What Is Rogers RO4835 Laminate and What Are Its Dk, Df, CTE, and PCB Fabrication Specifications?

Introduction

In the rapidly evolving world of wireless communications, automotive radar, and high-frequency electronics, selecting the right PCB substrate material is critical to achieving optimal performance, reliability, and cost-efficiency. Rogers RO4835™ laminates represent a significant advancement in high-frequency circuit materials, offering enhanced oxidation resistance while maintaining the proven electrical and mechanical properties of the widely adopted RO4350B™ laminates.

As operating frequencies increase beyond 500 MHz, the selection of suitable laminates becomes significantly limited. RO4835 material addresses this challenge by providing the properties needed for RF microwave circuits, matching networks, and controlled impedance transmission lines—all while being fabricable using standard FR-4 epoxy/glass processing techniques.

This article provides a comprehensive overview of RO4835 laminate properties, a detailed 2-layer PCB design example, and key sourcing information for engineers and procurement professionals.

What Is Rogers RO4835 Laminate?

Rogers RO4835 is a hydrocarbon ceramic laminate belonging to the RO4000® series family. It is designed to offer superior high-frequency performance with low-cost circuit fabrication. Unlike PTFE-based high-performance materials, RO4835 laminates do not require specialized via preparation processes such as sodium etch, making them significantly easier and more economical to fabricate.

The material is a rigid, thermoset laminate that can be processed by automated handling systems and standard scrubbing equipment used for copper surface preparation. Its glass transition temperature (Tg) exceeds 280°C, ensuring stable expansion characteristics across the entire range of circuit processing temperatures.

Key Differentiator: Oxidation Resistance

Oxidation affects all thermoset laminate materials over time and temperature, including FR-4. Long-term oxidation can lead to small increases in dielectric constant and dissipation factor, potentially impacting circuit performance. RO4835 laminate is significantly more resistant to oxidation than other hydrocarbon-based materials, making it ideal for applications demanding greater stability at elevated temperatures over extended product lifetimes.

Properties of RO4835 Laminate

Notes:
1. The IPC clamped stripline method can potentially lower the actual dielectric constant due to air gaps between laminates under test and the resonator card. Actual Dk in practice may be higher.
2. The design Dk is an average from multiple tested lots on the most common thicknesses.

Features and Benefits Summary

Standard Offerings

RO4835 laminates are available in a variety of standard thicknesses, panel sizes, and copper cladding options.

Notes:

Additional non-standard thicknesses available from 0.0066" to 0.060" in increments of 0.0033"

Additional panel sizes and cladding weights available upon request

RO4835 is also available with Rogers' proprietary LoPro® reverse-treated copper foil for low insertion loss applications

2-Layer PCB Design Example Using RO4835

To demonstrate the practical application of RO4835, the following is a complete 2-layer rigid PCB design case.

PCB Design Specifications

Design Observations

The relatively simple structure with only 2 nets and 18 components suggests this board is likely a dedicated RF functional module—possibly an antenna feed network, a filter section, or a simple RF front-end circuit. Key design choices include:

No solder mask on top or bottom layers – A deliberate choice for applications requiring extremely low loss or specific dielectric environments where solder mask could introduce parasitic effects

No silkscreen on pads – Ensures clean solder joints and avoids contamination of RF contact areas

ENIG surface finish – Provides excellent solderability, flatness, and oxidation resistance for RF connections

IPC-Class-2 compliance – Ensures reliability for commercial and automotive applications

Manufacturing Process Highlights

FR-4 compatible processing – RO4835 can be fabricated using standard epoxy/glass processes, reducing cost and lead time compared to PTFE-based materials

No sodium etch required – Unlike PTFE materials, RO4835 does not require specialized via preparation

Fine-pitch capability – 5/6 mil trace/spacing supports high-density RF designs

100% electrical testing – Guarantees functional integrity of every board

Typical Applications

RO4835's unique combination of properties makes it ideal for a wide range of high-frequency applications:

- Automotive Radar and Sensors

- Point-to point Microwave

- Power Amplifiers

- Phased - Array Radar

- RF Components

Conclusion

Rogers RO4835 laminates offer a compelling combination of high-frequency performance, oxidation resistance, and cost-effective fabrication. With a dielectric constant of 3.48 ± 0.05, dissipation factor of 0.0037 @ 10 GHz, and glass transition temperature exceeding 280°C, RO4835 delivers reliable electrical and mechanical performance for demanding applications.

Key advantages include:

Significantly improved oxidation resistance compared to other hydrocarbon materials

Standard FR-4 processing – no specialized via preparation required

Low CTE (10/12/31 ppm/°C) for excellent dimensional stability

Lead-free process compatible – withstands high assembly temperatures

RoHS compliant and UL 94 V-0 – meets global regulatory requirements

Whether used in automotive radar systems, point-to-point microwave links, or power amplifier modules, RO4835 provides a reliable, cost-effective solution for high-frequency circuit designs. The PCB case study presented here demonstrates how this material can be successfully fabricated into a functional 2-layer board using standard manufacturing processes.