A printed circuit board testing method and apparatus

Abstract

The embodiment of the present application relates to the technical field of PCB manufacturing, and particularly relates to a printed circuit board testing method and device, the present application obtains a workpiece to be tested, and performs pre-baking treatment on the workpiece to be tested; places the workpiece to be tested in a reflow soldering device; performs real-time RST testing on the workpiece to be tested in a preset first reflow environment, and then performs real-time RST testing on the workpiece to be tested in a preset second reflow environment; repeatedly performs step S3 to perform RST testing according to a preset number of tests, and obtains a test result. The present application can dynamically monitor the performance change of the printed circuit board online, discover potential defects in time, realize real-time reliability monitoring of the printed circuit board, greatly improve the testing efficiency, and reduce the production delay by including pre-baking treatment, placing in a reflow soldering device, and performing real-time RST testing in a preset reflow environment and repeatedly performing.

Description

Technical Field

[0001] This invention relates to the field of PCB manufacturing technology, specifically to a printed circuit board testing method and apparatus. Background Technology

[0002] In the manufacturing and quality assessment of printed circuit boards (PCBs), thermal shock testing, as a core reliability test to evaluate the ability of materials and structures to withstand extreme temperature alternation, is crucial for ensuring the long-term operational stability of products. With the rapid evolution of artificial intelligence technology, high-performance electronic devices such as AI computing cards and AI servers are generally under high-intensity, uninterrupted computing loads. Their core component, the printed circuit board (PCB), must maintain the integrity of electrical connections and mechanical structures under complex temperature cycling conditions. Therefore, not only is rigorous verification of sample reliability necessary during the R&D phase, but continuous and effective reliability monitoring is also required during mass production to prevent batch quality risks and meet the market's urgent demand for highly reliable products.

[0003] However, current industry-wide monitoring methods primarily rely on sampling inspection and offline testing. This involves randomly selecting a small number of samples from the production line and sending them to a laboratory for thermal shock testing, then inferring the quality of the entire batch based on the limited sample results. This approach has significant drawbacks: the low sampling rate makes it impossible to comprehensively capture the actual reliability status of all products during mass production; the testing cycle is lengthy and costly; and it's difficult to achieve real-time or near-real-time quality feedback during the production process. Consequently, potential process fluctuations or material defects are often delayed in being exposed, making timely intervention and correction impossible. Especially with the accelerated mass production of AI hardware products, traditional post-production sampling mechanisms are no longer sufficient to meet the requirements of efficiency, comprehensiveness, and online operation for end-to-end reliability monitoring, severely hindering the improvement of product consistency and quality assurance capabilities. There is an urgent need to develop a thermal shock testing solution that can seamlessly integrate into the mass production cycle, support real-time dynamic monitoring, and operate efficiently. Summary of the Invention

[0004] In view of the above problems, embodiments of the present invention provide a printed circuit board testing method and apparatus to solve the problems that existing testing schemes cannot adapt to mass production pace and cannot achieve comprehensive monitoring and efficient and reliable thermal shock testing and monitoring.

[0005] According to one aspect of the present invention, a method for testing printed circuit boards is provided, the method comprising: S1, Obtain the workpiece to be tested and pre-bake the workpiece to be tested; S2, Place the workpiece to be tested in the reflow soldering equipment; S3, perform real-time RST test on the workpiece under test in a preset first reflow environment, and then perform real-time RST test on the workpiece under test in a preset second reflow environment. S4. Repeat step S3 to perform RST test according to the preset number of test times to obtain the test results.

[0006] In some optional embodiments, in step S1, the workpiece to be tested is pre-baked, specifically including: The workpiece to be tested is placed in a baking equipment and baked at a baking temperature of 120±20℃ for at least 60 minutes to pre-bake the workpiece.

[0007] In some optional embodiments, in step S3, the workpiece to be tested is subjected to a real-time RST test in a preset first reflow environment, specifically including: S31, perform the first heating process at the first heating rate to raise the temperature of the reflow soldering equipment from the initial temperature to the first preset value; S32, perform a second heating process at a second heating rate to raise the temperature of the reflow soldering equipment from the first preset value to the second preset value.

[0008] In some alternative embodiments, in step S31, after the temperature of the reflow soldering equipment reaches a first preset value, the temperature of the reflow soldering equipment is maintained at the first preset value for a first set time.

[0009] In some alternative embodiments, in step S32, after the reflow soldering equipment temperature reaches the second preset value, the reflow soldering equipment temperature is maintained at the second preset value for a second set time period.

[0010] In some optional embodiments, in step S31, the first heating rate is 0.85±0.1℃ / s; the second heating rate is 0.39±0.05℃ / s; the first preset value is 210℃-230℃; the second preset value is 255℃-260℃; the first set time is 50 seconds-70 seconds; and the second set time is 30 seconds-50 seconds.

[0011] In some optional embodiments, in step S3, the workpiece to be tested is subjected to real-time RST testing in a preset second reflow environment, specifically including: S33, the temperature of the reflow soldering equipment is reduced from the second preset value to the third preset value at the first cooling rate, and step S4 is executed when the temperature of the reflow soldering equipment reaches the third preset value.

[0012] In some optional embodiments, in step S33, the first cooling rate is 0.95±0.05℃ / s; the third preset value is 40±3℃.

[0013] In some alternative implementations, in step S3, the resistance change rate of the workpiece under test is monitored and acquired in real time during the RST test, and the test is terminated when the resistance change rate exceeds 5%.

[0014] According to one aspect of the present invention, a printed circuit board testing apparatus is provided, the apparatus being used to perform the above-described printed circuit board testing method to manufacture a printed circuit board.

