Solving the Endoscope Reliability Bottleneck: Kinji Group’s 4-Layer Rigid-Flex PCB for Next-Gen Minimally Invasive Surgery

Minimally-invasive diagnostics and therapies are gaining global momentum, making medical endoscopes one of the fastest-growing segments within high-end medical equipment. With the ongoing evolution toward miniaturization, ultra-high definition, extreme flexibility, and long-term stability, the traditional “rigid board + flexible board + connector” approach is increasingly revealing its inherent limitations in dynamic bending, high-speed transmission, and long-term reliability. These shortcomings have become a critical bottleneck for advanced flexible endoscope development.

Kinji Group has developed an in-house, 4-layer medical-grade rigid-flex integrated solution tailored to customer needs. From base material selection and structural design to process control and multi-scenario clinical validation, we provide a truly compliant, mass-producible, and globally competitive core circuit solution for high-end endoscopic devices.

Market and Policy Tailwinds: The Urgent Need for Supply Chain Diversification

The global medical endoscope market continues to expand rapidly. In 2025, the Chinese endoscope system market alone reached USD 12.5 billion, with projections of USD 13.8 billion in 2026 and potentially exceeding USD 22 billion by 2030, representing a compound annual growth rate of 12.5%—well above the global average. However, the supply structure for high-end flexible endoscopes remains heavily concentrated, with critical components such as core circuit boards and high-speed transmission assemblies facing long lead times and limited sourcing options.

Meanwhile, endoscope technology iteration is placing unprecedented demands on PCB systems: 4K ultra-HD imaging chips require high-speed, low-loss transmission; repeated catheter bending demands ultra-high durability in flexible sections; and repeated sterilization requires extreme material resilience. Traditional multi-board solutions have long struggled with connector detachment, signal attenuation, structural redundancy, and instability under dynamic operating conditions. Image stuttering, noise, or even signal interruption during procedures are common issues that can no longer meet the clinical requirements of advanced minimally invasive surgery.

Core Solution: An Integrated Rigid-Flex Architecture That Systematically Addresses Engineering Challenges

Kinji Group’s 4-layer medical-grade rigid-flex PCB replaces the traditional multi-board assembly approach with an integrated rigid-flex lamination process. The entire workflow is designed in compliance with medical device regulatory standards, and has undergone multiple rounds of reliability verification, mass production validation, and multi-site clinical deployment—fundamentally resolving structural deficiencies at the hardware level.

1. Medical-Grade Material System: Ensuring Safety and Compliance from the Source

Medical endoscope circuit boards directly impact diagnostic and therapeutic safety, demanding far more stringent requirements for ionic contamination control, thermal stability, electrical reliability, and full traceability than industrial-grade PCBs. Our solution employs ITEQ IT180F base material (Tg ≥ 180°C) for rigid sections, offering high heat resistance, low dielectric loss, and anti-deformation advantages; flexible sections use Shengyi SF305 base material to ensure exceptional dimensional stability. We also use medical-grade, ultra-low ionic contamination bonding sheets to prevent harmful ion leaching, eliminating the risk of leakage and corrosion under body fluid contact or high-temperature, high-humidity conditions.

The entire manufacturing process strictly adheres to ISO 13485 medical device quality management system requirements and IEC 60601-1 medical electrical safety international standards. Finished product reliability meets IPC-6013 Class 3 (the highest level) and medical supplementary standards. We archive all mass production parameters and inspection data. Clients can directly cite these records for NMPA, FDA, or CE submissions—eliminating the need for third-party supplementary testing and greatly shortening product registration cycles.

