High-Density Interconnects Made Simple. Boost Performance by 40%.

When I first looked at HDI PCB design, I saw the same concern from many engineering teams: more components, less board space, tighter signal rules, and no room for avoidable delays.

The phrase “40% more performance” sounds attractive, but it needs context. HDI does not create a fixed performance gain for every board. The result depends on stack-up design, trace length, signal speed, materials, thermal planning, and production quality.

A well-planned HDI design can help a product use space more effectively, shorten critical connections, and support higher component density.

Where HDI can improve a board

HDI, or High-Density Interconnect, uses features such as microvias, fine traces, and sequential build-up layers. These features help connect small-pitch components without making the board larger.

I usually look at four areas:

• Signal path length
• Component placement
• Power delivery
• Thermal balance

A shorter signal path can reduce delay and unwanted noise. Better placement can free space for batteries, sensors, connectors, or cooling parts. A stronger power layout can help the board handle changing loads with fewer voltage drops.

The actual gain should be measured through testing. Useful data may include signal loss, thermal readings, boot time, power stability, and board size.

A practical design example

Imagine a compact medical monitoring device that needs a processor, wireless module, memory, display connector, and several sensors.

A traditional multilayer PCB may require more surface area to route all connections. The product team may then face a larger enclosure or limited space for the battery.

An HDI structure can place components closer together and route signals through microvias. The board may fit inside a smaller housing while keeping the same main functions.

The improvement is not only about speed. A smaller board can also support a lighter enclosure and a shorter connection path between high-speed parts. The final result still depends on material selection, impedance control, assembly accuracy, and test coverage.

How I assess the possible gain

I start with the product requirements instead of promising a fixed percentage.

1. Review the current board

I check the board size, layer count, component pitch, high-speed interfaces, power rails, thermal areas, and known production issues.

This gives me a baseline. Without a baseline, “40% more performance” has no clear meaning.

2. Mark the critical signals

PCIe, USB, MIPI, DDR, RF, and other fast interfaces may need controlled impedance and short routing paths. I review their length, via count, return path, and nearby noise sources.

A shorter route can help, but it does not replace proper stack-up planning.

3. Build the HDI stack-up

The layer structure should match the signal and manufacturing needs. Microvia size, dielectric thickness, copper weight, trace width, and sequential lamination all affect the design.

I also confirm that the selected fabricator can produce the proposed structure with stable results.

4. Check power and heat

A dense board can save space while creating new heat concerns. I review current paths, copper areas, thermal vias, regulator placement, and airflow.

A layout that looks efficient on screen may still need changes after thermal testing.

5. Compare measured results

I compare the HDI version with the previous design using the same test conditions. The comparison may include:

• Board area
• Signal integrity
• Power stability
• Maximum temperature
• Data transfer rate
• Assembly yield
• Number of design revisions

This process shows whether the board gained speed, saved space, reduced heat, or improved production stability.

What can affect the result

HDI is not a shortcut for weak circuit planning. A poor stack-up can create impedance problems. Small vias can raise manufacturing demands. Tight spacing can increase inspection and repair difficulty.

Material choice also matters. A high-speed board may need a material with suitable dielectric performance and stable behavior across temperature changes. A low-speed control board may not need the same material structure.

Cost should be reviewed with the whole product in mind. HDI may raise fabrication requirements, yet it can reduce enclosure size, cable count, or the number of separate boards.

A safer way to present the 40% claim

I would not present “40% more performance” as a guaranteed result.

A clearer message would be:

“HDI design can help compact electronic products improve routing efficiency and signal performance. Some projects may achieve gains close to 40% after testing, but the result depends on the original design and the selected manufacturing process.”

This wording gives engineers useful direction without hiding the conditions behind the claim.

For my projects, the best HDI result is not the smallest board alone. It is a board that meets its electrical targets, passes thermal checks, can be manufactured with stable quality, and leaves enough room for testing and service. Clear requirements and measured data make the performance claim more useful than a single percentage.

