HDI PCB Definition
A PCB with more connections while taking up less area is known as a high-density interconnect (HDI). As a result, the circuit board becomes smaller. While the board area is greatly decreased and the components are positioned closer together, the functionality is unaffected.
To be more specific, an HDI PCB is one that has 120 to 160 pins per square inch on average. The HDI design features flexible routing and dense component arrangement. The HDI made microvia technology widely used. By using microvias, buried vias, and blind vias, a denser circuitry is created. In an HDI design, the drill to copper is decreased.
Benefits of HDI PCBs
Without sacrificing quality, a 6-layer HDI board may perform the same functions as an 8-layer through-hole conventional PCB.
These boards are a powerful protection against harsh environmental conditions because to the use of stacked vias.
3.Better signal integrity:
HDI uses blind via and via-in-pad technologies. By bringing the components closer to one another, the length of the signal route is reduced. The HDI technique eliminates through stubs, which lowers signal reflections and enhances signal quality. As a result of shorter signal routes, it significantly enhances signal integrity.
The amount of board space needed is reduced by using buried vias, blind vias and microvias together.
Where weight, space, dependability, and performance are the top priorities, HDI boards are the best choice.
HDI PCB VS Normal PCB
Because small blind and buried vias eliminate all stray capacitances and inductances, HDI naturally performs better in terms of signal integrity than non-HDI. The impedance of microvias is very near to the trace impedance since there are no stubs. A conventional via has a substantially higher stray capacitance than a microvia, which results in a larger impedance discontinuity. Below is a summary of some of the key distinctions between HDI and traditional PCBs:
|Content||Normal PCB||HDI PCB|
|Layer number||Higher number of layers||Lower number of layers|
|Hole drilling||Mechanical drilling||Laser direct drilling|
|Hole||Through-holes||Implementation of microvias, buried and Blind|
|component density||Lesser compared to HDI||Higher component density per square inch|
|weight||Heavier boards||lighter boards with more functionality|
|size||Larger boards||Smaller boards|
|compatibility||May face compatibility issues with low pitch packages||Compatible with high pin count and low pitch packages|
HDI PCB Stack-up
HDI PCBs are the multilayer PCB boards with densely routed layer construction. The boards are kept together by the lamination process, and various through types are used to electrically link the layers.
The inner copper layers are first etched to start the lamination process. Later, they are stacked like a book with prepreg layers on top and bottom and divided by partly cured laminates. The prepreg is then melted by pressing and heating the stack-up sufficiently. These cooled, liquified prepregs adhere the layers together.
For stack-ups of blind and buried vias, the PCB will go through several successive laminations. The cost of the board increases with the number of laminations.
Designers add more layers to boost routing density, creating a complicated stack-up. Sequential lamination techniques are used by manufacturers to construct such intricate patterns.
HDI PCB DFM Requirements
Despite the strict DFM requirements for clearances on an HDI PCB, they may be met by making use of the design rules in your PCB design program. Before planning and routing, it’s crucial to obtain certain DFM criteria, such as:
- If available, impedance profiles for the chosen stackup or layer pairs
- The board’s material system ensures regulated impedance in the necessary stackup.
- Limitations on the annular ring and aspect ratio, particularly for high reliability designs
- restrictions for trace width and spacing
Your ability to design your HDI circuit board to meet these DFM specifications depends heavily on your design tools. With the appropriate set of design tools, routing impedance-controlled traces on your HDI PCB is relatively simple. Simply set your preferred trace width and an impedance profile while keeping your manufacturer’s DFM recommendations in mind. As you design your HDI architecture, the online DRC engine in your routing software will verify your routing. To make sure you’ve considered all the pertinent HDI DFM requirements, make sure you obtain a comprehensive set of specifications for your fabricator’s process.
HDI PCB performance:
Engineers now have more freedom and flexibility than ever before when it comes to design thanks to the development of PCB HDI technology. Designers that use HDI high density connection techniques may now, if they so want, add additional components to both sides of the bare PCB. In essence, an HDI PCB provides designers more room to work with while enabling them to cram even more compact components in. Thus, a high-density interconnect PCB yields quicker signal transfer and improved signal quality in the end.
HDI PCB is frequently utilized to improve electrical performance while also reducing weight and overall product dimensions. Mobile phones, touch-screen gadgets, laptop computers, digital cameras, and 4G network communications all often use high-density PCBs. A number of electronic aircraft parts and components, as well as medical gadgets, notably use the HDI PCB. High-density interconnect PCB technology appears to have virtually endless potential.
HDI PCB Application:
- Medical industry: Monitor, Diagnostic, Pacemaker
- Automotive: automotive sensor
- consumer products: VR headsets and other wareable devices
- Military defence systems
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