Home > Blog > Overall Introduction to Complex PCB, Design, and Manufacturing

Overall Introduction to Complex PCB, Design, and Manufacturing


Thur, Apr 20, 2023

icon 120
Rating: icon_staricon_staricon_staricon_staricon_star

A printed circuit board (PCB) is a laminated board with circuit layers embedded. It loads electronic components. Nowadays, as electronic products are more and more advanced, complex PCBs are put to more use in electronic industries. What is a complex PCB? In this article, we'll go over an overview of complex PCBs, and what to do to ensure the success of a complex PCB.

Part 1: What is a Complex PCB

complex PCB

If you have a project for any middle and high-end applications, the PCB is probably complex. What makes a PCB complex? It is the circuit design complexity, fine traces, buried/blind holes, multiple circuit layers, or special laminate materials that gives special features to the circuit board.

A complex PCB is a circuit board either with complex circuits in multiple layers, having special PCB structures, or made of special materials that are difficult to fabricate and process. And the applications of complex PCBs include automotive, industrial, communication, computing, defense, medical, and consumer electronics.

medical flexible PCB

We can say that except for easy PCBs, all the other PCBs are complex PCBs, such as multilayer PCBs, flexible PCBs, rigid-flex PCBs, HDI PCBs, high-frequency PCBs, and ceramic PCBs.

As biological electronics and artificial intelligence develop, there are even transparent PCBs that can be used for electronic skins and glass PCBs that are transparent and can withstand extremely high temperatures.

What is the most complex PCB so far? The probe card and load board for IC testing and high-frequency baseband unit (BBU) in telecommunications are the most advanced and complex PCBs. And you can see their pictures below.

IC load board
baseband unit PCB

The one-stop complex PCB manufacturer PCBONLINE fabricates and assembles complex PCBs from prototypes to massive production. If you want to know more information about the mentioned complex PCBs, you can check the PCB Fab pages on our website.

Part 2: Complex PCB vs Easy PCB

Early PCBs are paper-based (FR1 and FR2) PCBs with 1 circuit layer or one component-mounting side. They are easy PCBs. But today, these paper-based PCBs are almost no longer in use, and PCBs are getting more advanced so that they can work for modern applications. However, easy PCBs like CEM3 and FR4 PCBs are still in use for simple consumer electronics, and many hobbyists and beginners are designing easy PCBs.

Easy PCBs in use include composite paper (CEM-1 and CEM-2) PCBs, composite glass cloth (CEM-3) PCBs, glass fiber (FR4) PCBs, and aluminum PCBs in 1 or 2 layers on one or two-component mounting sides. CEM-1, CEM-2, and CEM-3 have rare uses.

complex PCBs

Complex PCBs have far more substrate types, such as FR4, aluminum, copper, ceramic, PTFE, polyimide, polyester, and glass, and the circuit layers range from 1 to 64 so far. Besides, a complex PCB features a small trace width/space, a high-density circuit, or a higher copper thickness. And there are hybrid substrate PCBs such as Rogers/FR4/copper PCBs used for military uses.

We compare complex PCBs and easy PCBs in the table below.

Easy PCB
Complex PCB
PCB layer
1 or 2
1 to 64
Component-mounting side
Single or dual
Single or dual
PCB substrate
CEM-1, CEM-2, CEM-3, FR4, aluminum
FR4, aluminum, copper, polyimide, polyester, ceramics, PTFE, glass
Copper thickness
0.5oz, 1oz
1/3oz, 0.5oz, 1oz, 2oz, 3oz, 4oz, 5oz...14oz
PCB holes
PTH, buried via, blind via, staggered via, stacked via, skip via
Trace space/with
Minimum at 1.6mil/1.6mil
OEMs for simple electronics, hobbyists
Original equipment manufacturers (OEM), business makers, research institutes
Simple consumer electronics such as toys, circuit engineering learning
Industrial, medical, computing, communications, defense, biological, agricultural, and consumer electronics
Surface finish
ENIG, HASL (LF HASL), OSP, immersion tin, immersion silver, hard gold plating, carbon ink, ENEPIG, peelable mask

Complex PCBs give much larger space and possibilities for engineers to design. However, complex PCBs are usually more costly than easy PCBs. PCBONLINE not only provides complex PCBs. It achieves fully automatic aluminum PCB fabrication. In easy aluminum PCBs, PCBONLINE also has price competitiveness.

Part 3: Types of Complex PCB

Complex PCBs include many types.

According to different PCB substrate materials, there are:

rigid-flex PCB
  • Polyimide and polyester PCBs. They are thin and can fit in really compact spaces, and they are flexible PCBs,
  • Polyimide-core PCBs with FR4 external layers. They have the advantages of both rigid FR4 and flexible polyimide, and they are rigid-flex PCBs,
  • FR4 PCBs that have a middle or high TG, thicker copper thickness, or multiple layers,
  • Aluminum PCBs that have 4 layers or resin-insulated vias,
  • Copper-based PCBs that can carry large currents,
  • PTFE PCBs. They can transmit and receive microwave-frequency and radio-frequency signals,
  • Ceramic PCBs that can overbear a thousand degrees Celsius and high pressure,
  • And hybrid substrate PCBs or a composite structure with an inlay in the substrate in different materials.

