The test method described in this part of IEC 62137 applies to surface mount components with a thin and wide basal plane, such as QFP and BGA. This test method evaluates the endurance of the solder joints between component leads and lands on a substrate by cyclic bending of substrate.This test also evaluates the effects of repeated mechanical stress, such as key pushing in cell phones, the strength of the solder joint between component terminals and lands on a substrate.In this test method, the evaluation requires first to mount the surface mount component on the substrate by reflow soldering, then cyclically bend the substrate to a certain degree of depth