HDI PCB -

HDI PCB

An HDI PCB (High-Density Interconnect) is a board with higher wiring density than a conventional multilayer PCB. It uses laser-drilled microvias, blind and buried vias, and finer lines and spaces — typically ≤100 μm traces and microvias under 150 μm — instead of relying only on mechanically drilled through-holes.

Built as 1+N+1, 2+N+2, or any-layer stack-ups, HDI shortens signal paths and opens routing under fine-pitch BGAs. That is why it shows up in smartphones, 5G modules, automotive controllers, medical devices, and other compact, high-speed products.

Category	Standard	Sample
HDI structure	Up to 3+N+3	Up to 6+N+6
Any-layer interconnect	Yes	Yes
Layer count	Up to 16 layers	Up to 20 layers
Min. laser blind via	70 μm	60 μm
Blind-via aspect ratio	0.8:1 (60–200 μm)	1:1
Laser hole position accuracy	≤10 μm	—
Layer-to-layer registration	≤50 μm	≤50 μm
Board thickness	0.3–3.2 mm	0.2–3.2 mm

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HDI Design & Manufacturing Guides

HDI Design Guide: Stackup, Microvias and BGA Escape
HDI Manufacturing Guide: Microvias, Structures and Process Control

HDI design is not just finer traces and smaller holes. Stackup, via architecture, routing and manufacturing limits have to be set together. This guide walks through 1+N+1, 2+N+2 and any-layer stackups; stacked versus staggered microvias and aspect-ratio limits; escape routing for 0.5 mm and 0.4 mm BGAs; impedance and return-path control on thin dielectrics; and DFM checks before the board goes to CAM. Rather than treating HDI features as isolated design rules, the guide connects layout decisions with the capabilities and tolerances of the manufacturing process. The goal is to help designers select an HDI structure that meets electrical and mechanical requirements while remaining practical to fabricate and inspect.
Learn HDI PCB Design Guide
HDI production is defined by how laser microvias are formed, filled and stacked — not by treating the board as a standard multilayer with smaller drills. This guide covers 1+N+1 through any-layer structures; core versus RCC and laser-drillable prepreg; copper-filled and epoxy-filled microvias; sequential lamination risks such as registration and warpage; and the process controls CEZON holds in production, including blind-via dimple ≤25 μm and board warpage ≤0.75%. The guide connects these manufacturing controls with practical DFM considerations, helping designers understand which HDI structures can be produced consistently rather than only meeting the requirements on paper.
Learn HDI PCB Manufacturing Guide

HDI PCBs Manufacturing Insights

4 Layer HDI PCB

HDI PCB Stack-ups

1+N+1 Structure: The most common entry-level HDI design. Features one laser-drilled microvia layer on each side of the core. Suitable for smartphones, tablets, and other compact consumer devices.

2+N+2 Structure: Includes two microvia layers on each side of the core. Offers higher wiring density and better signal integrity, ideal for 5G modules, high-speed communication, and automotive electronics.

3+N+3 and Higher Structures: Advanced HDI designs with multiple stacked vias for ultra-high density interconnections. Commonly used in high-performance computing, aerospace, and military systems.

Any-Layer HDI (ELIC): Every layer can be interconnected directly through laser vias. Enables maximum routing flexibility and miniaturization, often used in flagship smartphones and advanced IoT devices.

HDI PCBs FAQs

Q1. How do I choose between 1+N+1, 2+N+2 and any-layer HDI?

A1. Start from BGA pitch and how many build-up layers you need to escape the package — not from the highest structure the factory can run. 1+N+1 is enough for many first-order designs; 2+N+2 is the usual step when 0.5 mm devices need a second microvia layer; any-layer is for designs that must connect adjacent layers throughout the stack. CEZON builds up to 3+N+3 as standard and up to 6+N+6 on samples, including any-layer. Use the design guide to pick the lowest structure that routes the board.

Q2. What laser microvia size and aspect ratio can CEZON build?

A2. Standard production: minimum laser blind via 70 μm, blind-via aspect ratio 0.8:1 (60–200 μm). Samples: 60 μm vias and up to 1:1 aspect ratio. Laser hole position accuracy is ≤10 μm; layer-to-layer registration is ≤50 μm. If the dielectric is thicker than the via can support at these ratios, the stack-up has to change — do not only shrink the drill.

Q3. When do I need via-in-pad or filled microvias?

A3. Via-in-pad is typical at 0.5 mm BGA and usually required at 0.4 mm and below, so escape does not consume the fan-out ring. Those vias must be filled and planarized (copper fill or resin plug plus cap) or solder will sink and the pad will not stay flat. Stacked microvias also need a qualified fill; staggered vias are often the more stable choice when density allows. The manufacturing guide covers copper-fill vs epoxy-fill and the dimple limit held in production.

Q4. Are sample and volume HDI built to the same rules?

A4. No. Samples can use the tighter window: up to 6+N+6, 20 layers, 60 μm laser vias, 0.2 mm minimum thickness. Standard production stays at up to 3+N+3, 16 layers, 70 μm vias and 0.3–3.2 mm thickness. Qualify on the structure you will actually buy in volume, or plan a deliberate step-down after the first articles. Full limits are on the HDI capability page.

Q5. Which materials are used on CEZON HDI boards?

A5. The core is usually high-Tg FR-4 for stability through sequential lamination. High-speed and high-frequency laminates (Shengyi, Panasonic, Rogers, Isola, ITEQ and others) are used when loss or impedance needs them. Build-up layers use laser-drillable prepreg or RCC so the microvia ablates cleanly. Material should be locked with the stack-up before Gerber release, not after.