[0015] The printed circuit board (PCB) testing method and apparatus of the present invention have the following advantages: The present invention acquires the workpiece to be tested and pre-baks it; places the workpiece to be tested in a reflow soldering equipment; performs a real-time RST test on the workpiece to be tested in a preset first reflow environment, and then performs a real-time RST test on the workpiece to be tested in a preset second reflow environment; repeats step S3 to perform the RST test according to a preset number of tests to obtain the test results. The present invention, by including pre-baking treatment, placement in a reflow soldering equipment, and real-time RST testing in a preset reflow environment and repeated execution, can dynamically monitor the performance changes of the PCB online, promptly detect potential defects, achieve real-time reliability monitoring of the PCB, and greatly improve testing efficiency and reduce production delays.

[0016] The above description is merely an overview of the technical solutions of the embodiments of the present invention. In order to better understand the technical means of the embodiments of the present invention and to implement them in accordance with the contents of the specification, and to make the above and other objects, features and advantages of the embodiments of the present invention more apparent and understandable, specific embodiments of the present invention are described below. Attached Figure Description

[0017] The accompanying drawings are for illustrative purposes only and are not intended to limit the invention. Furthermore, the same reference numerals denote the same parts throughout the drawings. In the drawings: Figure 1 A schematic flowchart of the printed circuit board testing method according to Embodiment 1 of the present invention is shown; Figure 2 A first flowchart of step S3 of embodiment 2 provided by the present invention is shown; Figure 3 The diagram shows a second process flow diagram of step S3 in Embodiment 2 provided by the present invention. Detailed Implementation

[0018] Exemplary embodiments of the invention will now be described in more detail with reference to the accompanying drawings. While exemplary embodiments of the invention are shown in the drawings, it should be understood that the invention can be implemented in various forms and should not be limited to the embodiments set forth herein.

[0019] Example 1: Figure 1 This paper illustrates a first embodiment of the printed circuit board testing method of the present invention, which addresses the problems of existing testing schemes being unable to adapt to mass production schedules and failing to achieve comprehensive, efficient, and reliable thermal shock testing and monitoring. The method includes: S1, Obtain the workpiece to be tested and perform pre-baking treatment on the workpiece to be tested; S2, Place the workpiece to be tested into the reflow soldering equipment; S3, perform real-time RST test on the workpiece under test in a preset first reflow environment, and then perform real-time RST test on the workpiece under test in a preset second reflow environment. S4. Repeat step S3 to perform RST test according to the preset number of test times to obtain the test results.

[0020] In steps S1-S4, the printed circuit board, commonly referred to as a PCB, is a substrate in electronic products used to support electronic components and achieve electrical connections between them. It consists of insulating materials and conductive patterns and is a core component of electronic devices. In this method, the workpiece under test specifically refers to the printed circuit board requiring reliability testing. This workpiece can be a finished product, a semi-finished product, or a sample from the R&D stage. Pre-baking treatment refers to the process of heating the printed circuit board before reflow soldering or RST testing. This treatment aims to remove moisture from the inside or surface of the printed circuit board, thereby preventing defects such as board bursting and delamination that may occur during subsequent high-temperature processing, ensuring the accuracy of the test and the integrity of the workpiece. Reflow soldering equipment is an industrial production device whose main function is to melt and cool the solder paste to solidify by controlling the temperature profile, thereby fixing surface mount components onto the printed circuit board. This equipment can simulate the thermal environment of the actual soldering process, providing the necessary temperature conditions for RST testing. RST testing, or reflow shock testing, is a reliability testing method specifically used to evaluate the thermal shock that a printed circuit board experiences during simulated reflow soldering. This test, through rapid temperature cycling, evaluates the performance and durability of printed circuit board (PCB) solder joints, materials, and overall structure under thermal stress. The first reflow environment refers to the temperature profile and time parameters set for the first high-temperature reflow process during the RST test. This environment simulates typical reflow soldering conditions experienced by PCBs in actual production. The second reflow environment refers to the temperature profile and time parameters set for the second high-temperature reflow process during the RST test. This environment typically differs from the first reflow environment and aims to simulate complex or harsh real-world application scenarios to comprehensively evaluate the reliability of the PCB.

[0021] This embodiment provides a printed circuit board testing method, characterized by the following steps: First, step S1 is executed to acquire the workpiece to be tested and pre-baking it. There are various ways to acquire the workpiece; for example, it can be manually selected by an operator from the production line or accurately grasped by an automated robotic arm system. After acquiring the workpiece, it needs to be pre-baked. This process can be achieved by placing the workpiece in a constant temperature oven. For example, the oven temperature can be set to 100℃ and baked continuously for 60 minutes, or set to 150℃ and baked for 30 minutes, to ensure the removal of internal moisture from the workpiece.

[0022] Next, step S2 is performed, placing the workpiece to be tested into the reflow soldering equipment. This placement process can be done manually, positioning the workpiece on the conveyor belt or test area of ​​the equipment. Alternatively, an automated conveying system or robotic arm can be used to automatically transport the workpiece from the pretreatment area and place it at the designated position in the reflow soldering equipment.

[0023] Next, step S3 is executed, performing a real-time RST test on the workpiece under test in a preset first reflow environment, and then performing a real-time RST test on the workpiece under test in a preset second reflow environment. In the first reflow environment, a preset temperature profile can be set; for example, the equipment temperature is raised from the initial temperature to 220°C at a preset heating rate, held at that peak temperature for 40 seconds, and then cooled. In the second reflow environment, another temperature profile can be set; for example, the equipment temperature is raised to 240°C at a different heating rate, held at that peak temperature for 20 seconds, and then cooled. Throughout the entire testing process, real-time RST testing of the workpiece is required. This means that during temperature cycling, important parameters such as the electrical continuity or resistance of the workpiece under test are continuously monitored to promptly detect and record any abnormal changes.

