**The Difference Between 5G High Frequency and Millimeter Wave, and How PCBs Are Evolving in the 5G Industry**
What is the next-generation communication standard “5G”?
There are three key advancements in 5G technology:
1. Multiple simultaneous connections;
2. Ultra-high speed and large capacity;
3. Low latency.
Compared to 4G, 5G communication speed is 20 times faster, latency is reduced to one-tenth, and the number of simultaneous connections is 10 times greater. (For context, 4G is 15 times faster than 3G.)
5G is a significant leap forward from previous standards, with the primary breakthrough being the ability to support high-capacity communications and a massive number of simultaneous connections without any noticeable delay. This opens the door to applications like telemedicine, ultra-high-definition VR games and movies, and integrating vast amounts of sensor data and image processing for technologies like autonomous vehicles and smart cities.
**High Frequency and the Difference Between 5G and Millimeter Wave**
Both the frequency range used for 5G communication and the frequency band known as the millimeter wave are considered high-frequency bands. The 5G frequency range is divided into Sub6 and millimeter wave bands. Sub6 refers to frequencies below 6 GHz, which can still rely on existing communication technologies like 4G (LTE) or Wi-Fi. However, in the Sub6 band, ultra-high-speed, high-capacity communication doesn’t see significant improvements.
The remarkable speed and capacity of 5G are largely due to the millimeter wave frequency band.
Typically, millimeter waves are defined as frequencies above 30 GHz, but since the 5G communication band around 28 GHz is close to this range, it is often grouped together with millimeter waves.
Replacement Materials for High-Frequency Substrates
To meet the requirements of the millimeter-wave range, the dielectric loss of insulating materials must be minimized. Dielectric loss refers to the energy loss as heat when an AC electric field is applied to a dielectric, resulting in signal degradation. In the millimeter-wave region, this degradation is particularly significant, making the choice of insulating material for the circuit board crucial.
Fluorocarbon resin, such as Teflon and polytetrafluoroethylene, is a representative material with low transmission loss. It offers excellent heat resistance, moisture resistance, and chemical stability. However, it is quite rigid and difficult to process during PCB manufacturing.
Liquid Crystal Polymer (LCP) is another material with low transmission loss, but it suffers from high thermoplasticity and potential defects caused by the high-temperature processes used in PCB production.
Currently, companies are focusing on developing resin materials with low transmission loss for use in the millimeter-wave region.
Even for high-frequency products, it is not always necessary to use low transmission loss materials for the entire insulating layer of a printed circuit board. Instead, a method can be used where only the high-frequency circuit layer or a specific part of an RF module that emits radio waves is made with low transmission loss material.
What type of board is used for 5G communication?
The circuit board in a PCB base station is responsible for transmitting and receiving 5G radio waves. Most base station boards are high-throughput through-hole designs with multiple insulating and pattern layers. The RF module for 5G communication is integrated into 5G smartphones and surveillance sensors, typically using ultra-high-density laminate specifications. Most radars used in autonomous driving also employ relatively large composite board specifications.
