5G communication technology, with its characteristics of high speed, low latency, and large connectivity, has become a key driving force for social development. The core of 5G communication equipment - , the quality of its processing technology directly determines the performance and reliability of 5G communication. Advanced processing technology is the cornerstone for achieving efficient operation of 5G communication.
1, Special requirements for pcb boards in 5G communication
High frequency and high-speed performance
The high-frequency band of 5G communication (such as millimeter wave band) requires pcb boards to have excellent high-frequency characteristics. This means that pcb board materials need to have low dielectric constant and low dielectric loss factor to reduce signal attenuation and distortion during transmission. At the same time, the design of the circuit should meet the requirements of high-speed signal transmission, such as strictly controlling impedance matching to ensure that signals can be transmitted quickly and accurately on the pcb board, avoiding signal reflection and interference.
In order to meet the design trend of miniaturization and lightweighting of 5G base stations and terminal devices, pcb boards need to achieve higher integration. This requires more functional modules and complex circuits to be arranged in a limited space, which puts higher demands on the number of layers, wiring density, and via design of the pcb board. For example, adopting a multi-layer board structure, increasing the number of inner circuit layers to accommodate more circuit connections, while reducing via size to improve wiring space utilization.
5G communication devices typically require long-term stable operation in various complex environments, so pcb boards must have high reliability. During the processing, it is necessary to ensure that the connection of the circuit is firm and stable, and to prevent problems such as open circuits and short circuits. At the same time, there are strict requirements for the anti vibration, anti impact, moisture-proof, anti-corrosion and other performance of pcb boards to adapt to different working environments.
2, Key processing steps
Substrate selection: High performance substrates with low dielectric constant and low dielectric loss factor values, such as polytetrafluoroethylene and its modified materials, high-speed glass fiber reinforced epoxy resin, are preferred for 5G communication pcb boards. These materials can effectively reduce signal transmission losses and meet the requirements of high-frequency and high-speed communication.
Copper foil treatment: High quality electrolytic copper foil or rolled copper foil is used to ensure that the purity and surface roughness of the copper foil meet the requirements. Before processing, the copper foil is pre treated, such as roughening, to enhance the adhesion between the copper foil and the substrate, ensuring that the copper foil is not easily peeled off during subsequent processing and use.
Multi layer board lamination: 5G communication pcb boards are mostly multi-layer structures, and lamination processes are crucial. Stack the inner circuit board, semi cured sheet, and outer copper foil neatly according to the design requirements and place them in the laminating machine. Under high temperature and high pressure conditions, the semi cured sheet melts and flows, filling the gaps between the inner layers of the circuit and tightly bonding the layers together. During the compression process, it is necessary to accurately control the temperature, pressure, and time to ensure good interlayer bonding of the multi-layer board, without defects such as bubbles and delamination.
Micro hole and blind hole processing: In order to achieve high-density wiring and high integration, 5G communication pcb boards often use micro hole and blind hole technology. Micro holes usually refer to vias with a pore size of less than 0.3mm, while blind holes are vias that only connect to a portion of the circuit layer. Using laser drilling technology to process micro and blind holes can achieve high-precision and high-efficiency drilling operations. Laser drilling can accurately control the position and diameter of holes without damaging the surrounding circuits and substrates, meeting the processing requirements of 5G pcb boards for small through holes.
Surface treatment: The surface treatment processes for 5G communication pcb boards mainly include chemical nickel plating, organic solderability protective film, silver immersion, etc. Chemical nickel plated fittings have good conductivity, solderability, and oxidation resistance, which can improve the electrical performance and reliability of pcb boards, and are suitable for 5G communication equipment with high surface quality requirements. OSP technology has the advantages of low cost and simple process, which can form a protective film on the surface of the pcb board to prevent copper oxidation and ensure welding performance. The silver immersion process has a uniform and smooth coating, good solderability, and has also been applied in the processing of 5G pcb boards.
3, Quality Control and Testing
Impedance testing: Use a professional impedance tester to conduct impedance testing on key circuits on the pcb board to ensure that the circuit impedance meets the design requirements. By analyzing the test data, timely detection and correction of impedance anomalies can be made to ensure the stability of signal transmission.
Signal integrity testing: Using high-speed oscilloscopes and other equipment, perform signal integrity testing on high-frequency signals on pcb boards. Detect the transmission delay, rising/falling time, eye diagram and other parameters of the signal, evaluate the transmission quality of the signal on the pcb board, and determine whether there are problems such as signal distortion and reflection.
Insulation resistance test: Measure the insulation resistance between different circuits on the pcb board and between the circuit and the substrate to ensure good insulation performance and prevent electrical faults such as leakage.
Appearance inspection: Inspect the appearance of the pcb board through manual visual inspection or automated optical inspection equipment. Check the circuit for defects such as short circuits, open circuits, uneven etching, copper foil scratches, as well as whether the surface treatment is uniform and whether there are any issues such as missed plating.
X-ray testing: using X-ray testing equipment to detect the internal circuit connections, via quality, and interlayer bonding of multi-layer boards. X-rays can penetrate pcb boards, clearly display internal structures, and help inspectors detect internal defects that cannot be observed by the naked eye, such as incomplete vias, interlayer bubbles, etc.
Dimension measurement: Use high-precision measuring instruments to measure the external dimensions, circuit width, via hole diameter, etc. of the pcb board to ensure that the machining dimensions meet the requirements of the design drawings.