UGPCB In-Depth Analysis: 6-Layer Rigid + 4-Layer Flexible Yellow Soldermask Rigid-Flex Board – Ushering in a New Era of High-Density Interconnection

In today’s rapid evolution toward lightweight, dünn, kurz, and compact electronic devices, Die Starrflex-Leiterplatte has become indispensable in high-precision fields such as telecommunications, medical instruments, und Luft- und Raumfahrt. Its unique combination of rigid support and three-dimensional flexibility makes it a critical interconnect component.

Als Profi Leiterplattenhersteller, UGPCB introduces its high-performance Yellow Soldermask Rigid-Flex PCB (R-FPCB) . This article explores this advanced board, built with FR-4 + PI materials und a 6-layer rigid plus 4-layer flexible Struktur. We will examine its design principles, Herstellungsprozesse, and applications, showing how it enables more stable signal transmission and a more compact system layout.

1. Produktdefinition und Übersicht

UGPCBYellow Soldermask Rigid-Flex Board integrates a rigid PCB and a flexible circuit board into a single interconnect solution through a lamination process.

Schlüsselspezifikationen:

• Layer -Stackup: 6 Schichten (6L) in rigid sections / 4 Schichten (4L) in flexible sections

• Material Combination: FR-4 (rigid areas) + PI (Polyimid, flexible areas)

• Surface Color: Yellow soldermask (starr) / White coverlay (flex)

• Fertige Dicke: 0.4mm (rigid sections) / 0.2mm (flex sections)

This design retains the structural support and component-carrying capacity of rigid areas while utilizing the bendability of flexible sections. It achieves a true rigid-flex integration, eliminating the need for traditional connectors and ribbon cables.

2. Design Principles and Technology

A. Arbeitsprinzip

The core of rigid-flex technology lies in seamless interconnection. UGPCB laminates flexible PI layers with rigid FR-4 layers under high temperature and pressure. In flexible zones, FR-4 material is removed, leaving the PI base with a coverlay to allow bending. In rigid zones, FR-4 remains to support Komponenten. This structure eliminates physical contact points from connectors, significantly enhancing Signalintegrität (UND) and vibration resistance.

B. Konstruktionsüberlegungen

• Impedanzkontrolle: For high-frequency communication PCBs, strict control of 3.5mil trace width and spacing ensures consistent differential impedance (z.B., 100Oh).

• Transition Zone Protection: The junction between rigid and flexible sections (the stub) is a stress point. UGPCB’s design uses rounded transitions and tapered trace widths to prevent cracking during bending.

• Stackup Matching: Uniform 1OZ copper thickness is maintained to prevent fatigue failure in the flexible sections during dynamic flexing.

3. Material and Performance Analysis

A. Kernmaterialien

• FR-4 (Strenge Bereiche): A fiberglass-reinforced epoxy laminate. It offers high mechanical strength, Wärmewiderstand, and insulation, providing a stable platform for mounting heavy components like chips and connectors.

• PI (Flexible Bereiche): Polyimide film. It provides excellent high-temperature resistance (operating >150°C), a low dielectric loss factor (Df), and a high flex life.

• Oberflächenbeschaffung: Immersionsgold (ZUSTIMMEN). This chemical process deposits a nickel-gold layer over copper.

  • Vorteile: High surface flatness suitable for fine-pitch circuits (3.5mil spacing), strong oxidation resistance, and good solderability along with aluminum wire bonding capability.

B. Key Performance Specifications

4. Structural Classification and Features

A. Structural Classification

Bei diesem Produkt handelt es sich um ein asymmetric structure (6-layer rigid + 4-layer flexible) within the category of multi-layer rigid-flex boards. Allgemein, rigid-flex boards are classified as:

• Layered Type: Flexible layers extend out independently, as seen in this product.

• Non-layered Type: The entire board uses flexible material, with stiffeners added to specific areas.

B. Produktmerkmale

• Hohe Zuverlässigkeit: The immersion gold finish combined with PI material ensures stable electrical performance even in harsh environments (high temperature and humidity).

• Hohe Präzision: Manufacturing capabilities for 3.5mil fine lines and 0.1mm micro vias solve high-density interconnect challenges.

• Platzoptimierung: Replaces connectors, reducing installation volume by over 60% and lowering overall product weight.

• Visual Differentiation: The yellow soldermask provides a unique appearance and offers clearer contrast during SMT assembly, facilitating optical inspection.

5. Manufacturing Process and Quality Control

To ensure the reliability of this complex 6L+4L structure, UGPCB follows a rigorous production flow:

1. Inner Layer Circuit (Flex Area): Fine 3.5mil circuits are formed on the PI base material using laser or photolithography.

2. Coverlay Lamination: A protective film is laminated onto the flexible circuit, leaving only the pad areas exposed.

3. Laminierung: Rigid and flexible layers are aligned and laminated under vacuum. Key controls are the temperature profile and resin flow to prevent voids.

4. Bohren & Überzug: 0.1mm micro vias are drilled. Electroless copper deposition creates interlayer connections.

5. Äußere Schicht & Soldata: Yellow soldermask is applied to rigid areas; white coverlay remains on flexible areas.

6. Oberflächenbeschaffung: Immersionsgold (ZUSTIMMEN) is applied with controlled thickness: 0.05-0.1μm Au / 3-5μm Ni.

7. Profilierung & Elektrische Prüfung: Laser routing or die punching defines the final shape. 100% AOI and fliegende Sonde testing verify electrical integrity.

6. Anwendungen

This product is primarily targeted at thecommunication PCB sector. Key applications include:

• 5G-Kommunikationsbasisstationen: Used for flexing connections in RF modules, solving compact interconnect needs between antennas and mainboards.

• Smartphones & Wearables: The 0.2mm flexible section enables dynamic bending in foldable phone hinges.

• Medizinische Elektronik: Used in devices like ultrasonic endoscope probes, leveraging PI’s biocompatibility and high-density routing.

• Kfz -Elektronik: ADAS camera modules that must withstand constant vibration and thermal shock.

7. Warum wählen Sie UGPCB??

Engineers often face challenges with low yields and long lead times for complex rigid-flex designs. UGPCB is a reliable supply chain partner offering:

• Fertigungsfähigkeit: Mass production capability for 3.5mil trace/space, overcoming high-density interconnect barriers.

• Materialbeschaffung: Uses high-quality materials from suppliers like Shengyi/ITEQ for FR-4 and DuPont/Tayoho for PI, ensuring quality from the source.

• Technische Unterstützung: Provides free DFM (Design für die Herstellung) checks to help optimize designs, especially in the rigid-flex transition zone.

Are you designing a circuit board that must both carry complex ICs and flex within a tight space?

UGPCB now offers prototyping and mass production services for this6-layer rigid + 4-layer flexible yellow soldermask rigid-flex PCB.

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