[0024] Finally, step S4 is executed, repeating step S3 for the RST test according to the preset number of tests to obtain the test results. The preset number of tests can be set according to actual needs, for example, 10, 20, or 50 cycles. After completing one test cycle of S3, the system will restart the S3 test process after the workpiece under test has cooled to the predetermined temperature, until the preset number of tests is reached. After all cycles are completed, the test results will be obtained, which may include the electrical performance data of the workpiece after each cycle, or record the specific cycle number when the workpiece failed.

[0025] Compared to the sampling inspection and offline testing modes commonly used in existing technologies, this method achieves online or near-online monitoring of printed circuit board (PCB) reliability by performing real-time RST testing in reflow soldering equipment. For example, in the example above, by performing real-time RST testing on the PCB in step S3 and continuously monitoring its electrical performance, any abnormalities can be detected immediately. This "real-time" characteristic solves the problems of delayed test results and inability to detect process fluctuations or material defects in traditional methods, thereby providing timely feedback to the production line and improving the efficiency of quality control.

[0026] Furthermore, this method enhances the comprehensiveness and rigor of the test by introducing a pre-set first reflow environment and a second reflow environment for alternating testing. In the example, the two different reflow environments simulate the complex and variable thermal shock conditions that printed circuit boards may experience in real-world applications. This multi-environment testing strategy allows printed circuit boards to be evaluated under conditions closer to actual operating conditions, thereby accurately reflecting their long-term reliability under high-performance, high-intensity operating environments, which is difficult to achieve with a single thermal shock test.

[0027] Furthermore, by repeatedly performing the RST test according to a preset number of test cycles in step S4, this method achieves aging assessment of the printed circuit board. Through multiple cycles of thermal shock, defects in the printed circuit board, such as solder joint fatigue or material delamination, can be exposed in a shorter time. This accelerated testing mechanism shortens the testing cycle, reduces testing costs, and provides lifetime prediction data, thus better meeting the demands of large-scale mass production for efficient and reliable monitoring.

[0028] In summary, the printed circuit board testing method of this embodiment provides an efficient, comprehensive, and mass production-adaptable reliability assessment solution by combining real-time monitoring, multi-environment simulation, and repetitive cyclic testing. This solution can promptly identify and correct potential quality problems, prevent batch quality risks, and thus improve the quality assurance level of printed circuit boards.

[0029] Example 2: Based on Embodiment 1, the present invention provides a second embodiment of the printed circuit board testing method to further describe steps S1-S4 in Embodiment 1.

[0030] In some optional embodiments, in step S1, the workpiece to be tested is pre-baked, which specifically includes: placing the workpiece to be tested in a baking device and baking it at a baking temperature of 120±20℃ for at least 60 minutes to pre-bake the workpiece to be tested.

[0031] In this embodiment of the invention, the baking equipment is a specialized device for heating printed circuit board (PCB) workpieces to be tested. Its main function is to provide a stable and controllable heating environment to promote the evaporation of moisture inside the workpiece. This equipment typically has a temperature control system and a timing system, capable of precisely setting and maintaining the baking temperature and time. One implementation method is to use a forced convection oven, which circulates hot air through a fan to ensure uniform temperature inside the oven, thereby ensuring uniform heating of the workpiece and improving moisture removal efficiency. Another implementation method is to use a vacuum oven, baking in a vacuum environment, which can lower the boiling point of moisture and accelerate moisture evaporation, especially suitable for temperature-sensitive workpieces or those requiring more thorough drying. The baking temperature of 120±20℃ refers to the temperature range that the baking equipment should maintain during the pre-baking process, i.e., between 100℃ and 140℃. This temperature range is chosen to effectively evaporate any moisture that may be absorbed inside the PCB workpiece while avoiding excessively high temperatures that could cause thermal damage or performance degradation to the workpiece material. In practice, the temperature controller of the baking equipment can be set to precisely control the internal temperature of the oven at 120℃, allowing for fluctuations of ±20℃ to accommodate the characteristics of different batches of workpieces or the equipment's own precision. Alternatively, the baking temperature can be set to 100℃ or 140℃ based on the specific material properties and moisture absorption of the workpiece to optimize baking efficiency and workpiece protection while ensuring effective moisture removal. Baking for at least 60 minutes means the pre-baking process should last no less than 60 minutes. This time parameter is set to ensure that at the set baking temperature, the moisture inside the workpiece has sufficient time to evaporate and escape, achieving thorough drying. In practical applications, the baking time can be set to 60 minutes based on the size, thickness, material type, and moisture absorption of the workpiece to meet basic drying requirements. Alternatively, to ensure a more thorough drying effect, especially for highly hygroscopic or large workpieces, the baking time can be extended to 90 minutes or longer to further reduce the internal humidity of the workpiece.

[0032] The solution proposed in this application involves first acquiring the workpiece to be tested and pre-baking it in the printed circuit board (PCB) testing method. This pre-baking process, performed before placing the workpiece in the reflow soldering equipment for real-time RST testing, plays a crucial role. Specifically, by placing the workpiece in the baking equipment and baking it at a temperature of 120±20℃ for at least 60 minutes, it is ensured that the moisture absorbed inside the workpiece is effectively and fully evaporated and removed. This controlled moisture removal process avoids physical damage such as delamination and board bursting that may occur during the subsequent high-temperature reflow soldering test (step S3) due to the rapid expansion of moisture inside the workpiece. Such damage not only compromises the structural integrity of the workpiece but, more importantly, introduces additional stress or defects, thereby interfering with the accuracy of the RST test results and preventing the monitoring of the resistance change rate from truly reflecting the performance of the PCB under thermal stress. Therefore, by precisely controlling the pre-baking temperature and time, this solution provides a dry and stable testing foundation for subsequent RST testing, ensuring the reliability and validity of the test data and making the performance evaluation of the PCB more accurate.

