By Published On: 12 December 2025Categories: PCB Knowledge Center

Advanced Manufacturing Technologies for High-Current, High-Shielding FPCB Solutions

A High-Shielding FPCB combines flexibility, thick copper traces, and shielding capability. Manufacturing such boards demands stepped copper from 245 μm to 105 μm, conductor thickness above 105 μm (3 oz), and integrated shielding layers that suppress radiation from parasitic inductance or stray capacitance.

Why Demand for High-Shielding FPCB Is Rising

With the rapid development of the intelligent connected vehicle industry, demand for flexible printed circuit boards (FPCBs) has continued to grow. Statistics indicate that each smart connected vehicle utilizes over 100 FPCBs. FPCBs are also increasingly replacing rigid circuit boards in fields such as low-altitude aircraft and military applications, enabling high reliability and advanced technical functionality, and pushing the FPCB industry toward high-end and specialized development.

What Defines a High-Shielding FPCB

The primary characteristics of high-current-carrying shielded flexible circuit boards are based on traditional FPCBs, integrating three key elements: “flexibility,” “thick copper traces,” and “shielding capability.” This enables such boards to withstand bending, carry high currents with thick copper, and shield against interference.

Traditional FPCBs feature relatively thin copper layers, with their manufacturing processes being relatively mature. Achieving a copper layer thickness of ≥105 μm combined with shielding layers presents new manufacturing challenges.

Analysis of Influencing Factors

Table 2 Properties of Several Typical Shielding Materials

Table 1 Primary Reasons for Using Thick Copper in Circuit Design

Design Considerations for a high-current, high-shielding FPCB

According to the standard “T/CPCA 1001—2022 Electronic Circuit Terminology” published by the China Electronic Circuit Industry Association, a thick copper printed circuit board (PCB) is defined as a board with conductor copper thickness exceeding 105 μm (3 oz).

Thick copper traces in high-current-carrying, high-shielding FPCBs primarily achieve electrical performance, specifically high current-carrying capacity. The expression for the loadable current I is:

I = U/R = US/ρL = Uwh/ρL

Where: I is the current-carrying capacity, A; U is the voltage, V; R is the resistance, Ω; S is the cross-sectional area of the trace, m²; ρ is the resistivity, Ω·m; L is the trace length, m; w is the trace width, m; h is the trace thickness, m.

Equation (1) indicates that the proposed flexible high-current high-shielding circuit board employs a stepped thick copper trace design transitioning from 245 μm to 105 μm, further increasing manufacturing complexity.

High-Shielding Design Requirements

Flexible high-current-carrying, high-shielding FPCBs are primarily used within electronic modules, requiring shielding to mitigate unwanted radiation from parasitic inductance or stray capacitance generated by the circuit patterns. Therefore, shielding layers must be designed and fabricated for such FPCBs.

Traditionally, shielding functions on PCBs are achieved by designing ground planes around soldered components or by incorporating dedicated shielding modules like shielding covers or cages. However, these approaches struggle structurally to meet the demands of increasingly miniaturized and flexible designs.

Structural Analysis

Table 3 Key Parameters of Flexible High Current Carrying High Shielding Circuit Boards

Figure 1. Structure of flexible high current carrying, highly shielded circuit board

The product examined here combines stepped thick copper traces with shielding layers, with copper thickness transitioning from 245 μm to 105 μm. This structure increases manufacturing complexity because the copper step and the shielding layers must coexist within a flexible board that can still withstand bending.

Key Technical Solutions for Manufacturing Shielded Flexible Circuits

Figure 5. Microsection of the cover film directly laminated onto a thick copper flexible circuit board

Figure 4. Micro section of thick copper stepped circuit

Figure 3. Fabrication process of thick copper stepped circuit

Figure 2. Fabrication process of double sided etching for thick copper high current carrying hollow circuits

Stepped Copper Thickness Control

The manufacturing process must handle a copper thickness transition from 245 μm to 105 μm.

Shielding Layer Fabrication

Shielding layers are designed and fabricated into the FPCB to mitigate unwanted radiation from parasitic inductance or stray capacitance.

Bending and Current Carrying

The board must withstand bending while carrying high currents with thick copper. The combination of flexibility, thick copper traces, and shielding capability frames the main technical challenge for this product.

Product Outcomes

This paper investigates and analyzes the key manufacturing techniques for a specific FPCB product featuring stepped thick copper traces and shielding layers, used in a brand of smart connected vehicles. The goal is to achieve efficient production of high-current-carrying, high-shielding flexible circuit boards.

Conclusion

Achieving a High-Shielding FPCB for high-current applications requires controlling thick copper at or above 105 μm (3 oz), managing a stepped copper transition from 245 μm to 105 μm, and integrating shielding layers that suppress parasitic radiation. These factors define the path toward efficient production of high-current-carrying, high-shielding flexible circuit boards.

FAQ

What is a High-Shielding FPCB?

A High-Shielding FPCB is a flexible printed circuit board that integrates flexibility, thick copper traces, and shielding capability, so it can bend, carry high currents, and shield against interference from parasitic inductance or stray capacitance.

What copper thickness counts as thick copper in PCB manufacturing?

Under “T/CPCA 1001—2022 Electronic Circuit Terminology,” published by the China Electronic Circuit Industry Association, a thick copper printed circuit board has conductor copper thickness exceeding 105 μm (3 oz).

Why is stepped thick copper difficult in a High-Shielding FPCB?

The investigated high-current, high-shielding FPCB uses stepped thick copper traces transitioning from 245 μm to 105 μm, and this stepped design further increases manufacturing complexity.

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