Rogers RT/duroid 5880 + High Tg FR-4 4-Layer Hybrid PCB with Step Cavity and ENIG Finish

1. RT/duroid 5880 Material Introduction

RT/duroid 5880 is a glass microfiber-reinforced PTFE composite developed by Rogers Corporation, specifically designed for high-frequency and broadband applications requiring ultra-low dielectric loss . The material features randomly oriented microfibers that provide mechanical reinforcement while maintaining exceptional electrical uniformity. With the lowest electrical loss among reinforced PTFE materials, RT/duroid 5880 is ideal for precision stripline and microstrip circuit applications . The material is resistant to solvents and reagents used in etching and plating processes, and performs exceptionally well in high-moisture environments .

2. RT/duroid 5880 Key Features and Benefits

Ultra-low Dk 2.20 ± 0.02 at 10 GHz ensures consistent impedance control with tight tolerance
Extremely low Df 0.0009 at 10 GHz minimizes signal loss for critical RF and microwave circuits
Isotropic dielectric constant provides uniform electrical properties in all directions
Low moisture absorption 0.02% maintains stable electrical performance in humid environments
Thermal conductivity 0.20 W/m/°K enables effective heat dissipation
CTE X:31 ppm/°C, Y:48 ppm/°C, Z:237 ppm/°C
UL 94 V-0 rated for safety compliance
Low outgassing characteristics suitable for space and aerospace applications
Excellent chemical resistance withstands etching and plating solutions
Well-established material with proven reliability in high-frequency designs

3.What is a Hybrid PCB?

A hybrid PCB (or mixed-pressure PCB) is a multilayer circuit board that combines two or more different material types within a single lamination structure.This approach allows designers to optimize electrical performance, thermal management, and cost by using specialized materials only where needed.

Key Characteristics of Hybrid PCBs:

Material diversity: Combines high-frequency materials (e.g., RT/duroid 5880, RO4000 series) with standard materials (e.g., FR-4) to balance performance and cost
Selective performance optimization: RF/microwave sections use low-loss materials while digital/power sections use economical FR-4
Signal integrity enhancement: Proper material selection reduces signal distortion and interference in mixed-signal designs
Thermal management integration: High-thermal-conductivity materials can be placed strategically for heat dissipation

Manufacturing Challenges:

Hybrid PCBs require careful material matching to address differences in CTE, which can cause warpage or delamination during thermal cycling.PTFE-based materials like RT/duroid 5880 require special surface activation for reliable plated through-holes, typically using sodium etch or plasma treatment.The Z-axis CTE of RT/duroid 5880 (237 ppm/°C) is significantly higher than FR-4, creating potential reliability concerns for plated through-holes, especially when the total PTFE thickness exceeds 20 mils . Specialized bondply materials and controlled lamination parameters are essential for successful hybrid construction.

4. PCB Construction Details

5. PCB Stackup (4-Layer Rigid Structure)

L1 (Top): 1oz Copper
Core 1: RT/duroid 5880, 1.575mm
L2: 0.5oz Copper
Prepreg: 2116 (RC53%) × 2 sheets, total 0.24mm
Core 2: High Tg 170°C FR-4, 0.5mm
L3: 0 copper (Note: Stackup shows 0 thickness)
L4 (Bottom): 1oz Copper

6. Primary Application Areas

Commercial Airborne Antennas and broadband communication systems
Microstrip and Stripline Circuits for precision RF designs
Millimeter Wave Applications including 5G/6G infrastructure
Radar Systems for defense and automotive applications
Guidance Systems and aerospace navigation equipment
Point-to-Point Digital Radio Antennas for backhaul networks
Satellite Communications requiring low outgassing materials
Test and Measurement Equipment for high-frequency signal analysis

7. Quality Assurance

Artwork supplied: Gerber RS-274-X
Accepted standard: IPC-Class-2
Availability: Worldwide