[0033] The following is a specific example illustrating the printed circuit board (PCB) testing method. First, the workpiece to be tested is acquired. In step S1, during pre-baking, the workpiece can be placed in a forced convection oven. The oven's temperature controller is set to maintain the internal temperature at 120°C, allowing fluctuations between 100°C and 140°C. The baking timer is set to at least 60 minutes, for example, 75 minutes. During this baking process, hot air within the oven circulates through a fan, ensuring uniform heating of all surfaces of the workpiece, thereby promoting the full evaporation of absorbed moisture. After pre-baking, the workpiece is removed and cooled to room temperature, then proceeds to step S2, where it is placed in a reflow soldering apparatus for subsequent RST testing.

[0034] The above technical solution involves a precisely controlled pre-baking process for the printed circuit board (PCB) workpiece before testing. This pre-baking effectively removes absorbed moisture from the workpiece, significantly reducing the risk of physical damage such as delamination and board bursting caused by thermal expansion of moisture during subsequent reflow soldering tests. This not only protects the integrity of the workpiece but, more importantly, ensures that the RST test is conducted under moisture-free conditions, thereby improving the accuracy and reliability of the test results and making the performance evaluation of the PCB under thermal stress more realistic and effective.

[0035] In some alternative implementations, in step S3, see Figure 2 The workpiece under test is subjected to real-time RST testing in a preset first reflow environment, specifically including: S31, perform the first heating process at the first heating rate to raise the temperature of the reflow soldering equipment from the initial temperature to the first preset value; S32, perform a second heating process at a second heating rate to raise the temperature of the reflow soldering equipment from the first preset value to the second preset value.

[0036] In steps S31-S32, the first heating process refers to the process of gradually increasing the temperature of the reflow soldering equipment from a lower starting point to a certain intermediate target temperature. Its purpose is to fully preheat the workpiece, ensuring a uniform temperature rise throughout the workpiece to reduce thermal shock and provide suitable conditions for subsequent solder activation. The first heating rate refers to the rate at which the temperature of the reflow soldering equipment changes over time during the first heating process. This rate setting directly affects the uniformity of workpiece heating and the activation effect of the solder. For example, it can be controlled by adjusting the heating power or conveyor belt speed of the reflow soldering equipment, or by precisely adjusting the output of the heating element through a PID controller to ensure that the temperature curve rises according to a preset slope. The initial temperature refers to the ambient temperature or internal temperature of the reflow soldering equipment when the first heating process begins, typically room temperature or slightly above room temperature. The first preset value refers to the target temperature to be achieved in the first heating process. This temperature is usually a preheating temperature below the solder melting point, designed to fully preheat the workpiece while preventing premature solder melting. For example, it can be set to a specific temperature range below the solder melting point, or determined according to the specific preheating requirements of the solder. The second heating process refers to the process of raising the equipment temperature from the first preset value to a higher target temperature after the first heating process. Its purpose is to ensure the solder reaches the temperature required for complete melting and the formation of a good solder joint, making it a crucial stage in reflow soldering. The second heating rate refers to the rate at which the reflow soldering equipment temperature changes over time during the second heating process. This rate setting is critical to the quality of the solder joint formation; too fast a rate may lead to thermal shock, while too slow a rate may result in low production efficiency or solder oxidation. For example, it can be controlled by adjusting the heating zone power or conveyor belt speed of the reflow soldering equipment, or by using a multi-zone reflow oven where each heating zone has its temperature and airflow independently controlled to achieve a precise heating profile. The second preset value refers to the final target temperature to be achieved in the second heating process, typically the peak reflow temperature of the solder, ensuring that the solder fully melts and wets the solder pads. For example, it can be set to the peak reflow temperature of the solder, or an optimal temperature can be determined based on the heat resistance of the workpiece and the characteristics of the solder.

[0037] This application's solution constructs a preset first reflow environment by precisely controlling the heating process of the reflow soldering equipment. This simulates the thermal stress during actual reflow soldering in the RST test of printed circuit boards and accurately assesses the reliability of the workpiece under test. Specifically, firstly, the reflow soldering equipment starts from an initial temperature and performs a first heating rate until a first preset value is reached. The main purpose of this stage is to fully preheat the workpiece, ensuring a uniform temperature rise throughout the workpiece, reducing thermal shock, and providing suitable conditions for solder activation. Subsequently, the equipment continues with a second heating rate, raising the temperature from the first preset value to a second preset value. This stage is crucial for solder melting and solder joint formation. By controlling the second heating rate and the final second preset value, it ensures that the solder fully melts and wets the pads while avoiding damage to the workpiece from excessively high temperatures. This segmented, rate-controlled heating strategy allows the workpiece under test to undergo a controlled thermal cycle that simulates a real production environment during the RST test, thereby more accurately exposing potential defects under thermal stress and improving the reliability and validity of the test results. By precisely controlling the heating rate and target temperature, this solution effectively solves the problem of inconsistent test results caused by coarse temperature curve control in traditional RST testing, providing more refined and repeatable test conditions for reliability assessment of the workpiece under test.

[0038] The above technical solution refines the first reflow environment in RST testing into a segmented heating process. First, the equipment temperature is raised from the initial temperature to a first preset value at a first heating rate, and then raised from the first preset value to a second preset value at a second heating rate. This refined temperature profile control allows the workpiece under test to undergo more precise and controllable thermal stress cycling during RST testing. This not only more realistically simulates the thermal shock and heat accumulation effects during actual reflow soldering but also helps to expose potential defects caused by improper temperature change rate or peak temperature control, such as solder joint fatigue, delamination, or cracking. Therefore, this solution significantly improves the accuracy and reliability of RST testing, making the reliability assessment of printed circuit boards more comprehensive and effective. This allows for earlier detection and resolution of potential problems in product design or manufacturing processes, thereby improving product quality.

