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Mutlilayer PCBs

Mutlilayer PCBs

Multilayer PCBs typically consist of at least three layers, with the potential to expand to 30 or more layers depending on specific requirements. Laminated copper foils are joined together, yet insulated from each other to form a single piece. Nowadays, almost all systems and devices require multilayer PCBs due to the complexity of design, the increased number of components and the shrinking size of devices. Typically, the number of layers helps determine the complexity as well as cost.

At HT Global Circuits, we offer custom multilayer PCB manufacturing and assembly with stringent testing and inspection processes. From basic 3-layer boards to complex 16+ layers stackups, we engineer PCBs for durability, density, and performance.

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Multilayer PCB Capabilities

We offer engineering support for DFM, stack up, and layout. Here are some of our multilayer PCB capabilities and technical specifications.

Specification Capability
Number of layers
8-32 layers
Materials
Core – (Aluminum, Copper), Dielectric – (FR-4, Polyimide, CEM3)
Copper thickness
16 oz inners and 30 oz outers
Minimum trace length and spacing
2.4 / 2.4 mils
Maximum PCB thickness
0.2mm-8mm (8-320 mil)
Maximum board size
1105mm x 610mm (44″x24″)
Specialized Materials
High-performance materials (RO4350, Bergquist HT, MEG6)
Surface finishes
ENIG, Imm Ag, HASL/HASL-LF, OSP, Immersion Tin, Hard/Flash Gold, ENEPIG
Minimum drill hole size
Laser – 0.05mm 2mil, CNC – 0.15mm 6mil
Special Technical capabilities
Embedded Copper Coin, Backdrill, Class 3, Via in pad, Beveling, Countersinks, Counterbore, Edge plating, conductive hole filler, gold fingers, half-hole (PTH/NPTH)
Controlled impedance
Tight tolerances (±5%)
Line width and spacing
0.05mm / 2mil
Blind/Buried Vias
1+n+1, 2+n+2, 3+n+3, 4+n+4, 5+n+5, ELIC
Quality Certifications
ISO9001:2015 ISO14001 ISO45001 MIL-55110
Industry-specific certifications
TS 16949 AS9100 (TBD) MIL-PRF-31032 (TBD) ISO 13485
Material certifications
RoHS UL 94V-0 UL-C UL ZPMV2

How Are Multilayer Circuit Boards Made?

Internal signal routing in multilayer PCBs uses a stack up of copper layers and insulating prepreg/core materials to direct signals between layers via vias. Placing high-speed signals between ground planes and minimizing via transitions ensures signal integrity. 

A robust stack up design, which details the order of copper foil, prepreg, and core materials, is crucial for connecting components and achieving reliable performance. Various via types like through-hole, blind, and buried vias are used for different layer connection needs. HTG’s technical competence is reflected in the manufacturing process we follow. Here are the steps involved in the multilayer PCB manufacturing process.

Prepreg and Core Lamination

This step involves core preparation, prepreg application, and lamination. The core material, made from laminated copper, is a foundation that provides conductive pathways that interconnect the layers. The prepreg material made of FR4 bonds all the layers of the board during the lamination stage. The core and prepreg are stacked together in layers, and the assembly is placed into a high-pressure lamination press. The layers are subjected to both heat and pressure, resulting in a reliable multilayer structure.

Layer capability

We accommodate a wide range of layer counts, from 8 layers to 32 layers or even higher, depending on the complexity of design. We use advanced manufacturing techniques, such as sequential lamination and laser drilling, for PCBs used in high-performance applications, including servers, telecom, automotive electronics, and more. We utilize micro via technology for dense layer structures, where microvias (very small vias) are employed to maintain signal integrity and reduce the size of the PCB.

Sequential lamination for high-layer counts

Sequential lamination is required for high-layer counts. This step involves partial lamination, layer stacking, and pressing and curing. Sequential lamination enables high-density interconnections and complex designs, ensuring that electrical performance and integrity are maintained throughout the PCB.

Quality and inspection

We implement stringent quality and inspection methods to ensure accuracy and that custom requirements are met for specific applications. This includes visual inspection, electrical testing, automated optical inspection (AOI), X-ray inspection, impedance testing, and so on.

Drilling and vias

Holes are drilled into the board to form vias or electrical pathways connecting different layers. These may be through-hole, blind, or buried vias.

Beneficial Features of Multilayer PCBs

Here are some key benefits of multilayer PCBs, particularly in modern electronics.

