A novel mechanical shock test method to evaluate lead-free BGA solder joint reliability

Portable electronic products such as cell phones are often subjected to drop tests to simulate consumer usage and to ensure required field reliability is met. Product-level drop tests can cause solder joint failures in both lead-free and tin-lead BGA packages due to the combination of highly localized strain created by high strain-rate mechanical shock. In order to understand this phenomenon at the package level, a 4-point dynamic bend test was developed to produce repeatable and scalable strain levels on printed circuit boards assembled with BGA packages deformed at high strain rates (surface strain rates > 5/sec). This test method requires a very simple set up that can be easily replicated. Initial determination of board strain level at the point of BGA solder joint failure was characterized for lead-free (SnAgCu) BGA assemblies. This test, in conjunction with a Weibull failure model, provides a method to effectively evaluate BGA solder joint reliability in dynamic environments.