[0039] In one optional embodiment of the above scheme, in step S31, after the temperature of the reflow soldering equipment reaches the first preset value, the temperature of the reflow soldering equipment is maintained at the first preset value for a first set time.

[0040] In this embodiment, after the reflow soldering equipment temperature rises from the initial temperature to a first preset value, the temperature is maintained at the first preset value for a first set time period. This ensures that the workpiece under test can fully absorb heat and achieve a uniform temperature distribution before entering the next stage of heating. Specifically, after acquiring the workpiece under test and performing a pre-baking treatment, it is placed in the reflow soldering equipment. Subsequently, during the real-time RST test of the workpiece under test in a preset first reflow environment, a first heating process is performed at a first heating rate to raise the reflow soldering equipment temperature from the initial temperature to the first preset value. Once the reflow soldering equipment temperature reaches the first preset value, the system starts timing and, within a preset first set time period, maintains the reflow soldering equipment temperature stably at the first preset value through a precise temperature control mechanism. This temperature holding stage is crucial for the workpiece under test, allowing sufficient time for various parts of the workpiece to reach thermal equilibrium, eliminating temperature gradients that may be caused by excessively rapid heating, and ensuring the overall temperature uniformity of the workpiece. In this way, a stable thermal foundation can be laid for the subsequent process of raising the temperature of the reflow soldering equipment from the first preset value to the second preset value at the second heating rate, thereby avoiding local overheating or underheating caused by uneven temperature, and significantly improving the accuracy and reliability of RST testing.

[0041] In one optional embodiment of the above scheme, in step S32, after the temperature of the reflow soldering equipment reaches the second preset value, the temperature of the reflow soldering equipment is maintained at the second preset value for a second set time.

[0042] In this embodiment, through steps S31 and S32, the workpiece under test is gradually heated to a second preset value, simulating the heating phase of the reflow soldering process. However, simply reaching the second preset value is insufficient to fully simulate the dwell time of the component at the peak temperature during actual soldering, which is crucial for solder joint formation and material stress accumulation. This application further proposes that after the reflow soldering equipment temperature reaches the second preset value, a precise temperature control system maintains the reflow soldering equipment temperature at the second preset value for a second set time. This process ensures that the workpiece under test undergoes a controlled and sufficiently long heat exposure time at the peak temperature. This continuous peak temperature exposure allows the materials inside the workpiece under test, especially the solder joints and substrate, to fully absorb heat energy and undergo cycles of thermal expansion and contraction at this temperature, thereby more effectively simulating the thermal stress accumulation that may occur during actual reflow soldering. By maintaining the temperature at the second preset value, potential defects such as solder joint fatigue, delamination, or microcracks can be induced more accurately, thereby improving the accuracy and reliability of the RST test and enabling the test results to more realistically reflect the performance and lifespan of the printed circuit board in actual use.

[0043] By maintaining the reflow soldering equipment temperature at the second preset value for a second set time after it reaches that value, the testing method of this application can more realistically simulate the peak temperature dwell time experienced by printed circuit boards during actual reflow soldering. This controlled and continuous peak temperature exposure allows the workpiece under test to fully accumulate thermal stress, thereby more effectively inducing potential material fatigue, solder joint defects, or delamination problems. Compared to testing methods that only reach the peak temperature and then begin cooling, this approach significantly improves the rigor and accuracy of the RST test, enabling the test results to more reliably predict the long-term reliability and failure modes of printed circuit boards in practical applications, thus providing more accurate data support for product design and process optimization.

[0044] In one optional embodiment of the above scheme, in step S31, the first heating rate is 0.85±0.1℃ / s; the second heating rate is 0.39±0.05℃ / s; the first preset value is 210℃-230℃; the second preset value is 255℃-260℃; the first set time is 50 seconds-70 seconds; and the second set time is 30 seconds-50 seconds.

[0045] In this embodiment, in step S31, a first heating process is performed at a first heating rate to raise the temperature of the reflow soldering equipment from an initial temperature to a first preset value, and this temperature is maintained for a first set time. Subsequently, in step S32, a second heating process is performed at a second heating rate to raise the temperature of the reflow soldering equipment from the first preset value to a second preset value, and this temperature is maintained for a second set time. By precisely defining the first heating rate, the second heating rate, the first preset value, the second preset value, the first set time, and the second set time, the solution of this application can ensure that the workpiece under test experiences a highly standardized and repeatable temperature profile during the RST test. Specifically, the precisely defined heating rate ensures the smoothness and uniformity of the temperature rise, avoids unnecessary instantaneous thermal shock to the workpiece under test, and ensures the full reaction of the solder at different stages. The preset temperature range and the corresponding holding time ensure the full activation of the flux and the complete melting and wetting of the solder, thereby applying consistent and controllable thermal stress to the printed circuit board in each test. This refined temperature profile control makes the RST test results more comparable and accurate, and can more reliably reflect the actual reliability level of printed circuit boards.

[0046] In one specific implementation, when performing RST testing on a printed circuit board, a first heating rate can be set to 0.85°C / s to raise the reflow soldering equipment temperature from an initial temperature (e.g., room temperature) to a first preset value of 220°C. After reaching 220°C, the reflow soldering equipment maintains the temperature at 220°C for a first set time of 60 seconds. Subsequently, a second heating rate of 0.39°C / s is performed to raise the reflow soldering equipment temperature from 220°C to a second preset value of 258°C. After reaching 258°C, the reflow soldering equipment maintains the temperature at 258°C for a second set time of 40 seconds. The entire process is precisely executed by the reflow soldering equipment's control system to ensure that the workpiece under test is tested according to the predetermined thermal profile.

