Is there only one way for RF devices to innovate in materials?  Of course not.  Aside from professional issues, whenever anything is considered to have only one way to go, this view is worthy of our questioning and discussion.  So,We might as well discuss the future innovation of RF devices.

 

           

Overview of RF devices
 RF device is the core of wireless connection and the basic part to realize signal transmission and reception.  RF devices include RF switch and LNA, RF PA, filter, antenna tuner and millimeter wave FEM. Among them, filter accounts for about 50% of the RF device market, RF PA accounts for about 30%, RF switch and LNA account for about 10%, and others account for about 10%.  It can be seen that filter and PA are important parts of RF devices. PA is responsible for signal amplification of transmission channel, and filter is responsible for filtering received signal of transmitter.  At present, the main markets of RF devices are as follows:  Mobile phone and communication module market, accounting for about 80%;  WiFi router market, accounting for about 9%;  Communication base station market, accounting for about 9%;  NB IOT market, accounting for about 2%.  Nowadays, with the increasing maturity of 5g technology, the commercialization trend is accelerating.  5g needs to support new frequency bands and communication systems. As the core of wireless connection, core devices such as filters, power amplifiers, switches, antennas and tuners in RF front-end have become the tuyere of the current market.  Analysts predict that by 2023, the market scale of RF front-end is expected to exceed US $35.2 billion, with an annual compound growth rate of 14%.  The fast-growing market gives the industry opportunities. New RF companies are constantly emerging. Domestic RF manufacturers have become the pursuit of many manufacturers to build their own RF supply chain. However, looking at the current situation, the gap is still obvious.  Focusing on the domestic market, with the joint efforts of local RF manufacturers, the replacement rate of 2G RF devices is as high as 95%, that of 3G is 85%, and that of 4G is only 15%, while that of 5g RF is basically zero.  
 
 

       

   Domestic RF device manufacturers are as follows:  Filter manufacturer  

• Saw filter domestic manufacturers:goodreach, 26 Institute andMai Jie, San'an integration, 55 Institute;
• Domestic manufacturer of BAW filter:Tianjin North, Xiamen Kaiyuan communication, Suzhou hantianxia

Main manufacturers of 4G pa  

• Vijet core:4G PA shipments are the largest in China and have been integrated with loda
• Loda:Acquired by MTK and sold based on MTK platform.
• Zhanrui RF product line:Sales based on Spreadtrum platform.
• Huizhiwei:Rely on SOI architecture innovation to achieve low cost.
• Angruiwei:3G PA is the main supplier, and some 4G customers adopt it.
• Feixiang Technology:The customer base is good.

Major domestic 3G PA manufacturers  

• Loda:The customer base is good, the price is on the high side.
• Angruiwei:The cost of PA is low and the performance is good through CMOS process. It is the main supplier of 3G PA in the market.
• Feixiang Technology:The main shipment is the reliance project in India.
• Zhanrui RF product line:There are not many shipments, mainly India's reliance project.

Main domestic WiFi PA / FEM manufacturers:    

• Vertical product Electronics:Taiwan listed companies, with acceptable shipments, have gradually eroded the sky market.
• Kangxi Electronics:In 2018, the products were launched, and some customers began to import them. At present, the shipment volume is small.
• Zhanrui RF product line:Mass production and shipment began in 2018, and several major Netcom customers have been imported into Huawei.
• Sanwuwei:Founded in 2018, it focuses on WiFi PA / FEM, and its products are in the R & D stage.

Main domestic switch manufacturers:  

• Zhuo Shengwei:The largest switch supplier in China.
• Zhanrui RF product line:It is also a Samsung supplier, accounting for only a small share, and the total amount of switch shipments is general.
• Vertical product Electronics:Switches were mass produced and shipped in 2018, with a certain shipment volume.

In addition, the manufacturing and sealing test of RF devices can be completed by domestic manufacturers.  The domestic RF chip industry chain has been basically mature, and a complete industry chain has been formed from design to wafer OEM, and then to packaging and testing.  However, in terms of international competitiveness, the domestic RF design level is still at the middle and low end. There is still a large gap in sales and market share between the above RF device manufacturers and large international manufacturers.  It can be seen that domestic manufacturers are still in the initial stage and there is still a lot of room for growth.  

