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 PCB Rigid vs Flex: Making the Right Choice for Your Electronics

PCB Rigid vs Flex: Making the Right Choice for Your Electronics

Introduction

PCBs, both rigid and flexible widely utilised in the electronic computer. And communication, aerospace, and home appliance industries. So what about PCB Rigid vs Flex? A rigid PCB, as the name implies, is a circuit board built on a rigid base layer that cannot bent. whereas a flexible PCB (also known as FPC, Flexible PCB) has a high wiring density, light weight. and thin thickness, and reliable, flexible base capable of bending, twisting, and folding.

Although standard rigid PCBs and flexible FPCBs serve the same basic purpose. there are significant distinctions between them. Flexible circuits are more than just bent PCBs. They made differently than rigid PCBs. and have many performance benefits and drawbacks.

PCB Rigid vs Flex

Rigid PCBs, often abbreviated as PCBs, what most people think of when they imagine circuit boards. These boards connect electrical components using conductive tracks. and other elements arranged on a non-conductive substrate. On rigid circuit boards, the non-conductive substrate usually contains a glass cloth. that reinforces the board and gives it strength and stiffness. Rigid circuit boards provide good support for components and offer good thermal resistance.

Although flexible PCBs also have conductive traces on a non-conductive substrate. this type of board uses a flexible base material, such as polyimide (PI). Flexible bases enable flexible circuits to withstand vibration. dissipate heat and fold into various shapes. Due to their structural advantages, flexible circuits used as an option for compact devices. such as smart wearables, cell phones and cameras.

In addition to the material and rigidity of the base layer. significant differences between PCBs and flexible circuits include:

1, Conductive Materials:

Because flexible circuits need bend. softer rolled annealed copper serves the purpose instead of conductive copper.

2, The Manufacturing Process:

Flexible PCB manufacturers do not use soldermask. but instead use a process known as overlay film. or cover layer to protect the exposed circuit graphics of the flexible PCB.

3, Typical Cost:

Flexible circuits usually cost more than rigid circuit boards. However, because flexible circuit boards installed in compact spaces. engineers can reduce the size of their products, thus indirectly saving costs.

How To Choose Between Rigid and Flexible PCBs

Rigid and flexible FPCs used in many different products. although certain applications may benefit more from one type of board. For example, rigid PCBs make sense in larger products. such as appliances and computers, while more compact products. such as smartphones and wearable technology, require flexible FPCs.

When choosing between rigid PCBs and flexible FPCs. consider the needs of your application, the industry’s preferred board type. and how profitable the effects of using one or the others.

Rigid PCBA
gesflex flex board pcb
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When To Use Flex Circuit Vs. Rigid Circuit Boards

The choice between FPC and rigid circuit boards. depends on the specific requirements of the electronic device or application. Each type of board has its strengths and weaknesses. and the decision based on factors. such as form factor, space constraints, mechanical considerations, and intended application. Here are some scenarios when each type of board commonly used:

With Flex Circuit Boards

→ Space-Constrained Applications:

FPCs are ideal for devices where space limited. or where the board needs to fit into tight or irregularly shaped spaces. Their ability to bend and conform to the design requirements. makes them a preferred choice in compact devices.

→ High-Flexibility or Bendability Requirements:

If the device or application requires frequent bending or flexing. FPCs are the natural choice due to their flexible nature. They can handle continuous bending without failure.

→ Weight-Sensitive Applications:

FPCs are generally lighter than rigid boards, making them suitable for weight-sensitive applications. like aerospace, automotive, and portable electronics.

→ Dynamic or vibration-prone environments:

FPCs can withstand vibrations and movement better than rigid boards. making them suitable for applications subjected to constant motion or vibrations.

→ High-Density Interconnections:

FPCs can accommodate complex, high-density interconnections. due to their flexibility and ability to have multiple layers.

→ Custom Form Factors:

FPCs designed to fit specific form factors and follow the contours of the product. offering more design freedom for custom-shaped devices.

With Rigid Circuit Boards

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→ Standard Electronic Devices:

For most conventional electronic devices like computers, smartphones, and consumer electronics. rigid PCBs are the standard choice due to their reliability and cost-effectiveness.

→ High Component Density:

Rigid PCBs can support higher component density. making them suitable for complex designs with numerous components.

→ Static or Fixed Applications:

In applications where the board does not require bending or flexing. rigid boards more appropriate as they provide a stable, fixed platform for components.

→ High-Temperature Applications:

Rigid PCBs can often handle higher operating temperatures compared to flexible boards. making them more suitable for high-temperature environments.

→ Economical Mass Production:

Rigid PCBs are more cost-effective for high-volume production runs. due to well-established manufacturing processes and automation.

