In today's era of relentless semiconductor breakthroughs, “high-density interconnect stacking” has evolved from technical jargon into the core engine driving computational innovation. This is not merely an incremental refinement of packaging technology, but a paradigm shift fundamentally reshaping the internal architecture of chips—transforming traditional planar wiring into intricate three-dimensional traffic networks. Understanding this technology not only reveals the source of advanced chip performance but also offers insights into the future evolution of cutting-edge fields like artificial intelligence and high-performance computing.This blog will provide an accessible yet thorough analysis of its principles, applications, and its revolutionary advancement beyond traditional packaging.
In this article:
Part 1. What is Stacking of High Density Interconnects Part 2. Applications on High-End PCBs Part 3. High-Density Interconnect Stacking vs. Traditional PackagingWhat is Stacking of High Density Interconnects
This is a highly core and cutting-edge technology in the field of advanced semiconductor packaging. We can break it down into two parts for understanding:
High-Density Interconnect (HDI): Refers to achieving a large number of fine electrical connections within an extremely small space. It's like transforming a wide, multi-lane highway with sparse traffic into a multi-level, densely packed, and highly efficient super interchange. Traditional circuit board trace widths and spacings may measure tens of micrometers, whereas HDI achieves dimensions of several micrometers or even smaller.
Stacking: This involves building these high-density interconnect layers in three dimensions, layer upon layer, much like constructing a building.
Combined, high-density interconnect stacking is an advanced packaging technology that achieves an extremely high number of electrical interconnections within a minuscule volume through three-dimensional stacking. This enables the integration of multiple chips or chip modules.
Applications on High-End PCBs
The stacking of high-density interconnects is essentially an advanced semiconductor packaging technology that primarily functions within chips themselves, rather than on the ordinary PCBs we encounter daily. The core of this technology involves stacking multiple chips layer upon layer in three-dimensional space, much like constructing a building, and establishing massive electrical connections between them through ultra-fine micron-level circuits. This enables the achievement of exceptionally high performance and bandwidth within an extremely compact volume.
While this technology itself isn't directly used to manufacture PCBs, it profoundly dictates which PCBs must be designed to complement it. PCBs housing these “super chips” are far from ordinary; they must be top-tier circuit boards serving the most cutting-edge applications. These PCBs play the role of carrying and connecting these highly integrated chip components, and thus must themselves possess exceptional performance. They are typically high-speed, high-layer-count circuit boards manufactured using arbitrary-layer high-density interconnects and advanced processes. They must meet extreme data transfer rates and have near-demanding requirements for signal integrity, power integrity, and thermal management.
Specifically, you'll find them in: accelerator cards housing GPUs and high-bandwidth memory in AI servers; high-speed switches and routers within data centers; and motherboards designed for ultimate performance and slim profiles in the latest smartphones.
High-Density Interconnect Stacking vs. Traditional Packaging
Traditional packaging operates more like a two-dimensional layout. Its core task is to provide a protective shell for a single chip and “translate” the hundreds of internal contacts—via wires or other means—to pins on the package shell for soldering onto a PCB board. The “roads” (wiring) between these pins are relatively wide with large spacing, resulting in low interconnect density. When integrating multiple chips, they could only be laid side-by-side on the circuit board. Communication between chips required traversing lengthy PCB traces, resulting in slow speeds, high latency, and significant power consumption.
High-density interconnect (HDI) stacking represents a revolutionary leap forward, tackling the problem in three-dimensional space. The core distinction lies in the terms “high density” and “stacking.” Rather than settling for planar layouts, it employs technologies like through-silicon vias (TSVs) and microbumps to stack chips vertically, akin to constructing skyscrapers. This reduces inter-chip communication distances from centimeters to micrometers. Simultaneously, materials such as silicon interposers enable the creation of intricate wiring networks on the surface, comparable in precision to those within chips themselves. This achieves interconnect densities and bandwidths far surpassing traditional packaging.
