Any printed circuit board that offers dense placement of components and denser interconnections can be regarded as a high-density PCB or high-density interconnect (HDI) PCB.
High-density PCBs consist of features such as blind and buried vias, layers with through vias, coreless construction with pairs of layers, alternative coreless construction with layer pairs, and passive substrate construction with no electrical connection.
There are fewer signal integrity issues in HDI boards and a significant decrease in crossing delays, signal losses, etc.
Instead of through holes in standard PCBs, HDI PCBs utilize micro via technology
Miniaturized electronic circuit boards are used in various industries: consumer electronics, communication systems, the automotive and aerospace industry, the healthcare sector, etc. In all these industries, high-density PCBs, otherwise called high-density interconnects (HDI PCBs), are of critical importance. HDI technology enables smaller-footprint devices to be produced at a competitive cost without compromising quality, performance, or board reliability.
Any printed circuit board that offers dense placement of components and denser interconnections can be regarded as a high-density PCB or high-density interconnect (HDI) PCB. These PCBs offer higher wiring density per unit area compared to traditional PCBs.
High-density PCBs consist of:
- Blind and buried vias
- Layers with through vias
- Coreless construction with pairs of layers
- Alternative coreless construction with layer pairs
- Passive substrate construction with no electrical connections
- A higher number of interconnections
With these features, high-density boards are compact and establish smaller dimension boards with smaller pads, vias, spaces, and traces. The high wiring density in HDI boards makes them lightweight, miniaturized circuits with a lower number of layers. With all these features, it is worth replacing a few PCBs on a product with a single HDI board.
IPC 2226 Defined Structures of HDI Boards
According to IPC 2226, HDI PCBs are boards with:
Lines and spaces 100μm
Smaller vias <150μm
Capture pads <400μm
Connection pad density ＞20 pads/cm2
Single micro via layer on at least one side of the core. Interconnections are established using PTH and plated micro via technology. No buried vias present, but blind vias are present.
Single micro via layer on at least one side of the core. Interconnections are made through PTH and plated micro via technology. Both blind and buried vias are present.
At least two layers of micro vias on single or both sides of the core. Interconnections made through PTH and plated micro via connections. Both blind and buried vias are present.
Advantages of HDI PCBs
High-density PCBs are extensively used in consumer electronics such as touch screens, mobile phones, tablets, computers, digital cameras, laptops, etc. HDI boards are smaller than traditional boards, without compromising on performance. The advantages of HDI PCBs are:
- Lightweight and compact sizing - Populating more components on either side of HDI PCBs leads to smaller footprints and lightweight boards with improved functionality.
- Low-cost boards - With HDI technology, it is possible to reduce the raw material quantity, number of layers, and even the number of boards, which leads to an overall reduction in cost.
- Improved performance and reliability - As components become closer and the number of transistors per unit area is higher, it is clear that the performance is improved in HDI boards. There are fewer signal integrity issues in HDI boards and a significant decrease in crossing delays, signal losses, etc. The use of micro vias over through holes has a remarkable impact on the reliability of the HDI board due to the former’s smaller aspect ratio and high-quality construction.
- Shorter time-to-market - The HDI PCB production process exhibits outstanding design efficiencies and shortens the time to market. With HDI boards, design and testing also speed up.
Comparing HDI PCBs and Traditional PCBs
Here are some other differences between HDI PCBs and standard PCBs.
Size and weight
Large and heavy
Small and light
Through hole, blind, and buried vias
Blind, buried, and micro vias
Compatible to high pin count devices
May or may not
Compatible to small pitch devices
May or may not
Number of layers
High-density PCB designs will continue to replace standard PCB designs due to their advantageous features, and the technology of high-density PCBs will continue to evolve to improve the degree of compactness and miniaturization. Cadence OrCAD PCB Designer software offers comprehensive PCB solutions for designing HDI boards with advanced routing and component placement technology.
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