→ High-Frequency Applications:

For applications requiring high-frequency performance, rigid boards can offer better electrical characteristics.

In some cases, a combination of rigid and flexible boards (rigid-flex PCBs) used to leverage the advantages of both types. The decision to use flex or rigid boards ultimately depends on the specific needs. and constraints of the application. so careful consideration of the design requirements is crucial to making the right choice.

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Rigid & Flexible PCB Design Considerations Difference

Rigid and flexible PCB designs have some key differences in their considerations due to their distinct nature. Here are the main differences in the design considerations between rigid and flexible PCBs:

Board Flexibility:

The primary difference between the two is, of course, flexibility. Rigid PCBs are inflexible and cannot bend or flex. while flexible PCBs designed to be flexible and can bend or fold without damage. This fundamental difference affects the design choices throughout the PCB layout.

Material Selection:

Rigid PCBs typically use rigid substrate materials such as FR4. while flexible PCBs use flexible materials like polyimide (PI) or polyester. The choice of material influences the mechanical. and thermal properties of the board and affects how the PCB used.

Mechanical Constraints:

Rigid PCBs have strict mechanical constraints due to their inflexibility. They require more precise planning and adherence to standard board shapes. (e.g., rectangular or square). Flexible PCBs offer more design freedom as they can take on custom shapes. and follow the contours of the device or product they integrated into.

Bending and Folding:

Flexible PCBs designed with bending and folding in mind. Designers need to ensure that critical components, traces. and vias can withstand the intended flexing without failing due to stress or fatigue.

Layer Stackup:

The layer stackup of a flexible PCB is different from rigid PCBs. Flexible PCBs typically have fewer layers. and the arrangement of conductive and dielectric layers may vary to accommodate bending.

Routing and Trace Considerations:

In rigid PCBs, traces routed in straight lines with right-angle bends. However, in flexible PCBs, it’s best to avoid right-angle traces and opt for smooth. gradual curves to prevent stress concentration during bending.

Component Mounting:

The mounting of components on rigid PCBs is relatively straightforward. following standard surface mount technology (SMT) practices. In flexible PCBs, components selected and placed carefully. To avoid stress on the board during flexing.

Electrical Performance:

Rigid PCBs may offer slightly better electrical performance. due to the rigidity of the materials used. Flexible PCBs, have slightly higher parasitic capacitance and inductance due to their construction.

Reliability:

Rigid PCBs generally have higher reliability in static applications. while flexible PCBs excel in dynamic applications where repeated bending or vibration involved.

Manufacturing Complexity:

The manufacturing process for flexible PCBs is more complex than rigid PCBs. which can affect production time and cost.

Designers must carefully consider these differences when choosing between rigid and flexible PCBs. and select the appropriate board type based on the specific requirements. and constraints of the application. In some cases, a combination of rigid and flexible boards (rigid-flex PCBs). That the best solution to take advantage of both design options.

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IPC Standards for Rigid and Flexible PCBs

IPC (Institute for Printed Circuits) is a global association. that establishes standards and provides guidelines for the design. manufacture, and assembly of printed circuit boards (PCBs). For both rigid and flexible PCBs, IPC has developed specific standards. to ensure consistent quality and reliability in the industry. Here are some of the key IPC standards relevant to rigid and flexible PCBs:

IPC-2221: Generic Standard on Printed Board Design:

This standard provides guidelines for the design of rigid PCBs. It covers various aspects, including conductor spacing, trace width. hole sizes, material selection, thermal considerations, and electrical properties.

IPC-2223: Sectional Design Standard for Flexible/Rigid-Flexible Printed Boards:

IPC-2223 is specific to flexible and rigid-flex PCBs. It covers design considerations unique to these types of boards. such as bending radius, flex area protection, layer stackup. flexible circuit termination, and dynamic flexing considerations.

IPC-6011: Generic Performance Specification for Printed Boards:

This standard establishes the qualification and performance requirements for rigid PCB materials. including base materials, conductor materials, and surface finishes.

IPC-6013: Qualification and Performance Specification for Flexible Printed Boards:

IPC-6013 addresses the qualification and performance requirements for flexible PCB materials. including polyimide and polyester-based substrates.

IPC-A-600: Acceptability of Printed Boards:

IPC-A-600 defines the acceptance criteria for bare rigid and flexible PCBs. including requirements for surface conditions, hole quality, conductor width, spacing. and other manufacturing-related features.

IPC-A-610: Acceptability of Electronic Assemblies:

While not specific to PCBs, this standard addresses the acceptability criteria for electronic assemblies. including rigid and flexible PCB assemblies. It covers soldering criteria, component mounting, and other assembly-related considerations.

