Electronic devices have become an important part of our everyday lives. Today’s devices are no longer bulky and complicated. They are simple, sleek, and stylish. All this has happened due to the advancement of HDI PCB. If you are new to the world of computers and technology and wondering what is HDI PCB, simply read on!
What is HDI PCB?
HDI or High-Density Interconnect is a kind of PCB that has more interconnections with limited space. This leads to the miniaturization of the overall circuit board. In the PCBs made today, the board space is remarkably reduced and the components are placed with minimum spaces among them. However, no compromises are made with functionalities.
While answering the question, “What is PCB?”, it can be mentioned that a PCB that contains around 120-160 pins/square inch, is treated as an HDI PCB. The HDI design involves intense component placement with versatile routing.
Benefits of HDI PCB:
Some advantages are as follows:
HDI PCBs are highly versatile with performance, reliability, space, and weight being the primary concerns.
The space requirement on the board is reduced through the unique combination of micro vias, buried vias, and blind vias.
Improved signal integrity:
HDI involves the blind via technology as well as via-in-pad. As a result of this, the components can be placed close to one another reducing the signal path length to a great extent. By removing the via stubs, the HDI technology decreases the signal reflections and resultingly improves its quality. Due to shorter signal paths, the signal integrity gets improved.
These boards work excellently against severe environmental conditions. This has been made possible due to the incorporation of stacked vias.
Value for money:
A standard PCB with an 8-layer HDI board can be lowered to a 6-layer HDI board and that too, without compromising its efficiency and quality.
Design Tips for HDI PCB Manufacturing:
Select via types to reduce process complexity:
The selection of vias is crucial as it determines both the equipment and the steps involved in the manufacturing process. It also influences additional costs and processing time. Though the use of buried, blind or micro vias reduces the material costs and number of layers, the choice of using via-in-pad in place of near pad or dogbone vias, influences the complexity involved in the process.
Select minimum components to apply HDI:
Along with the selection of each component, optimizing the component selected is more crucial for HDI PCB boards. The components decide trace widths, locations, sizes, and types for stack up and drill holes. While choosing your components, consider performance capability along with availability, packaging, and traceability.
Space components should reduce stress with EMI:
When you place the components improperly, the stress gets distributed unevenly throughout the board. This may lead to warpage. If again, components are densely packed, signals or the components themselves might introduce EMI or Electromagnetic Interference hampering the signal quality.
Inductances from neighboring pins or pads as well as parasitic capacitances might also influence signal quality. Thus, while designing it is advisable to use EMI modeling for extracting parasitics.
Decrease issues related to signal integrity by routing traces:
Design trace widths in such a way that they achieve the best signal integrity. This involves using briefest trace lengths, consistent path impedances, sufficient ground planes, analog, power, and digital signal isolation.
Select stack up to cut down on material costs:
The PCB stack up that you select also impacts the manufacturing cost of HDI PCB electronic devices. Both the number of layers and the material types determine how many drilling cycles and lamination would be required. When making such decisions, the cost should remain one of the factors.
HDI PCB Manufacturing Process Explained:
Now that we are aware of what is HDI PCB, it is time to know its manufacturing process. Manufacturing HDI PCB electronics requires specialized equipment along with expertise. The system of manufacturing HDI PCB involves certain steps that are not used in regular boards. These steps include forming traces and vias in all layers.
The following steps are to be followed:
Photoresist deposition with exposure:
This defines the spots to be etched which leaves a set of conductors on the laminate.
Etching followed by cleaning:
A solution of ferric chloride can be used for etching. After the etching process is completed, the remaining photoresist is reclaimed along with proper cleaning of the resulting conductor panel.
Drilling and via formation:
Vias are defined either through laser or mechanical drilling. When the via density is high, chemicals help in removing the holes.
Once the vias have been defined, they are given a merallized form to have a constant conductive interconnect.
Applications of HDI PCB:
Aerospace and military:
Several military equipment, such as communications devices and strategic equipment incorporate HDI PCBs. These are excellent for severe climates making them appropriate to be used in military and aerospace applications.
PCBs are being increasingly used by car manufacturers to save space in their cars. With the expansion of the digital world, today’s carmakers are focusing on offering a better driving experience.
Medical devices are generally HDI so that they can be fit appropriately in such as imaging equipment and implants. Though the size of the cameras is reduced, the quality of the pictures is not compromised. HDI PCB technology has made all these advancements possible.
Tablets and smartphones:
All the smartphones that we use today are HDI PCBs along with Every Layer Interconnection construction. It is due to this that, smartphones nowadays are thinner, lighter, and more portable.
Wearable technology has become much popular, especially among the youths. Today’s generation use wearables like Apple watch and VR headsets. All these would have been never possible without HDI.
With the changes in the size of the components, PCB makers altered the manufacturing method. They followed the changing trend which gradually led to the growth of HDI design. HDI PCBs are versatile and efficient making them always in demand in different industries.