 In contrast to the market layout of the international RF industry, according to the statistics of relevant institutions, 80% of the global market share of SAW filter is occupied by Murata (typical filter products:  SF2433D、SF2038C-1、SF2037C-1Tdkqualcomm rf360 (typical filter products:  DEA162690LT-5057C1、DEA165150HT-8025C2、DEA252593BT-2074A3）Taiyo Yuden (RF device:  D5DA737M5K2H2-Z、AH212M245001-TEtc.), BAW filters applied in 4G / 5G are occupied 95% of the market space by Broadcom and qorvo, and more than 90% of the global market of PA chips are concentrated in skyworks, qorvo and Broadcom.  In addition to occupying most of the market, the above RF manufacturers have basically completed the layout of the whole RF front-end product line, have a special manufacturing and packaging chain, and consolidate their great advantages in design capability, product performance and capacity control with IDM mode.  At the same time, the patent technology reserve also gives RF giants a broader moat, making it difficult for latecomers to surpass in the short term.
 

Challenges and innovations of RF devices

During the evolution from 4G to 5g, the complexity of RF devices is gradually increasing Qi, and the products will undergo progressive changes in design, process and materials.  At the same time, the RF front-end still faces many technical problems, such as power consumption, size, number of antennas, chip design, temperature drift, signal interference, harmonious coexistence of different types of signals and so on.  How to solve these problems has become the focus of the industry and the innovation of RF devices.  With the development of semiconductor materials, the improvement of power consumption, efficiency, heating problem and size brought by the replacement of RF materials such as Si, GaAs and GaN and packaging substrate materials such as ceramics and glass is naturally an important innovation for the development of RF devices.  But in addition to material innovation, what are the innovative ways of RF devices?  
 

 
 manufacturing process  At present, the main processes involved in RF devices are GaAs, SOI, CMOS, SiGe, etc.  GaAs：  GaAs has a good electron migration rate and is suitable for high frequency circuits with long distance and long communication time.  Because the electron mobility rate of GaAs components is much higher than that of Si, special processes are adopted. In the early stage, it was MESFET metal semiconductor field effect transistor, and later it evolved into HEMT (high electron mobility transistor), PHEMT (interface strained high electron mobility transistor), and now it is HBT (heterojunction double carrier transistor).  GaAs production mode is very different from the traditional silicon wafer production mode. GaAs needs to be manufactured by epitaxial technology. The diameter of this epitaxial wafer is usually 4-6 inches, which is much smaller than 12 inches of silicon wafer.  Epitaxial wafers need special machines. At the same time, the cost of GaAs raw materials is much higher than that of silicon, which eventually leads to the high cost of finished GaAs IC;  SOI：  The advantage of SOI process is that it can integrate logic and control functions without additional control chips;  CMOS：  The advantage of CMOS technology is that it can integrate RF, fundamental frequency and memory components into one, and reduce the component cost at the same time;  SiGe：  In recent years, SiGe has become one of the most valued wireless communication IC process technologies.  According to the material characteristics, SiGe has good high-frequency characteristics, good material safety, good thermal conductivity, mature process, high integration and low cost.  SiGe not only has the advantages of integration, yield and cost of silicon process, but also has the speed advantages of class 3 to 5 semiconductors such as gallium arsenide (GaAs) and indium phosphide (INP).  As long as metal and dielectric laminations are added to reduce parasitic capacitance and inductance, SiGe semiconductor technology can be used to integrate high-quality passive components.  SiGe process is compatible with almost all new process technologies in silicon semiconductor VLSI, which is the trend in the future.  However, SiGe needs to continue to work on breakdown voltage, cut-off frequency and power in order to replace GaAs.  The processes used for RF PA are GaAs, SOI, CMOS and SiGe respectively;  The RF switch adopts SOI and GaAs technology;  The processes adopted by LTE LNA are mostly SOI and CMOS.  In the 5g era, the materials and technologies of RF components may change in the sub-6ghz and millimeter wave stages.  SOI may become an important technology, with the potential to make a variety of components, and is conducive to subsequent integration.  