When a product needs more functions but less space, the PCB often becomes the limiting factor. Components compete for room, signal paths become harder to route, and the board may need more layers to support a compact design.

I see this challenge in smartphones, wearable devices, medical instruments, automotive sensors, and handheld scanners. High-Density Interconnect, or HDI PCB technology, offers a practical way to place more connections into a smaller board area.

HDI does not simply mean “make the board smaller.” It means using controlled microvias, fine traces, smaller pads, and stacked or staggered connections to use the available space with greater care.

A smaller board can support a stronger product design when the layout, materials, manufacturing process, and testing plan work together.

Why HDI helps reduce board size

Traditional through-hole vias pass through the full thickness of a PCB. They take up more room and may block routing space across several layers.

HDI PCBs use microvias, which are much smaller laser-drilled connections between selected layers. This gives designers more routing options near dense component areas.

I can place a microvia inside or near a component pad when the design and manufacturing process allow it. That shortens the connection path and frees space for nearby signals.

Common HDI features include:

• Microvias
• Fine line and fine space patterns
• Via-in-pad structures
• Sequential lamination
• High layer-to-layer connection density
• Shorter paths for high-speed signals

These features support smaller board outlines while keeping the layout organized.

A practical example

Consider a handheld barcode scanner used in a warehouse. The product may need a camera module, wireless communication, a display, a battery system, buttons, and a charging circuit.

A larger PCB could make routing easier, but it may increase the size of the scanner housing. That can affect grip comfort, battery placement, and the space available for other parts.

An HDI PCB may place the processor, memory, camera connector, and wireless section closer together. Microvias can help route signals through dense areas without using large through-hole vias.

The result is not automatically a better product. The design team still needs to review heat, signal integrity, assembly limits, repair needs, and production cost. HDI creates more layout freedom, but each design choice must match the product requirements.

Where the extra design value comes from

I usually look at HDI benefits through four areas.

More usable routing space

Fine traces and small vias allow more connections in crowded sections. This can reduce the need for a larger board outline.

Shorter signal paths

Short connections can support high-speed designs by reducing unnecessary trace length. The electrical result depends on impedance control, stack-up planning, material selection, and layout quality.

Better component placement

HDI technology gives designers more freedom to place small-pitch packages and compact modules. A well-planned layout can reduce unused areas between parts.

Potential layer reduction

Some boards can achieve the required routing density with a more efficient layer structure. The actual layer count depends on signal quantity, power design, mechanical limits, and manufacturing capability.

How I approach an HDI PCB project

I do not start with the smallest possible board outline. That approach can create manufacturing and testing problems later.

I start with the product requirements:

1. Define the target board size and shape.
2. List the major components and their package types.
3. Mark high-speed, power, RF, and sensitive analog areas.
4. Review the expected production volume.
5. Confirm the PCB fabricator’s minimum trace, space, and microvia limits.
6. Build the layer stack-up before detailed routing.
7. Check thermal paths and component access.
8. Review assembly, inspection, and test methods.
9. Run signal, power, and reliability checks.
10. Confirm the design with prototype testing.

This process helps connect the electrical design with the production plan. A layout that looks good on a screen may still need changes when drilling, lamination, soldering, or inspection limits are considered.

Cost needs careful review

HDI can reduce board size, but it may raise manufacturing cost. Laser drilling, sequential lamination, tighter registration control, and more demanding inspection can affect the quotation.

I compare the full product impact instead of looking only at the PCB price.

A smaller board may reduce enclosure size, cable length, assembly space, or product weight. It may also allow more functions inside the same housing. These factors can change the value of HDI for each project.

For a simple, low-density control board, a standard multilayer PCB may be a better fit. For a compact device with fine-pitch components and limited internal space, HDI may offer a stronger design path.

