Application advantages of self-locking tuning screws in communication filters and RF equipment
Self-locking tuning screw is a special precision fastener for cavity filter, duplexer, combiner and other RF communication devices. Compared with ordinary tuning screws and glue-dispensing locking screws, it has obvious advantages in frequency stability, passive intermodulation, assembly repair, mass production efficiency and other dimensions, and is the preferred scheme for improving the long-term reliability of RF devices for 5G base stations, private network communication and satellite communication.
First, anti-vibration and anti-looseness, effectively suppressing frequency drift. In the process of transportation, installation and long-term operation, communication equipment is continuously affected by fan vibration, road bumps and cyclic alternating stress at high and low temperatures. Ordinary tuning screws are located by the pre-tightening force of the thread, which is prone to slight rotation, and the depth of the screw extending into the resonant cavity changes, which directly causes the center frequency of the filter to shift, the insertion loss to deteriorate and the standing wave to exceed the standard. The self-locking tuning screw relies on the elastic self-locking structure of the thread to form a continuous and stable thread friction locking force, and no additional auxiliary locking parts are needed. After the reliability verification of vibration and temperature cycling, the position is not easy to shift after debugging, which ensures the long-term stability of the radio frequency index and greatly reduces the index repair rate of the equipment during field operation and maintenance.
Second, there is no need to dispense glue, avoiding many hidden dangers brought by glue. The traditional scheme uses a large number of thread glue to prevent loosening, and the glue is easy to age and overflow at high temperature. When the glue drops into the resonant cavity, it will pollute the cavity, change the electromagnetic field distribution and deteriorate the passive intermodulation index. At the same time, after the glue is cured, the thread is stuck, which makes it difficult to disassemble during later repair and re-tuning. Forced disassembly is easy to cause thread slipping and cavity scrapping. The self-locking structure does not need to be coated with glue, which eliminates the problems of glue pollution and aging from the root. The screws can be screwed in and out repeatedly, and the second debugging, maintenance and rework are convenient without damaging the threads in the cavity, which is very suitable for the scene of prototype debugging and after-sales maintenance.
Thirdly, the passive intermodulation performance is controllable, which is suitable for high-power RF scenes. Radio frequency communication devices have strict requirements on passive intermodulation index, and screw substrate, coating and thread matching state are all key factors. Self-locking tuning screws are generally made of high-conductivity base materials such as brass and beryllium copper, with uniform and dense coatings such as silver plating, gold plating and nickel plating, and the roughness of the machined surface is strictly controlled. The self-locking structure is stable, and the thread contact surface will not produce tiny gaps and non-linear points of ignition due to looseness, thus avoiding intermodulation interference and lifting. Compared with the dispensing scheme, there is no interference of the adhesive layer medium to the RF field, which can stably meet the PIM index requirements of base station filters and high-power RF devices.
Fourthly, debugging and mass production assembly are more efficient, which is convenient for automatic production. When using glue-dispensing screws, gluing, waiting for curing and retest after curing will take up a lot of man-hours. Inconsistent glue thickness will also bring about the dispersion of locking torque, which will increase the debugging difficulty. The self-locking tuning screw can be directly locked and positioned after debugging, with stable locking torque interval and good repeatability, which makes manual production line debugging more worry-free. It is also suitable for automatic production lines such as electric screwdrivers and automatic tuning equipment, which is easy to establish standardized debugging process, unify screwing depth and locking torque, reduce human differences of debugging personnel, improve the first-time yield of production line and shorten the production beat of single device.
Fifth, the structure is simple, does not occupy extra space in the cavity, and adapts to the miniaturization trend. At present, the communication filter continues to develop towards miniaturization and integration, and the internal space of the cavity is compact. The self-locking function is integrated on the screw thread body, and additional parts such as a spring washer, a stop washer, a locknut and the like are not needed, so that the number of parts is small, the assembly is simple, the limited space of a resonant cavity is not occupied additionally, and the radio frequency parasitic effect caused by redundant parts is reduced, which is beneficial to the lightweight and compact design of the device structure.
Sixth, batch consistency is good, quality traceability is convenient, and the difficulty of supply chain management and control is reduced. The regular self-locking tuning screw adopts precision turning and thread rolling technology, and strictly controls the total length, thread middle diameter, head groove type, top shape and coating thickness, and the dispersion of locking torque and self-locking force of the same batch of products is small. The unified part characteristics allow the debugging parameters of filter manufacturers to be solidified, and it is not necessary to re-explore the debugging curve for each batch; The products are accompanied by materials, coatings and reliability testing data, which meet the requirements of material traceability and supplier quality control system in communication industry.
Seventh, strong environmental adaptability and stable operation under wide temperature conditions. The base station and outdoor communication unit work in outdoor high, low and humid environment for a long time, and the common anti-loosening method is vulnerable to temperature change. The self-locking structure relies on the elastic cooperation of metal threads, and the attenuation of self-locking force is small under the temperature change, and it will not soften at high temperature and embrittle at low temperature like glue, so it is suitable for communication equipment in indoor computer rooms, outdoor base stations, vehicle communication and other scenarios.
On the whole, the core value of the self-locking tuning screw is to give consideration to * * accurate tuning and positioning, long-term locking stability, good RF performance, repairability and easy mass production * *, which can well solve the most troublesome pain points in the RF filter industry, such as frequency drift, intermodulation deterioration and difficult repair, and provide stable and reliable fastener solutions for RF equipment such as 5G, private network and satellite communication.
