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HDI Rigid-Flex PCB Layout & Design

HDI Rigid-Flex PCB Layout & Design

Name: HDI Rigid-Flex PCB Layout & Design

Designable layers: 1-32 layers

Minimum line width and line spacing: 3mil

Minimum laser aperture: 4mil

Minimum mechanical aperture: 8mil

Copper foil thickness: 18-175цm (standard: 18цm35цm70цm)

Peel strength: 1.25N/mm

Minimum punching hole diameter: single side: 0.9mm/35mil

Minimum hole diameter: 0.25mm/10mil

Aperture tolerance: ≤φ0.8mm±0.05mm

Hole tolerance: ±0.05mm

Hole wall copper thickness: double-sided/multi-layer: ≥2um/0.8mil

Hole resistance: double-sided/multi-layer: ≤300цΩ

Minimum line width: 0.127mm/5mil

Minimum pitch: 0.127mm/5mil

Screen printing color: black, white, red, green, etc.

Surface treatment: lead/lead-free tin spray, ENIG, silver, OSP

Service: Provide OEM service

Certificate: ISO9001.ROSH.UL

It’s not only you, HDI Rigid Flex PCB layout and design are complex for everyone. As the electronic devices are getting more and more complicated each year, working with HDI rigid-flex PCBs has become tough.

But fear not, as this guide is here. We will discuss everything about HDI Rigid-Flex PCBs.

So let’s start.

Understanding HDI Rigid-Flex PCBs

HDI Rigid-Flex PCBs are advanced types of printed circuit boards that combine the features of the rigid and flexible PCBs.

HDI stands for High-Density Interconnection Technology, which enables greater mounting density of components and interconnecting lines within a smaller space.

Rigid-flex characteristics enable this type of PCB to be composed of rigid sections that will keep structural rigidity and flexible sections that can bend or be folded, allowing many more versatile design options with electronic devices.

Now let’s discuss the structure and components of HDI Rigid-Flex PCBs.

Structure and Components of HDI Rigid-Flex PCBs

As mentioned above, HDI Rigid-Flex PCBs are a combination of rigid and flexible features to result in versatile circuit assemblies.

Let’s discuss them in detail:

1.Flexible Layers:

Absolutely critical to adaptability, these are generally polyimide layers that can be bent in any shape. This enhances flexibility in design, making PCBs that conform to available space and complex layouts.

2.Rigid Layers:

The rigid layers, such as with FR-4 material, are in place to give strength and support, maintaining the shape and integrity of the PCB.

They serve as the base onto which the components are mounted, and the electrical interconnection is precisely assured.


Microvias are small, through-holes in the layers of a PCB, providing high-density interconnection with minimal invasiveness.

These are used for signal routing, which improves electrical performance and signal integrity in small-sized electronic designs.

Advantages of HDI Rigid-Flex PCBs Over Traditional PCBs

HDI Rigid-Flex PCBs offer many advantages over conventional PCBs.

Some of them are:


HDI rigid-flex PCBs allow them to bend and shape into very different shapes without performance loss. It is this very ability that allows the development of electronic gadgets that are slim and compact, with very unique form factors.

- Space Savings

Compact micro-vias and flexible layers on the HDI Rigid-Flex PCBs maximize space being used by electronic devices to minimize sizes and weight.

This space-saving approach optimizes the footprint of PCBs in such a manner that it does not affect the functioning of the device.

- Performance Improvements

The HDI Rigid-Flex PCB is designed by shortening signal paths and optimizing the routing for improved electrical performance and reliability. Minimized impedance and reduced signal loss guarantee improved signal integrity and high operation speed.

- Design Freedom

HDI Rigid-Flex PCBs set design freedom to the next level, making designers capable of any complex circuit configuration and laying innovations in packaging.

This flexibility gives a creative hand in developing cutting-edge electronic devices.

Applications of HDI Rigid-Flex PCBs

There are lots of applications of HDI Rigid-Flex PCBs that you must know:

  1. Aerospace and Defense: Essential to avionics, satellite communication, and military electronics, providing robustness in severe environments.
  2. Medical Devices:Integral to implants, diagnostics, and medical imaging, they offer flexibility and reliability in healthcare when it is needed most.
  3. Automotive Electronics: Used in vehicle infotainment, ADAS, ECUs, and sensors, enhancing safety and performance in automobiles.
  4. Consumer Electronics: Found in smartphones, wearables, and IoT devices, due to their small and feature-rich designs.
  5. Industrial Automation:It is found within the control systems, robotics, and IoT devices, providing ruggedness and connectivity for such applications.
  6. Telecommunications:Utilized in networking equipment, base stations, and fiber-optic systems, supporting high-speed data transmission and reliability in communication networks.

HDI Rigid-Flex PCB Design Considerations

Now that you are familiar with the fundamentals of HDI Rigid-Flex PCBs, let’s go over a few critical design guidelines that will help you:

  • Material Selection: Materials are selected on the basis of environmental requirements for dielectric qualities, flexibility, and thermal considerations.
  • Stackup Optimization: Optimization of the number of layers, thickness, and copper distribution for better electrical and mechanical performance.
  • Microvia Design: Particular attention should be given to the size, spacing, and routing of the vias to ensure there are reliable interconnections with minimum signal distortion.
  • Signal integrity and EMI: Techniques for controlled impedance routing and shielding to keep levels of electromagnetic interference low and maintain signal integrity.

Now let’s learn the fabrication and assembly process of HDI Rigid-Flex PCBs.

Fabrication and Assembly Processes

Creating HDI Rigid-Flex PCBs involves several critical steps for quality and reliability:

  1. Material Lamination: Bonding flexible and rigid layers forms the PCB core, requiring precise alignment for structural integrity.
  2. Microvia Formation: Small drill and plating for connectivity between layers that have to be uniform and reliable.
  3. Patterning and Etching: Copper is selectively removed to form circuit traces with high precision and intricate geometries.
  4. Component Placement and Soldering: This is for automatic alignment to place the electric components correctly and solder them to make a good interconnection.


In essence, HDI Rigid-Flex PCBs are an intelligent solution to the electronic needs of today. The technologies used in the combination of Rigid and Flex PCBs give unmatched flexibility, space-saving benefits, and the superiority of performance over traditional PCBs.

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