“Since Huawei developed the high-speed, high-capacity next-generation communication standard “5G”, it has really entered our lives with the release of 5G-compatible smartphones. This time, I’m going to introduce the difference between 5G high frequency and millimeter wave, and how PCBs are changing in the 5G industry and the types of PCBs that are used for various purposes.
Since Huawei developed the high-speed, high-capacity next-generation communication standard “5G”, it has really entered our lives with the release of 5G-compatible smartphones. This time, I’m going to introduce the difference between 5G high frequency and millimeter wave, and how PCBs are changing in the 5G industry and the types of PCBs that are used for various purposes.
1. What is the next-generation communication standard “5G”?
5G has three major changes:
1. Multiple simultaneous connections;
2. Ultra-high speed and large capacity;
3. Low latency.
Compared with 4G, the communication speed is 20 times, the delay is 1/10, and the number of simultaneous connections is 10 times. (The communication speed of 4G is 15 times that of 3G. At that time, I thought 4G was very fast.)
5G is too fast for previous standards, and the point is that high-capacity communications and multiple connections can be done without delay. This will enable telemedicine, provide high-definition VR games and movies, and combine massive amounts of sensor information and image processing for autonomous driving and smart cities.
1. High frequencies and the differences between 5G and mmWave
Both the frequency band used for 5G communications and the frequency band called millimeter wave are high frequencies. The frequency bands used in 5G are divided into Sub6 and mmWave. Sub6 is a frequency band less than 6 GHz that can be achieved by applying the same communication technology as 4G (LTE, Wi-Fi). However, in the Sub6 band, ultra-high-speed, high-capacity communication has not improved significantly.
The characteristics of ultra-high speed and large capacity are attributed to the characteristics of the millimeter wave band.
Generally, millimeter waves are frequencies above 30 GHz, but since the 5G communication band of 28 GHz is close to millimeter waves, it is indiscriminately called millimeter waves.
1. Replacement material for high frequency board
In order to meet the millimeter wave range, the dielectric loss of the insulating material must be reduced. Dielectric loss refers to the loss of energy as heat when an AC electric field is applied to a dielectric, resulting in signal degradation. Especially in the millimeter wave region, the influence of signal degradation due to dielectric loss is large, so the selection of insulating materials for printed circuit boards is very important.
Fluorocarbon resins are representative resins with low transmission loss, and Teflon and Teflon are famous. It has excellent heat resistance, moisture resistance and chemical resistance, but is too hard and has poor workability when manufacturing printed circuit boards. LCP (Liquid Crystal Polymer) is another material with low transmission loss, but its disadvantage is that it has high thermoplasticity and defects due to high temperature processing during panel fabrication.
Currently, each company is developing resin materials with low transmission loss in the millimeter wave region.
For example, Panasonic’s MEGTRON6 is used as a substrate for CCL (copper clad laminate), and Beflon has better processability during substrate manufacturing.
Even for products that support high frequency, it is not necessary to use the above-introduced materials with low transmission loss to manufacture the insulating layer of the entire printed circuit board. There is a method in which only the high-frequency circuit layer or only the part of the RF module that emits radio waves is used as a substrate for transmission loss.
What is the board used for 5G communication?
Printed circuit boards are used in base stations to send and receive 5G radio waves, 5G smartphones, various surveillance sensors for implementing smart cities, and radars for autonomous driving. Most base station boards are high-throughput through-hole boards with multiple layers of insulation and patterning. RF modules for 5G communications are installed in 5G smartphones and surveillance sensors, and the board typically has ultra-high density any-layer specifications. Most radars for autonomous driving have relatively large combined board sizes.
For high-frequency applications, as of 2020, the research phase involves many parts, and there are no clear directions in some areas. However, as 5G communications are put into practical use in countries around the world, we expect many products to be commercialized at a faster rate. By the time the base station infrastructure is ready, I think all devices will be equipped with 5G communication modules, which will provide us with a more convenient life.