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Rigid-Flex PCB Fabrication: Crafting Lighter, More Flexible Electronic Devices

Introduction

The Rigid-Flex PCB combination board technology is an innovative method that integrates both rigid and flexible characteristics, helping to create lighter and more flexible electronic products. Here is some important information about PCB rigid-flex combination board technology.

Material Selection

Rigid-Flex PCB combination boards typically use a combination of rigid materials (such as FR4) and flexible materials (such as polyester film). The choice of materials is crucial for the flexibility and stability of the board.

Design Flexibility

Designing PCB rigid-flex combination boards requires consideration of bending, folding, or curving sections to accommodate the product’s spatial layout and shape requirements. The design should fully leverage its flexibility.

Manufacturing Process

The manufacturing process for Rigid-Flex PCB combination boards is relatively complex and requires precise processing and control. During lamination and molding, ensuring a secure connection between the rigid and flexible parts is essential.

Testing and Validation

After production, rigorous testing and validation of PCB rigid-flex combination boards are essential. Electrical tests, bending tests, vibration tests, and other methods should be employed to ensure the board’s quality and reliability.

Application Areas

Rigid-Flex PCB combination boards are widely used in automotive, medical, and smart wearable devices, providing lighter and more flexible solutions for electronic products.

Conclusion

The PCB rigid-flex combination board technology, integrating rigid and flexible characteristics, helps create lighter, more flexible electronic products. Through appropriate material selection, design flexibility, manufacturing process control, and strict testing and validation, high-quality PCB rigid-flex combination boards can be achieved to meet the needs of various application fields. Gekunflex offers high-quality rigid-flex board services. To learn more about our services, please visit https://gekunflex.com/.

Introduction to rigid-flexible boards

Rigid flex boards combine the properties of both flexible and rigid boards by integrating thin flexible layers with rigid layers into a single component. This combination forms a circuit board that goes beyond the traditional 2D planar design, expanding into a 3D spatial concept. While this innovation offers significant convenience in product design, it also presents considerable challenges.

Designers of Rigid flex boards can use a single component to replace complex printed circuit boards connected by multiple connectors, cables, and ribbon cables. This approach enhances performance and stability while limiting the design scope to one component. Similar to folding a paper swan, designers can optimize the use of space by bending and folding the circuits.

Rigid-flex boards are multi-layer printed circuit boards that feature both rigid and flexible layers. A typical four-layer rigid-flex PCB consists of a polyimide core, which is copper-clad on both sides. The outer rigid layers are made of single-sided FR4, laminated onto both sides of the flexible core to form a multi-layer PCB. Rigid-flex boards are widely used across various industries, but their production is more time-consuming and costly due to the mixed-use of different materials and the complex manufacturing processes involved. When manufacturing multi-layer Rigid-flex boards, the processing of the flexible layers differs significantly from that of the external FR4 layers. Each layer, made of different materials, must be laminated together before drilling and plating. As a result, creating a typical four-layer rigid-flex PCB can take 5 to 7 times longer than producing a standard four-layer rigid PCB.

The primary applications of Rigid flex boards include aerospace, such as high-end aircraft-mounted weapon navigation systems, advanced medical equipment, digital cameras, portable camcorders, and high-quality MP3 players. Rigid-flex PCBs are most commonly used in the manufacturing of military aircraft and medical devices. Rigid-flex PCBs offer significant benefits for military aircraft by improving connection reliability while reducing weight. Additionally, the reduced overall size of the components provides further advantages.

Although rigid-flex PCBs are more expensive than traditional rigid boards, they offer an ideal solution for many projects. By using flexible substrates for interconnections instead of multiple PCB connections, rigid-flex PCBs reduce space usage and weight, which are critical for many design requirements.

Due to their bendable and foldable characteristics, rigid-flex PCBs can be used to create custom circuits that maximize available space. This capability reduces the space occupied by the entire system. Although the overall cost of rigid-flex PCBs is relatively high, as the industry matures and advances, these costs are expected to decrease, making them more cost-effective and competitive.

Gekunflex is at the forefront of this innovative technology, providing high-quality rigid-flex PCB solutions that meet the demanding requirements of aerospace, medical, and military applications. Choosing Gekunflex ensures that your designs benefit from the best in reliability, performance, and space optimization.

Managing Glue Overflow in Flexible Printed Circuit Manufacturing

Introduction

Glue overflow in Flexible Printed Circuit (FPC) manufacturing occurs when the adhesive from the overlay flows out during the lamination process, leading to undesirable glue stains on the FPC pads. This issue is often triggered by the rise in temperature during lamination, causing the adhesive to become more fluid. Several factors contribute to glue overflow, and it is essential to address each one specifically to ensure optimal manufacturing quality. Below, we explore the primary causes of glue overflow and provide effective solutions to mitigate this common problem.

