Single Layer Flex PCB

Single-layer flex PCB is a circuit structure characterized by its straightforward design and process, making it one of the most fundamental types of circuits. This circuit board is composed of a flexible dielectric film laminated onto a single copper sheet. During the manufacturing process, the designed circuit pattern is printed onto the copper foil and then formed into conductors through etching techniques.

While its structure is simple, it plays a crucial role in the electronic world by optimizing internal electronic space while reducing costs. However, due to its fragile nature, it requires additional protection. Therefore, a overlay is typically applied to the circuit board to provide insulation and protection functions.

Single Layer Flex PCB

What Is a Single-Layer Flexible PCB

Includes two concepts: single layer and flexible

In PCB, we define the number of layers by the internal copper layers. A single-layer PCB means there is only one copper layer located on the top of the PCB for component connections.

フレキシブルプリント基板 refers to that can bend and fold, suitable for scenarios with high demands for internal electronic space and a need for compact designs.

Although flexible PCB can achieve a multi-layer structure, in many applications, lower-layer flexible PCB are commonly used, mainly due to cost considerations. Flexible PCB themselves have a higher cost, and a multi-layer structure would further increase manufacturing expenses.

Single layer flexible PCB structure

A single-layer flexible PCB is one of the most cost-effective flexible circuit structures. However, because component terminations can only be done from one side, through-holes can be designed on the base film for the pins of electronic components to pass through, achieving electrical interconnection through soldering.

Applications of Single-Layer Flex PCB

The number of layers in a PCB is a key parameter reflecting its performance. Generally, we consider that the more complex an electronic project is, the higher the number of layers its PCB will have. This enhances PCB integration, providing better electromagnetic compatibility and inter-layer interconnectivity. However, single layer flex circuits also have unique applications due to their flexible characteristics.

Firstly, for portable medical electronic devices such as home blood pressure monitors and pulse oximeters, which have relatively simple internal structures, the demand for 多層PCB is not high. The focus is more on portability and quality. In such cases, a single layer flexible PCB can provide both lightweight characteristics and meet quality requirements.

Medical Flexible PCB

Secondly, in the field of automotive electronics, entertainment systems or display instruments in vehicles usually do not require overly complex circuit structures, so a single-layer structure is sufficient to meet application needs. For automotive electronics, bumps may lead to damage to internal components, and flexible PCB can mitigate such impacts. In applications where high performance is not required but resistance to physical shocks is needed, single-layer flexible PCB have unique advantages.

Automotive Flexible PCB

In the consumer electronics sector, the demand for miniaturized designs has driven the widespread use of flexible circuits. However, flexible PCB are relatively expensive, and consumer electronic products are cost-sensitive. Therefore, single-layer flexible PCB become the preferred choice.

Consumer Electronics Flexible PCB

Furthermore, single-layer flexible PCB not only excels in the above aspects but can also be combined with リジッドPCB to form a リジッド・フレックスPCB, providing more robust functionality. Overall, single layer flex PCB are suitable for applications where projects exhibit the following characteristics:

    — Price sensitivity

    — Frequent exposure to vibrations

    — Requirements for miniaturized designs

    — Complex internal spaces

Key Points in Single-Layer Flexible PCB Design

Although the design of a single-layer flexible PCB is a straightforward process, ensuring the reliability and performance of the circuit requires attention to the following key points:

Routing:

Due to the potential for folding and bending during use, routing may be more prone to breakage. To address this, consider appropriately increasing the thickness of the traces. Additionally, maintain sufficient spacing between traces.

Layout:

To avoid additional stress at bends, layout should be linear along the bending direction, and abrupt turns in the vertical direction of the bend axis should be avoided.

Bend Areas:

For dynamically bending single-layer flexible PCB designs, it’s not recommended to place more traces in bend areas. To improve bending lifespan, consider adding reinforcement ribs to enhance the structural design.

Solder Pads:

In flexible PCB assembly, solder pad design is crucial for SMT assembly, which is a surface-mount assembly method. Therefore, design sufficient bonding material around the solder pads to enhance the shear strength of solder joints and ensure secure and reliable connections.

Annular Rings:

Single-layer flexible PCB may require the assembly of through-hole components. This part is prone to damage during bending. It is advisable to retain sufficient annular rings around the electroplated through-holes to increase the adhesion force in the hole area.

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