UGPCB Camera Rigid-Flex PCB: Technical White Paper for Mobile Camera Module Applications

Produktübersicht: The Neural Hub of Mobile Camera Modules

Smartphone camera modules keep getting more complex—multi‑camera, high pixel counts, periscope zoom. Space inside the module becomes extremely tight. Traditional solutions use a rigid PCB plus a separate FPC and a BTB connector. That approach wastes space and risks signal loss or contact failure.

UGPCB solves these problems with our Camera Rigid‑Flex PCB. We integrate rigid and flexible circuit boards into one seamless structure. This board carries the image sensor, autofocus driver, and OIS circuits without any connector.

As a true rigid‑flex PCB, our product combines FR‑4 mechanical strength with polyimide flexibility. UGPCB leverages years of PCB and PCBA manufacturing experience to push precision to new limits. Unser minimum line width/space is 0.05mm and total thickness is only 0.3mm. These specs perfectly meet the ultra‑thin, high‑density needs of today’s mobile camera modules.

Einstufung & Konstruktion: IPC‑6013 Type 4 Precision Build

Wissenschaftliche Klassifikation

We design and manufacture the UGPCB Camera Rigid‑Flex PCB to meet IPC‑6013 Type 4 – Multilayer Rigid‑Flex Printed Board. IPC defines a rigid‑flex board by three features: rigid and flexible materials, three or more conductive layers, and plated through‑holes (PTH). Our product satisfies all three.

Following IPC‑6012 (starre Bretter) and IPC‑6013 (flex boards), rigid‑flex boards fall into three categories: starr, flexibel, and combined. Our product belongs to the third category, designed for mixed assembly.

Multi‑Layer Construction

Our 4‑ to 6‑layer stack‑up uses the following structure:

The rigid zone uses FR‑4 – the classic rigid PCB material. It offers high mechanical strength and good electrical insulation. The flexible zone uses Polyimid (PI) Film. PI has a low CTE (down to 10 ppm/° C.), excellent flexibility, Wärmewiderstand, and chemical resistance. It maintains electrical performance under repeated bending.

We choose 0.012 mm (≈1/3 oz) inner copper to reduce bending stress. Der 0.025 mm (≈2/3 oz) outer copper provides impact strength. For the flexible area, copper thickness stays within 12‑18 μm – proven to balance flex life and electrical performance.

Total finished thickness is only 0.3 mm. Typical rigid‑flex boards measure 0.5‑0.8 mm. Our ultra‑thin design saves more than 50% of Z‑height, giving phone designers valuable space.

Arbeitsprinzip: Rigid Support + Flexible Interconnect + Seamless Transition

Our rigid‑flex PCB works on three principles:

Rigid zones act as the skeleton – FR‑4 supports the CMOS sensor, autofocus driver, and power management ICs. These components solder onto the rigid surface, forming the module’s brain and heart.

Flexible zones act as joints – PI base material with ultra‑thin copper allows bending at any angle without breaking circuits. The camera module folds into the phone body – for example, bending 90° from the main board to align with the lens opening.

Rigid‑flex transition zones enable seamless connection – Copper traces directly connect rigid and flexible sections during lamination. No connectors, no jumper wires. This eliminates contact resistance, signal reflection, and mechanical loosening. IPC standards note that dielectric changes at the transition can cause impedance fluctuation. UGPCB controls this fluctuation within acceptable limits through precise stack‑up design and impedance tuning.

Schlüsselspezifikationen

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Leistungsvorteile: Why UGPCB Stands Out

1. Ultra‑Fine Line Capability – 0.05 mm Line/Space

Our Camera Rigid‑Flex PCB achieves 0.05 mm (2 Mil) minimum line width and space. This precision ranks among the industry’s best. Global leaders are pushing toward 40 µm-Linien, but UGPCB already mass‑produces 50 µm-Linien.

Why does this matter? A CMOS image sensor (CIS) often has 0.4 mm pin pitch. Finer lines let you fan out more signals in a small area, supporting higher pixel counts and faster frame rates.

When routing on the flexible area of a rigid‑flex PCB, you must keep line width deviation within ≤0.02 mm across the same bend zone. Ansonsten, local stress points cause cracks. UGPCB’s precise etching keeps line width tolerance within ±10% across the entire board, fully compliant with IPC‑A‑600 acceptability requirements.

2. ENEPIG Surface Finish – No More Black Pad

We use Enepic (Elektrololes Nickel Elektrololless Palladium Immersion Gold) as our surface finish. The layer stack is:

• Nickel (In): 3‑5 μm – diffusion barrier between copper and upper layers

• Palladium (Pd): 0.05‑0.1 μm – the key innovation that stops Black Pad

• Gold (Au): 0.03‑0.05 μm – oxidation protection and solderability

The palladium layer completely eliminates the Black Pad defect common with traditional ENIG. Palladium forms a dense film over the nickel, preventing the gold bath from corroding the nickel. This ensures long‑term solder joint reliability.

