With stronger functions and higher performance of electronic
products, higher requirements have also been put forward for circuit boards.
Nowadays, an increasing number of devices require high-density and compact
circuit designs, which is the reason for the emergence of multilayer PCBs.
Multilayer circuit boards are made by stacking
three or more conductive copper layers between layers of insulating material.
This allows for more complex routing and ensures more stable signal
transmission.
This article will introduce the basic
concepts of multilayer PCB design, explain the common PCB layer structures, and
detail the complete process of multilayer PCB manufacturing. Whether you are
designing high-speed servers or developing a smart wearable device, this guide
will help you fully understand the key aspects of multilayer boards.
Understanding PCB Layers
Understanding the structure of PCB
layers is helpful for determining the complexity and application of the circuit
board. According to the number of conductive layers, printed circuit boards are
classified into three types: single-layer, double-layer and multilayer PCBs.
Single-Layer PCBs
A single-layer PCB has only one side
with a copper layer and is also known as a single-sided board. Its structure is
simple and is usually composed of a copper layer, insulating materials and
silkscreen. Due to having only one conductive layer, the routing space is
limited and it is not suitable for complex or high-speed applications.
Double-Layer PCBs
A double-layer PCB has copper traces
on both the top and bottom surface of the circuit board, with the two PCB
layers re-connected by vias. Its structure consists of a copper layer,
substrate and another copper layer. Usually, plated through holes are used to
achieve the conduction between the top and bottom layers. Compared with
single-layer boards, it offers more flexible routing and is suitable for
circuits of medium complexity. However, it still has limitations in terms of
signal integrity and high-frequency performance.
Multilayer PCBs
Multilayer PCBs contain three or more
conductive copper layers. They are alternately stacked with insulating layers
and laminated into a single structure through lamination processes. Multilayer
circuit boards can offer higher routing density and are commonly found in
fields with extremely high-performance requirements, such as high-speed
computing, medical devices, smartphones, and aerospace. However, the process of
multilayer PCB manufacturing is more complex, with higher costs, longer
processing cycles, and stricter requirements for design and inspection.
The primary components of a multilayer
PCB include:
• Inner copper layers (signal routing or
planes)
• Prepreg and core layers (insulation
and support)
• Vias (through-hole, blind, or buried)
to connect the PCB layers
• Solder mask and silkscreen on outer
layers
Multilayer PCB Design Essentials
To achieve a stable and reliable
multilayer PCB design, a balance must be struck among performance,
manufacturability and cost. The following are several key aspects:
Signal Layer Management
When designing the PCB layer structure, the positions of the
signal layer, power layer and ground layer should be reasonably arranged. A
common approach is to sandwich the signal layer between the ground layers,
which can reduce signal interference and improve signal quality.
Via Strategy
In multilayer PCBs, different layers need to be connected
through vias. When designing, through holes, blind holes or buried holes can be
selected based on the structure of the board and the budget. Choosing the right
through-hole type helps save space and control manufacturing costs.
Controlled Impedance
For high-speed signals, impedance matching is very important. Impedance
is affected by trace width, layer spacing and the dielectric constant of the
material. A good multilayer PCB design requires precise control of these
parameters to ensure stable signal transmission.
Design for Manufacturability (DFM)
To simplify production, process limitations should be taken into
consideration during the design. For example, it is necessary to ensure that
the layers can be precisely aligned with each other, the drilling dimensions
meet the requirements, and the trace spacing is reasonable. Following the DFM
design principles can reduce the error risk and improve production efficiency.
CAD Tools
The use of appropriate software tools can greatly improve design
efficiency. Software such as Altium, KiCad, and Cadence support stackup
configuration, routing check, and electrical rule validation and are reliable
multilayer PCB manufacturing and design platforms.
Multilayer PCB Stackup Planning
In multilayer PCB boards, the stackup
refers to the arrangement and functional distribution of each layer. A
reasonable stackup design not only affects the
transmission quality of signals but also influences the mechanical strength and
manufacturing difficulty of the circuit board. A good stackup design is a basis
for achieving high-performance and high-reliability multilayer printed circuit
boards.
When planning a multilayer PCB stackup,
the following aspects need to be given particular attention:
Symmetrical Design
The stackup should be as symmetrical as possible. For example,
the distribution of copper on the top and bottom layers should be balanced.
This can effectively prevent board warping caused by uneven heating during the
multilayer PCB manufacturing process.
Prepreg and Core Material Selection
Different materials will affect the dielectric constant and
thermal stability of the board. Selecting the appropriate prepreg and core
materials helps ensure signal speed and overall thermal stability. This is an
indispensable part of multilayer PCB design.
Power and Ground Plane Layout
In the design, the placement of power and the ground layer
should be carefully arranged, and it is best to be placed close to the signal
layers. This can provide a stable return path for signals, reduce interference
and improve signal integrity.
Interlayer Spacing Control
The distance between different layers directly affects impedance
control and electromagnetic compatibility. Smaller spacing can enhance coupling
and reduce crosstalk. But at the same time, the balance between manufacturing
capacities and electrical performance should also be considered.
An optimized multilayer PCB stackup
can effectively enhance the performance of the circuit. For any electronic
product that requires high frequency, high speed or high reliability, the
design of the stackup is a key step.
