5G mobile phones involve technological upgrading of the entire industry chain. What is the difference between it and 4G mobile phones? Which technologies will play a key role in the popularization of 5G mobile phones? Let’s talk about the three key technologies behind 5G mobile phones: motherboard, antenna and heat dissipation.
The “foundation” of 5G mobile phones: SLP technology
Disassembling a 4G mobile phone, you will find that the components contained on the PCB have almost reached the limit. How to maintain the thickness and weight of the fuselage on the basis of more components on the 5G mobile phone, SLP technology plays a key role.
What is SLP? SLP is Substrate-like PCB. Through advanced soldering process, it can connect the circuit of multi-layer PCB board, thus changing the motherboard from “2D to 3D”, making full use of the space of the body. iPhone X, XS The multi-layer motherboard technology used in the series and 11 Pro series benefits from the SLP process.
Why use SLP? According to estimates by the RF industry giant Skyworks, the 5G mobile phone’s RF front-end parts will increase significantly, the number of filters will increase from 40 to 70, and other RF devices such as antennas, PAs, RF switches, and LNAs will also almost double.
The SLP process not only makes better use of the three-dimensional space inside the fuselage, but also makes the components of the PCB board more “compact”, that is, further reducing the line width and line spacing, so as to put more 5G components. The minimum line width/line distance of Anylayer HDI used in the past is about 40μm, and the current SLP is already less than 30/30 μm. It is understood that the SLP process used in the new iPhone this year will be further reduced to 25 um/30 um.
The space released by the SLP technology is quite obvious. Taking the iPhone as an example, after the iPhone X introduced the SLP technology, the volume of the same number of components was reduced to 70% of the original, bringing more battery space. However, the SLP technology has not been widely introduced in the Android camp. It is expected that SLP technology will gradually become mainstream in the flagship 5G mobile phones in 2020.
The “foundation” of 5G mobile phones: SLP technology
As mentioned earlier, an obvious difference between 5G mobile phones and 4G mobile phones is the substantial increase in radio frequency components. As a “highway” for signal transmission, mobile phone antennas are also regarded as “leading” elements for 5G mobile phone upgrades. What is LCP substrate? LCP uses Liquid Crystal Polyester, which is widely used in 5G mobile phone antenna substrates.
LCP has excellent electrical characteristics: in the entire radio frequency range up to 110GHz, it can maintain almost constant dielectric constant and good consistency; the tangent loss is very small, only 0.002, even at 110 GHz, it only increases to 0.0045, which is very suitable Millimeter wave application; thermal expansion characteristics are very small, can be used as an ideal high-frequency packaging material.
Why use LCP substrate? One is to reduce communication loss, and the other is to improve the antenna’s miniaturization capability.
Reduce communication loss
As mentioned earlier, the main reason for the excellent electrical characteristics of LCP antennas, especially under the conditions of 5G high-band communications. For example, a traditional PI flexible board antenna will produce an electromagnetic loss of about 2% to a 2.4G radio frequency signal, and as the frequency increases, the loss is greater. The loss of LCP base material is only 2‰-4‰, which is 10 times smaller than the former, which can effectively reduce the loss.
As the internal space of 5G mobile phones has been further reduced, the number of antennas has increased, and antenna miniaturization has become a trend. LCP has good physical properties, which can improve the miniaturization ability of the antenna. In terms of bending performance, the LCP antenna can fit the fuselage midframe, which has no obvious rebound effect compared with the traditional FPC antenna.
At the same time, the thickness of the circuit board of the flexible board using LCP material is only 0.2 mm, which is used to integrate the antenna and the coaxial cable will reduce the overall thickness and provide more clearance area for the antenna.
With the rise of full-screen mobile phones, LCP-related industries started earlier, and many 4G mobile phones have used LCP antennas, which is why we see the proportion of mobile phone screens becoming higher and higher. With higher requirements, ID design also puts forward higher requirements on the related industry chain.
5G mobile phone cooling: soaking plate (VC)
SLP technology and LCP substrates have the same goal, that is, to insert as many components as possible in the limited space of 5G mobile phones. The more components, the higher the heat generated, and the increased density of components makes heat dissipation Put more pressure.
According to the forecast of the Prospective Industry Research Institute, the CAGR (annual compound growth rate) of the heat dissipation industry will increase by 8% in 2018-2023, while the heat dissipation CAGR of smartphones will reach 26%. To cope with the heat dissipation problems caused by the high-performance, dense components and IC control of 5G mobile phones, the traditional graphite heat sink scheme has gradually been unable to load, and the soaking plate (VC) will be the standard for future 5G mobile phones.
What is a soaking plate (VC)? The function and working principle of the Vapor Chamber is consistent with the heat pipe. It is operated by the evaporation and condensation cycle of the actuating fluid enclosed in the plate-shaped cavity, so that it has the characteristics of rapid temperature uniformity, which has rapid heat conduction and The function of thermal diffusion. The composition of the soaking plate is similar to the heat pipe, which is composed of a metal shell, a capillary structure and an actuating fluid.
At present, the average unit price of the soaking plate is 2–3 US dollars, which is 5–10 times that of the heat pipe, and the unit price of the ultra-thin soaking plate required for 5G mobile phones is higher. As the cost of ultra-thin heat spreading plates further declines, investment institutions predict that by 2020, the penetration rate of heat pipes/VC in mobile phone terminals is expected to increase to 15%. Based on the 1.5 billion mobile phone shipments, the average unit price of heat pipes/VC is assumed If it is 1.5 USD, the market space in 2020 will be 338 million USD.