1、 Application scenarios

Rigid Flex PCB is suitable for applications that require high reliability, high-density integration, and complex structures due to its combination of rigid PCB and flexible PCB characteristics. The following are the main application areas of soft hard composite boards:

1. Consumer Electronics

Smartphones: used for antenna modules, camera modules, foldable screen connection parts, etc., supporting device miniaturization and high performance. Wearable devices: applied to smart watches, fitness trackers, smart glasses, etc., Bluetooth earphones, etc. to meet the requirements of flexibility and reliability. Tablets and laptops: used for screen connectivity, battery modules, and high-density signal transmission. AR/VR devices: Display modules, camera modules, and sensors for AR/VR head mounted devices, supporting lightweight and high-performance.

2. Automotive Electronics

In car entertainment and information system: supports complex connectivity requirements for touch screens, navigation systems, and sound systems. Advanced Driver Assistance Systems (ADAS): Used for connecting radar modules, cameras, and sensors to provide high reliability. Electric vehicles (EVs) and battery management systems (BMS): support high temperature and high vibration environments, providing stable electrical performance. Lighting system: used for car headlights and other high-performance LED lighting components.

3. Medical equipment

Wearable medical devices, such as heart rate monitors, blood glucose monitoring devices, etc., require miniaturization, lightweight, and durability. High end medical imaging equipment: used for signal transmission in CT, MRI and other equipment. Minimally invasive surgical equipment: supports the complex circuit requirements of precision medical tools.

4. Industry and Automation

Industrial robots: used for robot joints and control modules to meet complex motion and signal transmission requirements. Sensors and control modules: used for industrial control equipment, measuring instruments, and automated production equipment. Programmable Logic Controller (PLC): Provides high-density integration and high reliability connectivity.

5. Communication equipment

5G equipment: used for high-frequency and high-speed circuit connections between 5G base stations and terminal devices. Optical communication module: supports high-speed signal transmission and high-density integration.

6. Aerospace and Defense

Satellite communication equipment: used for complex circuit design and lightweight requirements. Flight control system: applied to the navigation and control circuit parts of aircraft or drones. Military electronic equipment: meets reliability requirements in harsh environments (high temperature, vibration, high humidity).

7. Internet of Things (IoT)

Smart home devices: such as smart speakers, home surveillance cameras, and other scenarios that require high-density connectivity. Edge computing equipment: complex circuits used to process and transmit large amounts of data.

8. Electricity and Energy

New energy equipment: such as control modules for wind power generation and photovoltaic inverters, providing reliable connections. Smart grid equipment: supports high-density integration and durability requirements.

2、 Difficulties in control

The combination of soft and hard boards combines the stability of a hard board with better wiring and bonding capabilities, allowing for more complex circuit designs to be completed; At the same time, it also has the bendability of soft boards, which can be assembled in 3D and save more space, making soft hard composite boards increasingly popular. However, due to the fact that it is a product of the fusion of two forms of circuit boards, and also has high complexity and low yield, it brings many difficulties to the production and manufacturing of soft hard combination circuit boards, mainly reflected in the following aspects:

1. Designers: Due to the combination of soft and hard boards in the combination of soft and hard boards, higher requirements are placed on CAM engineers. They need to be familiar with both the CAM and MI of the hard board and the soft board. In addition, due to the wider application scenarios of the combination board, such as static assembly, dynamic bending, fatigue resistance, etc., engineers need to have rich design experience to understand these application scenarios.

2. Material compatibility and coefficient of thermal expansion (CTE) matching: Material differences: FR-4 and epoxy resin are commonly used for rigid parts, while polyimide (PI) or polyester (PET) are commonly used for flexible parts, with a large difference in their CTE. During high-temperature lamination or welding, uneven expansion may lead to delamination and warping.

3. Control of lamination process

Temperature and pressure: It is necessary to accurately control the laminating temperature (usually 170-200 ℃) and pressure to avoid excessive compression of flexible parts or weak adhesion of rigid parts. Bubbles and delamination: The interface between soft and hard materials is prone to residual air, and vacuum lamination technology should be used to optimize the preloading time and pressure curve. Multiple pressing: Complex structures require multiple presses, and accumulated thermal stress may lead to material fatigue or deformation.

4. Drilling and cutting accuracy

Micro hole processing: High precision drilling (such as laser drilling) is required for through holes or blind holes at the soft hard joint, and any deviation may cause electrical connection failure. Cutting process: The flexible part needs to be laser cut or precision stamped to avoid burrs or tears; V-CUT slotting for rigid parts or CNC controlled deep slotting, with precise depth control to prevent damage to the flexible layer.

5. Copper plating and circuit uniformity

Soft hard transition zone electroplating: Due to differences in material thickness at the junction, uneven flow of electroplating solution can easily lead to inconsistent copper thickness, affecting impedance control. The bending tolerance of flexible circuits: The copper foil needs to be made of rolled copper (RA copper) to improve its bending resistance, but the bonding strength between rolled copper and the substrate is low, and the processing technology needs to be optimized.