  • High functionality in a compact form factor: Multilayer PCBs enable the integration of a greater number of components and connections to be integrated into a smaller, more compact space. This enables OEMs to include advanced and complex features and functionalities into their electronic devices without increasing the overall size of the product. Additionally, we produce compact and lightweight multilayer PCBs for optimal fitment into tight spaces.
  • Improved signal integrity: Multilayer PCBs help maintain signal integrity by providing controlled impedance and minimizing interference between layers. With multiple layers available, high-frequency signals can be routed more efficiently and separated to reduce crosstalk and noise. This is especially important in high-frequency and high-speed applications that are prone to noise, leading to signal distortion.
  • High-speed capabilities: Multilayer PCBs are designed to support high-speed signal transmission as their design allows for shorter trace lengths and optimized routing. This helps reduce signal distortion and losses, which is essential in high-speed data transfer applications such as networking and telecommunications. Multiple layers better support high-frequency components and high-speed circuits compared to single- or double-sided boards.
  • Greater design flexibility: Multiple layers provide designers with a better scope and increased flexibility to route complex circuits. With a greater number of layers, some layers can be used for specific purposes such as power, ground, or high-speed signal traces, which improves the overall design efficiency and functionality of the device or system. This flexibility enables the creation of more intricate designs that meet specific electrical, mechanical, or thermal requirements, particularly for advanced electronic products in medical, automotive, defense, and consumer electronics sectors.
  • Single connection point: Multilayer PCBs are designed to work on a single connection point unlike a single-sided PCBs that require multiple connection points. Hence, it makes the operation easy.

Key Industries and Applications

Our multilayered PCBs are applicable across industries. Here are some of the application areas.

  • Aerospace & Defense: Here, multilayer boards are used in avionics, radar systems, navigation systems, missile guidance systems, and communication equipment.
  • Automotive: Here, multilayer PCBs are used in advanced driver-assistance systems (ADAS), infotainment systems, electronic control units (ECUs), electric vehicles (EVs), and sensor technologies.
  • Medical Devices: Here, multilayer PCBs are used in diagnostic equipment such as MRI and CT scanners, patient monitoring systems, wearables, and implantable devices such as pacemakers and hearing aids.
  • Industrial Control: Here, multilayer PCBs are used in automation systems such as SCADA, robotics, factory machinery, process control, and power management.
  • Telecom & Networking: Here, multilayer PCBs are used in telecom infrastructure and networking equipment, including routers, switches, data centers, wireless communication systems, and satellite communication.

Why Do Engineers Choose HT Global Circuits?

Here are some reasons why OEMs prefer to partner with us for their multilayer PCB requirements.

  • Experience and expertise: As an experienced multilayer PCB manufacturer with over three decades of market visibility, we had the privilege of working with diverse clients. This has helped us develop expertise in this segment and build our brand. We have also developed a strong vendor network and set up a robust supply chain process. This helps us in exact part procurement on time. We have a proven track record of on-time delivery exceeding 98%, which ensures our clients can rely on us for consistent and timely PCB supply for their projects.
  • Research and innovation: We invest significantly in research and advanced technologies that help us improve our capabilities. This, in turn, helps our clients stay ahead in terms of technological advancements in their products.
  • Quality: We are committed to quality and accuracy and have proven quality systems. We adhere to stringent quality certifications, including IPC Class 2/3 standards, IATF 16949 for automotive applications, and AS9100 for aerospace and defense sectors. This commitment to quality ensures we offer reliable and durable PCBs suitable for mission-critical applications.
  • Global footprint: We have state-of-the-art manufacturing facilities in the United States in St. Petersburg and Milwaukee and cost-effective operations in China, Taiwan, and Thailand. This enables us to offer a global reach with localized service and engineering support as well as on offshore multilayer PCB projects. Our international presence ensures scalability and flexibility for engineers working on projects of varying sizes and complexities, while achieving cost effectiveness.
  • Quick-turn prototypes: We offer multilayer PCB prototypes in as little as 24-72 hours, depending on the complexity. We can produce small to medium batches as well as full-volume production.
Frequently Asked Questions
What is the process of drilling in multilayer PCBs?

Drilling involves creating holes for vias and through-holes. Specialized equipment is used to ensure precise drilling without damaging the delicate layers of the PCB. After drilling, the vias are plated with copper to establish electrical connections between layers.

How do multilayer PCBs handle heat dissipation?

Multilayer PCBs are designed with thermal management in mind. In fact, with the increasing number of layers, some can be dedicated to power and ground planes that help spread heat across the board. We include heat sinks, thermal vias, or copper planes that help dissipate heat more efficiently, ensuring the board performs reliably in high-power applications.

Can multilayer PCBs be recycled?

Yes, multilayer PCBs can be recycled; however, the process is more complex than recycling single-layer PCBs. Specialized recycling techniques are used to separate materials like copper, fiberglass, and resin for reuse.