Questions to ask your PCB supplier

Before starting production, I would ask the supplier:

• What is the minimum laser-drilled microvia size?
• Can you support via-in-pad, and how is it filled?
• Which stack-up structures do you produce regularly?
• What trace width and spacing can you control in volume?
• How do you inspect microvias and inner-layer alignment?
• What surface finishes are available?
• Can you support the required impedance values?
• What prototype and production testing methods do you use?
• Which design files and fabrication notes do you need?

Clear answers at this stage can prevent layout changes after engineering work is complete.

Smaller does not mean simpler

A compact HDI PCB can improve space use, but density also raises the need for careful planning. Heat may build up near processors or power parts. Repair access may become limited. Fine-pitch packages can require tighter assembly control.

I recommend treating HDI as a complete design method rather than a single PCB feature. The best result comes from cooperation among the layout engineer, mechanical team, component engineer, assembler, and PCB manufacturer.

When the design goal is clear and the process limits are known, HDI can help a product use less board space while supporting the required functions. The right question is not only “How small can the board become?” It is also “What size gives the best balance of performance, reliability, cost, and production control?”

Many PCB teams face the same problem: the board must carry more signals, fit into a smaller space, and maintain stable performance. A standard multilayer PCB may reach its routing limit before the design is ready for production. Long traces, crowded escape areas, and poor power paths can affect signal quality and make layout changes expensive.

HDI PCB technology can help solve these issues. It uses microvias, fine lines, smaller pads, and high-density routing structures to create shorter and more direct connections. A performance gain of up to 40% may be possible in a specific design, but the result depends on the original PCB structure, signal speed, power layout, materials, and test method. HDI is not a fixed percentage upgrade for every product.

Where HDI Can Improve PCB Performance

I usually look at four areas before recommending HDI: signal integrity, routing density, board size, and power delivery.

Shorter interconnects can reduce parasitic inductance and unwanted signal reflection. This can support high-speed interfaces such as USB 3.x, PCIe, MIPI, DDR memory, and other fast digital links.

Microvias also give designers more routing options between layers. A signal can move between nearby layers without using a large through-hole via that blocks space across the whole board. This helps when the design contains fine-pitch BGA packages, compact connectors, or dense sensor modules.

A smaller board may also improve product integration. Smartphones, wearable devices, medical instruments, and compact industrial controllers often use HDI structures because component density is high and enclosure space is limited.

The benefit is not limited to size. A better layer structure can shorten critical paths and make return current paths easier to control. That can reduce debugging work during prototype testing.

How I Evaluate a 40% Performance Claim

A percentage claim needs a clear measurement method. I do not treat “40% better” as a general promise.

I ask these questions:

• What does performance mean in this project?
• Is the target higher data speed, lower insertion loss, smaller board size, better thermal behavior, or fewer signal errors?
• What was the original PCB stackup?
• Which test equipment and test points will be used?
• Will the comparison use the same components, firmware, and operating conditions?

For example, if a conventional board has long high-speed traces that create signal loss, an HDI redesign may reduce path length and improve eye-diagram results. If the original board already has a strong stackup and well-controlled routing, the HDI gain may be smaller.

This approach protects the project from vague marketing claims. It also gives the engineering team a useful target that can be checked through simulation and testing.

Step 1: Review the Existing PCB

I start with the current design files, stackup, component placement, and failure records.

The review should cover:

• Layer count and copper thickness
• Via type and via field restrictions
• Trace width and spacing
• BGA pitch and escape routing
• High-speed net length
• Power and ground distribution
• EMI test results
• Thermal limits
• Fabrication yield and repair history

A board may appear crowded because of poor placement rather than a lack of layers. Moving a processor, memory device, or connector can reduce routing pressure before HDI is introduced.

Step 2: Select the Right HDI Structure

HDI does not mean using the most complex structure available. A simple 1+N+1 design may be enough for one product, while a dense mobile device may require a more advanced stacked or staggered microvia structure.