[0047] The above technical solution precisely and optimally defines key thermal parameters in the RST testing process, including heating rate, preset temperature value, and temperature holding time. This significantly improves the standardization and repeatability of the RST testing process, ensuring a high degree of consistency in the thermal stress conditions experienced by the workpiece under test in each test. Therefore, the obtained test results are more accurate and reliable, effectively eliminating errors caused by fluctuations in test conditions. This allows for a more precise assessment of the long-term reliability and potential defects of printed circuit boards, providing a solid data foundation for product quality control and process optimization.

[0048] In some alternative implementations, in step S3, see Figure 3 The workpiece under test is subjected to real-time RST testing in a preset second reflow environment, specifically including: S33, the temperature of the reflow soldering equipment is reduced from the second preset value to the third preset value at the first cooling rate, and step S4 is executed when the temperature of the reflow soldering equipment reaches the third preset value.

[0049] In step S33, the first cooling rate refers to the rate at which the temperature of the reflow soldering equipment decreases. Setting this rate is crucial for controlling the cooling profile of the workpiece under test, affecting solder joint formation and stress release. Different cooling rates can be achieved through natural cooling, forced air cooling, or water cooling. Forced air cooling can control the cooling rate by adjusting the fan speed or airflow; water cooling can be controlled by adjusting the coolant flow rate or temperature. The temperature of the reflow soldering equipment decreasing from the second preset value to the third preset value describes the starting and target points of the cooling process. The second preset value is the peak temperature reached during the previous heating phase, while the third preset value is a lower temperature set in the test procedure, typically close to room temperature or a safe operating temperature. For example, the third preset value can be set to 40°C to ensure that the workpiece under test is in a stable state when entering the next test cycle or being removed. Step S4 is executed when the reflow soldering equipment temperature reaches the third preset value, clarifying the termination conditions of the cooling process and subsequent operations. This means that step S4 of the RST test will only be triggered when the device temperature drops to a preset lower temperature, thus ensuring the stability and consistency of the test environment and avoiding unnecessary repeated testing under high temperature conditions or the next round of heating before sufficient cooling, which would affect the accuracy of the test.

[0050] The solution in this application introduces a controlled cooling step S33 after the printed circuit board completes the high-temperature reflow test. Specifically, the reflow oven temperature is actively reduced from a second preset value (peak temperature) to a third preset value at a first cooling rate. This controlled cooling process ensures that the workpiece under test undergoes a complete and accurate thermal cycle simulating actual soldering conditions. By specifying the first cooling rate, the thermal stress experienced by the workpiece under test during cooling can be effectively managed, thereby avoiding potential damage or inaccurate test results that may result from uncontrolled or excessively rapid cooling. Furthermore, the condition setting of "execute step S4 when the reflow oven temperature reaches the third preset value" establishes a clear test phase transition point. This ensures that subsequent RST test re-execution (step S4) only begins when the workpiece under test has cooled to a stable, lower temperature. This effectively prevents test result deviations that may be caused by heat accumulation in multiple test cycles and ensures that each subsequent test cycle starts from a consistent temperature baseline, thereby significantly improving the reliability and comparability of the overall RST test results. This controlled cooling and explicit process transition mechanism greatly improves the consistency and accuracy of the multi-cycle RST testing process.

[0051] Through the above technical solution, after the printed circuit board completes the high-temperature reflow test, the reflow soldering equipment temperature can be reduced from the peak temperature (second preset value) to a stable third preset value at a controlled first cooling rate. This explicit cooling process avoids uncertain natural cooling of the workpiece under test at high temperatures, effectively controls the cooling curve of the workpiece under test, and reduces stress that may be caused by sudden temperature changes or uneven cooling, thereby improving the accuracy and repeatability of RST test results. Simultaneously, setting the subsequent repeated test steps only after the reflow soldering equipment temperature reaches the third preset value ensures that each test cycle starts from a stable, lower temperature baseline, greatly improving the reliability and consistency of multi-round RST tests and optimizing the efficiency and safety of the entire testing process.

[0052] In some optional embodiments, in step S33, the first cooling rate is 0.95±0.05℃ / s; the third preset value is 40±3℃.

[0053] In this embodiment, the solution of this application achieves standardized and refined management of the cooling process during testing by precisely setting the first cooling rate to 0.95±0.05℃ / s and specifying the third preset value as 40±3℃ during step S33. After the workpiece under test completes the high-temperature reflow treatment, the reflow soldering equipment cools down at a controlled rate of 0.95±0.05℃ / s. This specific cooling rate effectively balances testing efficiency and thermal stress control of the workpiece under test, avoiding both excessively slow cooling leading to a lengthy testing cycle and excessively rapid cooling potentially causing damage to the internal structure of the workpiece or distortion of test results. The cooling process continues until the temperature of the reflow soldering equipment stabilizes at the third preset value of 40±3℃. Once this temperature is reached, the workpiece under test is considered to have been sufficiently cooled and is in a stable state, thus providing a reliable starting condition for subsequent testing, such as repeating step S4 or ending the test. This precise temperature control and cooling rate setting ensures high consistency and repeatability in each RST test cycle, thereby significantly improving the accuracy and reliability of the entire testing method and providing a more solid data foundation for the quality assessment of printed circuit boards.

[0054] In one specific implementation method of printed circuit board testing, when the reflow soldering equipment temperature begins to drop from a second preset value (e.g., 255°C), its control system activates the cooling module, for example, by starting multiple cooling fans or adjusting the cooling gas flow rate. The system is programmed to reduce the equipment temperature at a rate of 0.95°C / s and monitors temperature changes in real time to ensure the actual cooling rate remains between 0.90°C / s and 1.00°C / s. For example, if the equipment temperature is 200°C, the system will continue cooling until the temperature drops to 40°C. Once the temperature sensor detects that the equipment temperature has reached the range of 37°C to 43°C, which meets the third preset value, the cooling process stops or enters a maintenance mode, triggering a signal to execute the subsequent step S4. This precise parameter setting and control makes the cooling process highly controllable and repeatable, ensuring the standardization of the testing environment.

