4-Layer Hybrid High-Frequency PCB – RT/duroid 5880 + FR4 (Immersion Gold, Controlled Depth Trench)

4-Layer Hybrid High-Frequency PCB – RT/duroid 5880 + FR4 (Immersion Gold, Controlled Depth Trench)

We present our 4-Layer RT/duroid 5880 + FR4 Hybrid PCB – a high-performance, ultra-low-loss circuit board engineered for demanding millimeter-wave, Ku-band, and aerospace applications. The top RF section utilizes Rogers RT/duroid 5880 glass microfiber-reinforced PTFE laminate (Dk 2.20 ±0.02, Df 0.0009 @ 10 GHz), while the bottom layers use High Tg FR4 for mechanical support and cost optimization. This hybrid construction features a 6-layer copper structure (4-layer PCB with additional copper planes), finished with Immersion Gold (2µ") , blue solder mask, and white silkscreen. The board includes controlled depth trenches and meets IPC-6012 Class 3 reliability standards, with 25µm copper plating in each via.

Key Specifications

PCB Stackup (4-Layer with 6-Layer Copper Structure)

What is RT/duroid 5880?

RT/duroid® 5880 is a glass microfiber-reinforced PTFE composite from Rogers Corporation, designed for exacting stripline and microstrip circuit applications. Unlike woven-glass reinforced materials, the randomly oriented microfibers eliminate Dk variation caused by glass weave effects – delivering exceptional dielectric constant uniformity from panel to panel and across frequency.

With the lowest dissipation factor (0.0009 @ 10 GHz) of any reinforced PTFE material, RT/duroid 5880 extends its usefulness to Ku-band, K-band, Ka-band, and millimeter-wave frequencies (up to 100 GHz+). It is easily cut, sheared, and machined to shape, and resistant to all solvents and reagents used in etching printed circuits or plating edges and holes.

Key Properties of RT/duroid 5880

Standard Thicknesses Available for RT/duroid 5880

Additional thicknesses available from 0.0035" to 0.375" in varying increments.

Key Advantages of RT/duroid 5880

Typical Applications of RT/duroid 5880

Millimeter-Wave Radar (Automotive, defense, weather)

Phased Array Antennas (5G/6G, satellite, defense)

Commercial Airline Broadband Antennas (In-Flight Connectivity)

Microstrip & Stripline Circuits (Filters, couplers, power dividers)

Satellite Communication Systems (Low out-gassing required)

Point-to-Point Digital Radio Antennas (Backhaul, microwave links)

Guidance Systems (Missile, drone, navigation)

Test & Measurement Fixtures (Up to 100 GHz)

Space-Grade RF Electronics

What is a Controlled Depth Trench?

A Controlled Depth Trench (also known as controlled depth routing, cavity routing, or pocket milling) is a precision machining process that removes material from specific layers of a PCB to a controlled and precise depth, without cutting through the entire board.

In this product, the controlled depth trench is machined into the RT/duroid 5880 section or specific FR4 layers to create:

• Component cavities – for embedding components flush with the board surface
• Air gaps – for improved isolation or antenna performance
• Step cavities – for hybrid assembly (SMT + wire bond)
• Thermal management features – for direct heat sink attachment

Key Characteristics

Types of Controlled Depth Trenches

Applications of Controlled Depth Trenches in RF PCBs

Design Considerations for Controlled Depth Trenches

Advantages of Controlled Depth Trenches

Challenges & Mitigations

We support prototype to volume production with global shipping. Contact us for:

Trench depth measurement reports

Impedance control test coupons

Phase matching verification

Volume pricing and lead times