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Step Structure Rigid-Flex PCB

  • Step-Structure-Rigid-Flex-PCB

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Item Rigid-Flex PCB
Max Layer 36L
Inner Layer Min Trace/Space 3/3mil
Out Layer Min Trace/Space 3.5/4mil
Inner Layer Max Copper 6oz
Out Layer Max Copper 3oz
Min Mechanical Drilling 0.15mm
Min Laser Drilling 0.1mm
Aspect Ratio(Mechanical Drilling) 12:1
Aspect Ratio(Laser Drilling) 1:1
Press Fit Hole Ttolerance ±0.05mm
PTH Tolerance ±0.075mm
NPTH Tolerance ±0.15mm
Countersink Tolerance ±0.15mm
Board Thickness 0.4-3mm
Board Thickness Tolerance(<1.0mm) ±0.1mm
Board Thickness Tolerance(≥1.0mm) ±10%
Impedance Tolerance Single-Ended:±5Ω(≤50Ω),±10%(>50Ω)
Min Board Size 10*10mm
Max Board Size 22.5*30inch
Contour Tolerance ±0.1mm
Min BGA 7mil
Min SMT 7*10mil
Surface Treatment ENIG,Gold Finger,Immersion Silver,Immersion Tin,HASL(LF),OSP,ENEPIG,Flash Gold;Hard gold plating
Solder Mask Green,Black,Blue,Red,Matt Green
Min Solder Mask Clearance 1.5mil
Min Solder Mask Dam 3mil
Legend White,Black,Red,Yellow
Min Legend Width/Height 4/23mil
Strain Fillet Width 1.5±0.5mm
Bow & Twist 0.05%
Table of Contents
Primary Item (H2)

Don’t you want smaller and more lightweight printed circuit boards? We are sure the answer is yes, and that is why we have brought to you the finest advancement, i.e., step structure rigid-flex PCB. With every advancement in this field, PCB boards are designed to be reliable and highly functional. 

So, what is such a big deal with these step-structure rigid-flex PCBs?

Well, for starters, the step structure rigid-flex PCB combines the benefits of rigid and flexible PCBs. This way, you can fix all the challenges of modern electronics. 

We have curated a detailed article so that you can explore all about step structure rigid-flex PCB in one place. Let’s begin. 

Understanding Step Structure Rigid-Flex PCBs

To begin, you have to first understand what step structure actually means. The “step structure” basically refers to the change in the structure from rigid to flexible sections on the PCB. 

In simpler words, some parts of the board are solid and inflexible, using regular rigid PCB materials like FR-4. On the other hand, some parts are flexible and use bendable substrates such as polyimide or polyester. 

The best part is that this step-like design provides a smooth transition from a rigid to flexible structure. This step-like design serves a dual purpose: it ensures the structural integrity of the PCB as a whole while enabling adaptability in areas requiring flexibility.

The purpose of this innovative design is to optimize space within electronic devices. In fact, it also provides mechanical stability to elements in the rigid section of the PCB board to enhance reliability. 

Simplified Table

Here is a simple table for you to understand each point closely. 

Aspect Description
Composition Luckily, the step structure rigid-flex PCB is a combination of both rigid and flexible sections within a single PCB.
Materials used Rigid sections typically use materials like FR-4; flexible sections use polyimide or polyester.
Purpose The main purpose of step structure rigid-flex PCB is to achieve a balance between structural stability and adaptability.
Transition zones There is a smooth shift from rigid to flexible sections to prevent stress concentrations.
Component placement The rigid sections are for stable components, and the flexible sections are for adaptability.
Connectivity You have to have a careful routing of conductive paths and signal traces across both rigid and flexible sections.
Mechanical stability Rigid sections provide support and stability to components.
Reduced interconnects You do not have to have any additional connectors or cables.
Manufacturing techniques Advanced methods like laser drilling and precise lamination for optimal rigidity and flexibility.
Testing and simulation With thorough testing and simulation, PCBs can perform well under different conditions.
Standardization Standards are established for consistent design, manufacturing, and testing.

