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Reliability testing of lead-free solder joints mainly includes thermal load test (temperature impact or temperature cycling test) of electronic assembly products; mechanical stress test of electronic device joints according to fatigue life test conditions; life evaluation using model. At present, the well-known model has low cycle fatigue Cofin-Manson model, which generally considers the shadow of average temperature and frequency. The modified Coffin-Manson model is used at the time of sound, and the Coffin-Manson model is used when considering the temperature characteristics and creep relationship of materials.
The reliability testing methods of lead-free solder joints include appearance inspection, X-ray inspection, metallographic section analysis, strength (tensile, shear), fatigue life, high temperature and humidity, drop test, random vibration, etc.
The appearance of lead-free and lead-free solder joints is different. At the same time, virtual soldering increases in lead-free spherical solder joints, so the detection requirements of equipment are improved.
In the reliability test of lead-free solder joints, it is more important to conduct temperature-related fatigue test for different thermal expansion coefficients of solder joints and connecting components. It includes isothermal mechanical fatigue test, thermal fatigue test and corrosion resistance test. According to the test results, it can be confirmed that different lead-free materials have different mechanical stress resistance at the same temperature. At the same time, some studies show that different lead-free materials show different failure mechanisms and different failure modes.
For manufacturers, reliability is a relatively high-level consideration, but the manufacturing process is still the most basic, there is no reliability without manufacturing process. Therefore, the improvement of material and process is the key to solve the reliability and failure defects of lead-free soldering.
