This is a 6-layer hybrid PCB purpose-built for 5G RF, microwave communications, radar systems, and other high-frequency/high-speed applications—featuring Rogers RO4350B on the top and bottom layers, ITEQ IT-180A in the middle, combined with blind via structures, edge plating, and ENIG surface finish to deliver the optimal balance of signal integrity, reliability, and cost.

What is a "Hybrid Stack-up" Strategy?

The core logic of a hybrid PCB is elegantly simple: zonal material selection. RF signal layers are routed on low-loss, high-frequency substrates to ensure signal quality, while power planes, ground planes, and low-speed digital signal layers are built on cost-effective FR-4 materials. All layers are laminated together in a single pressing cycle, achieving seamless integration of two material systems.

The direct benefits of this architecture are clear: RF performance approaches that of a full high-frequency board, while material costs can be reduced by 30%–50%. At the same time, the FR-4 layers maintain high reliability and compatibility with standard manufacturing processes.

Stack-up Breakdown of This Product

This product features a 6-layer copper design, representing a typical high-frequency hybrid structure. Let's walk through the stack-up from top to bottom:

Top and Bottom Layers (L1 & L6):

Rogers RO4350B high-frequency laminate, 0.254mm thick

RO4350B is Rogers' ceramic-filled hydrocarbon laminate designed for commercial RF applications. It offers a stable dielectric constant and ultra-low dissipation factor, while being compatible with standard epoxy/glass fabric processing routes.

Middle Layers (L3–L4):

IT-180A laminate from ITEQ, 0.55mm thick

IT-180A is a high-Tg (175°C–180°C) epoxy-based material with excellent thermal resistance and CAF (conductive anodic filament) resistance, making it ideal for high-reliability digital circuit layers.

Bonding Layers:

Between L2–L3 and L4–L5: two plies of 1080 prepreg (RC64%) each, with a single-ply thickness of 0.075mm

These prepreg sheets are formulated with the IT-180A resin system, ensuring lamination compatibility across the different core materials.

Copper Foil Configuration:

Outer layers (L1, L6): 1.42oz finished copper (base 0.035mm + plating build-up)

Inner layers (L2–L5): 1oz copper (0.035mm)

Final Finished Board:

Total pressed thickness: 1.57mm (nominally 1.6mm)

Surface finish: ENIG (Electroless Nickel Immersion Gold)

Solder mask: Green on both top and bottom sides, with white legend printing

Panel size: 110mm × 110mm = 1 piece per unit

Key Manufacturing Features: Blind Vias and Edge Plating

This product incorporates two important process features:

Blind Via Structure (L1–L2, L3–L6)

Blind vias are plated holes that connect an outer layer to an inner layer without penetrating the entire board. This design includes two sets:

• L1–L2 blind vias: connecting the top layer to layer 2
• L3–L6 blind vias: connecting layer 3 to the bottom layer

The advantages of blind via design include:

• Increased routing density, freeing up valuable board space
• Elimination of signal via stubs, improving signal integrity
• Reduced parasitic inductance and capacitance, critical for high-speed/high-frequency designs

Edge Plating

Edge plating refers to the metallization applied along the board perimeter, extending copper from the top edge to the bottom edge. This feature delivers:

• Reliable edge interconnection and shielding
• Improved current-carrying capability and enhanced EMC performance
• Robust edge connectors for modular board assemblies

Why Choose This Hybrid Board?

1. An Optimal Architecture for 5G RF Applications
In architectures such as Massive-MIMO, RF channels require low-loss substrates while digital control layers demand high thermal resistance. Hybrid construction provides the only practical engineering path forward.

2. Precise Impedance Control in Manufacturing
Impedance calculations for hybrid boards must account for the different Dk (dielectric constant) values of each material—RO4350B at ≈3.48 and IT-180A at ≈4.1 (at 10 GHz). Our mature process capability ensures precise impedance control across the entire stack-up.

3. Proven Reliability
The low-CTE characteristics of IT-180A, combined with the process compatibility of RO4350B, effectively mitigate warpage and delamination risks during multi-layer lamination. The ENIG finish further ensures solderability and long-term oxidation resistance.

Conclusion

This 6-layer hybrid PCB achieves a well-engineered balance between high-frequency performance and cost efficiency through the strategic pairing of RO4350B and IT-180A materials. With the inclusion of blind via structures, edge plating, and an ENIG surface finish, it is ideally suited for demanding signal-integrity applications such as 5G base station RF boards, microwave communication modules, and radar systems.

If you are looking for a reliable, mature, and performance-driven hybrid high-frequency board solution, this product deserves your serious consideration.