Your Guide to Multilayer PCBs – Design, Manufacturing, and Applications
If you’ve wondered whether a multilayer printed circuit board (PCB) is right for your next project, this guide is for you. Read on to learn more about this popular type of PCB, including where and how they are used, potential cost drivers, advantages and challenges, and much more.
What Are Multilayer PCBs?
Multilayer PCBs contain three or more copper conductive layers — usually with plated through holes. If a board is constructed with both flexible and rigid materials, it’s known as a rigid-flex PCB. A rigid-flex circuit board is a 3D interconnect that can be bent and folded into almost any shape. Rigid-flex technology allows designers to replace multiple PCBs with interconnecting wires and/or cables into one single unit, offering improved performance and increased reliability.
Multilayer PCB Use Applications
Multilayer PCBs are extremely common and can be found in a variety of applications and industries, including:
- Computers and laptops
- Consumer products
- Cell phones
- Industrial controls
- Medical equipment (heart monitors, X-ray machines, and other types of equipment and devices)
- GPS technology
- Military and defense
Multilayer PCB Fabrication Process
Engineers construct multilayer PCBs by joining all the layers and materials at a high temperature, which removes any trapped air. Various reinforced resin types and adhesive materials are used to join layers together.
Multilayer PCB Costs
The price of a printed circuit board correlates with the number of layers — the more layers, the higher the cost. Also, some multilayer PCBs may require more manufacturing time, which can impact the price of a project.
Ultimately, the cost of a multilayer PCB comes down to a few things:
- The number of layers
- Level of complexity
- Number of fabrication requirements.
For example, a PCB for a dishwasher is less complex than a PCB for the military industry, which must adhere to specific guidelines and certifications.
Multilayer PCBs also become most costly if they include HDI — high-density interconnect. HDI PCBs are characterized by thin lines, closer spaces, more dense wiring, and blind and buried vias, which allow for a faster connection while reducing the size and bulk of a project.
Advantages of Multilayer PCBs
Multilayer PCBs offer improved performance and higher density, which allows for greater functionality, capacity, and speeds. These types of printed circuit boards allow you to reduce the size of PCB, which saves space. Increased flexibility is also a major advantage.
Challenges of Multilayer PCBs
Even though multilayer PCBs are popular, they are not without their challenges. Here are some of the more common ones:
- Higher cost than single- or double-sided PCBs
- Potentially complicated production
- Skilled designers and engineers are required
- Potentially longer fabrication time
Multilayer vs. Double-sided Layer PCBs
In a double-sided (or double layer) PCB, both sides of the material (or substrate) have a metal layer. They are often found in many consumer electronics, such as cell phones, and other devices such as power monitoring, test equipment, and amplifiers.
Whether you need multilayer or double-sided PCBs is driven by functionality and schematic requirements. One of the first steps in the PCB layout process is creating a schematic, which refers to the design at the electrical level of the board’s purpose and function. In developing the schematic, the principal engineer will determine whether the materials and components can work within a double-side layer or whether more layers are needed.
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