Development Status of High Speed Ball Pull for Pb-Free BGA Characterization

Current methods for characterizing the integrity of BGA solder ball attachment include both ball shear and ball pull. These are currently limited to slow speeds, 5 mm/second for pull and 0.6 mm/second for shear. The results from these tests are of limited use in predicting brittle failures that are sometimes seen early in product lifetime. This paper will discuss the status of our work on implementing the highspeed ball pull test that should be of much greater utility in highlighting brittle failure modes. A JEDEC standard, JESD 22-B115, has recently been published that governs solder ball pull test methods. In this paper, the software and hardware set-up for high speed ball pull will be described and its limitations and operating window will be discussed. The various failure modes for high speed pull will be illustrated along with set-up issues that can impact the failure mode. The response variables for this test include peak force and fracture energy. Force-distance plots will also be shown and correlated test hardware / set-up issues. Finally issues associated with using this test as a process monitor will be discussed.