Jiwei Network reported that under the trend of high frequency, the frequency band spacing of smart phones has gradually decreased, the difficulty of frequency band isolation has been increasing, and the performance requirements such as bandwidth, insertion loss and size have also been further improved, which have put forward higher challenges for the design and production of RF filters.
On the other hand, from 2G to 5G, smart phones are becoming more and more thin, the battery capacity is getting larger and larger, and there are more and more RF front-end devices integrated in smart phones, making the space left for RF front-end PCBs inside mobile phones more and more limited, and RF front-end modularization will become a long-term trend. With the continuous maturity of domestic RF front-end devices, miniaturized and integrated filter resources have not only become a scarce resource in module design, but also the most prominent shortcomings of domestic RF front-end modules.
In this context, the filter has become the key to the domestic RF front end from low-end discrete devices to high-end modules, hangzhou zuolan microelectronics technology co., LTD. (hereinafter referred to as "zuolan microelectronics"), which was founded in 2016, is becoming the pioneer in this wave of modularization.
Stable shipment of rf filters in all categories, towards both discrete devices and modularization
In the face of the new opportunities brought by the 5G era, as the only company in China that has realized the research and development of all-category RF filters, Zuolan Microelectronics has developed a number of product series focusing on high-end products, respectively, to cope with the different needs of the high-end and low-frequency bands, including: conventional SAW, medium-high-performance TC-SAW and high-performance PESAW and PEBAW. The product range mainly covers Rx filters, Tx filters, dual filters, duplexers and highly integrated RF front-end modules.
With excellent technical strength, Zuolan Microelectronics' filter products have passed the test and certification of more than 100 domestic manufacturers, and continue to obtain orders to achieve batch delivery, with shipments exceeding 100 million. Under the trend of modularization, Zuolan Microelectronics successfully stepped into the modularization track in 2021, and on the basis of consolidating the bulk shipment of filter products, launched two diversity antenna RF link DiFEM module products with integrated RF switches and filters: SPDM001, SPDM003, which have the advantages of small size, high integration, strong performance, and stable reliability.
According to Bruce, sales leader of Zuolan Microelectronics, Zuolan Microelectronics SPDM001 diversity receiver module adopts LGA package, the package size is 3.2mm*3.0mm, adopts the standard MIPI-RFFE V2.0 communication protocol, supports WCDMA/LTE network bands B1, B2, B3, B8, B26, B40, B41, and supports B1+B3 downstream carrier aggregation. At the same time, the module integrates 4 AUX paths, supporting customers to expand the frequency band according to system requirements, and is widely used in 4G/5G smartphones, smart wearable devices and module products.
Figure: Diversity module SPDM001
The SPDM003 diversity receiver module also adopts LGA package, the package size is 3.7mm*3.2mm, and the standard MIPI-RFFE V2.0 communication protocol is used. The module integrates dual antenna port switches to support WCDMA/LTE network bands B1, B3, B7, B8, B26, B34, B39, B40, B41, and supports B1+B3+B7/40/41, B34+B39+B41, B7+B40 and MHB+LB carrier aggregation. At the same time, the module integrates 4 LB_AUX and 3 MHB_AUX paths, supporting customers to expand the frequency band according to system requirements, and can meet the application needs of 4G/5G high-end smartphones and module products.
Figure: Diversity module SPDM003
It is worth mentioning that both SPDM001 and SPDM003 are packaged in WLP SAW. At present, the packaging process mainly used in SAW filters includes wafer-level packaging (WLP) and chip-scale packaging (CSP), of which the size of the CSP package is large, which can be integrated and partially matched, which can form a protection for the filter wafer, and at the same time have lower requirements for the packaging process of the module, which has certain cost advantages. "In contrast, the WLP package can achieve a smaller size, can be combined with PA, LNA, etc., can achieve wafer-level integration of multiple filters, and has advantages in the design of other modules in the module, which is the development direction of the filter in the module in the future." Bruce said.