Manufacturing Process-Induced Glue Overflow

Glue overflow can be a direct result of issues within the manufacturing process. To prevent this, FPC manufacturers like Gekunflex should implement stringent incoming material inspections. If the adhesive overflow exceeds acceptable limits during sampling, it is crucial to coordinate with suppliers to return or exchange the materials. Failure to control the quality at this stage can make it challenging to manage glue overflow later in the production process.

Environmental Storage Conditions

Improper storage conditions can also lead to glue overflow. FPC manufacturers should invest in specialized refrigeration units to store protective films under optimal conditions. If overlay (CL) adhesives become moist due to inadequate storage, a low-temperature pre-baking process can significantly reduce the occurrence of glue overflow. Additionally, any unused CL should be promptly returned to the cold storage after use to maintain its integrity.

Localized Glue Overflow on Small PADs

One of the most common quality issues encountered by FPC manufacturers is localized glue overflow around small pads. Adjusting process parameters solely to address this problem can lead to other issues, such as bubbles or insufficient peel strength. Therefore, it is essential to carefully balance and adjust process parameters to minimize glue overflow without compromising other quality aspects.

Operator-Induced Glue Overflow

Improper handling during the production process can also cause glue overflow. During the pre-lamination alignment process, operators must ensure precise positioning and calibration of alignment fixtures. Increasing the frequency and rigor of alignment checks can prevent misalignment, which is a common cause of glue overflow. Additionally, it is important to maintain a clean working environment by implementing “5S” practices, such as inspecting the overlay for contamination or rough edges before alignment.

Conclusion

Addressing glue overflow in FPC manufacturing requires a comprehensive approach that involves careful inspection of materials, optimal storage conditions, precise process adjustments, and meticulous handling by operators. By implementing these solutions, manufacturers like Gekunflex can significantly reduce the occurrence of glue overflow, ensuring higher quality FPC products and improved production efficiency.

Comparison of Flexible and Rigid-Flex PCBs: A Comprehensive Overview

Gekunflex is a professional flex PCB manufacturer offering products such as flexible circuits and rigid-flex PCB, multilayer flex PCB, and PCB assemblies. Gekunflex delivers high-quality services to fulfill your order requirements with excellence.

Performance:

1. Flexibility for Moving Parts: Flexible PCBs excel in applications where components need to move, offering high cycle flex life for dynamic connections.

2. Versatile Assembly: Components can be assembled on a flat surface and then bent to fit the product’s shape, allowing for versatile designs.

3. Easy Repairs: If necessary, flexible PCBs can be flattened for repairs, making maintenance straightforward.

4. Efficiency Boost: They significantly enhance assembly efficiency, reducing the time and effort required for complex constructions.

Cost:

1. Reduced Assembly Costs: Flexible PCBs can cut assembly costs by 20% to 50% by simplifying the wiring process compared to traditional cables.

2. Error Reduction: They lower the chances of errors in fixed connection points and orientation, simplifying inspection and rework processes.

3. Simplified Processes: Flexible PCBs eliminate the need for complex procedures like wire cutting, stripping, and handling, making the process more efficient.

While rigid PCBs offer more dimensional stability, flexible PCBs require additional processes, tools, and tolerances. Made from polyimide resin, flexible PCBs are more expensive per unit area compared to rigid PCBs. However, incorporating flexible PCBs can reduce the overall amount of rigid PCBs and cabling needed, making integration easier and improving product reliability by reducing the number of parts and connections.

Historical Evolution

Initially, flexible PCBs were mainly used as cables for point-to-point connections, often in single- or double-sided designs. These early flexible PCBs consisted of copper foil laminated onto PET or PI substrates. Over time, flexible PCBs have evolved to handle continuous dynamic flexing in various applications.

Flexible PCBs first gained prominence in U.S. military applications, with Japan being a major early adopter. By the late 1970s, flexible PCBs were used in computers, cameras, printers, car audio systems, and more. The U.S. later expanded its use to consumer electronics, including hard drives, optical drives, laptops, cell phones, and digital cameras, where their dynamic flexing capabilities are crucial.

For easier handling and dimensional stability during assembly, flexible PCBs are sometimes reinforced with backing or stiffener plates. In high-power applications, they may incorporate additional cooling techniques similar to rigid PCBs.

Due to their ability to absorb thermal expansion and contraction stresses, flexible PCBs rarely fail in fatigue tests even in direct “leadless” component connections. With the trend towards high-density assembly, flexible PCBs are not only enhancing direct chip installation feasibility but are also becoming vital in 3D assembly solutions.

Summary

The comparison between flexible and rigid-flex PCBs highlights their unique advantages and applications. Flexible PCBs, known for their high flexibility and ease of assembly, excel in dynamic environments and simplify complex designs, reducing assembly costs and errors. They also enhance maintenance and repair processes, offering significant efficiency improvements.

However, rigid PCBs provide greater dimensional stability. While flexible PCBs are typically more expensive per unit area due to their polyimide resin construction, they can reduce the overall need for rigid PCBs and cabling, thus improving product reliability. Gekunflex integrates advanced flexible PCB technology, addressing both cost and performance considerations, while continuously evolving to meet the demands of high-density and 3D assembly applications.