Specifically, this approach delivers fundamental performance advantages: First, a leap in performance—significantly reduced latency in inter-chip data transmission, markedly lower power consumption, and bandwidth increases by orders of magnitude, perfectly meeting the massive data throughput demands of artificial intelligence and high-performance computing. Second, it achieves a qualitative leap in integration through “heterogeneous integration.” This enables the efficient consolidation of chips from different manufacturers, different manufacturing processes, and different functionalities (such as CPUs, memory, and sensors) within a single package. This allows each component to maximize its strengths while drastically reducing the overall physical size of the system.
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Integration Scale
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2D Planar Mounting
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3D Vertical Stacking
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Interconnect Density
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Low-density (mm-level spacing)
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High-density (µm-level spacing)
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Performance Profile
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High latency, Limited bandwidth
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Ultra-low latency, High bandwidth
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System Architecture
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Single-chip or Multi-chip Module (MCM)
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Heterogeneous Integration & System-in-Package
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Enabling Technology
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Wire Bonding, BGA Packaging
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TSV, Silicon Interposer, Hybrid Bonding
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In summary, high-density interconnect stacking technology marks the semiconductor industry's transition from an era of “drawing circuits” on a flat plane to a new epoch of “building cities” in three-dimensional space. Through micron-level vertical interconnections, it pushes the boundaries of performance, power consumption, and integration to their limits, becoming the cornerstone for meeting the computational demands of the intelligent era. From the massive GPUs powering AI to the smartphones held in our hands, this technology is quietly accelerating the entire digital world. In the future, through the deep integration of heterogeneous integration and 3D stacking technologies, it will undoubtedly usher in a new era of computing characterized by higher performance and greater energy efficiency.
One-Stop HDI PCB Manufacturer and Its PCB Via Filing Capabilities
If you're looking for turnkey HDI electronics manufacturing services (EMS) from hardware development to PCBA fabrication and box-build assembly, you can work with the one-stop HDI PCBA manufacturer PCBONLINE.
Founded in 1999, PCBONLINE has R&D capabilities for HDI projects and EMS manufacturing capabilities, including via filling for stacked vias. It provides 4-to-64-layer HDI PCB fabrication, assembly, and PCBA box-build assembly. You can order various HDI PCBs from PCBONLINE, such as FR4, polyimide (flexible PCB), polyimide + FR4 (rigid-flex PCB), and PTFE/Rogers (high-frequency PCB).
3000m² of production capacity per day for HDI PCBs with builds of 1+N+1, 2+N+2, 3+N+3,4+N+4, and arbitrary interconnection in any layers.
PCBONLINE has hardware and software R&D capabilities for IoT applications requiring HDI design, including PCBA and enclosures.
We can manufacture complex PCBs with stacker vias, via-in-pad, microvias, inlay boards, heavy copper designs, and hybrid and fine structure lay-ups.
Besides HDI PCB fabrication, we have powerful capabilities in fine-pitch assembly for HDI PCB assembly.
We have rich R&D and manufacturing experience for HDI applications such as FPGA boards.
High-quality HDI PCB and PCBA manufacturing certified with ISO 9001:2015, IATF 16949, RoHS, REACH, UL, and IPC-A-610 Class 2/3.
Here'e the PCB via filing capabilities at PCBONLINEL:
- Micriavia filling with copper: laser via size 0.1-0.125mm, priority 0.1mm
- Finished hole size for via-in-pad filling with resin: 0.1-0.9mm (drill size 0.15-1.0mm), 0.3-0.55mm normal (drill size 0.4-0.65mm)
- Max aspect ratio for via-in-pad filling with resin PCB - 12: 1
- Min resin plugged PCB thickness: 0.2mm
- Max via-filling ith resin PCB thickness: 3.2mm
- Making different hole sizes with via filling in one board: Yes
- Via filling with copper/silver: Yes
If you need HDI PCBAs or any other PCBAs requiring via filling, please send your email to PCBONLINE at info@pcbonline.com. We will provide one-on-one engineering support to you.
Conclusion
Via filling is used for creating stacked vias in HDI PCB fabrication, BGA/CSP/QFN IC packaging, and filling PCB via-in-pad with resin during multilayer PCB fabrication. If you need one-stop electronics manufacturing for your HDI PCBA project, contact the one-stop advanced PCB manufacturer PCBONLINE for high-quality PCBA and box-build solutions tailored to your project's needs.
PCB fabrication at PCBONLINE.pdf