Types Of Step Structure Rigid-Flex PCBs

There are some common types with a combination of flexible and rigid PCB boards. Take a closer look:

  • Single-layer flex rigid-flex PCB: This type of structure has a single flexible layer sandwiched between rigid layers. You can use this for applications that need flexibility in one direction.
  • Double layer flex rigid-flex PCB: Next, you have a model where two flexible layers are integrated between rigid layers. With this design, you can have flexibility in multiple directions. This will provide more versatility.
  • Multilayer flex rigid-flex PCB: This design has multiple flexible layers between rigid layers. You can use it in complex electronic systems where a high level of integration and connectivity is required.

Some other types include dynamic flex rigid-flex PCB, customized flex rigid-flex PCB, torsion-flex rigid-flex PCB, and more.   

Sections of Step Structure Rigid-Flex PCBs

There are separate sections present on a step structure rigid-flex PCB board, and each one of them has a specific purpose. They maintain a balance between rigidity and flexibility. Some of the sections are:

  • Rigid sections: This section has rigid PCB material like FR-4. The main purpose of this area is to provide structural stability and mechanical support to the components present on the board. Now, components like connectors, switches, integrated circuits, etc, all stand solid because of the rigid sections.  
  • Flexible sections: So to incorporate bendable substrates, i.e., polyamide or polyester, you need a flexible section. These areas allow the whole board to bend or move without losing its strength. This is useful in devices that need to change shape or move around. 
  • Transition zones: These are the areas where the board changes from being solid to flexible. However, the change is gradual, like tiny steps. Therefore, you must avoid too much stress in that particular spot on the board. This way, the board stays strong while adjusting to different needs.
  • Component mounting areas: There are certain spots in the solid sections that are reserved for attaching components. For example, connectors are put in these areas to make sure they connect well and stay secure. Designers choose these spots carefully for efficient use.
  • Signal traces and conductive Paths: Both the solid and bendy parts have paths that carry electrical signals. These paths are carefully planned to make sure signals move smoothly between components, even when the board bends or flexes.
  • Bend radius zones: In the flexible areas, designers think about the smallest bend the board can handle without getting damaged. You know these zones are important if you want to keep the bendy parts from straining too much. This will give the board a long shelf life, especially in devices that bend often. 
  • Connector and interface regions: Solid sections are used for attaching connectors and interfaces. This gives them a strong base. The strong material will add reliability to these important parts and make sure they work well. 

Now that you know the different sections of step structure rigid-flex PCB, we must move forward to its advantages.

Advantages of Step Structure Rigid-Flex PCBs

As we already know, the step structure rigid-flex PCB can combine both rigid and flexible elements within a single circuit board. Let’s explore some more advantages. 

Space Optimization

The primary reason to use step structure rigid-flex PCBs is the efficient utilization of space. It has a fine strategy where rigid sections have components that are densely packed. You might also see some connectors and mounting points, which are also required. This way, the designers can achieve a more compact and space-saving layout. 

This is particularly important in applications such as wearable devices, medical implants, and aerospace electronics, where every square millimeter matters.

Enhanced Reliability

Traditional rigid PCBs are known for their structural stability and robustness. On the other hand, flexible PCBs are good for applications that need bending or flexibility. Luckily for you, step-structure rigid-flex PCBs combine the strengths of both, resulting in enhanced reliability. 

The rigid sections provide mechanical support to components and connectors, reducing the risk of damage during handling or stress. In contrast, the flexible sections accommodate the need for bending or folding in the device.

Reduced Interconnects

Interconnects are potential points of failure in any electronic system. Step structure rigid-flex PCBs minimize the need for additional connectors and cables, reducing the overall number of interconnects. This not only improves reliability but also simplifies the assembly process, leading to cost savings in production.

Weight Reduction

The combination of rigid and flexible sections can help you eliminate excessive use of materials. Therefore, you end up with less weight in the overall design. It is beneficial for applications like automotive electronics and aerospace. Especially where weight is an important factor. 