2. Precision Process Parameters: Balancing Miniaturization and High Performance

Leveraging high-precision manufacturing capabilities, our core product specifications deliver several key performance breakthroughs:

· Seamless lamination structure completely eliminates connector loosening risks;

· Ultra-thin board body can be embedded in endoscope catheters ≤ 6mm—in a pediatric gastroscope project, we helped reduce probe outer diameter from 5.8mm to 5.2mm, significantly lowering patient trauma;

· ITEQ IT180F base material withstands 3+ cycles of 260°C reflow soldering without delamination or deformation; SF305 flexible base material shows zero dimensional drift under high-temperature, high-humidity conditions, eliminating intraoperative image distortion;

· 0.3mm laser micro-vias enable single-board integration of imaging, illumination, and sensing signals—in a choledochoscope project, circuit integration density improved by 40% compared to multi-board solutions;

· 4.5mil fine traces with impedance control perfectly support MIPI 2.5Gbps/lane high-speed transmission; measured eye diagram opening exceeds 75%, with zero crosstalk or noise in 4K imaging;

· Outer layer thick copper provides stable power supply with driver loop voltage drop below 50mV, completely eliminating intraoperative light source flicker;

· ENIG immersion gold finish withstands 200 cycles of standard 2% glutaraldehyde sterilization, with contact resistance stable at ≤ 50mΩ and resistance change rate < 3%—resolving the oxidation failure issue common with OSP finishes after repeated sterilization.

Compliance Enablement Example: A Shenzhen-based endoscope startup leveraged our full DFM analysis, impedance testing, X-Ray inspection, and ionic contamination reports to compress their PCB-related registration correction cycle from 8 weeks to just 2 weeks, dramatically accelerating time-to-market.

Three-Dimensional Breakthrough in Structural Design: Miniaturization, Bending Durability, and High-Speed Transmission in Parallel

Unlike the structural deficiencies of multi-board solutions, our integrated lamination design achieves seamless rigid-flex transitions with uniform stress distribution, directly addressing three core challenges:

· High Bending Durability: Flexible sections withstand > 12,000 repeated bending cycles at a 5mm bend radius and 1Hz frequency without fracture or delamination, with impedance fluctuation ≤ ±5%. A Grade A tertiary hospital in Guangzhou deployed our solution in gastroscope equipment, with a single procedure accumulating over 400 bends and signal error rate < 1×10⁻¹²; the equipment has operated stably for 28 months without signal failure, far exceeding the industry norm of 18 months before contact issues commonly arise in multi-board solutions.

· Extreme Space Utilization: Rigid areas concentrate active components, while flexible sections are < 0.4mm thick, closely conforming to the catheter inner wall. In an ultra-thin transnasal gastroscope project, the probe outer diameter was compressed to 4.9mm (compared to the industry mainstream 5.4mm), reducing patient intubation pain VAS scores from 5.2 to 3.1—significantly improving diagnostic comfort. Overall circuit space occupation is only 60% of multi-board solutions, leaving ample room for multi-function integration.

· High-Speed Stable Transmission: The integrated architecture simultaneously carries HD imaging power supply, 300mA+ light source drive, 2.5Gbps/lane video transmission, and multi-channel sensor acquisition, completely eliminating crosstalk. Full-load testing by an East China endoscope manufacturer showed zero frame loss and zero bit errors over 200 hours of continuous operation under dynamic bending conditions, with image latency stably controlled within 33ms—fully meeting the real-time imaging requirements of high-precision minimally invasive surgery.

Multi-Site Clinical Validation: Comprehensive Deployment Across Five Core Scenarios

To date, this solution has been deployed in volume by over ten mainstream endoscope manufacturers across China, covering gastrointestinal, ENT, biliary, urological, and pediatric minimally invasive diagnostic and treatment scenarios, with cumulative installations exceeding 8,000 units. Clinical performance has demonstrated consistent stability, serving as a competitive alternative to equivalent components from global suppliers.

· HD Gastrointestinal Electronic Endoscopy: As of July 2026, a Grade A tertiary hospital in Shandong completed over 6,000 gastrointestinal endoscopy procedures with zero image abnormalities or signal interruptions. Imaging clarity and color reproduction fully match imported high-end equipment; the integrated structure significantly simplifies assembly processes, reducing overall equipment cost by 40%.