If the PCB has micro vias, the complex PCB is an HDI PCB that has blind/buried vias and fine traces.

complex transparent PCB

If the PCB has a polyester or glass substrate, it is a transparent PCB that can have a transparency of up to 90%.

If the PCB has more than two circuit PCB layers, it is a multilayer PCB.

If the PCB has a copper thickness of more than 2oz, it is a thick-copper PCB.

As technology improves, a PCB not only carries and connects electronic components but also achieves electrical and mechanical functions, such as high-frequency PCBs and flexible PCBs. Ceramic PCBs manufactured in the HTCC method can even embed resistors and capacitors during manufacturing.

Part 4: What to Do with a Complex PCB Design

If you have a complex PCB design and plan to make it manufactured, you can do such things below to ensure its success.

  • Break down the PCB design into smaller pieces: you can break an overwhelming complex PCB design down into smaller pieces as they are more manageable. This allows you to focus on a section at a time and you can work on them one by one.
  • Test and validate the PCB design: with the help of PCB design software, you can check out the design flaws. If possible, you can do a design for manufacturing (DFM) for PCBs and a design for testing (DFT). And before massive PCB manufacturing, you can have PCB prototyping to validate the PCB works as expected.
  • Consult with complex PCB experts: If you can't validate a complex PCB design, you can contact a complex PCB manufacturer like PCBONLINE to get suggestions and engineering help. PCBONLINE has 24 years of R&D and manufacturing experience in complex PCB design, fabrication, and assembly. From PCBONLINE, you can get one-on-one engineering support throughout your project and troubleshoot any issues.

Part 5: Complex PCB Manufacturing

Complex PCB manufacturing is a process of generating circuits on the PCB core layers and laminating layers on the core and generating circuits, and finally coating the PCB with a solder mask. For different complex PCBs, the fabrication process is different, and there are many steps.

For example, single-layer flexible PCB fabrication involves cutting laminates, etching copper, surface finish, automatic optical inspection, cutting coverlay, attaching coverlay to the flex PCB while drilling, silkscreen printing, and testing.

Ceramic PCB manufacturing is more complicated, and the manufacturing methods are diverse, including HTCC, DBC, LTCC, thick film, DPC, thin film, and AMB. Below you can see how we laser de-panel ceramic PCBs, which is close to the end of ceramic PCB manufacturing.

If you want to see real-time complex PCB manufacturing, such as multilayer PCBs, high-frequency PCBs, HDI PCBs, copper-base PCBs, and so on, you can have an online meeting with PCBONLINE, where we can show you real-time PCB manufacturing through the monitor in our factories.

Part 6: Complex PCB Manufacturer from A to Z

PCBONLINE is a one-stop complex PCB manufacturer from prototypes to massive production. Founded in 1999, we have two large advanced PCB manufacturing bases and one PCB assembly factory. Over the past 24 years, we have served OEMs, business makers, and research institutes around the world.

Here are reasons for you to order complex PCBs from PCBONLINE:

  • From PCBONLINE, you can have any complex PCBs manufactured from A to Z without a quantity limit.
  • Besides complex PCB fabrication, PCBONLINE provides PCB assembly, component sourcing, and EMS PCBA value-added services.
  • PCBONLINE is a source factory manufacturer and offers affordable complex PCBs.
  • Our experienced CAM engineer provides you with free PCB DFM and DFT. If you order complex PCB assembly, we provide design for assembly (DFA) and excellence (DFX) for PCBA box builds.
  • We offer one-on-one engineering support and can reduce your project fabrication price with the optimum PCB design.
  • Complex PCB manufacturing, PCB assembly, and PCBA box-build assembly from PCBONLINE are certified with ISO, IATF, IPC, RoHS, REACH, and UL.

If you need complex PCBs for industrial, automotive, communication, aerospace, defense, medical, and consumer electronics, feel free to send your Gerber to PCBONLINE by email at info@pcbonline.com. We will review your design and ensure the success of the complex PCBs/PCBA and end product success.


This article gives a comprehensive introduction to complex PCBs, including what makes a PCB complex, which types of complex PCBs are, what to do with a complex PCB design and complex PCB manufacturing. Besides, we made a comparison between complex PCBs and easy PCBs. For high-quality A-Z complex PCBs from prototypes to massive production, or if you want to consult about complex PCBs, you are welcome to contact PCBONLINE.

© This article is an original work of the PCBONLINE team. Please indicate the author PCBONLINE if you reprint. If the article is reproduced without permission or indicating the author's source, PCBONLINE reserves the right to investigate the infringement.