The test method described in this part of IEC 62137 applies to area array packages, such as BGA. This test method is designed to evaluate the fatigue life of the solder joints between component leads and lands on a substrate as shown in Figure 1. A temperature cyclic approach is generally used to evaluate the reliability of solder joints. Another method is to mechanically cycle the solder joints to shorten the testing time rather than to produce the strains by changing temperatures. The methodology is the imposition of shear deformation on the solder joints by mechanical displacement instead of relative displacement generated by CTE (coefficient of thermal expansion) mismatch, as shown in Figure 2. In place of the temperature cycle test, the mechanical shear fatigue predicts the reliability of the solder joints under repeated temperature change conditions by mechanically cycling the solder joints. In this test method, the evaluation requires first to mount the surface mount component on the substrate by reflow soldering, then cyclic mechanical shear deformation is applied to the solder joints until fracture of the solder joints occurs. The properties of the solder joints (for example solder alloy, substrate, mounted device or design, etc.) are evaluated to assist in improving the strength of the solder joints. NOTE This test, however, does not measure the strength of the electronic components. The test method to evaluate the robustness of the joint to a board is described in IEC 60068-2-21.