HDI Rigid-Flex PCB

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With the evolution of technology, our devices are steadily becoming more efficient, faster, smarter, and of course, smaller. Even if we don’t count nanotechnology, our everyday devices have shrunk to minuscule sizes, and they are becoming smaller every day, thanks to technological advances like HDI Rigid-Flex PCB.

HDI Rigid-Flex PCB

What is it, you may ask, other than being a mouthful? To put it simply, it is a small circuit board. It combines two conventional types of PCBs into a clever little configuration that is smaller and more efficient than either type.

But before delving further into it, let’s break down the name and fully understand it.


A circuit is comprised of electrical or electronic components connected through conductive wires. A Printed Circuit Board (PCB) makes a circuit smaller and efficient by removing the need for wires and connectors. A PCB is usually made up of non-conductive material like fiberglass or plastic. Instead of wires, the non-conductive material has copper lines on it.

These copper lines are pathways that are printed (etched) onto the PCB. Electronic components like resistors, transistors, and diodes are soldered onto the board, and they connect via copper pathways to make the circuit. Whenever you open an electronic device and see a green or yellow board with a lot of lines on it, that’s a PCB.

The three design types of PCB are Rigid, Flex and Rigid-Flex PCBs.

Rigid PCB

A rigid PCB is a solid board. It has copper lines on one or both sides of it and soldered or mounted components. A rigid PCB cannot be molded into other shapes and devices, and it usually has to be designed to accommodate the whole PCB.

Flex PCB

The same principle as a Rigid PCB, but unlike a solid board, a Flex PCB is printed on a flexible material that can be folded and molded into many shapes. This allows circuits and their devices to be more compact and flexible in design. They are also lighter than rigid PCBs. However, they are costly and require more delicate handling and careful design.

Rigid-Flex PCB

If you have a complex electronic device that requires a lot of components, a Rigid PCB might be too big and a flex PCB might be too delicate. A Rigid-Flex PCB however, is better than both, especially for larger and complicated circuits.

It combines the features of both other types. Rigid PCB areas are used to mount components and are interconnected through Flex PCBs. It allows for multiple layer circuits and eliminates the need for wires, electronic connectors, and sockets. Allowing the device to become much smaller than any single Flex or Rigid PCB could make.

Rigid-Flex PCBs help reduces the volume and weight of the device. They allow for more reliable and long term safer connections by decreasing the number of connection points. They allow for better three-dimensional designing and are generally more robust.

Before diving into the last part of the name, HDI, let’s understand some basic features of a PCB. The copper pathways (or tracks) that form the conductive lines of a PCB, along with the electronic components, can be called a ‘layer’ of PCB. Most simple PCBs are single layer. They have one layer on one side of the non-conductive material (substrate). Two layers mean copper tracks and components on both sides of the substrate. But modern PCBs have taken it even further, and multilayer PCBs are available where there are copper pathways and components present between the top and the bottom layer. These layers are insulated from each other thanks to the presence of a substrate in between them.

This presence of multiple layers in one PCB allows for a much higher component density. To put it simply, a two-layer PCB can be equal to two same sizes single-layer PCBs, while a four-layer PCB can be equal to four single-layer PCBs, and so on.

Now, these layers are electrically connected with each other through VIAs (vertical interconnect access). A VIA is a hole that may run through all the layers of a PCB (starting from the top surface and ending at the bottom surface). By running or integrating a conductor through this hole, different layers can be connected.

There are other types, micro vias that connect different layers to each other without connecting the top and bottom surfaces of a PCB. Two basic types are blind via – open to one surface of the PCB and buried via – not exposed to any surface (top or bottom) and connect internal layers with each other.


HDI stands for High-Density Interconnector. HDI is a special type of PCB that offers much more compaction in circuit and quality than normal PCBs. And they reduce the size of PCBs even more. HDI PCBs have Higher connection pad densities (more connection pads means more electronic components), thinner conductor lines, and micro vias (holes made by laser). Micro vias are incredibly tiny, with a diameter of 0.075mm or less. Manufacturers like us can drill micro vias as small as 0.05mm.

Compactness and small size are not the only defining features of an HDI. Thanks to efficient conduction, and compact design, which means that component is much closer to each other, HDI PCBs allow much-improved signal transmission. In the long run and over-all built, HDI PCBs cost much less than if you use a conventional PCB.


Now that we understand HDI and Rigid-Flex PCB, it is easier to see what an incredible combination an HDI Rigid Flex PCB is. Thanks to an incredible component density, an HDI PCB itself reduces the size of a circuit considerably. If you combine that with the Rigid-Flex PCB, you will have a circuit that is compact, efficient, and much more versatile than a conventional PCB.

To put things into perspective, we provide HDI PCBs with up to 68 layers. Imagine the possibilities for your circuit when it can be compacted and miniaturized to such extent. Employing the power of HDI Rigid-Flex PCB, you can create electronic devices and components of much smaller sizes and designs.

You will not have to design your product to accommodate your circuit; your circuit will be small and efficient enough to be easily incorporated in your design. Medical equipment, implants, aerospace applications, smartphones, smart devices, and robotics are just a few areas where HDI Rigid-Flex PCBs can work their magic.


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