Common options include:

• Microvia build-up layers
• Staggered microvias
• Stacked microvias
• Buried vias
• Via-in-pad
• Any-layer HDI

Each choice affects cost, manufacturing controls, reliability, and inspection needs. Via-in-pad can help with fine-pitch BGA routing, but it needs proper filling and planarization. An unsuitable process can create soldering or reliability problems.

I prefer the least complex HDI structure that meets the electrical and mechanical targets. This keeps the design easier to manufacture and review.

Step 3: Build a Controlled Stackup

A good HDI stackup supports both routing and signal behavior.

The stackup should define:

• Dielectric thickness
• Copper weight
• Impedance targets
• Reference planes
• Microvia diameter
• Capture pad size
• Finished board thickness
• Material selection

High-speed traces need a stable reference plane. A narrow trace without a continuous return path can create noise, even when the trace length looks acceptable.

Material choice also matters. Standard FR-4 may work for many products, while higher-speed or higher-temperature designs may need a material with suitable dielectric and thermal properties. The decision should come from simulation, operating conditions, and production capability rather than a general material label.

Step 4: Simulate Before Fabrication

I use simulation to check whether the HDI change solves the actual problem.

Useful checks include:

• Impedance control
• Insertion loss
• Return loss
• Crosstalk
• Eye diagram
• Power integrity
• DC drop
• Thermal distribution

A shorter route can improve signal behavior, but it does not fix every issue. Connector quality, package escape, layer transitions, power noise, and grounding can still limit system performance.

A practical example is a compact camera module with a high-speed image sensor. If the data lanes pass through several long routes and layer transitions, an HDI redesign can place the sensor and processor closer together, reduce route length, and create cleaner reference paths. The actual gain should be confirmed through measurement rather than assumed from the HDI label.

Step 5: Check Manufacturing Risk

HDI performance depends on process control.

Before release, I confirm the fabricator’s capability for:

• Laser-drilled microvias
• Copper filling
• Fine-line etching
• Registration accuracy
• Via reliability testing
• AOI and X-ray inspection
• Impedance testing
• Final surface finish

The design rules should match the selected supplier. A trace width that works in a laboratory prototype may create low yield in volume production.

I also review thermal cycling, via fatigue, soldering conditions, and component assembly. A board can pass electrical tests and still face field issues if the via structure is not suited to the product environment.

Cost and Design Trade-Offs

HDI can reduce board area and support higher routing density, yet it may raise fabrication and inspection costs. More build-up layers, stacked microvias, filled via-in-pad structures, and tighter registration requirements can increase the manufacturing burden.

For that reason, I compare the full project cost rather than the PCB unit price alone. A smaller board may reduce enclosure size, assembly complexity, or the number of interconnect parts. A better signal path may also reduce repeated prototype cycles. These savings should be calculated from the actual product plan.

HDI is a strong option when the board has dense components, fast signals, limited space, or repeated routing failures. It may not be the right choice for a low-speed board with plenty of room and simple manufacturing needs.

The best result comes from matching the HDI structure to a measurable engineering problem. Define the performance target, review the existing layout, select a suitable stackup, simulate the critical nets, and confirm the result through testing. A 40% improvement can be a valid project target in some cases, but the board structure and test data must support the claim.

Many PCB teams face the same design problem: the product needs more functions, yet the available board space keeps shrinking. More components are packed into smaller areas, signal paths become harder to control, and power delivery leaves less room for error.

HDI technology can help, but simply choosing an HDI stack-up does not guarantee a better board. The result depends on how the layout, materials, fabrication limits, and testing plan work together.

I look at HDI from a practical angle: reduce wasted space, protect signal quality, and make the board easier to build and test.

What HDI changes

High-density interconnect boards use features such as microvias, fine lines, small pads, and sequential build-up layers. These features allow connections to pass between nearby layers instead of routing every signal through a full through-hole path.

