With the rapid development and large-scale deployment of 5G technology, 5G base station, as a key node of the whole network, its performance and reliability directly determine the coverage quality, transmission rate and stability of the network. In the complex architecture of the base station, the PCBA (Printed Circuit Board Assembly) is the key hardware unit that carries its high-performance RF, digital signal processing and power management functions. Compared to previous generations of communication equipment, 5G base station PCBAs have reached new heights of complexity, integration, and performance requirements. Therefore, it is crucial to develop and execute a rigorous and efficient PCBA test plan. High-standard PCBA processing lays a solid foundation for testing, while multi-level and all-round testing is necessary to ensure its final quality.
The design and manufacture of 5G base station PCBAs face many challenges, which are also directly reflected in the test requirements:
1、High Frequency and Wide Band: 5G uses higher frequency bands (including millimeter wave) and wider bandwidth, which requires that the radio frequency (RF) circuit design, layout and testing of PCBAs must be able to handle the loss, reflection and interference of high frequency signals, which puts forward a very high requirement on the frequency range and accuracy of test equipment. High requirements for the frequency range and accuracy of the test equipment.
2、Massive MIMO and beam fouling: Massive MIMO (Massive MIMO) technology means that the base station has a large number of antenna units, each unit contains a complex RF transceiver path and digital processing unit, PCBA needs to be highly integrated with these complex circuits, testing needs to verify the consistency of the many channels and the ability to work together.
3、Complex digital signal processing: 5G base stations need to deal with more complex modulation and demodulation, channel coding and beam fouling algorithms, which relies on high-performance ASIC, FPGA and other digital chips. Testing needs to verify the data processing capabilities of these chips and their peripheral circuits, high-speed interface signal integrity.
4、High power and heat: especially power amplifier (PA) PCBA, need to deal with high-power signals and generate a lot of heat. Test not only to verify the power output, but also to assess its performance stability at different temperatures and the effectiveness of thermal solutions.
5、The deployment of harsh environments: 5G base stations are usually deployed outdoors, need to withstand long-term high and low temperatures, humidity, salt spray, sand and other harsh environments, the reliability of the PCBA needs to be verified through rigorous environmental and accelerated life testing.
6、High reliability and availability: as a critical infrastructure, 5G base stations require extremely high stability and long trouble-free operation time. any potential defects in the PCBA may lead to network interruption, so the test must maximise the discovery and exclude the risk of early failure.
In order to meet the above challenges, the test programme for 5G base station PCBAs is usually comprehensive, covering multiple levels from manufacturing process to functional performance:
1、Manufacturing process testing: This is the initial barrier to ensure the quality of PCBA processing.
Solder Paste Inspection (SPI) and Automated Optical Inspection (AOI): Used to check whether there are positional deviations, missing parts, wrong polarity and other cosmetic defects in solder paste printing and component mounting, which is the first round of testing after PCBA processing.
In-circuit test (ICT): Through the probe contact PCBA test point, detect the open and short circuit of the circuit, the basic parameter value of the components. Although there are limitations for highly integrated boards with few test points, it is still an effective means to detect manufacturing defects.
X-ray inspection (X-ray): For BGA, QFN and other package forms of the chip, the solder joints are located under the chip, the naked eye or AOI can not be detected, X-ray inspection is to verify the quality of welding (such as voids, bridges) is an important method.
2、Function Test (FCT): This is the key link to verify the core function and performance of the PCBA.
Digital baseband function test: verify the baseband processing chip, memory, high-speed interface (such as CPRI/eCPRI) data processing, transmission and control functions. Required to simulate input signals and verify the correctness of output data.
Radio frequency (RF) front-end function test: This is the most complex part of the 5G base station PCBA test. It is necessary to use professional RF test instruments (such as vector signal source, spectrum analyzer, vector network analyzer, power meter) to test the power output, linearity (ACLR, EVM), efficiency of the amplifier, the noise figure and gain of the low-noise amplifier (LNA), as well as the performance indicators of the filter, mixer and other devices in a shielded environment, to ensure that the RF signal chain’s transmitting and receiving performance meets the standards.
Power Management and Power Consumption Test: Verify the output voltage, current, efficiency and ripple of the power supply module, as well as the overall power consumption of the PCBA in different operating conditions, to ensure that the requirements of energy saving and stable power supply are met.
Control interface and communication test: Verify that the communication interface and control signals between PCBA and the main control unit of the base station or other modules work properly.
3、Environment and reliability test: simulate the actual deployment environment, assess the long-term reliability of the PCBA.
High and low temperature cycling test: Cycling in the specified high and low temperature range to expose the material stress or welding defects caused by temperature changes.
Vibration testing: Simulates vibration during transport and installation to verify the robustness of the PCBA structure and the vibration resistance of the components.
Accelerated Life Testing (HALT) / Highly Accelerated Stress Screening (HASS): By applying temperature, vibration and other stresses far beyond the rated value, the potential weaknesses of the PCBA are quickly exposed, which is used for design improvement and production screening to improve product maturity.
No matter how advanced the test programme is and how sophisticated the test equipment is, if the processing quality of the PCBA itself is not up to scratch, the test results cannot truly reflect the reliability of the product. Poor soldering, component placement errors, board defects, pad contamination and other problems in the PCBA processing chain can directly lead to functional failure or potential early failure. These problems may be found in the functional test, but they may also become hidden dangers, affecting the long-term stability of the equipment in harsh environments.
Therefore, strict implementation of quality control during PCBA processing, from incoming inspection (IQC), production process control (IPQC) to shipping inspection (OQC), from material selection, process parameter setting to personnel operation specification, is to ensure that the PCBA can pass the subsequent rigorous testing of the premise. High-quality PCBA processing not only reduces the number of defects found during testing and improves the production through rate, but also ensures the high reliability of 5G base stations and reduces operation and maintenance costs.
The testing of 5G base station PCBAs is a complex and critical process that requires a combination of advanced manufacturing process testing, sophisticated digital and RF function verification, and harsh environmental reliability assessment. Only on the solid foundation of high-quality PCBA processing, supplemented by a comprehensive and effective test programme, can we ensure that 5G base station PCBAs meet the stringent technical requirements, and provide strong support for the construction of high-performance and highly reliable 5G networks!