[0055] Through the above technical solution, in step S33 of the printed circuit board (PCB) testing method, the first cooling rate is precisely set to 0.95±0.05℃ / s, and the third preset value is clearly defined as 40±3℃. This enables precise control of the cooling process of the PCB after the RST test. This not only effectively solves the problem of prolonged test cycles or reduced reliability of test results caused by improper cooling parameters, but also ensures that the workpiece under test reaches a stable and repeatable temperature state at the end of each test cycle. This standardized cooling process significantly improves the accuracy and reliability of the RST test, makes the test results more comparable, optimizes the overall test efficiency, and provides a more solid data foundation for the quality assessment of PCBs.

[0056] In some alternative implementations, in step S3, the resistance change rate of the workpiece under test is monitored and acquired in real time during the RST test, and the test is terminated when the resistance change rate exceeds 5%.

[0057] In this embodiment, real-time monitoring of the resistance change rate of the workpiece under test refers to continuously measuring and recording the resistance value of the workpiece during the RST test, and calculating the change in resistance based on this real-time data. The resistance change rate is an important indicator for measuring the electrical performance stability of the workpiece under test; a sudden or significant change usually indicates damage or failure of the internal structure. Real-time monitoring can be achieved in various ways. For example, a high-precision resistance measurement module can be connected to key test points of the workpiece under test. This module can collect resistance data at a preset sampling frequency and transmit the data to the control system for processing. Alternatively, a dedicated sensor array integrated in the reflow soldering equipment can be used to directly sense the resistance state of the workpiece under test and convert analog signals into digital signals for real-time transmission and analysis. When the resistance change rate exceeds 5%, "exiting the test" means setting a warning threshold. Once the resistance change rate of the workpiece under test reaches or exceeds this threshold, the current RST test process is immediately terminated. Here, "exiting the test" means stopping the heating control of the reflow soldering equipment and possibly initiating a rapid cooling program, while simultaneously stopping data acquisition and the test cycle. The 5% threshold is an empirical value, generally considered a significant indicator of electrical failure in printed circuit boards (PCBs) during RST testing. This threshold can be adjusted based on different PCB types, material properties, and testing standards. By setting this threshold and implementing an exit mechanism, meaningless subsequent testing of failed PCBs can be avoided, thereby protecting the PCBs, saving testing resources, and improving testing efficiency.

[0058] The solution in this application introduces intelligent control of the testing process during RST testing in step S3 of the printed circuit board testing method. Specifically, during real-time RST testing of the workpiece under test in a preset first reflow environment and a preset second reflow environment, the system continuously and uninterruptedly monitors and acquires the resistance change rate of the workpiece under test. This means that the electrical integrity of the workpiece under test is always monitored throughout the entire heating, holding, and cooling cycle. Once the resistance change rate of the workpiece under test is detected to exceed a preset 5% threshold, this usually indicates that the solder joints or connection structure inside the workpiece under test has failed, such as the appearance of microcracks or fractures, resulting in a significant change in its electrical performance. At this time, the testing system will respond immediately and execute the test exit operation, that is, interrupt the current test cycle, stop heating, and possibly start cooling, thereby avoiding unnecessary subsequent testing of the already failed workpiece under test. This mechanism, combined with traditional fixed cycle number or fixed time testing methods, makes the entire testing process more efficient and intelligent. It can detect failures in a timely manner, avoiding the waste of resources on invalid testing after a failure occurs, thus significantly improving the relevance of testing and resource utilization.

[0059] In one specific implementation, during RST testing of a printed circuit board, high-precision resistance sensors can be pre-connected to key test points (e.g., representative pads or interconnects) of the workpiece under test. These sensors are connected via wires to a data acquisition module that integrates an analog-to-digital converter (ADC) and a microcontroller. At the beginning of step S3, the microcontroller records the initial resistance value of the workpiece under test as a reference. Subsequently, throughout the RST test in both the first and second reflow environments, the microcontroller continuously reads the current resistance value from the resistance sensors at a frequency of once per second. After each read, the microcontroller calculates the rate of change of the current resistance value relative to the initial resistance value. For example, if the initial resistance is 100 milliohms and the current resistance becomes 106 milliohms, the rate of change is 6%. The microcontroller compares this calculated rate of change with a preset 5% threshold. Once the rate of change exceeds 5%, the microcontroller immediately sends a stop heating command to the heating control unit of the reflow soldering equipment and simultaneously triggers an alarm signal indicating that the test has been terminated due to failure. In addition, the test data recording system marks the time point of this failure event and the corresponding temperature profile for subsequent analysis.

[0060] Through the above technical solution, real-time intelligent judgment of the test status can be achieved during the RST test of printed circuit boards. When the resistance change rate of the workpiece under test exceeds a preset threshold, the test can be terminated in time, avoiding meaningless test cycles when the workpiece under test has failed. This significantly improves test efficiency, saves test time and energy consumption, and effectively prevents further damage to failed workpieces. At the same time, since the test is interrupted at the first moment of failure, it helps to more accurately locate the failure point and analyze the failure mode, providing more timely and accurate feedback information for the design and manufacturing process improvement of printed circuit boards, thereby improving the overall reliability assessment level of printed circuit boards.

[0061] Example 3: Based on Embodiment 1 or Embodiment 2, this embodiment of the invention provides a printed circuit board testing device, which is used to perform the above-described printed circuit board testing method to manufacture printed circuit boards.

