Huatian Technology: RF front-end modularization promotes the transformation of filter packaging technology and helps domestic take-off

At the end of August, without warning, Huawei suddenly launched the "HUAWEI Mate 60 Pro Pioneer Program", and the unreleased flagship Mate 60 Pro was put on sale in a low-key manner, and then the discussion about the Kirin 9000s and whether it has 5G capabilities detonated global public opinion. In fact, since October 2020, when Huawei released the Mate 40, the last smartphone with full 5G capabilities, one of the key reasons for the stagnation of Huawei's smartphone business is the limited supply of domestic high-performance filters in 5G RF front-end modules. It can be said that behind the return of Huawei Mate 60 to "5G", there is a contribution from the unremitting efforts of domestic RF front-end chip manufacturers.

With the uncertainty of the global semiconductor market and supply chain changes brought about by the Sino-US trade dispute, domestic substitution, including filters and other chips, has become the general trend. As the last level in the field of RF front-end, the domestic filter industry has made great progress in recent years, but most of the domestic related manufacturers operate in fabless mode, which is relatively lagging behind the international IDM leader in terms of technology and scale, and the foundry and packaging and testing capabilities are still scarce resources, especially in the trend of miniaturization, integration and modularization of RF filters, which puts forward higher requirements for the packaging process.

In the face of the dilemma of a vast domestic market and a very low domestic production rate, it is urgent to break the foreign technical blockade and market barriers and accelerate the process of filter localization. As a leading RF device packaging and testing leader in China, Huatian Technology has been committed to providing a variety of solutions for filter packaging. 

The volume and price of the filter market are rising, and the prospect of domestic substitution is promising

Although the demand for the RF front-end industry has been sluggish since last year due to the impact of the epidemic and weak terminal demand, in the medium and long term, Yole expects the RF front-end market to reach $26.9 billion by 2028, and the new 5G technology specifications will continue to promote RF front-end technology innovation. The industry is investing in R&D and preparing for the next wave of growth.

With the increase of the frequency band in mobile phones, RF filters, as the largest market segment of RF front-end, are still expanding in the value of RF front-end. Professional organizations predict that the value of filters in RF devices will increase from 33% of 3G terminals to 57% of 4G LTE terminals, and the 5G era will further increase (especially bulk acoustic wave filters), and the value of filters for a single mobile phone will reach more than $10. IDC predicts that the global filter market size will reach $18.33 billion in 2024. Due to China's strong support for the development of 5G technology and its position as a major consumer of filters, the market share is expected to continue to increase, and the market size will reach $5.67 billion in 2024.

In the case of higher and higher requirements for mobile communication by end users, the performance of filters such as full screen and mobile phone thinning, high-frequency communication, and frequency resource congestion have put forward higher requirements for the performance of filters, and filters that adapt to high-frequency communication, good thermal stability, small size and high integration will be the main development direction in the future. Among them, due to the relative maturity of the industry, SAW and TC-SAW have certain cost advantages, SAW filters will still be the main products in the filter market in the short term, but in the era of 5G and higher frequency communications, BAW filters have the technical advantages of high frequency and wide frequency bands, and have better performance in high-frequency application scenarios such as base stations, mobile phones, and Internet of Things terminals, and will gradually become the mainstream of the market.

Therefore, in general, due to the limitations of process complexity, technology and cost, more low-end market RF front-ends under the current communication standard use SAW filters, and with the improvement of 5G penetration, the excellent performance and high-frequency support of BAW filters will make it the mainstream device of mobile phone RF front-end. IDC predicts that the market penetration of BAW filters is expected to reach 65% by 2024.

With the control of processes and patents, the monopoly pattern of several major international manufacturers in Japan and the United States has become a pattern. The main suppliers of SAW filters are Murata, TDK, Taiyo Yuden and other Japanese manufacturers, while BAW filters are Broadcom and Qorvo, which occupy more than 95% of the global share, and the demand for localization is urgent.

