In 2019, the construction of 5G base station grows vigorously all over the world, including China, the US, South Korea and the Middle East.
To meet the requirements of 5G network capacity, the traditional MIMO technology will be upgraded to MassiveMIMO, to help improve spectrum utilization rate and reduce interference. The number of antennas with 5GMassiveMIMO technology will increase geometrically to 64/128/256, which will drive the antenna needs of a single station. Antenna vibrator, as the core component of antenna, is mainly responsible for amplifying the signal and controlling the radiation direction of it, which can also make the electromagnetic signal received by the antenna stronger.
According to the antenna configuration, the antenna vibrator also includes a variety of configurations, such as rod-shaped, planar, etc. According to the processing technology, it varies mainly from sheet metal to PCB, plastic, etc. The traditional 4G antenna vibrator is mainly made of sheet metal, and assembled by manual work, which is inefficient. 5G plastic antenna vibrator, with high precision, low-weight and low-cost features, is expected to gradually become the mainstream of the market. And it can’t be possible without polyphenylene sulfide (PPS).
For general 5G base stations, the back-side material is die-cast aluminum alloy, the front side facing users is plastic radome, which usually consists of PP + GF modified materials. Inside the base station, it consists of antenna vibrator, connector, filter, transceiver module, and circuit board. The antenna vibrator material is 40% GF reinforced PPS. After injection molding, the insert is roughened by laser, and then electroless plated to form a circuit. The selective electroplating laser process is suitable for larger equipment, including macro station antennas.
Compared with metal, PPS is light-weighted and conducive to the integration of antenna and feeder. It adopts the injection molding process and then metallization, which has high production efficiency and low labor costs.
One possible manufacturing method includes the following steps:
§? To produce structure-predetermined vibrator thru injection molding;
§? To machine the vibrator surface and then clean it up via ultrasonic technique;
§? To treat the vibrator with electroless nickel plating process, which forms electroless nickel layer on the surface of it;
§? To separate the vibrator surface-treated layer into plated area and non-plated area with laser engraving technique;
§? To form a copper plating layer on the plated area of the vibrator with copper plating process;
§? To remove the nickel layer on the non-plated area of the vibrator with relative removing technique;
§? To form a tin plating layer on the copper plating layer and perform tin protection treatment;
Advantage of PPS plastic vibrator:
§? Lower cost than that of metal vibrator and even of PCB vibrator
§? Reduced antenna assembly test workload by 2/3
§? With 1/10 weight of metal vibrator, and also lower-weighted than PCB vibrator;
§? High integrated structure, such as the size of 1 x 6 vibrator is not more than 350*50*20mm;
§? High overall product yield;
§? Improved stability of plastic parts and low cost for the same RF performance because of PPS+40%GF material;
The PPS metallization process here is a bit similar to the traditional modified material LDS process, with a slight difference that no LDS additives are added to the modified plastic. After being activated by a special process, it is then electrolessly plated. This three-dimensional surface metallization process can realize three-dimensional circuits on mostly ordinary non-metal materials. It can realize mass production of a variety of plastic vibrators in the size range of 650 * 650 * 650mm (such as 1 × 6, 1 × 12, etc.). The production capacity can be quickly expanded.
In the mass production plan of 5G plastic antenna vibrators, plastic suppliers include: Celanese, DSM, SABIC, Tongyi, etc. It’s estimated that each base station can use 2KG PPS (including injection gate), which means that each million base station need about 2,000 tons, and the cost of materials needed is about 200 million Yuan. However, the added value of the material is not the highest. The output value of the antenna vibrator is at least five times that of the plastic material. The output value of the antenna vibrator of 1 million base stations is at least 1 billion Yuan.
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