[0062] In this embodiment, by configuring the testing device to perform real-time RST testing, online reliability assessment of printed circuit boards is achieved. Specifically, the device includes a reflow soldering unit for temperature control of the pre-set reflow environment of the workpiece under test and for real-time monitoring of parameters such as resistance change rate during the test. Since traditional methods rely on low-ratio sampling and offline laboratory testing, resulting in long testing cycles and inability to provide timely feedback on process fluctuations, this device, by integrating a reflow soldering unit with real-time monitoring, can directly perform pre-baking treatment, multi-stage reflow environment testing, and repeated cycle testing on the workpiece in the production environment. During the test, the reflow soldering unit first pre-baks the workpiece to remove internal moisture, then performs real-time RST testing alternately in a pre-set first and second reflow environment, repeating the test according to a pre-set number of times, while continuously monitoring whether the resistance change rate exceeds a threshold. Based on the above technical solution, this device can accelerate the exposure of potential defects such as solder joint fatigue and material delamination, providing near real-time quality data feedback, thereby effectively avoiding the batch quality risks caused by testing delays in traditional methods. Through the aforementioned technical means, this device significantly improves the efficiency of reliability monitoring of printed circuit boards used in high-performance electronic devices such as AI computing cards and AI servers, meets the requirements of full-process, high-coverage quality assurance in the mass production stage, and ensures the electrical connection and mechanical structure integrity of the product under complex temperature cycling conditions.

[0063] Numerous specific details are set forth in the specification provided herein. However, it will be understood that embodiments of the invention may be practiced without these specific details. Similarly, for the sake of brevity and to aid in understanding one or more aspects of the invention, in the description of exemplary embodiments of the invention above, various features of the embodiments are sometimes grouped together in a single embodiment, figure, or description thereof. The claims, which follow the detailed description, are hereby expressly incorporated into that detailed description, wherein each claim itself is a separate embodiment of the invention.

[0064] Those skilled in the art will understand that the modules in the device of the embodiment can be adaptively changed and placed in one or more devices different from that embodiment. Modules, units, or components in the embodiment can be combined into a single module, unit, or component, and further, they can be divided into multiple sub-modules, sub-units, or sub-components, except that at least some of such features and / or processes or units are mutually exclusive.

[0065] It should be noted that the above embodiments are illustrative of the invention and not restrictive, and that those skilled in the art can devise alternative embodiments without departing from the scope of the appended claims. In the claims, any reference signs placed between parentheses should not be construed as limiting the claims. The word "comprising" does not exclude the presence of elements or steps not listed in the claims. The word "a" or "an" preceding an element does not exclude the presence of a plurality of such elements. The invention can be implemented by means of hardware comprising several different elements and by means of a suitably programmed computer. In the unit claims enumerating several systems, several of these systems may be embodied by the same item of hardware. The use of the words first, second, and third, etc., does not indicate any order. These words can be interpreted as names. The steps in the above embodiments, unless otherwise specified, should not be construed as limiting the order of execution.

Claims

1. A method for testing printed circuit boards, characterized in that, The method includes: S1, Obtain the workpiece to be tested and pre-bake the workpiece to be tested; S2, Place the workpiece to be tested in the reflow soldering equipment; S3, perform real-time RST test on the workpiece under test in a preset first reflow environment, and then perform real-time RST test on the workpiece under test in a preset second reflow environment. S4. Repeat step S3 to perform RST test according to the preset number of test times to obtain the test results.

2. The printed circuit board testing method according to claim 1, characterized in that, In step S1, the workpiece to be tested undergoes a pre-baking process, specifically including: The workpiece to be tested is placed in a baking equipment and baked at a baking temperature of 120±20℃ for at least 60 minutes to pre-bake the workpiece.

3. The printed circuit board testing method according to claim 1, characterized in that, In step S3, a real-time RST test is performed on the workpiece under test in a preset first reflow environment, specifically including: S31, perform the first heating process at the first heating rate to raise the temperature of the reflow soldering equipment from the initial temperature to the first preset value; S32, perform a second heating process at a second heating rate to raise the temperature of the reflow soldering equipment from the first preset value to the second preset value.

4. The printed circuit board testing method according to claim 3, characterized in that, In step S31, after the temperature of the reflow soldering equipment reaches the first preset value, the temperature of the reflow soldering equipment is maintained at the first preset value for a first set time.

5. The printed circuit board testing method according to claim 4, characterized in that, In step S32, after the temperature of the reflow soldering equipment reaches the second preset value, the temperature of the reflow soldering equipment is maintained at the second preset value for a second set time.

6. The printed circuit board testing method according to claim 5, characterized in that, In step S31, the first heating rate is 0.85±0.1℃ / s; the second heating rate is 0.39±0.05℃ / s; the first preset value is 210℃-230℃; the second preset value is 255℃-260℃; the first set time is 50 seconds-70 seconds; and the second set time is 30 seconds-50 seconds.

7. The printed circuit board testing method according to claim 5, characterized in that, In step S3, a real-time RST test is performed on the workpiece under test in a preset second reflow environment, specifically including: S33, the temperature of the reflow soldering equipment is reduced from the second preset value to the third preset value at the first cooling rate, and step S4 is executed when the temperature of the reflow soldering equipment reaches the third preset value.

8. The printed circuit board testing method according to claim 7, characterized in that, In step S33, the first cooling rate is 0.95±0.05℃ / s; the third preset value is 40±3℃.

9. The printed circuit board testing method according to claim 1, characterized in that, In step S3, the resistance change rate of the workpiece under test is monitored and obtained in real time during the RST test. When the resistance change rate exceeds 5%, the test is terminated.

10. A printed circuit board testing device, characterized in that, The apparatus is used to perform the printed circuit board testing method according to any one of claims 1-9 to manufacture a printed circuit board.

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