That change can support:

• More components within the same board area
• Shorter connections between chips and memory
• Better routing around fine-pitch packages
• More flexible placement of power and ground paths
• Smaller via fields under or near compact components

A conventional through-hole via may pass through several layers even when the connection only needs to move one layer down. It can occupy routing space on every layer along the way. A microvia uses a shorter connection path, which gives the layout team more room.

The benefit is not only size reduction. Shorter paths may also reduce unwanted inductance and help control high-speed signals, provided the stack-up and return paths are designed correctly.

Faster design starts with clear limits

I do not begin an HDI project by asking how many layers can fit into the board. I start with the product requirements.

The design team needs clear answers about:

• Board outline and thickness
• Component package types
• Signal speed and interface standards
• Current levels and power zones
• Required layer count
• Minimum trace and space
• Via diameter and capture pad size
• Material selection
• Assembly process
• Expected production volume

A processor board with LPDDR memory has different needs from a compact sensor board. A high-speed interface may need controlled impedance and a carefully planned return path. A low-speed control board may gain more from space savings and component placement flexibility.

A clear design brief reduces late changes. It also helps the fabricator check whether the proposed structure fits available equipment and process control.

A practical HDI design path

1. Build the layer plan around signal flow

The stack-up should support the way signals move through the board. High-speed signal layers need nearby reference planes. Power layers need enough copper and a suitable path to the load. The outer layers must leave room for component pads, fan-out, and routing.

A common mistake is to add layers after routing problems appear. That may solve one issue while creating new problems with thickness, impedance, cost, or lamination.

I prefer to review the layer plan with the PCB fabricator before detailed layout begins. A small change at this stage can prevent a large redesign later.

2. Select the right via structure

HDI boards may use:

• Laser microvias
• Stacked microvias
• Staggered microvias
• Buried vias
• Through vias
• Via-in-pad structures

Each option affects cost, reliability, inspection, and manufacturing steps.

Staggered microvias can reduce some manufacturing pressure compared with fully stacked structures. Stacked vias may save more space, yet they require stronger process control. Via-in-pad can help with fine-pitch packages, but the vias often need filling and planarization before component assembly.

The correct choice depends on the package, layer transition, board thickness, and production plan. Smaller features are not automatically the right answer.

3. Route high-speed signals with their return paths

A signal trace is only part of the electrical path. Its return current also needs a stable route through the reference plane.

When a signal changes layers, the return path may need a nearby ground via. If the reference plane changes from ground to power, the transition deserves extra review. A long gap or split under the trace can increase noise and affect impedance.

For interfaces such as USB, PCIe, MIPI, or high-speed memory, I review:

• Trace length and matching
• Pair spacing
• Impedance targets
• Layer transitions
• Reference plane continuity
• Via stub length
• Crosstalk risk
• Connector launch design

Simulation can support these checks, but good layout decisions still begin with a sensible stack-up.

4. Keep power delivery close to the load

A compact board can still suffer from power problems. Narrow paths, poor plane connections, and long routes between the regulator and device may create voltage drop or unwanted noise.

I look at the complete power path:

1. Regulator output
2. Copper route or plane
3. Vias between layers
4. Local decoupling capacitors
5. Component power pins
6. Ground return

A capacitor placed near a device is useful only when the connection to the power and ground pins is short and low impedance. A large copper area does not solve every power issue if the current must pass through a small neck or limited via group.

A common example: compact memory routing

Consider a small computing board using a processor and LPDDR memory. The package pitches may leave little space for traditional fan-out routing. Through-hole vias can consume valuable channels, and long routes may make length matching more difficult.

An HDI structure can place microvias near the package pads and move selected connections to inner layers. This may create more routing channels around the processor while keeping memory traces closer in length.

The improvement does not come from the word “HDI” alone. It comes from the combination of:

• A suitable package escape pattern
• A controlled stack-up
• Short layer transitions
• Stable reference planes
• Careful length matching
• Early fabrication review

If the memory interface still shows timing or noise problems, the team should check the whole electrical path rather than assume that more microvias will fix it.

