Printed circuit boards, a crucial component of electronic devices, have evolved alongside the miniaturization and thinning of electronic products. Among them, the market for flexible printed circuits (FPC) — known for their thinness, light weight, and flexibility — continues to expand, driven by increasing demand in the telecommunications industry, the growth of connected devices, and advancements in automotive electronics. Mektec Corporation, the NOK Group company responsible for the Electronic Products Business, is actively expanding into overseas markets and works with manufacturers worldwide.

Essential for diverse designs and complex electronic devices

Inside the smartphones, computers, and digital cameras we use daily, various electronic components are interconnected through circuit boards. Traditionally, these boards were made from materials such as resin or glass. On the other hand, FPC use polyimide resin, an insulating material with exceptional flexibility and mechanical strength, allowing repeated bending and deformation. With their thin, lightweight, and highly flexible properties, FPC enable greater freedom in design, supporting the diversification of shapes and structures of electronic devices.
FPC have become an essential technology driving the rapid evolution of the digital society.

In recent years, FPC have been increasingly adopted in electric vehicles (xEV). Among these, FPC for battery voltage monitoring system (hereinafter referred to as "FPC for automotive batteries") are large-scale products unlike anything before. Traditionally, individual cells within automotive batteries were connected to a voltage monitoring system via wire harnesses to prevent over-discharge and overcharging. By replacing these with FPC, automakers achieve greater compactness and weight reduction. This shift is especially significant for EVs, which require larger battery capacity and advanced miniaturization to extend driving range. As a result, FPC are critical components that directly influence vehicle performance.

Differentiation through in-house material development

FPC are primarily composed of three key materials: polyimide film, copper foil, and adhesive. A base material is created by bonding copper foil to polyimide film using adhesive, and an electrical circuit is then formed on top before being laminated with a cover layer. The properties of the base and cover materials are critical in determining the functionality of FPC, as factors such as polyimide thickness and flexibility, copper foil bendability, and adhesive durability must be carefully selected and combined to meet specific performance requirements.

At Mektec, even the adhesive used to bond the base and cover materials is developed and manufactured in-house. This proprietary adhesive ensures that FPC remain flexible while maintaining exceptional adhesion strength, even after billions of bending cycles. Among the many FPC manufacturers, Mektec is the only one that develops and produces both the base and cover materials internally. Since its founding, Mektec has upheld the philosophy that material development is part of manufacturing. This expertise in materials has become one of Mektec’s greatest assets, and the ability to produce materials in-house provides a significant competitive edge, allowing the company to succeed in an industry marked by intense price competition.

Solving quality control challenges through cross-department teamwork

In 2023, a new production line for automotive battery FPC was established at MEK-J, a company located within Mektec’s Ushiku Plant, to supply major automotive manufacturers. Compared to products for smartphones and cameras, FPC for automotive batteries are significantly larger, measuring close to one meter in length. Since each product has a high unit cost, minimizing defects in the manufacturing process is an even greater priority than for smaller products. The quality and management requirements set by the manufacturers are also stringent, with no tolerance for contamination, dents, or deformation.

To address these challenges, many tasks that were previously performed manually were automated, reducing human error. Additionally, QR codes were also introduced for each product to ensure full traceability. In the event of a defective product, its batch of origin can be immediately identified and removed from the production line before proceeding to the next stage. Through these initiatives, we have achieved the stabilization and improvement of quality.

These production line improvements were made possible through close collaboration between multiple departments. Traditionally, the manufacturing department used equipment designed by the engineering department without modifications, leading to delays in implementing improvements on the production floor. However, when launching the new FPC production line for automotive batteries, the design, engineering, manufacturing, and quality departments worked together from the start. While each team had its non-negotiable priorities, they engaged in persistent discussions to find effective solutions.

At the Ushiku Plant, the development, design, and quality control departments are located near the manufacturing company, MEK-J. Through the project, the system for seamless information sharing has further evolved. The improved information-sharing system allows real-time feedback from the production site to be reflected in design, facilitating design improvements, quality enhancements, and cost reductions. This structure also enables product development that considers feasibility and production efficiency from the design stage.

Realizing Stable Supply Globally

FPC for automotive batteries have grown into one of the core pillars of the Electronic Products Business. With major automakers, OEMs, and Tier 1 suppliers, which supply parts directly to automakers, among its customers, Mektec now supplies approximately 500 companies worldwide. In addition to expanding sales strategies tailored to specific regions, including Europe, North America, China, Japan, and ASEAN, Mektec has also strengthened its prototype production capabilities in North America. Another key strength is its extensive production network, which ensures the ability to supply high-quality products worldwide in large volumes with stable reliability.
By sharing expertise across departments and regions, employees worldwide work together to deliver high-quality products around the globe, contributing to creating a more sustainable and prosperous society.

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