Comprehensive Introduction to Multilayer Flexible PCB

The design of electronic products is becoming increasingly unconventional, breaking away from our traditional understanding of PCB. In the past, we typically envisioned a PCB as a rigid green board inside computers, but today’s advancements present a variety of shapes. Screens are curving, smart bracelets, and phones can even fold. It may seem crazy, but the technological evolution behind this lies in the development of flexible circuits. This technology allows a circuit board to bend and fold without affecting its performance, providing greater flexibility in the design of electronic products.

Mobile phones using flexible technology

Table of Contents

Definition of Multilayer Flexible PCB

Structural diagram of multi-layer flexible PCB

Flexibility: This involves endowing the circuit with the ability to bend and fold based on the materials used. This technological approach allows circuit boards to go beyond rigid forms, adapting to more complex internal spaces.

Multi-layer: By stacking and laminating to create multiple circuit layers, typically, a PCB with four or more layers is defined as a multilayer PCB. This design significantly reduces the PCB’s footprint, transforming the circuit from a flat structure to a vertical one.

The combination of flexibility and the multi-layer concept gives rise to the innovation of multilayer flexible PCB. This groundbreaking design not only retains the bending and folding characteristics of flexible PCB but also, through a multi-layer structure, provides more space for component layout. The widespread adoption of multilayer flexible PCB in modern electronics manufacturing propels electronic devices toward greater miniaturization and high integration, accelerating the trend of electronic miniaturization.

Characteristics of Multilayer Flexible Circuits

Characteristics of Multilayer Flexible Circuits
  1. Reliability:

Due to the material properties, flexible circuits are often considered more fragile compared to rigid ones, which are deemed more reliable. However, the unique advantage of flexibility allows these circuits to absorb vibrational energy through elastic deformation and disperse it over a larger area, mitigating the propagation of vibrations. This makes multilayer flexible PCB perform exceptionally well in applications with prolonged exposure to high vibration, such as automotive electronics.

  1. Space Utilization:

In situations where a PCB needs to fit into a confined and intricate space, the power of multilayer flexible PCB comes into play. They can adapt to various spatial structures and enhance surface utilization through multi-layer designs, optimizing the internal space of electronic devices.

  1. Circuit Performance:

Common flexible materials include polyimide, polyester, polyether ketone, etc. These materials offer lower dielectric loss, allowing multilayer flexible PCB to maintain excellent circuit performance even in complex high-frequency environments where current and signals interact between conductors and insulators.

Further Reading: Which Flexible PCB Material is Best Suited for Your Project

  1. Power Efficiency:

The design of multilayer flexible PCB allows for the arrangement of power and ground lines on different layers, reducing resistance between power sources and loads, decreasing power supply noise, and improving power efficiency. Its flexible power and ground distribution make it more adaptable to specific sections of power requirements.

  1. Cost:

Under similar circumstances, the cost of flexible PCB is significantly higher than that of rigid PCB. This is mainly due to the higher cost of raw materials and the more complex manufacturing process. Particularly in multilayer designs, flexible PCB have a relatively higher failure rate, adding to the costs of maintenance and repairs. Therefore, cost is a factor that needs to be balanced for price-sensitive customers when considering the use of multilayer flexible circuits.

Further Reading: Complete Flexible PCB Manufacturing Process Flow

Applications of Multilayer Flexible PCB

The trend towards electronic miniaturization is driving the growing prominence of the flexible PCB industry. According to statistics, the compound annual growth rate of flexible PCB from 2016 to 2022 is 10.5%, and it is projected that by 2025, the industry’s value could reach 30 billion USD. Regarding multilayer flexible PCB, the development of IoT and 5G technologies is expected to usher in a wave of device iterations. These more advanced devices will leverage the power of multi-layer designs to accommodate denser circuits, enabling more robust functionalities. Here are some applications of multilayer flexible PCB:


  • Sensor modules in medical devices.
  • Satellite communication modules.
  • Industrial control sensor units.
  • Electric vehicle battery management systems.


  • Wearable health monitoring devices.
  • In-car infotainment systems.
  • Foldable smartphones.
  • Robot joint sensors.

How to Choose a Multilayer Flexible PCB Manufacturer

If you are seeking solutions for multilayer flexible circuits, you may find that most manufacturers struggle to construct flexible PCBs with more than 10 layers. Therefore, TechSparks recommends considering American manufacturers, even if it might lead to increased costs.

Printed circuit technology originated in the United States, and the use of flexible circuits began in the early 1960s. American manufacturers stand out in terms of industry experience and hardware equipment. In contrast, China and other Southeast Asian countries entered the scene later. Although some medium and small enterprises are gradually targeting the flexible PCB market, their manufacturing capabilities are not as advanced as those of some developed countries. As a result, you will come across dedicated American manufacturers specializing in flexible PCB online.

Further Reading: List of Leading Flex PCB Manufacturers in the USA

Additionally, due to the fragility of flexible PCB, issues such as cracks, gaps, delamination, or misalignment of layers may arise during the construction of multi-layer circuits. Therefore, when selecting a flexible PCB manufacturer, it is advisable to focus on those equipped with X-ray equipment. This can help inspect the internal circuits of multilayer flexible PCB to ensure production quality.

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