Better performance needs design checks

HDI boards need checks at several stages.

Design review

Review the stack-up, material set, via rules, impedance targets, and component escape strategy. Confirm that the proposed design can be produced with the selected process.

Layout review

Check plane continuity, spacing, copper balance, thermal paths, via locations, and keep-out zones. Pay close attention to connectors, crystal circuits, antennas, and switching power supplies.

Signal and power analysis

Use simulation where the interface speed or power demand makes it useful. Review insertion loss, return loss, crosstalk, timing margin, voltage drop, and current density based on the project requirements.

Fabrication review

Ask the manufacturer to confirm laser drill limits, via fill needs, registration tolerance, copper thickness, lamination cycles, and surface finish compatibility.

Prototype testing

Test high-speed links, power rails, thermal behavior, and mechanical fit. Inspect microsections or other process samples when the project risk justifies the added review.

Testing should answer specific questions. “Does the board work?” is too broad. A better question is whether the memory eye remains within the required margin, whether the power rail stays within its permitted range, or whether the via structure passes the planned reliability test.

Cost control without cutting useful features

HDI can raise fabrication cost because it may require laser drilling, sequential lamination, via filling, tighter registration, and extra inspection. The cost discussion should include the full product impact.

A smaller board may reduce enclosure size, cable length, assembly area, or system weight. A better component escape pattern may reduce layer count in another part of the design. A simpler via structure may lower board cost while still meeting the electrical target.

I avoid adding HDI features across the entire board without a clear reason. Some regions may need microvias, while other areas can use standard vias. A mixed approach can provide a practical balance between density and manufacturing effort.

Common mistakes I see in HDI projects

Treating every microvia as a free routing point
Microvias still require spacing, pad geometry, drill tolerance, and reliable registration.

Using via-in-pad without checking the assembly process
Unfilled or poorly controlled vias may cause solder loss, voids, or uneven component seating.

Ignoring copper balance
Uneven copper distribution can contribute to warpage and thickness variation during lamination.

Routing across plane gaps
The signal may meet its trace rule while the return path becomes poor.

Choosing materials only by price
Loss, thermal behavior, glass weave, and reliability can affect the final design.

Waiting until after layout to contact the fabricator
A stack-up that looks acceptable in CAD may not fit the selected production process.

Assuming a smaller board is always better
A very compact layout may create thermal, repair, inspection, or assembly problems.

A simple project checklist

Before releasing an HDI design, I check these points:

• Does the stack-up match the signal and power needs?
• Are all critical layer transitions supported by a return path?
• Are via types suitable for the package and fabrication process?
• Are impedance and length targets documented?
• Are fine-pitch areas reviewed for assembly risk?
• Is copper distribution reasonably balanced?
• Have thermal paths been checked?
• Has the fabricator confirmed the key dimensions?
• Are prototype tests linked to clear performance targets?
• Can the board be inspected, assembled, and repaired as planned?

HDI works best when it is treated as a complete design method rather than a small feature added near the end of layout. The goal is not to use the smallest trace or the most complex via structure. The goal is to create a board that uses space well, carries signals with control, delivers power reliably, and fits the production process.

When the electrical team, layout team, component engineer, and PCB manufacturer review the design together, HDI can support a smaller and more capable product without creating avoidable manufacturing risk.

We welcome your inquiries: mr.xu@lingchaopcb.com/WhatsApp +8613780181891.

References

IPC 2023 Design Guide for High Density Interconnects and Microvia Technology

John Lau 2022 Semiconductor and Package Design for High-Speed PCB Applications

Lee Ritchey 2021 Right the First Time Designing High-Speed Digital Systems

Eric Bogatin 2020 Signal and Power Integrity Simplified

IPC 2020 Generic Standard on Printed Board Design

Ragnar H. K. 2019 Advanced PCB Materials and High-Frequency Circuit Design