· ENT Ultra-Thin Endoscopy: An ENT specialty hospital in Shanghai adopted a 2.7mm ultra-thin ear endoscope, with flexible and maneuverable probe offering unobstructed field of view, reducing average procedure time by 12 minutes and significantly improving minimally invasive surgical efficiency.

· Biliary/Urological Interventional Flexible Endoscopy: Data from a Beijing Grade A tertiary hospital urology department showed intraoperative probe peak bending angles reaching 280°, with over 200 bends per procedure and stable 4K imaging throughout; after 60 glutaraldehyde sterilization cycles, insulation resistance remained > 100MΩ, with no abnormalities in electrical performance or physical structure, meeting high-frequency reuse requirements.

· Pediatric Ultra-Thin Endoscopy: Chongqing Children’s Hospital adopted a 5.0mm ultra-thin gastroscope, completing 6 months of clinical application covering 82 low-weight pediatric patients with 100% insertion success rate; postoperative adverse reaction rate decreased by 28% compared to imported equipment, providing gentler and safer hardware support for pediatric minimally invasive procedures.

Additionally, this solution can flexibly adapt to portable imaging handles, minimally invasive interventional sensing catheters, and other precision devices, expanding application scenarios across multiple high-end medical equipment categories.

Authoritative Measured Data: Fully Quantified, Reliable and Traceable

Through rigorous testing by third-party authorized institutions and our in-house laboratory, all core indicators meet and exceed medical standards:

Volume Delivery: Class 10,000 Cleanroom Production Line, Lean and Compliant with Full Traceability

Kinji Group operates a dedicated Class 10,000 cleanroom medical PCB production line, with medical-grade and industrial-grade production strictly separated. The entire process rigorously follows medical standards, ensuring batch consistency and clinical-grade reliability.

· R&D Stage: We offer free medical board-specific DFM reviews, proactively addressing signal integrity, stress concentration, and impedance matching issues. A Hangzhou-based endoscope company leveraged this service to shorten their R&D-to-prototype cycle by 40%, achieving schematic finalization to first-article approval in just 21 days.

· Volume Production Control: We implement a “Three-Uniform Quality Control Standard” (uniform base materials, equipment, and process parameters), with batch yield rate stably above 98.5% and dimensional accuracy CPK > 1.67, meeting top-tier high-end medical equipment standards.

· Full Chain Traceability: Complete process data is encrypted and archived, supporting 10-year full-chain traceability in full compliance with NMPA and FDA regulatory requirements. Complete inspection documentation is provided to facilitate rapid qualification applications.

· Flexible Customization: Flexible section length, copper thickness, immersion gold thickness, differential impedance, and other parameters can be adjusted on demand to meet diverse high-end endoscope customization R&D needs.

Summary and Outlook

As the “neural hub” of endoscopic equipment, PCBs directly determine imaging quality, operational stability, and clinical safety. Traditional multi-board solutions and industrial-grade materials can no longer support the iterative demands of advanced endoscopes. Kinji Group’s 4-layer medical-grade rigid-flex PCB, built on five core advantages—medical-grade materials, integrated structure, precision manufacturing, clinical-grade validation, and compliant volume production—precisely addresses the critical challenges of miniaturization, high bending durability, high-speed transmission, sterilization resistance, and high stability.

This solution has already achieved multi-scenario volume deployment, with comprehensive performance matching global benchmarks. With high cost-effectiveness, short registration cycles, flexible customization, and exceptional volume production stability, it effectively fills a critical gap in the global supply chain for advanced flexible endoscope core PCBs. Moving forward, Kinji Group will continue to deepen its expertise in medical precision PCBs, iterating technology and compliance systems to support the global advancement of minimally invasive medical equipment.

We welcome OEMs and design houses to partner with us for co-development and technical collaboration, embarking on a new journey toward self-reliability of high-end medical equipment.