     Solve antenna problems  Taking mobile phones as an example, due to the special requirements of 5g technology, 5g requires higher data rate and more antennas from the perspective of smart phone system architecture.  These antennas include multi band carrier aggregation, 4x4 MIMO and Wi Fi MIMO.  This brings challenges in antenna tuning, amplifier linearity and power consumption, and other system interference.  At the same time, the number of antennas increases, leaving less and less space for antennas.  Therefore, RF manufacturers can share one antenna for RF channels such as GPS, WiFi, if, HF and UHF, which can reduce the number of antennas and save space.  At present, the mainstream and mature scheme of millimeter wave antenna is the modular design of AIP (antenna in package). AIP scheme mainly has the advantage of low path loss because its RFIC is close to millimeter wave antenna array. Therefore, AIP scheme has been deeply studied and designed by many scholars and experts.  At present, AIP encapsulated antenna technology is developing along two technical paths.  One is called fan out encapsulated antenna technology (fo-aip), and the other is called flip chip encapsulated antenna technology (fc-aip).  The difference between the two is that one has a substrate and the other has no substrate.  

 Integration degree  In the future, RF devices such as filters will be miniaturized, improved device form and combined.  Just like 4G ten years ago, LTE connection is based on the existing 3G technology;  The early 5g function was realized by adding an independent chipset to the existing LTE design, which means that 5g components are basically bolted to the smartphone design rather than integrated into the core chipset, but it has a certain impact on the chip size, performance and power consumption.  For example, single-mode 5g modem, 5g RF transceiver and single band 5g RF front end, which are independent of the existing LTE RF link.  This first generation 5g modem design also requires additional support components.  Therefore, with the maturity of the industry, improving the integration of RF devices is an inevitable development direction. The industry will look forward to the further optimization of core circuit design.  A highly integrated and compact RF architecture to support both sub 6GHz and millimeter band 5g in one device will become people's expectation.     

   Packaging mode  In the 5g era, RF manufacturers pay more attention to the packaging innovation in RF front-end solutions, such as tighter component layout, double-sided mounting, conformal / zoned shielding, high-precision / high-speed SMT, etc.  5g frequency band is divided into millimeter wave and sub-6g. The higher the frequency band, the higher the requirements for miniaturized packaging. Through new packaging forms, the miniaturization, mass production, low cost, high precision and integration of device packaging are gradually realized.  In order to integrate antenna elements and RF components for 5g mobile communication, a variety of packaging solutions with different architectures are proposed in the market.  Based on the cost and mature supply chain, fan out WLP / PLP package benefits from high signal performance, low loss and reduced overall size. It is a promising AIP integration solution, but it requires double-sided rewiring layer (RDL).  With the exception of a few manufacturers, most OSATS are not ready to use this technology for large-scale manufacturing.  In the system level packaging (SIP) part, it is divided into the primary packaging of various RF devices such as chip / wafer level filters, switches and amplifiers and the secondary SIP packaging in the surface mount (SMT) stage, in which various devices are assembled on the SIP substrate together with passive devices.  SIP provides the required small size, shorter signal path and lower loss.  At the same time, as the increasing functions have higher requirements for integration, the market also puts forward more requirements for SIP packaging methods.  It can be seen that there are many researches on the ideal solution of RF device packaging in recent years, which are committed to seeking a balance between cost, volume and performance requirements. It will also be one of the innovative ways of RF devices in the future.

 

 

 

epilogue

The pursuit and replacement of RF devices requires domestic manufacturers to have the determination and perseverance to "sit on the bench", and also requires the government and investment institutions to give enterprises more patience. Under the general trend of 5g and the Internet of things, seize the breakthrough points of RF devices in new design, new process, new materials and new packaging, and take the market opportunity to catch up in continuous innovation.