Description
Data Sheet

4-Layer Multilayer PCB Technical Overview & Design & Manufacturing Specification

Name: 4 layer PCB
Brand: PCB Printed Circuit Board and PCBA manufacturing
Rating: 5 (1 reviews)

1. Definition of 4-Layer PCB

A 4-layer printed circuit board is a type of multilayer PCB constructed by laminating four conductive copper layers alternately with dielectric core and prepreg materials, forming an integrated multilayer structure.

2. Comparison Between 4-Layer PCB and 2-Layer PCB

The conductive copper layers serve as the primary signal transmission layers of the PCB. A 2-layer board contains two conductive layers, while a 4-layer board integrates four independent conductive layers. Dielectric and core materials are embedded between adjacent copper layers to provide electrical isolation and avoid short circuits. Both board types are equipped with solder mask to protect copper circuits from oxidation and external interference, as well as silkscreen legend for component identification and assembly guidance.

In a typical 4-layer PCB stackup, the top and bottom outer layers are configured as signal layers, while the two inner layers are designated as power plane and ground plane respectively. The internal power and ground structures provide effective electrical shielding and reduce signal interference. For simple circuits with large board area and sparse components, 2-layer PCBs are generally sufficient. For designs with routing congestion, layout constraints or high interference risks, 4-layer PCBs effectively resolve routing density and signal integrity issues.

As the most fundamental and cost-effective structure in the multilayer PCB category, 4-layer boards balance performance, complexity and manufacturing cost, making them widely adopted in mainstream electronic products.

4 Layer PCB stack up

3. Typical 4-Layer PCB Stackup Structures

Stackup Scheme 1

Layer 1: Signal Layer
Layer 2: Ground Plane
Layer 3: Power Plane
Layer 4: Signal Layer

This is the most commonly used standard stackup, where the ground plane is placed directly below the component mounting side, supporting optimal routing of critical signals on the top layer.

Stackup Scheme 2

Layer 1: Ground Plane
Layer 2: Signal Layer
Layer 3: Signal Layer
Layer 4: Power Plane

This configuration is suitable for boards dominated by through-hole components with simplified overall routing, relying primarily on a unified ground plane without dedicated internal power planes. Special attention is required for interface filter routing loops and radiation areas.

Stackup Scheme 3

Layer 1: Signal Layer
Layer 2: Power Plane
Layer 3: Ground Plane
Layer 4: Signal Layer

Similar to Scheme 1 but less commonly used, this structure is applicable in scenarios where main components or critical signals are routed on the bottom layer.

Compared with 2-layer PCBs, 4-layer boards provide larger continuous copper areas and greater routing capability, making them suitable for moderately complex circuits. However, increased structural complexity results in relatively higher cost and longer production cycles. Signal propagation delay and crosstalk must be controlled through rational stackup and layout design.

4. 4-Layer PCB Design Guidelines

Multi-node test points shall be sequentially connected with shortened routing length to facilitate testing.
Avoid routing around component pins, especially between and around IC pins.
Minimize parallel routing between adjacent layers to reduce capacitive crosstalk.
Use smooth routing transitions to reduce electromagnetic radiation.
Trace width for power and ground paths in multi-logic systems should be at least 10–15 mil.
Optimize ground copper continuity and increase grounding area for improved stability.
Reserve sufficient space for component assembly, insertion and soldering during early layout.
Maintain reasonable silkscreen placement to prevent obstruction after assembly.
Consider spatial clearance and component orientation; clearly mark polarity for SMT components.
Design minimum design rules typically follow 6 mil trace width, 8 mil spacing, and 12/20 mil pad, although 4–5 mil capability is available. Current-carrying capacity must be considered.
Group functional modules together for ease of debugging and maintenance. Keep noise-sensitive components away from LCD and zebra connectors.
Apply solder mask over vias for protection and insulation.
Avoid placing pads and vias beneath battery holders to ensure mechanical reliability.
Verify all electrical connections post-routing using connectivity checks.
Place oscillator components close to the associated IC, away from antennas and sensitive circuits, with ground pad directly beneath the crystal.
Use mechanical reinforcement and strategic cutouts to reduce radiation sources.

4 layer PCB

5. Layer Routing Arrangement

Internal ground layers may contain limited signal traces but should maintain continuous copper planes without excessive segmentation. Internal power planes are similarly dedicated to power distribution with minimal signal routing.

The four functional layers generally consist of Top Signal, Bottom Signal, Power Plane and Ground Plane. Interlayer connection is achieved through through-hole vias, blind vias and buried vias, with higher usage of micro-vias compared to 2-layer boards. Signal routing should be avoided on internal power and ground layers whenever possible.

6. 4-Layer PCB Manufacturing Process

Compared with 2-layer PCB production, 4-layer manufacturing adds inner-layer patterning and multilayer lamination processes.

Full Production Flow

Material Cutting
Inner Layer Circuit Fabrication
Inner Layer AOI Inspection
Multilayer Lamination
Drilling
Plated Through-Hole (PTH)
Outer Layer Circuit Fabrication
Outer Layer AOI Inspection
Solder Mask Coating
Silkscreen Printing
Hot Air Solder Leveling (HASL)
Surface Finish Treatment
Profile Machining
Electrical Testing
Final Quality Control
Packaging and Shipment

Inner Layer Process

Dry Film Lamination
Exposure
Development
Etching
Stripping

Photoresist dry film is used to protect defined circuit patterns during etching.

Core Lamination Process

Semi-cured prepreg is bonded under high temperature and high pressure to integrate inner layers and outer layers into a stable 4-layer structure. Lamination requires precise control of temperature and pressure profiles, with typical peak temperatures up to 200°C and pressure up to 250 N/cm². Standard H/Hoz copper foil has a thickness of approximately 17 μm.

7. Supplier Service Introduction

Maxipcb is a professional manufacturer specializing in 4-layer multilayer PCBs, providing high-quality and cost-effective solutions for both prototype and mass production. We offer competitive pricing optimized for performance between 2-layer and 4-layer alternatives.

To receive an accurate and efficient quotation, please submit your complete Gerber design files to our official email address. Our engineering team will evaluate your requirements and provide a formal quotation promptly.

Model: 4 Layer PCB

Material: FR4

Layer: 4 Layers

Color: Green/white/Red/Black

Finished Thickness: 0.3-6.0mm

Copper Thickness:0.502-60Z

Surface Treatment: lmmersion Gold/OSP/lead-free HASL

Min Trace: 3mil, 0.075mm

Min Space: 3mil, 0.075mm

Application: Consumer electronics

4 layer PCB

Description

Data Sheet