Ray Glover is an IPC Certified PCB Interconnect Designer with extensive experience designing high-speed, high layer count PCBs (including flex and rigid-flex) for a wide range of military and commercial electronics programs.
For most people outside the PCB industry, the terms blind vias, buried vias, and HDI stackups sound highly specialized, and they are. But for those of us working in PCB layout every day, they’ve become essential elements or solving one of the biggest challenges in electronics design: how to fit more performance into less space without sacrificing reliability or manufacturability.
Over the last several years, I’ve watched the industry steadily adopt ever-smaller components operating at ever-higher frequencies, with higher density component placement and trace routing. Successfully managing these modern integration requirements has led our team to deploy state-of-the-art CAE tools to ensure that the thermal, signal, and power integrity requirements are fully satisfied. These advanced layout implementations must not only be functionally robust but also practical to manufacture and cost-effective to build. Balancing density, robustness, and manufacturability is exactly where HDI PCB design lives.
HDI is most effective when treated as a complete design strategy rather than simply a fabrication technology. It requires experience, planning, and a deep understanding of how layout decisions can affect the entire product lifecycle. Whether we’re working on miniaturized electronics, high-speed digital systems, or ruggedized hardware for demanding environments, the goal is always the same: build the most robust and cost-efficient solution possible.
At Re:Build AppliedLogix, our teams regularly support customers developing high-speed, multilayer, and high-reliability electronic systems where PCB layout decisions directly impact manufacturability, signal integrity, and the product’s long-term reliability and performance.
HDI becomes necessary because of miniaturization. When circuit boards become smaller and components become denser, traditional through-hole vias can quickly become a barrier, and they consume internal trace routing channels and component placement area.
One of the best examples is when we find it necessary to implement 0.5mm pitch BGAs within a design. Routing signal traces through a 0.5 mm pitch BGA via field with conventional drilled through vias becomes extremely difficult without introducing manufacturability problems. In many cases, blind or buried vias become the only practical option.
At Re:Build AppliedLogix, we’ve successfully implemented HDI solutions across a multitude of projects involving dense component placement, with primary and secondary side active devices, and advanced signal routing requirements. But we don’t use HDI simply because it’s available. We use it when it makes sense. That distinction matters.
The key is understanding the entire system, not just the via structure itself. If HDI allows you to reduce board size, improve routing efficiency, and/or eliminate expensive secondary processes, then the economics can shift quickly in your favor.
Some teams are inclined to approach HDI with skepticism and fear because they haven’t worked with it enough. They hear about higher costs or reliability concerns and immediately avoid it, even when it might be the best engineering solution.
There are legitimate concerns surrounding HDI PCB fabrication, in-particular with stacked microvias.
Thermal cycling remains one of the biggest challenges. During a typical PCBA reflow oven-based assembly process, boards are exposed to very high temperature heating cycle(s). Once the boards are installed in the field, they must endure harsh operating environments. Aerospace, defense, automotive, and space applications, require the PCBAs to continue to function reliably during rapid thermal transients. Such conditions can create stress fractures within stacked microvias over time.
From what I’ve seen in industry research and conversations with fabricators, keeping stacked microvias limited to two-high is generally considered to be the most conservative approach. Beyond that, reliability risks begin increasing significantly depending on the application and manufacturing process.
That’s why HDI decisions can’t happen in isolation. You have to understand the board’s operating environment, thermal exposure, assembly processes, and long-term reliability requirements before committing to a stackup and via construction strategy.
One of the more difficult aspects of HDI design is balancing microvia structures with high-speed signal integrity requirements.
Modern high-speed boards rely heavily on carefully controlled stackups and trace routing, dedicated signal return planes, and careful consideration of the cavities that the electromagnetic waves are propagating within. But once you introduce microvias into that environment, routing flexibility can change dramatically. Suddenly, not every layer is equally accessible anymore.
That forces layout designers to think much further ahead. The stackup, impedance requirements, crosstalk mitigation, via strategy, and trace routing constraints all become tightly interconnected decisions.
This is where experience becomes incredibly important. PCB layout isn’t just about connecting traces or deploying the latest CAE tools. It’s all about understanding how every design decision affects manufacturability, performance, reliability, and cost simultaneously.
One mistake that I’ve seen quite often is the “overuse”of microvias across every layer pair within a board.
Technically, it works. But every additional microvia layer pair adds another drill and plating cycle during fabrication, driving board costs up very quickly. A few years ago, I completed the layout for a 12-layer board where there was physically no room for traditional vias. Every signal transition required stacked and staggered microvias. The board was only about one inch square and the manufacturing cost was shocking.
Sometimes that level of complexity is unavoidable. But more often, smarter early-stage decisions can prevent designs from being forced into expensive HDI solutions later.
One of the first questions I ask quite often when I am reviewing a schematic is: “Why was this fine-pitch component package chosen?” If a larger, more layout-friendly IC package can accomplish the same function, without forcing HDI adoption, then that conversation needs to happen early – preferably while the schematic design phase is still active.
At Re:Build AppliedLogix, one of our greatest strengths is the depth of experience across our engineering and layout teams. Many of our designers have 30 to 40 years of experience individually, and collectively we’ve worked across nearly every facet of electronics development.
We’ve handled everything from miniaturized electronics to high-voltage battery management systems, military hardware, healthcare electronics, and rigid-flex designs. That broad exposure helps us to recognize potential pitfalls early on and guide customers toward better long-term solutions.
In many ways, PCB layout is still equal parts engineering and art.
I often describe it as a giant crossword puzzle that eventually turns into a three-dimensional dot-to-dot. Every designer develops their own style, their own techniques, and their own way of solving problems. And yes, we all like making boards look clean and symmetrical when we can.
But ultimately, the goal isn’t to create something that just looks good. The goal is to create a robust, manufacturable, reliable product that delivers the best value for the customer. That’s what good design is really about.
HDI (High Density Interconnect) PCB design involves the deployment of microvias, blind vias, buried vias, and advanced multilayer stackups to support higher component density, faster signal routing, and smaller electronics packaging.
Microvias become important when dense BGAs, high-speed routing, or limited board space make traditional through-hole vias impractical.
Not always. While HDI fabrication introduces additional PCB fabrication complexity, it can reduce overall system cost by shrinking board size, improving routing efficiency, and eliminating secondary processing steps.
HDI PCB layouts are commonly used in defense, medical electronics, automotive systems, industrial automation, telecommunications, and compact consumer devices.
Re:Build AppliedLogix focuses on balancing electrical performance, manufacturability, reliability, thermal considerations, and long-term production readiness throughout the PCB layout process.
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