scope:

NPR-IEC/TS 62647-3 defines for circuit card assemblies (CCA): - a default method for those companies that require a pre-defined approach, and - a protocol for those companies that wish to develop their own test methods. The intent of this document is not to prescribe a certain method, but to aid avionics/defence suppliers in satisfying the reliability and/or performance requirements of IEC/TS 62647-1 as well as support the expectations in IEC/TS 62647-21. The default method (see Clause 5) is intended for use by electronic equipment manufacturers, repair facilities, or programs that, for a variety of reasons, may be unable to develop methods specific to their own products and applications. It should be used when little or no other information is available to define, conduct, and interpret results from reliability, qualification, or other tests for electronic equipment containing lead-free (Pb-free) solder. The default method is intended to be conservative, i.e., it is biased toward minimizing the risk to users of ADHP electronic equipment. The protocol (see Clause 6) is intended for use by manufacturers or repair facilities that have the necessary resources to design and conduct reliability, qualification, or process development tests that are specific to their products, their operating conditions, and their applications. Users of the protocol will have the necessary knowledge, experience, and data to customize their own methods for designing, conducting, and interpreting results from the data. Key to developing a protocol is a firm understanding of all material properties for the lead-free (Pb-free) material in question as well as knowledge of package- and board-level attributes as described in 5.3.2. As an example, research has shown that the mechanisms for creep can be different between tin-lead and tin-silver-copper (SAC) solders. Understanding these mechanisms is key to determining critical test parameters such as dwell time for thermal cycling. The protocol portion of this document provides guidance on performing sufficient characterization of new materials in order to accurately define test parameters. Use of the protocol is encouraged, since it is likely to yield more accurate results, and to be less expensive than the default method. The IEC/TS 62647-22 provides a comprehensive overview of those technical considerations necessary in implementing a test protocol. This specification addresses the evaluation of failure mechanisms, through performance testing, expected in electronic products containing lead-free (Pb-free) solder. One failure mode, fatigue-failure through the solder-joint, is considered a primary failure mode in ADHP electronics and can be understood in terms of physics of failure and life-projections. Understanding all of the potential failure modes caused by lead-free (Pb-free) solder of ADHP electronics is a critical element in defining early field-failures/reliability issues. Grouping of different failure modes may result in incorrect and/or misleading test conclusions. Failure analysis efforts should be conducted to insure that individual failure modes are identified, thus enabling the correct application of reliability assessments and life-projection efforts.