With the continuous development and innovation of science and technology, the application requirements in the fields of automobiles, communications, medical equipment, aerospace, and military industry are also constantly changing, which has led to an increasing demand for ultra-long flexible circuit boards. Next, let's take a look at the technologies related to ultra-long flexible PCB.
Difficulties in the production of ultra long flexible PCB
The production of ultra long FPCB (flexible PCB) is more complex compared to conventional flexible and rigid circuit boards, and mainly faces many challenges in materials, processes, and design. The following are several main difficulties in making ultra long flexible circuit boards:
1. Material selection and performance control
High material ductility requirements: Ultra long flexible PCB need to maintain excellent ductility, usually using flexible materials such as polyimide. These materials must maintain their strength and performance during prolonged bending and handling processes.
Selection of conductor materials: Copper foil is usually used for conductive lines, but copper foil may face issues of decreased conductivity and poor mechanical properties when extended over long distances. It is necessary to use copper materials with appropriate thickness, high conductivity, and fatigue resistance.
Thermal expansion problem: Ultra long circuit boards are easily affected by thermal expansion and contraction during temperature changes, which may lead to circuit failure. Therefore, substrates with good high-temperature stability are needed.
Flex Plus collaborates with reputable suppliers. These strategic alliances ensure that every inch of flexible PCB meets strict procurement quality assurance standards.
2. Manufacturing accuracy and consistency
Dimensional stability: When making ultra long flexible circuit boards, due to the large size of the circuit board, the material is prone to shrinkage or deformation during the production process, resulting in a decrease in circuit accuracy. Therefore, dimensional stability control is crucial.
Alignment accuracy: In the design of multi-layer circuit boards, the alignment between different layers must maintain high accuracy. As the length increases, any slight deviation accumulates, leading to more prominent alignment issues.
Laser cutting accuracy requirements: For ultra long FPCB, the cutting process must ensure that the edges of the circuit are neat and smooth, without burrs or irregular cutting, otherwise it will affect the circuit performance.
3. Signal transmission and loss
Signal attenuation and interference: The signal transmission distance on ultra long circuit boards becomes longer, which can easily lead to signal attenuation, increased latency, and signal interference, especially in high-frequency signal transmission. In order to reduce signal loss, special designs and materials are needed, such as adding shielding layers or using low loss dielectric materials.
Impedance control: In long-distance transmission, impedance matching becomes more important, and even a slight deviation may lead to signal reflection and distortion. Therefore, strict control of impedance is an important process difficulty to ensure signal integrity.
4. Balance between flexibility and mechanical strength
Balance between flexibility and strength: Ultra long flexible circuit boards not only need to have good flexibility, but also need to strike a balance between flexibility and mechanical strength. As the length of the circuit board increases, the distribution of mechanical stress becomes more uneven, and the board may be damaged during bending, folding, or use. Therefore, mechanical stress distribution should be considered during design, and reinforcement design or multi-layer stacking should be adopted.
Bending fatigue test: Long flexible PCBs require frequent bending and may suffer fatigue damage during long-term use. During the production process, strict bending fatigue testing must be conducted to ensure that the circuit board can maintain its functionality under multiple operations.
5. Difficulty in production and processing
Equipment requirements: The production of ultra long circuit boards requires higher equipment requirements. Due to their large size, traditional production lines are unable to accommodate the manufacturing of ultra long circuit boards, thus requiring special customized equipment.
Quality control: In large-scale manufacturing processes, maintaining consistency in the quality of each circuit board is an important challenge, especially in the case of ultra long dimensions. Any small errors that occur during the production process may lead to a decrease in overall quality.
Difficulty in interlayer bonding: For multi-layer ultra long flexible circuit boards, the bonding process between layers needs to be more precise. Due to the increase in length, defects such as local delamination and bubbles may occur between layers, requiring more precise lamination processes.
Flex Plus has a large exposure machine and customized processing tools. These advancements ensure the accuracy and consistency of the entire length of flexible PCB. Without specialized equipment, the skilled technicians of Flex Plus demonstrated their superb skills in partition assembly technology. They cleverly divided the flexible circuit board (flexible PCB) into easy to operate parts for precise assembly and handling, with a tolerance of 0.05 millimeters for each connection point. This innovative method can maintain the integrity and performance of flexible PCB without affecting its length.
