Electronics Miniaturization: How Small Can Modern Interconnections Be?
Electronics miniaturization is no longer just about making components smaller. The real challenge is connecting them reliably. Modern processors, FPGAs, DDR5 memory devices, and high-speed communication interfaces feature hundreds or even thousands of pins that must be interconnected within a very limited PCB area without compromising signal integrity.
Electronics Miniaturization Drives the Need for Microvias
This is where microvia technology becomes essential. As one of the key building blocks of modern HDI PCBs, laser-drilled microvias enable interconnections measuring only a few tenths of a millimeter. These structures allow PCB designers to achieve routing densities that would have been considered impractical only a few years ago.
As the trend toward electronics miniaturization continues, PCB manufacturing technologies must evolve accordingly. How small can modern interconnections actually be? And where are the true technological limits of PCB manufacturing?
What Is a Microvia?
A microvia is a very small plated hole used to electrically connect individual layers of a printed circuit board. Unlike conventional plated through holes (PTHs), which extend through the entire PCB thickness, a microvia typically connects only two adjacent layers.
According to current IPC standards, a microvia is defined not only by its diameter but also by its aspect ratio (≤ 1:1) and a maximum depth of approximately 0.25 mm.
Earlier IPC definitions specified a maximum diameter of 150 µm, but the ongoing trend toward electronics miniaturization continues to push these dimensions lower.
Microvias are manufactured using UV or CO₂ laser drilling, which allows extremely precise hole formation without mechanically stressing the PCB material.
Why Conventional Vias Are No Longer Enough
Twenty years ago, mechanically drilled holes with diameters of 0.3–0.5 mm were considered standard. Today, designers routinely work with:
- Processors with more than 3,000 pins
- BGA packages with 0.4 mm or even 0.3 mm pitch
- PCIe Gen5 and Gen6 interfaces
- USB4
- DDR5 memory
- 112G PAM4 and 800G Ethernet
In these applications, driven by the ongoing trend toward electronics miniaturization, conventional plated through holes occupy too much valuable board space. At the same time, they introduce undesirable electrical characteristics that can negatively affect signal transmission quality.
Microvias effectively overcome both of these challenges.
How Small Can Microvias Be?
There is no single answer to this question, particularly as the demand for further electronics miniaturization continues to grow. The achievable dimensions depend on several factors, including:
- The manufacturer’s process capabilities
- PCB material selection
- Dielectric thickness
- Required reliability level
- IPC quality class
Typical HDI PCB manufacturing capabilities
Production values
| Parameter | Typical Value |
| Laser-drilled hole diameter | 75–150 µm |
| Capture pad | 175–300 µm |
| Build-up layer thickness | 50–100 µm |
| Aspect ratio | ≤ 1:1 |
Leading PCB manufacturers can now produce laser-drilled holes as small as 50 µm. However, such dimensions are generally reserved for semiconductor packaging and advanced IC substrate applications.
For most industrial HDI PCBs, a hole diameter of 75–100 µm represents the best compromise between electronics miniaturization, manufacturing yield, and long-term reliability.
Types of Microvias
Modern HDI PCB designs use several basic microvia configurations.
Blind Microvia: Most common. Connects the outer layer to the first inner layer. This is the most widely used microvia type in HDI PCB manufacturing.
Buried Microvia: Internal only. Located entirely within the PCB and invisible from the outside. Commonly used in multilayer boards with very high interconnection density.
Staggered Microvia: Higher reliability. Multiple microvias are offset between successive layers.The staggered arrangement improves mechanical reliability and resistance to thermal stress.
Stacked Microvia: Maximum density. Microvias are positioned directly on top of each other. This configuration enables extremely high routing density but also requires the highest level of manufacturing precision and quality control. Improperly designed or manufactured stacked microvias are more susceptible to fatigue failures caused by repeated thermal cycling.
Why Are Microvias Electrically Superior?
The advantages of microvias are not only mechanical.
Shorter electrical connections provide:
- Lower inductance
- Lower parasitic capacitance
- Reduced signal reflections
- Lower crosstalk
- Improved signal integrity
- Easier impedance control
Compared with conventional plated through holes, microvias can exhibit approximately ten times lower parasitic electrical characteristics, which is especially important for high-speed digital interfaces.
This is one of the main reasons why microvias are now found in virtually every modern smartphone, server, and networking device.
How Are Microvias Manufactured?
Unlike conventional vias, microvias are not created by mechanical drilling. Instead, CO₂ or UV lasers are used to produce holes measuring only a few tens of micrometers in diameter.
The laser beam gradually removes dielectric material through a process known as laser ablation until it reaches the copper foil of the underlying layer, which acts as a natural stop.
The manufacturing process typically includes:
- Sequential lamination
- Laser drilling
- Chemical hole cleaning
- Metallization
- Electrolytic copper plating
- Copper filling or specialized via filling
- Surface planarization
The precision of each step directly determines the quality and reliability of the finished HDI PCB.
Every Reduction Comes at a Cost
As electronics continue to shrink, PCB manufacturing becomes increasingly demanding.
Manufacturers must achieve:
- More accurate layer registration
- Tighter drilling tolerances
- Higher-quality copper plating
- More precise laser process control
- More detailed optical inspection
- X-ray inspection
With the continued progress of electronics miniaturization, manufacturing yield decreases while quality control requirements become increasingly demanding.
Therefore, the goal is not to design the smallest possible microvias, but rather to achieve the smallest dimensions that are truly required for a specific application.
Where Are Microvias Used?
Today, microvias are used in virtually every application where high interconnection density, high-speed signal performance, or strict PCB size constraints driven by electronics miniaturization are key requirements.
Typical applications include:
- Smartphones
- Laptops
- AI accelerators
- Servers
- Networking equipment
- Automotive electronics
- Radar systems
- Medical devices
- Aerospace and defense electronics
As processors become more powerful and BGA pitches continue to decrease, the importance of microvia technology continues to grow.
The Future: Even Smaller Interconnections
Development is far from over.
PCB manufacturers are currently advancing technologies that enable:
- Finer laser drilling
- Narrower traces and spaces
- Higher interconnection density
- More complex multilayer HDI structures
- Low-loss hybrid materials
New build-up materials and increasingly precise IPC-compliant manufacturing processes are supporting the development of even more powerful and reliable electronic systems.
Conclusion
Microvia technology, combined with the continuing trend toward electronics miniaturization, represents one of the most significant innovations in PCB manufacturing over the past two decades.
Laser-drilled interconnections with diameters of 75–100 µm—and approximately 50 µm in specialized applications—make it possible to design electronic devices that are smaller, more powerful, and electrically superior to those using conventional plated through holes.
As the demand for smaller, faster, and more compact electronics continues to increase, future generations of microvias are expected to become even smaller while maintaining the reliability required for increasingly sophisticated electronic systems.
It is important to remember that electronics miniaturization is not an objective in itself. Successful HDI PCB design is about finding the right balance between routing density, electrical performance, manufacturability, and long-term reliability. This is precisely why microvias have become an indispensable part of modern electronics—from consumer devices and automotive systems to aerospace and space applications.