On the other hand, due to the strong coupling between the key links of the filter from design to manufacturing, packaging and testing, the industrialization of high-quality filters must rely on the IDM model to complete. Although some filter companies have grown in China in recent years, due to the limitation of production technology, the products are mainly concentrated in the low-end field, and the production line is less, the production capacity is limited, and most enterprises operate in the fabless mode, and they need better coordination and support from manufacturing and packaging and testing end enterprises.

Huatian Technology's BAW filter and SAW filter packaging technology began mass production in October 2018 and May 2021 respectively, which can provide a variety of lightweight, thin, short, highly reliable and high-performance packaging solutions for fabless design companies such as filters and duplexers.

RF front-end modularization promotes the evolution of filter packaging, and Huatian Technology helps the mass production of domestic devices

Under the trend of RF front-end integration, miniaturization, and modularization, the size of the filter is also shrinking and developing in the direction of miniaturization, and the most intuitive change is the evolution of packaging technology. Taking SAW as an example, its chip design and tape-out are relatively simple, and the design and tape-out costs are much cheaper than traditional IC chips, but it requires a long-term accumulation process. Since its cavity structure is formed at the packaging stage, the performance and reliability of the filter are more dependent on the packaging technology.

Huatian Technology pointed out that the miniaturization of filters generally goes through the following three ways: (1) optimizing the filter design and reducing the area of the chip itself; (2) by improving the packaging form of filter devices to greatly reduce the size of filters and multiplexers, the current filter packaging method has changed from the traditional metal packaging to the use of advanced new packaging technologies, such as wafer-level packaging (WLP), die-level acoustic meter packaging (DSSPTM), thin-film acoustic packaging technology (TFAPTM), (3) By encapsulating filters with different functions into modules, the area occupied by the PCB is reduced. Taking the SAW filter that has been developed for a long time as an example, after the packaging technology of the SAW filter has been updated and iterated for many times, the size of the discrete device has been reduced from the original 5.0x5.0mm2 to 1.1x0.9mm2, and the size has been significantly reduced.

After years of R&D layout, Huatian Technology officially mass-produced in May 2021, and the current packaging yield has exceeded 99.5%. Since the mass production of SAW/BAW filter packaging process, the daily production capacity is about 2KK, and the total shipment is nearly 600KK, which has provided high-quality packaging solutions for many filter manufacturers at home and abroad.

Huatian Technology takes the SAW filter as an example to introduce that the main process of packaging is to first plant gold balls on the UBM (Under Bump Metal) of the wafer, then through dicing, flip ultrasonic soldering to the packaging substrate, and then laminating to form cavities, then molding, and finally segmentation and testing, among which the core process is gold ball planting and lamination, because the characteristics of the cavity structure are closely related to the performance of the filter. Due to the different heights and spacing of the chips in the RF module, bubbles are prone to occur in the process of lamination, resulting in abnormal placement and bonding, and erosion of the filter interdigital transducer, resulting in low overall yield and high cost. However, the Golden Ball flip vacuum lamination cavity technology has the characteristics of simple process, low cost, high performance, miniaturization and high efficiency, and about 70% of SAW products use this packaging technology.

With the trend of RF front-end modularization, SAW, BAW filters, and dual/multiplexers are all evolving towards wafer-level packaging (WLP). In the module with a higher degree of integration, the filter is directly integrated in the form of a bare core, which further increases the requirements for the packaging process, and Huatian Technology is also preparing for the evolution of filter packaging technology. The company pointed out that wafer-level filter packaging needs to have capabilities such as RDL, as well as technical challenges such as addressing the heat dissipation and stress requirements of LT/LN materials, ensuring that wafer-level filters can withstand the molding pressure of SiP packages, and achieving reliable and low-cost wafer-level testing.

It is reported that Huatian Technology has the process capability of wafer-level filter packaging, and can design and package products according to customer needs at any time, cooperate with customers to achieve process optimization and production, and help domestic high-performance filters and RF front-end modules to achieve independent controllability as soon as possible. (Proofreading / Sammy)