideration for your next design:

Signal Integrity: The low dissipation factor (0.004) reduces dielectric loss significantly compared to FR-4, preserving signal quality through multilayer transitions.

Process Compatibility: FR-4-compatible lamination temperature (177°C/350°F) means standard fab equipment works without modification. This is a major cost advantage over PTFE-based systems.

Design Flexibility: Multiple Dk options (3.23 to 6.15) let you match bondply properties to your laminate selection or create intentional impedance transitions.

Reliability: Low z-axis CTE (43-60 ppm/°C) reduces stress on plated through-holes during thermal cycling, improving long-term reliability.

CAF Resistance: Conductive Anodic Filament resistance prevents copper migration between adjacent vias—increasingly important as via pitch shrinks.

Sequential Lamination: High Tg allows multiple lamination cycles without property degradation, enabling complex buildup structures.

Useful Resources and Downloads

For detailed technical specifications and fabrication guidance, these resources are essential:

Official Rogers Corporation Resources

• RO4400 Series Bondply Datasheet (RO4450F & RO4460G2): Direct PDF from Rogers containing complete electrical, thermal, and mechanical specifications
• RO4400T Series Bondply Datasheet (RO4450T): Spread glass variant specifications
• Processing Guidelines for RO4450B, RO4450F, and RO4460G2: Detailed lamination parameters and troubleshooting guidance
• Rogers Bondply Selector Tool: Interactive tool on rogerscorp.com for matching bondply to laminate requirements

Design Resources

• Rogers MWI Calculator: Microwave impedance calculator supporting RO4000 series materials
• IPC Slash Sheet Reference: UL file number E102763B for regulatory documentation
• Sample Request: Available through Rogers’ online request system for evaluation

Technical Support

Rogers maintains regional technical support centers. For North America, contact their Advanced Connectivity Solutions division in Chandler, AZ (480-961-1382).

Frequently Asked Questions

What’s the difference between RO4450B and RO4450F bondply?

RO4450F offers improved lateral flow capability compared to RO4450B. If you’re working with designs that have challenging fill requirements—heavy copper, tight via pitch, or opposing plane layers—RO4450F handles these situations better. For most new designs, RO4450F is the recommended starting point; RO4450B mainly supports legacy designs where direct replacement isn’t necessary.

Can I use RO4400 bondply with FR-4 cores in a hybrid stackup?

Yes, this is one of the key advantages. RO4400 bondply and low-flow FR-4 prepreg can be combined in non-homogeneous multilayer constructions using a single bond cycle at 177°C (350°F). This lets you place Rogers materials only on RF-critical layers while using cost-effective FR-4 elsewhere.

What’s the shelf life of RO4400 bondply?

When properly stored (10-30°C, protected from moisture and UV light, in original sealed packaging), RO4400 bondply maintains its properties for 6 months from the shipment date. Use first-in-first-out inventory management to ensure you’re working with fresh material.

Is RO4400 series compatible with lead-free soldering processes?

Yes. All RO4400 grades carry UL 94 V-0 flame rating and are compatible with lead-free assembly processes. The high Tg (>280°C for RO4450F) provides adequate thermal margin for lead-free reflow temperatures.

How do I choose between RO4450F and RO4450T?

For designs with 6 or fewer layers and standard impedance tolerances, RO4450F works well. Choose RO4450T when you’re working with high layer counts (8+ layers), need tighter thickness control, or require the multiple thickness options (3/4/5 mil) that RO4450T provides. The spread glass reinforcement in RO4450T also reduces surface roughness variation, which matters at mmWave frequencies.

Common Fabrication Challenges and Solutions

After working with RO4400 bondply across numerous projects, I’ve compiled the issues that catch engineers off guard and how to address them.

Poor Fill and Voids

Symptoms: Air pockets visible in cross-section, inconsistent dielectric thickness, delamination during thermal stress.

Root Causes and Solutions:

Dimensional Instability

When your finished board dimensions don’t match design intent:

• Pre-bake all inner layers before lamination (15-30 min at 115-125°C)
• Maintain consistent copper distribution across panels when possible
• Account for material shrinkage in your design rules—Rogers provides shrinkage factors in technical bulletins

Copper Adhesion Issues

Low peel strength typically traces back to surface preparation:

• Ensure oxide treatment covers all copper surfaces uniformly
• Verify surface cleanliness—RO4400 is packaged in dust-free environment for a reason
• Check that bondply hasn’t exceeded shelf life

Comparing RO4400 to Alternative Bonding Materials

Understanding where RO4400 fits in the broader material landscape helps you make informed selections.

RO4400 vs. Standard FR-4 Prepreg

The cost premium for RO4400 is significant, which is why hybrid constructions make economic sense. Use it where signal integrity demands it; don’t waste it on power planes.

RO4400 vs. PTFE-Based Bondplys

PTFE materials like Rogers 2929 or COOLSPAN offer even lower loss, but at significant processing complexity:

For most applications below 40 GHz, RO4400 delivers sufficient performance without PTFE processing headaches.

RO4400 vs. SpeedWave 300P

Rogers’ SpeedWave 300P is a newer ultra-low loss prepreg option:

SpeedWave targets the cutting edge of high-speed digital where every fraction of dB matters. For traditional RF work, RO4400 remains the proven choice.

Design Tips for RO4400 Series Bondply

A few practical guidelines from production experience:

Impedance Calculations: Use the actual pressed thickness, not nominal bondply thickness. RO4450F at 4 mil nominal presses to approximately 4 mil between flat surfaces, but this changes with copper distribution.

Via Design: The low z-axis CTE (46-60 ppm/°C) is your friend for PTH reliability, but don’t push aspect ratios beyond 10:1 without consulting your fabricator.

Copper Balance: Unbalanced copper distribution causes bow and twist. Plan your copper pours to achieve reasonable balance across the stackup.

Panel Utilization: Sheet size is 24″ × 18″ standard. Plan your panel array to minimize waste—Rogers materials aren’t cheap.

Moisture Sensitivity: Though moisture absorption is low (0.05-0.06%), boards should still be baked before assembly if stored in uncontrolled environments.

Industry Standards and Certifications

RO4400 series bondply meets relevant industry certifications:

• UL Recognition: File number E102763B, UL 94 V-0 flame rating
• IPC Compliance: Tested per IPC-TM-650 methods as documented in datasheets
• RoHS/REACH: Lead-free process compatible
• Automotive: Suitable for IATF 16949 quality management systems when procured through qualified channels

For military applications, verify that your specific construction meets MIL-PRF-31032 or applicable slash sheet requirements through qualification testing.

Conclusion

The RO4400/RO4400T Series Bondply fills an important niche in high-frequency PCB design—providing low-loss bonding materials that work with standard fabrication processes. Whether you’re building 5G base stations, automotive radar modules, or high-speed digital backplanes, understanding these materials helps you make better design decisions.

The key takeaways: match your bondply grade to your laminate selection, pay attention to lamination parameters (especially that low-viscosity temperature window), and leverage hybrid constructions to balance performance against cost.

Material selection is only part of the equation—proper fabrication execution determines whether your boards meet specification. Work with fabricators experienced in Rogers materials, and don’t hesitate to run pilot builds before committing to production volumes.

For specific design questions or material recommendations, Rogers’ technical support team is genuinely helpful—they’ve seen most of the failure modes and can point you toward solutions faster than trial-and-error allows.