6. Welding and assembly
Welding difficulty increases: As the length of the circuit board increases, temperature control and thermal distribution during welding become more complex. The reliability of welding points must be strictly guaranteed to avoid failure due to thermal expansion or stress during use.
Easy to damage during assembly: Ultra long flexible PCBs are more fragile during assembly and are prone to uneven stress during assembly or operation, which can cause damage. Therefore, they need to be handled more carefully.
7. High cost
The material cost, equipment investment, and complex process of producing ultra long flexible circuit boards will all increase production costs. Meanwhile, due to the high manufacturing difficulty and relatively low yield rate, it further increases the overall production cost.
In Flex Plus, we are able to create flexible circuit boards with 4 layers, 4 meters in length, or even exceeding 4 meters, while ensuring stable performance.
Performance parameters of ultra long flexible PCB
Ultra long flexible PCB exhibit many different characteristics from conventional flexible circuit boards in product data. These features are designed to meet its functional requirements in ultra long and complex bending scenarios. Here are some special features of ultra long flexible circuit boards in product data:
1. The length of ultra long flexible circuit boards can usually reach several hundred millimeters or even exceed one meter, depending on the specific application scenario. The width can be customized according to requirements, but it is usually kept narrow to accommodate narrow or curved spaces.
2. The thickness is usually maintained between tens of micrometers (usually 50 µm to 200 µm), and the thinner the material, the better the flexibility, but the mechanical strength may decrease. Ultra long flexible circuit boards need to find a balance between thickness and mechanical strength.
3. Low resistance:
In order to ensure the quality of signal transmission over long distances, ultra long flexible circuit boards usually use low resistance conductor materials (such as thick copper or gold plating), which have better conductivity than conventional boards. The thickness of the conductor is usually in the range of 17 µm to 70 µm, depending on the current demand.
4. Line width and spacing:
The design of ultra long circuit boards requires precise control of line width and spacing to reduce interference and loss during signal transmission. Line width and spacing data are usually adjusted according to specific application requirements, typically ranging from 50 µm to 150 µm.
5. Bending radius:
For ultra long flexible circuit boards, the minimum bending radius is usually between 3mm and 10mm, depending on the material thickness and design requirements. The smaller the bending radius, the better the flexibility. And it can withstand more than 10000 bends without affecting electrical performance.
6. Signal attenuation:
Due to its length, the loss data in signal transmission is more critical for ultra long flexible PCBs. For high-frequency applications, lower signal attenuation is better, with typical values ranging from 0.1dB to 1dB per meter of signal attenuation, depending on the specific application scenario and material selection.
7. Temperature resistance:
Ultra long flexible circuit boards are commonly used in complex environments, with a common operating temperature range of -40°C to+125°C. In high-temperature environments, especially for longer sized circuit boards, they are more susceptible to thermal expansion, so the material must have high temperature resistance.
8. Coefficient of thermal expansion:
The coefficient of thermal expansion (CTE) of flexible PCB material is another key data point, especially in long dimensions, where thermal expansion may cause structural problems. Usually, the CTE of materials such as polyimide is around 10-50 ppm/°C.
9. Tensile strength:
Ultra long flexible circuit boards need to have good tensile resistance. The tensile strength index value of flex PCB is usually between 150 MPa and 250 MPa to ensure that it does not fracture under stress.
10. Tear resistance:
During installation and use, ultra long flexible PCBs are prone to tearing due to improper operation. So its tear resistance strength is usually above 50 N/mm, ensuring sufficient mechanical toughness during bending and assembly.
11. Insulation resistance:
The insulation resistance requirements for ultra long flexible circuit boards are higher because their length increases the possible leakage paths. The insulation resistance value is usually between 100 MΩ and 1 GΩ, depending on the material used and specific application requirements.
12. Voltage endurance performance:
The voltage endurance of ultra long flexible circuit boards is usually 100V to 500V, and special applications may require higher voltage endurance indicators.
13. Electromagnetic shielding performance:
For certain high-frequency applications, ultra long flexible PCBs need to provide good electromagnetic shielding to prevent external interference. The typical value is 20 dB to 80 dB.
Summary:
The product data of ultra long flexible circuit boards exhibit different characteristics from conventional flexible PCBs in terms of size, mechanical strength, signal transmission performance, and environmental resistance. In order to cope with its more complex working environment, design and manufacturing need to carefully consider multiple parameters to ensure that it meets high standards in bending, stretching, and electrical performance.
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