As electronic components continue to shrink and packaging densities increase, printed circuit boards (PCBs) have evolved into more complex, multi-layered structures. The dimensions of traces, vias, and pads have significantly decreased, making the manufacturing process more intricate. A key challenge arises from the mismatch in thermal expansion coefficients between the copper conductors and the dielectric materials used in PCBs. For instance, the Z-axis coefficient of thermal expansion for FR4-based laminates is approximately 50×10â»â¶/°C, while that of copper plating in vias is around (15–17)×10â»â¶/°C. These differences become critical during high-temperature soldering or prolonged operation under power, where repeated temperature fluctuations can cause mechanical stress on the board’s internal structure. This stress increases the likelihood of interconnection failures, such as breakage of annular rings or separation of conductive layers, ultimately affecting the long-term reliability of the PCB.
To evaluate this reliability, temperature shock testing is commonly employed. This test method involves rapidly exposing a sample to two or more extreme temperature environments, either in liquid or gaseous form. The primary goal is to simulate real-world thermal stress conditions and identify potential defects caused by material expansion discrepancies. Among these tests, the temperature impact test chamber is widely used in the electronics industry. Most chambers use a gaseous medium due to its simplicity and historical prevalence in reliability assessments for both electronic components and PCBs. This approach aligns with both international and domestic standards, making it a reliable and established practice for ensuring product durability and performance.
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