IPC-TM-650: Test Methods Manual:

IPC-TM-650 provides a comprehensive collection of test methods. used in the PCB industry for evaluating materials, processes, and finished boards. It includes various mechanical, electrical. and environmental tests applicable to both rigid and flexible PCBs.

These IPC standards play a crucial role in ensuring the quality. reliability, and consistency of rigid and flexible PCBs. Manufacturers, designers, and assemblers in the industry. adhere to these standards to meet customer requirements and industry best practices.

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Will Flex Circuits Replace Rigid Circuit Boards For All Applications?

While flexible circuits (Flex PCBs) have significant advantages in certain applications. it unlikely that they will completely replace rigid circuit boards (Rigid PCBs) for all applications. Both types of PCBs have their unique strengths and weaknesses. making them suitable for different use cases. Here’s why Flex PCBs are unlikely to replace Rigid PCBs entirely:

Cost:

Rigid PCBs are generally more cost-effective to manufacture compared to Flex PCBs. The materials and processes involved in making Flex PCBs more specialized and complex. leading to higher production costs. For applications that do not need flexibility, the added cost of Flex PCBs justified.

Component Density:

Rigid PCBs can support higher component density. allowing for more complex and densely populated electronic designs. Flex PCBs have limitations the number of layers. and component density due to the bending and flexing considerations.

Reliability:

In certain applications, such as high-reliability aerospace or medical devices. the rigid structure of Rigid PCBs preferred over the potential mechanical stress. and fatigue that Flex PCBs could experience during flexing.

Standardization and Established Design Practices:

Rigid PCBs used for decades, and there are well-established design practices. manufacturing processes, and quality standards in place. For many conventional electronic devices, Rigid PCBs are sufficient and readily available.

Specific Requirements:

Some applications, like high-frequency RF circuits or high-power applications. have specific design requirements that may be better suited to Rigid PCBs.

Volume and Mass Production:

For high-volume consumer electronics and applications where cost is a critical factor. Rigid PCBs are often the more practical choice. due to economies of scale and established mass production capabilities.

While Flex PCBs offer tremendous advantages in space-constrained. dynamic, and custom-shaped applications. there will always be a place for Rigid PCBs in various industries and devices. The best approach to evaluate the specific requirements of each application. and choose the appropriate PCB type based on the functional. mechanical, and cost considerations. In many cases, a combination of Rigid and Flex PCBs, or even Rigid-Flex PCBs. that the most suitable solution to leverage the benefits of both types.

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The Perfect Combination 0f Upgrade-Rigid-Flex PCB

The birth and development of FPC and PCB. That have given birth to the new product of flexible and rigid combination board. Therefore, the combination of flexible and rigid boards. That a flexible circuit board and hard circuit board. after pressing and other processes. according to the relevant process requirements combined together. the formation of FPC characteristics and PCB characteristics of the circuit board. Flexible and rigid combination board at the same time. with the characteristics of the FPC and PCB characteristics. therefore, it used in some special requirements of the product. both a certain degree of flexibility area. there is also a certain degree of rigidity of the area. to save the internal space of the product, reduce the volume of the finished product. to improve product performance has a great deal of help.

※ Types of Rigid Flexible PCBs

Single-Sided Rigid-Flex PCB:

This type consists of a single rigid layer and a single flexible layer. interconnected with plated through-holes or connectors. It is the simplest form of a rigid-flex PCB. and suitable for applications with limited bending requirements.

Double-Sided Rigid-Flex PCB:

In this type, there are two rigid layers and at least one flexible layer. with conductive traces on both sides of the flexible layer. It provides more flexibility and allows for more complex designs.

Multi-Layer Rigid-Flex PCB:

rigid flex pcb

These boards have multiple rigid layers and flexible layers. allowing for complex three-dimensional designs while maintaining electrical connections between different sections.

Dynamic Rigid-Flex PCB:

Dynamic rigid-flex PCBs designed to withstand repeated bending. and flexing during the normal operation of the electronic device. They are commonly used in applications like wearable devices or products with moving parts.

Static Rigid-Flex PCB:

This type of rigid-flex PCB designed for limited or no movement during the device’s operation. It provides the benefits of both rigid and flexible PCBs without the need for frequent bending.

Double-Sided Dynamic Rigid-Flex PCB:

These boards combine the characteristics of double-sided rigid-flex PCBs. with the ability to withstand repeated flexing and bending. They are suitable for applications where both flexibility and durability are essential.

Multi-Layer Dynamic Rigid-Flex PCB:

These boards have multiple rigid and flexible layers and designed for applications. that require both complex interconnections and the ability to handle dynamic bending.

Each type of rigid-flex PCB has its advantages and suited to different applications. based on factors like required flexibility, space constraints, and environmental conditions. The design and manufacturing of rigid-flex PCBs are more complex than traditional rigid or flexible PCBs. and they may require specialized fabrication processes and assembly techniques.

