How does the material of self-locking tuning screw affect the mechanical reliability of 5G filter?
The material of self-locking tuning screw directly determines the structural stability and parameter consistency of 5G filter under vibration, temperature cycle, long-term service and other working conditions through the four core mechanical characteristics of hardness, toughness, fatigue resistance and thermal expansion matching, which is the key factor to ensure mechanical reliability. The following is a specific impact analysis:
1. Hardness and abrasion resistance: it determines the durability and anti-loosening effect of the thread structure.
The anti-loosening function of self-locking tuning screw depends on the pre-tightening force between threads or structural deformation (such as triangular teeth and elastic segments), and the hardness of material directly affects the anti-wear and anti-slip ability of threads.
High hardness material (quenched beryllium copper, 316 stainless steel)
After quenching, the hardness of beryllium copper can reach 35–45hrc, and the thread strength is high, so it is not easy to deform plastically when tightening. During repeated debugging (production calibration, operation and maintenance re-adjustment), the thread profile will not collapse and wear, which can maintain the pre-tightening force of the self-locking structure for a long time and resist the risk of loosening caused by the wind vibration of the base station and the vibration of equipment operation.
The hardness of 316 stainless steel is about 18–22 HRC. Although it is lower than that of quenched beryllium copper, its wear resistance is better than that of ordinary brass, and its corrosion resistance is strong. In outdoor high dust and humid environment, threads are not easy to get stuck or worn due to rust, which ensures the convenience of disassembly and assembly of tuning screws and structural integrity.
Low hardness material (ordinary brass, unquenched phosphor bronze)
The hardness of ordinary brass is only 8-12HRC, and the thread is soft. When the tightening torque is too large, it is easy to slip and deform the tooth shape, which leads to self-locking failure. Under long-term vibration, the thread contact surface will have a gap due to wear, which will lead to the drift of tuning parameters. It is only suitable for fixed scenes with low vibration and less debugging.
The hardness of unquenched phosphor bronze is about 10–15hr C, which has good toughness but average wear resistance. It needs to be matched with nickel plating to improve the surface hardness, otherwise thread loss will easily occur after long-term use.
2. Toughness and fatigue resistance: resisting structural failure under alternating stress.
When the 5G base station is deployed outdoors, the tuning screw is subjected to vibration alternating stress (such as wind shaking and equipment operation resonance) and temperature alternating stress (temperature difference between day and night, seasonal change) for a long time. The toughness and fatigue resistance of the material determine whether it will break or crack.
High toughness material (copper alloy series: beryllium copper, phosphor bronze)
Beryllium copper has high hardness and toughness, and excellent fatigue resistance. Under tens of thousands of alternating vibrations, metal fatigue cracks will not appear in the screw shaft and self-locking elastic section, and the pre-tightening force of elastic deformation and self-locking can be maintained continuously, so it is the first choice for high vibration scenes (such as wind power base stations and roadside base stations).
Phosphorus bronze has excellent toughness, and it is not easy to be brittle even under the stress of thermal expansion and cold contraction caused by temperature cycle, so it is suitable for extremely cold and high-heat areas with severe temperature difference.
Low toughness materials (martensitic stainless steel, carbon steel)
Some high-hardness stainless steels (such as 410 martensitic stainless steel) have high hardness but poor toughness, and are prone to brittle fracture under alternating stress, especially in low-temperature environment, which can not adapt to the complex working conditions of outdoor base stations. Carbon steel is easy to rust, and its fatigue resistance is much lower than that of copper alloy, so it is completely unsuitable for 5G filter scenarios.
3. Matching degree of thermal expansion coefficient: avoid structural stress and parameter drift under temperature cycle.
Aluminum alloy (CTE ≈ 23× 10/℃) is widely used in the cavity of 5G filter. The matching degree between the CTE of tuning screw material and the cavity determines whether structural stress will occur when the temperature changes, which in turn affects the mechanical stability and tuning accuracy.
CTE matching material (copper alloy: brass CTE ≈ 19× 10/℃, phosphor bronze CTE ≈ 17× 10/℃)
The CTE of copper alloy is close to that of aluminum alloy. When the temperature rises and falls, the expansion and contraction of the screw and the cavity are synchronized well, and internal stress will not be generated due to the expansion and contraction difference, thus avoiding the loosening of the screw and the deformation of the cavity, ensuring the stability of the tuning depth, and further maintaining the consistency of the center frequency of the filter.
CTE mismatch material (CTE of 304 stainless steel ≈ 17× 10/℃, CTE of titanium alloy ≈ 8.6× 10/℃)
The CTE of 304 stainless steel is slightly different from that of aluminum alloy, so slight stress will be generated during temperature cycling, and long-term accumulation may lead to the decrease of thread pre-tightening, so it is necessary to compensate the stress through elastic self-locking structure (such as deformation section), otherwise parameter drift will easily occur.
The CTE of titanium alloy is much lower than that of aluminum alloy, and there is a big difference in expansion and contraction when the temperature changes, which will produce significant structural stress, leading to screw loosening and even cavity damage. It is only used in special high-temperature customized scenes.
Fourth, corrosion resistance: to ensure the structural integrity of outdoor long-term service
The 5G base station faces harsh environments such as salt fog (coastal), humidity (rain forest) and dust (desert). The corrosion resistance of the material determines whether the screw will fail due to corrosion.
High corrosion resistance material (316 stainless steel, phosphor bronze, silver plated/nickel plated copper alloy)
316 stainless steel contains molybdenum, which has strong salt spray resistance and moisture resistance. It can be used in coastal areas for a long time without rusting, and the thread structure will not be stuck or its strength will not decrease due to rusting.
Phosphor bronze itself has excellent corrosion resistance, and after silver plating, it has both corrosion resistance and high conductivity, which is suitable for outdoor general scenes. Nickel-plated copper alloy coating is dense, which can isolate water vapor and air and prevent substrate oxidation.
Low corrosion resistance material (ordinary carbon steel, uncoated brass)
Ordinary carbon steel is easy to rust, and the corrosion products will lead to the thread being stuck, so it is impossible to disassemble and debug, and the corrosion will reduce the strength of the screw and cause the risk of fracture.
Uncoated brass is easy to produce patina in wet environment, which will fill the thread gap, destroy the pre-tightening force of self-locking structure, and at the same time lead to the increase of contact resistance, which will affect the RF performance.
Summary: Adaptability of different materials to mechanical reliability of 5G filter.
Material type, mechanical reliability, core advantages, limitations of adaptation scenarios.
Quenched beryllium copper has high hardness, high toughness, excellent fatigue resistance, and high vibration and high frequency debugging scenes have high cost.
316 stainless steel has strong corrosion resistance, stable thread strength and low conductivity in coastal and high humidity outdoor scenes, so it needs to be matched with low loss design.
Phosphor bronze (silver plated) has good toughness, high CTE matching and good corrosion resistance. The general outdoor scene with severe temperature difference has average wear resistance and needs to be strengthened by plating.
Ordinary brass has low cost, good machinability, low hardness, easy wear and corrosion resistance in indoor and low vibration fixed scenes.
