What does 'thermal fatigue' refer to in solder joints?

Thermal fatigue in solder joints specifically refers to the degradation that occurs due to repeated thermal cycling. This phenomenon happens when solder joints are subjected to fluctuations in temperature, causing them to expand and contract. Over time, this repetitive movement can lead to the formation of cracks and eventual failure of the joint. The thermal cycling process places stress on the solder material, which it may not be able to withstand indefinitely, especially if the thermal cycles occur frequently or under significant temperature differences.

When solder joints undergo this stress, the microstructural integrity of the solder can weaken, culminating in potential joint failure. Understanding thermal fatigue is vital for ensuring reliable performance in electronic components, as it directly affects the durability and lifespan of the solder connections used in various applications.