※ Rigid Flex PCB Assembly – Step by Step Process

A one-stop rigid-flex PCB assembly service refers to a comprehensive solution. offered by a single manufacturing partner or company. covering the entire process from design to the final assembly of rigid-flex printed circuit boards. This service streamlines the production and assembly process. providing convenience and efficiency to customers. Here’s an overview of what a one-stop rigid-flex PCB assembly service typically includes:

Design Support:

The service provider may offer design assistance and guidance. to help optimize the rigid-flex PCB layout. for the specific application and ensure manufacturability and reliability.

Prototype Fabrication:

They will handle the fabrication of prototype rigid-flex PCBs based on the provided design files. This may include both the rigid and flexible portions of the board.

Component Sourcing:

The service provider can assist in sourcing the required electronic components . They may have access to a wide range of components and can help customers find the most suitable parts.

Surface Mount Technology (SMT) Assembly:

SMT assembly involves the accurate placement of surface-mount components onto the PCB. A one-stop service provider will have advanced pick-and-place machines. and experienced operators to handle this process.

RAPID SMT PCB ASSEMBLY

Through-Hole Assembly:

In some cases, through-hole components used on the rigid-flex PCB. The service provider will have the capability to handle through-hole assembly as well.

Reflow Soldering:

After component placement, the rigid-flex PCB subjected to reflow soldering. where the solder paste melted to form reliable solder joints between components and the PCB.

Quality Control and Testing:

The provider will have quality control measures in place to inspect the assembled PCBs for defects. ensuring that they meet the required standards and specifications. Various testing methods, such as functional testing and electrical testing.

Final Assembly and Packaging:

After successful testing, the assembled rigid-flex PCBs are ready for final integration into the end product. The service provider may offer additional assembly services. such as enclosure assembly, final testing, and packaging.

Logistics and Delivery:

The one-stop service provider will manage the logistics. and delivery of the finished rigid-flex PCBs to the customer’s specified location.

 

Using a one-stop rigid-flex PCB assembly service can offer several benefits. including streamlined communication, faster turnaround times, reduced risk of errors, and cost-effectiveness. By having all processes handled by a single provider. customers can focus on their core competencies and product development. while relying on the expertise of the assembly service. to deliver high-quality rigid-flex PCBs ready for integration into their electronic products.

※ Application of Rigid-Flex PCB

Rigid-flex circuits offer unique design possibilities and advantages. making them well-suited for various applications across different industries. Some of the common applications for rigid-flex circuits include:

Aerospace and Defense:

Rigid-flex circuits are widely used in aerospace and defense applications. due to their ability to withstand harsh environmental conditions. reduce weight, and provide space-saving designs. They used in avionics, satellites, missile systems, and military-grade communication devices.

Medical Devices:

Rigid-flex circuits utilized in medical devices. where space constraints are crucial, and reliability is essential. Examples include pacemakers, implantable medical devices, hearing aids, and wearable health monitors.

Automotive Electronics:

In modern automobiles, where space limited, rigid-flex circuits employed. to create compact and reliable electronic systems. They used in vehicle control units, infotainment systems, and advanced driver-assistance systems (ADAS).

Consumer Electronics:

Rigid-flex circuits find applications in various consumer electronic devices. such as smartphones, tablets, laptops, and wearables. Their flexible nature enables innovative designs for sleek and compact consumer products.

Industrial Control Systems:

In industrial applications, rigid-flex circuits used to create robust and reliable control systems. They found in factory automation, robotics, process control systems, and instrumentation.

Telecommunications:

Rigid-flex circuits utilized in telecommunications equipment. including base stations, communication modules. and network switches, where space-saving and signal integrity are critical.

Wearable Technology:

Rigid-flex circuits are extensively used in wearable devices like smartwatches. fitness trackers, and health monitoring devices. The flexibility of these circuits enables comfortable wear. and better integration with clothing or accessories.

Internet of Things (IoT) Devices:

IoT devices often require small form factors and reliable connections. Rigid-flex circuits are suitable for various IoT applications. including smart home devices, sensors, and industrial IoT applications.

Aviation and UAVs:

In the aviation industry, rigid-flex circuits used in aircraft systems. and Unmanned Aerial Vehicles (UAVs) due to their lightweight, compactness. and ability to withstand vibration and temperature variations.

Test and Measurement Equipment:

Rigid-flex circuits utilized in test and measurement instruments. providing stable connections and reducing the need for external cables and connectors.

These applications demonstrate the versatility and value of rigid-flex circuits. in addressing the challenges posed by miniaturization. complex designs, and harsh operating environments. The ability to combine rigid and flexible sections within a single PCB. allows engineers to create innovative solutions. for a wide range of industries and electronic products.

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