Adhesion Evaluation
A destructive mechanical test measures the strength of the bond between a spherical solder contact and the substrate pad of a semiconductor package. This solder ball shear testing is conducted by applying a lateral force with a specialized tool to push the ball off the pad. The resulting maximum force and the mode of failure provide a measure of the reliability of the assembly.
Tool Alignment
The accuracy of the test depends on the height of the shear tool above the substrate. If the tool is positioned too high, it may cause bending rather than a pure shear failure.
Failure Categorization
Analysis of the fractured surface after the test reveals whether the failure occurred within the solder or at the intermetallic layer. Ductile failures within the solder are generally preferred because they indicate a strong intermetallic bond. Brittle interface failures often point to contamination or incorrect temperature profiles during the reflow process.
Quality Control
Manufacturing lines run this test regularly to monitor the quality of the ball grid array attachment process. Since thermal stress and humidity can degrade the solder joints over time, testing is often performed before and after environmental stress testing. This continuous monitoring helps prevent early field failures of microelectronic packages by identifying assembly weaknesses early in the cycle.
