What is the advantage of multilayer PCB?

There are several advantages of using a multilayer PCB over a single or double-layer PCB:

1. Higher Density: Multilayer PCBs allow for a much higher density of components and traces since they provide more layers for routing connections.

2. Increased Flexibility: With more layers available, designers can route signals through different layers and avoid signal interference, making multilayer PCBs more flexible and efficient.

3. Better Signal Integrity: Multilayer PCBs provide more layers for routing power and ground planes, which results in improved signal integrity and reduced EMI (Electromagnetic Interference).

4. Improved Thermal Management: Multilayer PCBs can incorporate power and ground planes, which help to dissipate heat generated by high-power components, leading to better thermal management.

5. Smaller Size: Multilayer PCBs can provide the same functionality as single or double-layer PCBs in a smaller space, making them ideal for applications where space is limited, such as in mobile devices.

6. Higher Reliability: Multilayer PCBs have improved reliability due to their ability to incorporate redundancy in the circuit design, ensuring that if one layer fails, the others can still function. 

Overall, multilayer PCBs provide a lot of benefits, including better signal integrity, increased density, improved thermal management, and higher reliability. They are ideal for complex electronic devices that require high-speed signals and efficient routing of components.