In Bruce's view, Zuolan Microelectronics has three major advantages in modular products:
The first is to have a variety of design capabilities. On the one hand, Zuolan's module design is based on the company's rich conventional SAW, TC-SAW, PESAW and PEBAW filter product lines, which can flexibly select the best design scheme for different frequency bands and performance needs of customers, such as using conventional SAW to meet low-cost needs, and filters using other high-performance technical routes can bring customers better interpolation loss, temperature coefficient, carrier aggregation and other performance indicators.
On the other hand, Zuolan's professional "module + sonometer collaboration" design mode can effectively reduce the matching loss of filters and other devices in the module, effectively shorten the cycle of product design iteration, and maximize the use of space. The filters, duplexers and other products involved in the module have completely independent intellectual property rights, and have applied for corresponding patents and integrated circuit layout designs.
Secondly, Zuolan has a perfect simulation and test design process. Through accurate simulation models and methods in the early design stage, the characteristics of the device can be quickly and accurately estimated, the research and development speed can be accelerated, the design error rate and the design modification cost can be reduced. The finished product passes comprehensive testing and reliability verification to ensure that the electrical properties and quality reliability of the product meet the customer's requirements.
In addition, Zuo Lan has a stable product yield. In the manufacturing process, Zuolan's existing module products use mature WLP SAW process, which can bring stable and reliable quality assurance; the matching circuit uses high-Q value SMD components, which can provide lower power RF characteristics and stability for the module than the integrated matching components in the substrate (high-frequency insertion loss can be increased by about 0.3dB); relying on the stable tape-out manufacturing and packaging and testing capabilities of domestic and foreign head foundries, the product front-channel tape-out baseline yield is more than 98%. The back-end package baseline yield is above 95%. In terms of module partners, the components such as RF switches in the module are provided by well-known domestic manufacturers, with mature and stable design and manufacturing capabilities, such as the yield of RF switches can generally reach more than 99%. Mature and stable manufacturing, packaging and testing and module close partners determine the high consistency and reliability of left blue module products.
Figure: SAW foundry tape-out yield
According to Jiwei Network, the above two latest DiFEM modules have been tested in a number of customer terminal projects and will soon achieve large-scale shipments. "This is the first two of the six module products planned by Zuolan, and the next step is planned in LFEM, PAMiD and other aspects, and it is planned to launch related products in the past two years." Bruce further said, "The mid- and high-frequency multiplexers are not even very good for Japanese manufacturers, so domestic manufacturers have not had much opportunity in the past two or three years in the mid- and high-frequency PAMiD modules." However, there are great opportunities for low-frequency PAMiD modules, and domestic supporting devices such as PA are more mature, so Zuolan's strategy is to first do the filters and duplexers required for low-frequency PAMiD modules, which is also the breakthrough point selected by Zuolan according to the current situation of the domestic industry. ”
Filter into domestic RF front-end modular constraints, how to go on the road to high-end?
With the popularity of 5G smartphones, the RF front-end solution of the flagship model mainly adopts the Phase7L and Phase 7LE architectures, and the diversity and main set are mainly modular products, and there are fewer discrete devices. The RF front-end solution in the low-end of 5G mainly adopts the Phase5N architecture, the receiving end is mainly a diversity module, and the transmitter is mainly a discrete filter and duplexer, and the miniaturization of the device is more and more widely used. Market research institute Yole predicts that the RF front-end module market size will reach $16.2 billion in 2025, accounting for about 69% of the total capacity of the RF front-end market, of which the market size of the diversity receiving module will reach $4.572 billion, with an average annual compound growth rate of 13%.
Mainland RF front-end chip manufacturers are still in their infancy, and the market discourse power is limited, but the demand for domestic chips after the Sino-US trade war continues to grow, and domestic supply chain manufacturers are expected to usher in major development opportunities. At the same time, in the RF front-end market controlled by international giants, modularization has become the home of future competition, and domestic PA, LNA, switches, antennas, etc. have developed more maturely, but filters, duplexers and multiplexers have become weaker shortcomings in localization capabilities.
