Ruggedness and reliability of lead free electronics

Little is understood about the behavior of new lead-free solders in harsh mechanical environments (shock and vibration). There is an interest in scientific understanding of the impact of lead-free electronics and an interest in mitigating lead-free reliability risks. Reliability under harsh environments has two primary needs -1) ability to ruggedize the product for the expected environment and 2) ability to effectively screen to prevent production flawed parts from being shipped. Tin-lead products have many decades of production experience. There is extensive experience establishing design capabilities and understanding of types of flaws and understanding of screening needs to find flaws. Decades of production method refinement have contributed to the current reliability capabilities. There are a broad range of ruggedization methods and screening methods used for developing a reliable product. Some of these methods are old, some new some more effective than others. One might question: How much of the reliability achieved today can be credited to the production process evolution and how much is due to the ruggedization and screening process? There is a strong need to have high reliability in lead-free. Lacking the many decades of production evolution and lacking in-depth understanding of lead-free capabilities, reliability can be maximized by elimination of old, less effective ruggedization and screening methods. Reliability can be enhanced by using only the "best of show" methods, capable of understanding products at solder joint level. The common military practice of predefining environmental stress screening (ESS) profiles is counter productive to reliability. Predefined ESS will be very damaging to reliability when applied to emerging technologies such as lead-free electronics. Predefined ESS for electronics should never be imposed by the military or accepted by developers as a requirement.