For camera modules, ENEPIG offers another critical benefit: compatibility with both aluminum wire bonding and soldering. The CMOS sensor chip connects via aluminum wire bonds, while passive components like capacitors need soldering. ENEPIG supports both – a true universal surface finish for rigid‑flex PCBs.

3. 0.3 mm Ultra‑Thin Design – Saves Valuable Space

Inside a smartphone, jeder 0.1 mm counts. Our rigid‑flex board measures just 0.3 mm fertige Dicke (≈0.2 mm rigid + ≈0.1 mm flex). Compare this to typical rigid PCBs at 0.8‑1.6 mm, or typical rigid‑flex boards at 0.5‑0.8 mm. Our design saves over 50% of thickness. Phone makers can use that space for a thinner body or a larger image sensor.

4. Rigid‑Flex Integration – No Connectors, Higher Reliability

Traditional solutions use three pieces: rigid board + FPC + BTB connector. This has three big problems:

• The connector takes up Z‑height

• Kontaktwiderstand (tens of milliohms) causes signal loss

• Vibration can loosen the connector

UGPCB’s rigid‑flex integration solves all three:

• Saves over 60% of assembly volume

• No connector means no contact failure

• Simplifies assembly – one board does it all

• Dynamic flex life reaches tens of thousands of cycles thanks to PI and thin copper

5. 4‑6 Layers – Flexible for Any Camera Module

Different camera modules need different complexity:

• Basic dual‑camera: 4 layers work well

• Triple or quad‑camera: 6 layers provide enough signal channels

• Periscope zoom: extra control lines for the zoom mechanism

• Foldable phone cameras: specially optimized stack‑up for high flex life

UGPCB offers both 4‑layer and 6‑layer configurations. You choose what fits your application.

Entwurfsrichtlinien: 5 Key Points for Engineers

1. Bend Area Routing – Follow the Golden Rules (IPC‑2223C)

The flexible zone must endure repeated bending. Follow IPC‑2223C guidelines:

• Trace width: 0.1‑0.2 mm (4‑8 mil) on the flex area. Vermeiden 0.05 mm traces there – they increase stress.

• Routing direction: Route at 45° or 90° to the bend axis. 45° spreads stress; 90° works for dense routing.

• Minimum bend radius: For dynamic bending, radius ≥ 6‑10 × total flex thickness. Mit 0.1 mm flex thickness, minimum radius ≥ 0.6 mm.

• No vias or pads in the bend area – they create stress concentration points.

2. Impedance Control – Smooth the Transition

The rigid‑flex transition zone changes the dielectric constant. Impedance can jump by up to 32% if not controlled. UGPCB recommends:

• Use a gradual line width compensation scheme

• Make the transition length at least 5× the dielectric thickness

• Work with UGPCB engineers early – use actual stack‑up parameters for impedance simulation

3. Thermal Management – Copper Thickness and Current

Rigid‑flex boards dissipate heat less effectively than rigid boards. For inner 0.012 mm copper, keep single trace current below 0.3 A (10°C temperature rise, per IPC‑2221). For power traces, use multiple parallel traces or route on the outer 0.025 mm copper.

4. Material Thermal Matching – CTE Difference

FR‑4 CTE (X/Y) is 13‑18 ppm/°C. PI flex CTE is 25‑35 ppm/°C. The difference exceeds 10 ppm/° C.. This creates stress during reflow. UGPCB controls this by: using low‑CTE PI film (CTE < 10 ppm/° C.), adding a buffer layer at the rigid‑flex interface, and optimizing the reflow profile.

5. Pads and Vias – Use Teardrops and Reinforcement

On rigid‑flex PCBs:

• Hinzufügen teardrop pads where traces meet vias or pads – this increases mechanical strength

• Coverlay openings should be 0.05‑0.15 mm larger than the pad on each side for reliable soldering

Herstellungsprozess: 13 Steps from Core to Finished Board

UGPCB follows IPC‑6013 Type 4 Anforderungen. The main process steps are:

1. Flex core cutting – High‑quality FCCL (flexible copper clad laminate) cut to size, then plasma treatment (300‑500 W, 60‑90 sec) to increase surface adhesion to Ra 0.4‑0.6 μm.

2. Inner layer circuit – Dry film lamination, Belichtung, Entwicklung, Radierung. Min line 0.05 mm with tight tolerance control.

3. Inner layer AOI – Automatic optical inspection detects opens, Shorts, and nicks.

4. Rigid core cutting and inner layer circuit – Same process for FR‑4 cores.

5. Stack‑up and lamination – FR‑4 and PI cores stacked and laminated under high heat and pressure using a stepped pressure profile.

