Open any mid-to-high-end multilayer PCB, and you will rarely see only one via specification. High-speed signal vias are commonly 0.2 mm, power and ground vias 0.5 mm, dedicated thermal vias are placed under power devices, and 0.1 mm-class laser microvias are used beneath high-density BGAs.

Many hardware engineers and purchasers ask: Can all vias be unified to the same aperture to simplify drilling and cut processing costs?

The answer: A “one-size-fits-all” via layout seems to streamline production, yet it sacrifices electrical performance, thermal performance and mass-production yield for superficial process convenience. This is a typical false economy in design.

A via is far more than a simple drilled hole on a PCB. It serves four core roles simultaneously: a transmission channel for high-speed signals, a current-carrying channel for power, a thermal conduction channel for power components, and a feature constrained by PCB fabrication processes. Vias for different functions have distinct requirements for aperture, copper thickness on barrel walls and manufacturing methods.

1. Four Types of Vias: Distinct Aperture Design Logic

✅ High-speed signal vias: Prioritise parasitic parameter control, not necessarily the smallest size

In high-speed links such as DDR5, PCIe 5.0 and USB4, vias introduce parasitic capacitance and series inductance. Larger apertures and associated pads increase parasitic capacitance, which triggers impedance discontinuity, signal reflection and waveform distortion, directly harming signal integrity.

For this reason, high-speed signal traces usually adopt 0.2–0.25 mm small-aperture vias paired with adjacent return ground vias to suppress parasitic effects.

However, apertures cannot shrink infinitely. For conventional mechanical drilling, below 0.2 mm, the aspect ratio rises, copper plating uniformity deteriorates rapidly and yield drops sharply. Microvias of 0.1 mm and smaller require HDI laser drilling, which brings higher process costs and technical barriers.

✅ Power/Ground Vias: Focus on current-carrying capacity and conductive cross-sectional area

Power and ground vias follow the opposite design logic from signal vias, with current carrying capability as the core consideration.

Via current capacity is determined by finished aperture, copper barrel thickness and allowable temperature rise. If 0.2 mm signal vias are used in parallel under a high-current chip to make up numbers, a huge quantity of vias will crowd routing space. Worse still, current is distributed unevenly among parallel vias, so the total current capacity cannot be simply summed, creating risks of overheating and board burnout.

✅ Thermal Vias: Reduce thermal resistance while balancing soldering performance

Thermal vias are laid under power device pads or large copper pours to transfer heat rapidly from the top layer to inner or bottom copper planes.

- Too small aperture: Thin plated copper barrel leads to high thermal resistance and poor heat dissipation.

- Too large aperture: Solder starvation and wicking easily occur during SMT reflow, resulting in cold joints.

Thermal via design must strike a balance between thermal conductivity and soldering reliability.

✅ DFM perspective for PCB fabrication: 0.3 mm is the cost-effective sweet spot

From the PCB manufacturer’s standpoint, mechanical drilling around 0.3 mm delivers the best overall yield, minimal bit wear and highest throughput, making it the optimal specification for mass production.

0.2 mm falls out of the cost-effective range; while manufacturable, it brings higher costs and greater scrap risks.

Sizes below 0.15 mm mostly rely on advanced laser drilling equipment and belong to high-end HDI processes.

It is worth noting that a single 0.3 mm via works for low-speed signals and general power nets, but is oversized for high-speed links, insufficient for high-current paths, and simply impossible to fit inside high-density BGA fanouts. No universal aperture suits all scenarios.

2. Hidden Risks of Uniform Via Aperture Across the Board

If a single aperture is enforced board-wide to reduce drill bit changes, you can only pick a compromise size that rarely satisfies signal integrity, current carrying, thermal dissipation and BGA routing at the same time.

1. Unified 0.3 mm aperture

Works for low-speed signals and regular power nets. But high-speed links suffer from elevated parasitic capacitance and degraded signal quality. High-current paths require far more parallel vias and eat up routing space. For BGAs with pitch below 0.5 mm, pads plus annular rings leave almost no room for fanout. For high-speed boards, stub resonance and crosstalk from through-vias become tangible hazards.

2. Unified 0.2 mm aperture

Better for high-speed signals and dense routing. Yet each power via has drastically reduced current capacity, thermal vias show higher thermal resistance. Drilling and plating difficulty rise across the whole panel, yield declines and PCB fabrication costs increase.

3. Unified 0.5 mm or larger aperture

Ideal for power delivery and heat dissipation. But large apertures introduce severe parasitic capacitance that ruins high-speed signal integrity. Larger pad footprints reduce routing density dramatically, and BGA fanout becomes impractical for high-density multilayer designs.

Design engineers understand that more via sizes mean more frequent drill changes, lower throughput and longer lead times — this is why DFM convergence matters.

Industry best practice is to limit via types to 2~3, prioritising standard sizes such as 0.2 mm and 0.3 mm for functional grouping.

Statistics show consolidating a messy list of over ten via sizes down to 2–3 standard specifications can cut PCB manufacturing costs by 15%–20%. By contrast, scattered aperture sizes and frequent drill changes may push mass-production costs up by over 30%.

The cost sweet spot is **few sizes with functional grading**, not one single universal aperture.

3. Professional DFM Workflow: Group by Function, Converge by Process

Via aperture selection is not about blindly choosing bigger or smaller holes. The target is to assign each via type a dimension that meets electrical and thermal requirements while remaining stable and producible.

Juehui Weiye Circuit shares these DFM recommendations for hardware design:

1. For regular boards, converge vias into two groups: one for signal/general use, another for power, ground and thermal vias, balancing performance and fabrication cost.

2. If the design contains high-speed channels or high-density BGAs, add HDI laser microvias as a third category, instead of forcing mechanical through-vias for dense fanouts.

3. Evaluate backdrilling for high-speed links to minimise stub-related signal degradation.

4. Confirm minimum drill size, aspect ratio and annular ring capability with your PCB vendor early in the design phase to avoid non-manufacturable layouts.

Vias of different sizes on a PCB reflect a fundamental engineering trade-off: signals, power delivery, thermal transfer and fabrication processes each have their own optimal aperture range, and no single hole size can satisfy all.

Using uniform apertures as a DFM convergence tactic is reasonable. But making it your starting design rule almost always introduces hidden risks such as unstable signals, inadequate thermal dissipation and insufficient current capacity. Many of these failures only surface during SMT assembly, system debugging or long-term reliability testing, resulting in expensive rework.

Conclusion

Great PCB via design balances signal integrity, current capacity, thermal dissipation, routing density, yield and cost.

Juehui Weiye Circuit specialises in high-speed multilayer PCBs, HDI boards, rigid-flex boards and server computing PCBs. We offer front-end DFM review, impedance simulation and BGA fanout optimisation to help hardware teams avoid common design pitfalls related to vias, stubs, board warpage and current limits. We reliably deliver high-end PCBs for AI computing, automotive, medical and industrial control applications.

FAQ

Q: Is it better to use as few different via sizes as possible?

A: Not the fewer the better. We recommend limiting via types to 2–3 standard sizes to balance cost and performance. A single uniform aperture carries significant risks.

Q: Are smaller vias always better for high-speed PCB signals?

A: No. Excessively small vias create plating and yield issues. 0.2–0.25 mm is the preferred range for most high-speed applications, paired with return ground vias for optimisation.

Q: Do vias under BGA components always need laser microvias?

A: 0.1 mm-class microvias normally require HDI laser drilling. Vias 0.2 mm and above can be mechanically drilled, subject to the BGA pitch.