High-temperature aging tests are essential for evaluating the reliability and stability of rigid PCB boards under extreme thermal conditions, ensuring that they can withstand the elevated temperatures encountered during operation or storage. These tests help to identify potential defects such as delamination, solder joint failures, and degradation of materials, which may occur over time due to thermal stress.

One common method is the constant high-temperature aging test. In this method, rigid PCB boards are placed in a temperature-controlled chamber set to a specific high temperature, typically ranging from 100°C to 200°C, depending on the application requirements. The duration of the test can vary from several hours to several weeks, with common test periods being 24 hours, 100 hours, or 1000 hours. During the test, the PCBs are monitored for changes in electrical parameters such as resistance, capacitance, and insulation resistance. After the test, visual inspections are carried out to check for signs of delamination, discoloration, or cracking of the substrate and solder masks. This method is effective in simulating long-term exposure to high temperatures, such as in automotive engine compartments or industrial ovens.

Another method is the temperature cycling test, which involves subjecting the rigid PCBs to alternating high and low temperatures. The temperature cycle typically ranges from -55°C to 125°C, with each cycle consisting of a heating phase, a high-temperature dwell time, a cooling phase, and a low-temperature dwell time. The number of cycles can be as high as several thousand, depending on the reliability requirements. This test is designed to simulate the thermal expansion and contraction that occurs in PCBs during operation, which can cause stress on solder joints, vias, and component leads. By repeating these cycles, potential failures such as solder joint fatigue, via cracking, and component detachment can be detected. Electrical testing is performed after a certain number of cycles to assess any changes in performance, and visual inspections are done to check for physical damage.

The high-temperature storage test is also widely used. In this test, rigid PCBs are stored at a constant high temperature (usually between 85°C and 150°C) for an extended period without being powered on. This test evaluates the stability of the materials used in the PCB, such as the substrate, copper traces, and solder mask, under prolonged exposure to high temperatures. After storage, the PCBs are tested for electrical performance and physical integrity. This method is particularly useful for assessing the long-term reliability of PCBs in applications where they may be stored in hot environments before use, such as in military equipment or outdoor electronics.

In all these test methods, it is important to control factors such as temperature uniformity within the test chamber, humidity (if applicable), and the rate of temperature change to ensure accurate and reproducible results. The test parameters are often specified according to international standards such as IPC-TM-650, which provides guidelines for PCB testing procedures.