How Signals Jump Between PCB Layers: Vias Explained
WHAT THIS VIDEO COVERS
This video clearly explains how electrical signals move between different layers in a multilayer PCB using vias - the plated holes that form vertical interconnections in the layer stack-up.
It covers the four main via types: through-hole vias, blind vias, buried vias, and microvias. You'll learn their construction methods (drilling, plating, and lamination sequencing), key performance characteristics such as inductance, signal path length, and routing density impact, plus real manufacturing considerations including cost and complexity.
Shorter vias (especially microvias in HDI PCB designs) deliver better high-speed performance and signal integrity, while through-hole vias remain the most economical and robust option for many applications. The video also touches on advanced variants like via-in-pad and back-drilled vias.
Understanding via selection directly affects board reliability, thermal management, and overall cost in demanding sectors such as aerospace, medical devices, automotive electronics, and high-frequency communication systems.
Get an instant PCB quote or explore our HDI PCB capabilities for advanced via technologies. For rigid-flex projects requiring complex via structures, see our rigid-flex PCB solutions.
KEY HIGHLIGHTS
- Through-hole vias offer the simplest and most cost-effective vertical connection but consume routing space on every layer they penetrate.
- Blind and buried vias improve routing density and signal integrity by connecting only specific layers, though they require precise depth control and additional manufacturing steps.
- Microvias (laser-drilled, <150 μm) are essential for HDI boards, delivering lower inductance and superior high-speed performance at higher cost.
FAQ
Q1: When should I use blind or buried vias instead of through-hole vias?
A1: Use blind or buried vias when you need higher routing density, shorter signal paths, or better signal integrity in compact multilayer designs. They increase cost and complexity, so they are justified primarily in HDI, high-speed, or space-constrained applications.
Q2: What are microvias and why are they important for modern PCBs?
A2: Microvias are tiny laser-drilled holes (usually under 150 μm) used in HDI PCBs. They enable higher layer counts and better electrical performance by reducing inductance and allowing stacked or staggered configurations critical for high-frequency and dense electronics.
Q3: How do vias affect PCB cost and manufacturing?
A3: More advanced vias (blind, buried, microvias) significantly raise fabrication cost due to extra drilling, plating, and lamination steps. Designers must balance performance needs against budget - using high-end vias only where they deliver clear value.
Ever wonder how signals travel between PCB layers?
They go through tiny copper holes — called vias!
A through-hole via drills through every layer.
It's plated with copper along the wall, forming a solid connection.
It cheap and robust — but it wastes routing space on every layer it passes.
A blind via connects an outer layer to inner ones.
It shortens signal paths and frees routing channels below.
But it needs precise depth control.
A buried via hides completely inside inner layers.
It saves outer space,but it must be made before final lamination, increasing process steps and cost.
Microvias are laser-drilled, tiny — usually under 150 μm.
They're used in HDI boards, stacked or staggered between layers.
Shorter vias mean lower inductance and better high-speed performance.
but the higher the cost and complexity.
There are also back-drilled, via-in-pad, and stacked vias——more advanced forms we'll cover later.
Always balance performance, density, and bud get —use the smallest via only when it truly helps,not just because it looks high-end.