Multilayer PCB Fabrication Process
The complete multilayer PCB
manufacturing process involves multiple high-precision steps. It is based on
the manufacturing of single-layer or double-layer PCBs and adds the processing
of inner-layer circuit preparation and multilayer lamination. Compared with
ordinary boards, the production of multilayer circuit boards is more complex
and has higher requirements for process control. The following is a typical
multilayer PCB manufacturing process:
Inner Layer Circuit Fabrication and Etching
First, copper foil is laminated onto an insulating core
material. Photolithography is used to transfer the circuit pattern onto the
copper foil, and chemical etching is then applied to remove excess copper,
leaving only the required traces. After this step, each inner layer circuit is completed.
Lamination and Alignment
All prepared PCB layers are stacked according to the
designed stackup structure. High temperature and high pressure are used to
laminate these layers into a single unified board. Precise alignment of each
layer is critical to avoid errors in later stages.
Drilling and Copper Plating
Holes are drilled through the laminated board to establish
electrical connections between different PCB multilayers. Then, a layer of
copper is deposited on the hole walls through chemical plating, creating
conductive pathways between layers. This step directly affects the reliability
of electrical connections.
Outer Layer Circuit Fabrication
The process for the outer layer is similar to that of the inner
layers. Photolithography is used to transfer the pattern, followed by etching
to form the final outer circuits. After this step, the board’s circuitry is
nearly complete.
Solder Mask and Silkscreen
A layer of solder mask ink is applied to the board’s surface to
protect non-soldering areas from contamination or short circuits. Silkscreen
printing is then used to add markings for component placement, company logos,
and other identifiers.
Surface Finishing
Finally, the exposed pad areas undergo surface finishing. Common
techniques include ENIG (Electroless Nickel Immersion Gold) and HASL (Hot Air
Solder Leveling). These finishes improve solderability, prevent oxidation, and
enhance corrosion resistance.
About PCBasic
Time is money in your projects – and PCBasic gets it. PCBasic is a PCB assembly company that delivers fast, flawless results every time. Our comprehensive PCB assembly services include expert engineering support at every step, ensuring top quality in every board. As a leading PCB assembly manufacturer, we provide a one-stop solution that streamlines your supply chain. Partner with our advanced PCB prototype factory for quick turnarounds and superior results you can trust.
Choosing the Right Manufacturer for Your Multilayer PCB
Choosing an experienced multilayer PCB
manufacturer is critical to ensuring the quality, delivery time, and
performance of your circuit boards. The manufacturer’s capabilities directly
affect the stability of your product and the overall progress of the project.
When selecting a partner, consider the following aspects:
• Capabilities: Can they support complex multilayer
PCB board designs, including HDI and fine-pitch?
• Certifications: ISO 9001, IPC standards, RoHS
compliance
• Equipment: Modern facilities for laser drilling,
X-ray registration, and AOI inspection
• Lead Time: Fast turnaround for prototyping and
production
• Support: Engineering feedback and multilayer
PCB design review
A reliable manufacturer can help
optimize your multilayer PCB fabrication and reduce time-to-market.
Multilayer PCB Manufacturing at
PCBasic
At PCBasic, we focus on high-precision
multilayer PCB manufacturing with over 10 years of experience in engineering
and project management. Our advanced equipment and skilled team allow us to
deliver reliable multilayer circuit board solutions for industries like
medical, automotive, industrial control, and consumer electronics.
Why Choose PCBasic for
Multilayer PCBs?
Strong Technical Team
Our PCB design and project teams each have 10+ years of
experience. We also work with PhD research teams from top universities to
improve multilayer PCB design and material performance.
Flexible Production Capacity
• Shenzhen factory: Ideal for high-mix, low-volume
multilayer PCB prototyping.
• Huizhou factory: Designed for cost-effective,
high-volume multilayer PCB manufacturing.
In-House Manufacturing Support
We own our stencil and fixture production lines, offer CNC
precision machining, and provide 1-hour stencil delivery. This helps speed up
and support complex multilayer board assembly.
Reliable Component Supply
Our smart central warehouse ensures all components are original
and in stock. With our one-click BOM import and instant quote system, customers
can easily manage the multilayer PCB fabrication process.
Certified Quality Assurance
PCBasic is a national high-tech enterprise with certifications
including ISO 13485, IATF 16949, ISO 9001, ISO 14001, and UL. We are an IPC
member and hold over 20 patents related to quality inspection and production
management systems.
Whether you need a 4-layer prototype or a 12-layer production
order, PCBasic is your trusted partner for fast, reliable, and scalable
multilayer printed circuit board manufacturing.
Conclusion
In today’s fast-moving and highly
integrated electronics industry, multilayer PCBs have become a core technology.
With higher layer density and better electrical performance, multilayer printed
circuit boards are used in many electronic products—from consumer devices to
industrial systems.
To use them successfully, you need the
right approach. That means proper multilayer PCB design, a well-planned
stackup, and a reliable multilayer PCB manufacturing process.
Whether you're working on a 4-layer
PCB for a wearable device or a 12-layer server motherboard, choosing the right
multilayer circuit board strategy and the right manufacturing partner is key to
your project’s success.