6. Cover film and solder mask alignment

Covering film bonding: The covering film (Coverlay) of the flexible part needs to be bonded to the circuit through high-temperature pressing, and the alignment deviation should be less than 0.1mm, otherwise it will affect the exposure or protection effect of the solder pad. Cracking of solder mask layer: The solder mask layer at the soft hard joint is prone to cracking when bent, and flexible solder mask ink (such as polyimide ink) should be used.

7. Structural design and reliability verification

Bending radius design: The bending radius of the flexible part should be ≥ 6-10 times the thickness of the material (such as 0.2mm thick PI substrate, the bending radius should be ≥ 1.2mm), otherwise it is prone to fatigue fracture. Stress concentration point: The soft hard transition zone should be designed as a circular arc or gradient structure to avoid stress concentration caused by right angles. Dynamic bending test: It is necessary to simulate the bending times in actual applications (such as more than 100000 times) to verify the conductivity of the circuit and the durability of the material.

8. Cost and yield control

High material cost: The price of polyimide substrate is 3-5 times that of FR-4, and the adhesive and special ink further increase the cost. Low yield: The process complexity is high, and the yield is usually lower than that of ordinary PCBs, resulting in a significant increase in scrap costs. Equipment investment: requires specialized equipment (such as vacuum laminating machines, laser drilling machines), with a large initial investment. Adhesive selection: The soft hard joint needs to be bonded with adhesive (such as acrylic or epoxy adhesive), which should meet both flexibility and high temperature resistance (such as lead-free soldering temperature of 260 ℃), otherwise it is easy to peel off. Moisture absorption: Polyimide has strong moisture absorption. If not fully pre baked, moisture vaporization during lamination can cause bubbles or delamination.

How is the company managed and controlled?

Designers: Our soft and hard composite board design and manufacturing team is independent, consisting of multiple engineers with over 10 years of experience and a deep understanding of optimizing soft and hard composite board design. Before production, a detailed EQ will be provided to fully understand the customer's usage scenarios and design intentions, in order to match the corresponding materials and adjust the corresponding design scheme.

In terms of materials: Our soft board substrate, covering film, and PP are all selected from top domestic and foreign brands such as Shengyi, Lianmao, Taihong, and Taiguang. Ensure that quality issues arise from the source.

Manufacturing aspect: Key equipment: We have fully automatic LDI lines, high-temperature laminating machines, automatic reflow lines, laser cutting machines, FPC fast pressing machines and other key equipment (without outsourcing) to ensure that the products are more stable and controllable at the manufacturing end, and to improve product quality stability. Key process control, there are usually more than 60 processes for the combination of soft and hard materials, among which key processes include: FPC part of the soft board, soft board circuit, soft board electroplating, fast pressing, material pasting, reinforcement, etc; The FR4 part of the hard board includes pressing, drilling, wiring, CNC opening, and appearance, all of which are key processes. We use engineers to follow up and supervise the entire process, rather than having production line employees directly produce it. This is because the soft board bonding board often requires special production techniques to improve yield.

Special process control: Due to the pursuit of higher integration, soft bonded panels are often combined with special processes and materials to further increase production difficulty, such as HDI, mechanical blind buried holes, back drilling, gold fingers, and the use of high-frequency and high-speed materials. Therefore, we have also developed specialized soft and hard bonded panel control plans, FEMA, and SOP documents for this type of feature to improve yield.

3、 What are our customers for soft and hard composite boards?

Our clients for soft and hard composite boards include BTL, Beijing Institute of Technology servo HARMAN ，flex， Multiple clients including Langke, Lixun Precision, Lianchuang Optoelectronics, Sinafu Medical, QCY, etc.

4、 Our advantages

1. Rich industry experience:

We have been importing the production of soft hard composite boards since 2015 and have 6 years of production experience. We are one of the earliest manufacturers in China to enter the field of soft hard composite boards. Our soft and hard combination board is widely used in drones, Bluetooth earphones, medical devices, smartphones, cameras, LED screens, digital cameras, tablets, wearable devices, etc, VR， Scenes such as battery protection boards.

The production process of soft hard composite board is relatively long, and many processes cannot be automated. The skills of personnel become the decisive factor in the production process of soft hard composite boards. In view of this, we have established a professional Soft Hard Composite Board Business Unit, which has the most effective technical team in the industry, and several senior engineers with over 20 years of experience in circuit board industry.

2. Strong process capability:

The above are the soft and hard board structures that we can produce:

3. Reliable quality:

We strictly adhere to management standards such as ISO9001, IATF16949, UL and other international certifications, and establish and improve quality monitoring and prevention systems to ensure the stability of product quality.

4. Flexible delivery capability:

We have good delivery times and can cooperate with customers to deliver quickly, helping them win market opportunities.