4-Layer Hybrid High-Frequency PCB with high Dk10.2 RO3210™ (ceramic-filled, woven fiberglass-reinforced PTFE)

4-Layer Hybrid High-Frequency PCB with RO3210™

1. Product Overview

This product is a 4-layer hybrid printed circuit board engineered for demanding RF and microwave applications requiring high dielectric constant (Dk ≈ 10.2) and excellent mechanical stability. The design uses a symmetric stack-up consisting of two outer layers of Rogers RO3210™ (ceramic-filled, woven fiberglass-reinforced PTFE) bonded with a RO4450F™ prepreg. The board measures 95 mm x 98 mm and is supplied as a single piece.

The structure incorporates controlled depth grooves from the top layer to inner layer 1, as well as blind vias (layers 1–3) to enable compact, high-density RF routing. Both top and bottom layers feature green solder masks, with white lettering on the top side only. The surface finish is a combination of silver plating and gold plating to accommodate both solderability and wire bonding requirements.

2. Product Specifications

Stack-Up Structure

3. RO3210™ Laminate: Introduction & Key Properties

RO3210™ is a ceramic-filled PTFE laminate reinforced with woven fiberglass, belonging to Rogers Corporation’s RO3200™ Series. This series was developed as an extension of the RO3000® Series with one distinguishing characteristic: improved mechanical stability.

According to the RO3210 datasheet:

RO3200 series laminates combine the surface smoothness of a non-woven PTFE laminate, for finer line etching tolerances, with the rigidity of a woven-glass PTFE laminate.

This makes RO3210 ideal for designs that require both high Dk (≈10.2) and dimensional stability under thermal and mechanical stress.

RO3210™ Datasheet Summary

Key Advantages of RO3210:

High Dk (10.2 ± 0.50) – Enables circuit miniaturization for lower-frequency RF designs (e.g., 1–10 GHz).

Woven glass reinforcement – Provides superior mechanical rigidity compared to non-woven PTFE laminates.

Good dimensional stability (0.8 mm/m) – Reduces registration errors during multilayer lamination.

Compatible with standard PTFE fabrication processes – Minor modifications as described in Rogers’ fabrication guidelines.

V-0 flammability rating – Suitable for commercial and industrial applications.

4. Application Areas

The combination of RO3210’s high Dk and mechanical stability makes this PCB suitable for:

Phased array radars, electronic warfare systems, satellite downconverters,

Base station filters, power dividers, couplers, and patch antennas

Note: While RO3210 is suitable for many RF applications, its dissipation factor (0.0027) is higher than RO3003 (0.0010). For extremely loss-sensitive millimeter-wave designs (≥30 GHz), RO3003 or RO3006 may be preferred.

5. Special Fabrication Features

This PCB includes two advanced features to support high-density RF routing:

5.1 Controlled Depth Groove (TOP → Inner Layer 1)

Purpose: Allows precise routing or shielding integration without penetrating the entire board.

Benefit: Enables co-planar waveguide (CPW) structures or partial cutouts for component mounting.

5.2 Blind Vias (Layer 1 → Layer 3)

Purpose: Electrical connection from top layer directly to layer 3, bypassing layer 2.

Benefit: Reduces parasitic inductance and enables compact RF signal routing.

Fabrication Notes for RO3210 (per Rogers’ Guidelines)

6. Summary

This 4-layer hybrid PCB leverages the high dielectric constant (10.2) and woven-glass mechanical stability of RO3210™ on all four layers, bonded with RO4450F™ prepreg. The inclusion of controlled depth grooves and blind vias (1–3) enables advanced RF routing in a compact 95 mm x 98 mm footprint. With green solder masks (white lettering on top), and a silver + gold surface finish, this board is ready for demanding aerospace, defense, automotive radar, and telecommunications applications.