Before getting ahead with anything else, here are some design considerations.

Design Considerations

Creating a step structure rigid-flex PCB requires skills, and you need to know some specific aspects. Read some of the considerations.

Material Selection

To begin the process, you first need to pick the right material. It will help you achieve the right balance between rigidity and flexibility. The rigid sections typically use standard FR-4 or similar materials, while the flexible sections may employ polyimide or polyester substrates. 

Proper compatibility of these materials will help you get rid of issues like mechanical failure and more.

Layer Stackup Design

Please remember to always have the layer stack up because it is critical for the performance of the PCB board. Carefully plan the arrangement of rigid and flexible layers. Always consider factors like signal integrity, impedance control, thermal management, etc. 

You know a well-optimized layer stack-up will give you the best functionality and reliability of the PCB. 

Bend Radius and Flexibility Requirements

Next up, you have to understand the bending requirements of the flexible sections. This is important to prevent any damage during the operation. Make sure to determine the minimum bend radius for the flexible portions of the PCB. However, ensure that components, traces, and vias can accommodate these bending constraints without compromising functionality.

Connector Placement

Connector placement is the key consideration in the entire setup. The rigid sections are often utilized for mounting connectors and other components that require a stable mechanical anchor. Proper placement and reinforcement of connectors contribute to the dependability and durability of the outcome.


Step structure rigid-flex PCBs are used in many applications and industries thanks to their unique characteristics. For example, they are space-efficient and reliable, offer weight reduction, and more. Some notable options are: 

Wearable Electronics

You know how important size and flexibility are for wearable devices, and step-structure rigid-flex PCB is the best solution for it. You can have sensors, microcontrollers, communication setups, and more in one device. This is possible because step-structure rigid-flex PCB is lightweight and compact. 

Medical Devices

Step-structure rigid-flex PCB helps with medical implants and portable devices. The reason is that these devices need a perfect combo of rigidity and flexibility. The best thing is that you can tailor the PCB structure to your needs. This way, you can have a reliable and compatible device that is good for the human body.

Automotive Electronics

Similarly, the automotive industry is also not behind. It is equally enjoying the benefits of step-structure rigid-flex PCB. The most significant benefit is the space-saving capacities and how they can be used in ADAS, infotainment systems, and more. 

Aerospace and Defense

The weight component is a big deal in the aerospace industry. That is why you can have a step-structure rigid-flex PCB to reduce weight and enjoy fuel efficiency better. This will enhance the performance and can also help you with the navigation system, control system, and more. 

Even though you can use step-structure rigid-flex PCB in many industries, you might have to face some challenges. 

Challenges With Step Structure Rigid-Flex PCBs

When you are thoroughly familiar with the challenges of step-structure rigid-flex PCB, tailor your requirements accordingly.

Material Innovations

Although step-structure rigid-flex PCB can make your applications run smoothly, scientists are working on making it better by using new and improved materials. But there is still research going on, and finding this model is going to take more time. 

Manufacturing Techniques

If you want the right mix of stiffness and flexibility, you need to be careful when you are making them. You can use advanced methods like laser drilling and special ways of putting layers together. This can make these PCBs even better at their work.

Simulation and Testing

As we know, step structure rigid-flex PCBs are tricky to handle; designers have to do a lot of testing and checking to make sure they work well. They sometimes have to use computer simulations to see how the PCBs behave under different circumstances. This will help you get a PCB that meets all the requirements and works reliably.


As more and more industries are using step-structure rigid-flex PCBs, the need to have common rules for everyone is also rising. You may call them standards, but they make it easy for the designers, manufacturers, testers, etc, to work together. You will end up with the best quality PCB when everyone is working together as a team. 

Wrapping Up!

We can confidently say that step-structure rigid-flex PCBs are surely a step forward in the field of PCB design. These PCBs can change the world of manu applications, i.e., medical electronics, automotive systems, aerospace applications, and whatnot. If you want to unlock the full potential of your devices, use step-structure rigid-flex PCBs.

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