"Looking at the domestic RF front-end market, under the trend that the global market has become integrated and modular, the domestic market is still dominated by discrete devices, and the homogenization of various market segments is serious, and most of them compete for the market in the middle and low end, and they urgently need to upgrade." In particular, the domestic advanced filter technology and technology, modularization capabilities are generally not strong. Bruce pointed out that "some RF front-end markets have even moved from 'domestic substitution' to 'replacing domestic production', but it is not enough to rely on low-cost substitution, and it must be able to provide products comparable to the performance level of foreign products to truly win from market competition." Starting from low-end products, moving towards the high-end in the 5G window period, becoming the development path for domestic manufacturers to break through, and is also the choice of Zuo Lan. ”
For the current RF front-end module design, the challenges of domestic manufacturers are mainly reflected in the design and manufacturing aspects. In terms of design, it is necessary to improve the performance of VARIOUS devices such as PA, LNA, switches, filters, etc., and strive to reach the level of similar products of foreign manufacturers, especially high-quality filters, while achieving high reliability and consistency mass production capabilities, at the same time, in the module design also needs strong system design capabilities, so as to achieve the organic integration of various functional modules; in terms of manufacturing, the international mainstream RF front-end manufacturers are IDM enterprises, and domestic manufacturers are mainly livingss, It is naturally disadvantaged in terms of improving product performance through manufacturing processes.
"The gap between the domestic RF front end is that there is a serious shortage of design talents, backward research on basic materials and acoustic theory; piezoelectric materials such as lithium tantalate and lithium niobate, and weak industrial chain foundations for filter manufacturing materials such as wafer-level ceramic substrates; poor manufacturing process control and production management levels, resulting in low product yields and poor product batch consistency." Bruce emphasizes, "On the road to modularization, the realization of pin-to-pin catch-up is the first step, and opening up the supply chain and realizing the project volume of the client is a prerequisite for survival." The second step is to directly communicate with the upstream and downstream of the industrial chain such as RF front-end manufacturers and mobile phone originals to achieve the definition of modules, so as to gradually catch up on some products. ”
Looking to the future, Zuo Lan plans to divide into three different stages:
In the short term, through the diversification and serialization of products, the company's comprehensive market competitiveness is enhanced, and the control of the company's core technology is formed in terms of product quality and customer base. Continue to deepen the technology and technology of the series of products, and actively expand the product range of diversity modules.
In order to maximize the optimal design results of RF filters, foreign leading enterprises mostly use IDM mode to maximize the ability of device design, material preparation, wafer and substrate manufacturing, packaging and reliability testing to improve product performance. Zuo Lan will also move in this direction in the future, at present, due to the lack of mature sealing and testing foundries in China, the company has invested tens of millions of yuan in the construction of the houdao sealing and testing production line. The front road is deeply bound with the foundry in the form of long-term contracts, and the future does not rule out the establishment of its own front road production line, which can better adapt to the characteristics of future module customization.
It is expected that in the future, domestic 5G will evolve from sub-6GHz to millimeter wave, which will cause major changes in the RF front-end market, and the demand for filters for RF front-end modules is expected to shift to integrated technology. For example, saw or BAW filters may be used at the edges, and the large middle bandwidth parts may be integrated with LTCC or IPD technology. Millimeter Wave 5G antennas are smaller than they are now and will be integrated directly into modules, making high frequencies and large bandwidths more challenging for RF front-end modules. In this trend, the entire RF front-end market will usher in a huge change, all technologies will be innovated to another level, is expected to usher in a transformation within a few years, so it is necessary to do a good job of forward-looking layout now.
epilogue
"With the acceleration of the modularization process, it is believed that within three or five years, the head of the enterprise will be integrated horizontally, and there are already domestic leaders in progress." Zuo Lan has always maintained an open and cooperative attitude, which will integrate the advantages of all parties in the industrial chain, and does not rule out strong alliances through mergers and acquisitions. Bruce said.
It is believed that in the future, the scope of 5G applications will not be limited to the field of smart phones, and the popularity of the Internet of Things, automotive electronics, telemedicine and other fields will promote the rapid growth of RF front-end demand. Domestic RF front-end manufacturers will also enter a new stage of growth under this big change and usher in new development opportunities.