6. Bohren – Mechanical drilling for PTH holes. Hole diameter tolerance ±0.05 mm.

7. PTH and copper plating – Electroless copper deposition followed by electrolytic plating to reach 0.012 mm (inner) oder 0.025 mm (outer) Kupferdicke. Hole wall integrity meets IPC‑A‑600 Class 2/3.

8. Outer layer circuit – Image transfer and etching for final traces.

9. Lötmaske – Black or white photoimageable solder mask applied, exposed, and developed.

10. Surface finish – ENEPIG – Sequential deposition of Ni (3‑5 μm), Pd (0.05‑0.1 μm), and Au (0.03‑0.05 μm).

11. Routenführung / Laserschnitt – Final shape cut. Rigid zones milled, flexible zones left intact.

12. Electrical test & fliegende Sonde - - 100% continuity and insulation test.

13. Final inspection & packing – Visual inspection per IPC‑A‑600, then vacuum packing.

UGPCB controls layer‑to‑layer registration strictly. Multilayer rigid‑flex boards need registration ≤ ±0.05 mm. Flexible cores can stretch 0.5‑1% during lamination. UGPCB uses a CCD automatic alignment system (positioning accuracy ±0.02 mm) to ensure precise registration.

Anwendungsszenarien

Szenario 1: Main Smartphone Camera Module

The rear main camera is the largest market for rigid‑flex PCBs. In a typical triple‑camera phone (wide + ultra‑wide + telephoto), our Camera Rigid‑Flex PCB routes all three image sensors to one rigid motherboard, then connects to the phone main board via a BTB connector.

Szenario 2: Periscope Telephoto Module

Periscope modules use a prism to reflect light 90° into a sideways lens assembly. This requires a 90° bend inside the module. Our flexible zone handles that bend easily – no extra FPC or connector.

Szenario 3: Front Camera & Under‑Display Camera

Front camera modules are extremely thickness‑sensitive. Unser 0.3 mm ultra‑thin rigid‑flex board slips into the narrow gap between the screen and the middle frame. It works especially well for under‑display camera designs.

Szenario 4: Foldable Phone Camera

Foldable phones require dynamic flex life of over 200,000 Biegezyklen. UGPCB’s PI flexible zone with optimized routing meets this tough requirement.

Szenario 5: Automobil & Überwachungskameras

Beyond mobile phones, automotive and security camera modules also need high‑reliability rigid‑flex PCBs. These applications demand more rigorous temperature cycling and vibration tests – for example, 1,000 cycles from -40°C to 125°C per IEC 60068‑2. Our ENEPIG finish and FR‑4+PI material combination meet this reliability level.

Qualitätssicherung: IPC Standards Throughout

UGPCB manufactures and tests Camera Rigid‑Flex PCBs to these international standards:

UGPCB holds IATF 16949 quality management certification. Our products comply with RoHS and REACH environmental directives.

The global rigid‑flex PCB market reached approximately $2.604 Milliarden in 2025 and is projected to grow to $3.726 Milliarden von 2032, bei einem CAGR von 5.25% (source: DIResearch). Driven by multi‑camera phones, foldable phones, and automotive cameras, demand for Camera Rigid‑Flex PCBs will keep expanding. UGPCB stands at the forefront of this growth with industry‑leading specifications and a rigorous quality system.

Why Choose UGPCB for Your Camera Rigid‑Flex PCB?

• ✅ Ultra‑fine process capability - - 0.05 mm line/space for high‑density camera modules

• ✅ ENEPIG surface finish – No Black Pad, supports both wire bonding and soldering

• ✅ 0.3 mm ultra‑thin design – Gives you more design space

• ✅ 4‑6 flexible layers – Covers dual‑camera to periscope

• ✅ IPC‑6013 Type 4 certified – Quality you can trust

• ✅ One‑stop PCBA service – From PCB fabrication to SMT assembly

Get a Quote and Technical Support Now

UGPCB provides complete solutions – from design review and prototyping to volume production and PCBA assembly. Whether you are in the concept stage or have ready‑to‑use Gerber files, our technical team will respond within 24 hours with a professional design review and a fast quote.

📧 Send your inquiry to: sales@ugpcb.com
🌐 Visit our website: www.ugpcb.com
📞 Technical support hotline: +86‑755‑2721 1481

Please include the following information for an accurate quote:

1. Layer count (4 oder 6 Schichten)

2. Finished dimensions and quantity

3. Farbe der Lötstoppmaske (black or white)

4. Whether you need PCBA assembly

*Technical data references: IPC‑6013E CN “Qualification and Performance Specification for Flexible/Rigid‑Flex Printed Boards”, IPC‑A‑600H “Acceptability of Printed Boards”, IPC‑2223C “Design Standard for Flexible Printed Boards”, IPC‑TM‑650 “Test Methods Manual”, IEC 60068‑2 series, DIResearch “Global Rigid‑Flex PCB Market Report 2025‑2032”.*