Rigid Flex PCB is a high-density interconnect board that integrates a rigid PCB and a flexible circuit (FPC) through a lamination process, combining the support of a rigid board with the flexibility of a flexible board. Its production process is complex and involvesMaterial combination, precise alignment, and multiple pressing of rigid and flexible zonesHere is a detailed explanation of the core process flow:

1、 Key material selection

2、 Core production process (10 steps)

1. Inner layer graphic production (independent processing of rigid and flexible zones)

• Rigid partFR-4 substrate cutting → drilling → copper deposition → pattern transfer (exposure/development) → etching

• Flexible partPI base film laser drilling → chemical copper deposition → cover film window opening (laser cutting) → cover film pasting (protecting the circuit)

2. Pre treatment of rigid flexible joint

• Flexible zone end treatmentExposed copper foil at the window opening of the covering film, with surface chemical nickel gold (ENIG) or tin deposition to enhance adhesion

• Combining zone structure designAdopting a "stepped" or "anchoring claw" structure (see figure below) to prevent delamination

Rigid zone FR-4- ┬ - │ Flexible zone PI adhesive filling layer - ┘

3. Laminated molding (core difficulty)

• Multiple legal presses(Mainstream process):

  • First press fitPre pressing of flexible zone and partially rigid substrate (temperature 180-200 ℃, pressure 300-400PSI)

  • Second pressingAdd an outer rigid plate and press it together as a whole (to control the difference in Z-axis expansion coefficient)

• key parameterHeating rate ≤ 3 ℃/min, vacuum compression to avoid bubbles

4. Interconnection between laser drilling and through-hole

• Micro hole processingCO ₂/UV laser drilling through holes (aperture 50-100 μ m), connecting rigid and flexible circuits

• hole metallizationPulse electroplating is used to fill holes, ensuring that the copper layer on the hole wall does not crack when the flexible area is bent

5. Outer layer graphics and surface treatment

• Graphic transfer → Plating thickening → Etching → AOI detection

• Surface treatment of flexible zone: Optional immersion gold (wear-resistant), OSP (low-cost) or PI covering film for direct protection

6. Contour Forming and Bending Control

• Rigid flexible separation cuttingPrecision milling cutter laser cutting flexible zone shape

• Bending radius controlThe design needs to meet the requirementsR ≥ 6 x thickness of flexible board(To avoid fatigue fracture of PI membrane)

• Stress relief grooveSlot at the edge of the rigid plate at the bend (width>0.5mm) to reduce stress concentration

3、 Technological difficulties and solutions

4、 Typical applications and process requirements

5、 Chinese manufacturing advantages (combined with PCBA industry chain)

1. Special material matchingShenzhen and Suzhou gather PI film suppliers (such as Ruihuatai) to reduce raw material costs by 30%

2. Precision machining capabilityTop manufacturers (such as Jingwang Electronics) have masteredLaser cutting at any angleTechnology, bending accuracy up to ± 0.1 °

3. Rapid sample cycleFrom design to sample delivery, it can be compressed to7 days(Usually takes 3 weeks in Europe and America)

4. cost controlThe mass production price is about 60% of the same specification boards in Europe and America (10 layer board average price of $120/piece vs $200/piece)

6、 Development Trends

• Materials InnovationLiquid crystal polymer (LCP) flexible substrate replaces PI (reducing dielectric loss by 50%)

• Embedded TechnologyEmbedding chips in rigid areas to reduce connectors (Intel EMIB solution)

• 3D printing additive manufacturingSilver nanoink direct writing flexible circuit simplifies traditional etching process

Choose Suggestions：
For high reliability requirements (military/medical), priority should be given to those withIPC-6013 Class 3Certified factories;
In the field of consumer electronics, attention can be paid to manufacturers in the Pearl River DeltaLCP Soft Hard BoardMass production capability (such as Dongshan Precision).

Mastering the process of combining soft and hard boards is the key threshold for entering high-end electronic manufacturing, and Chinese manufacturers are passing through itIntelligent Material Innovation EquipmentQuickly narrowing the technological gap with Japan and South Korea.