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5、2-12 Performance Testing for Aerospace and High Performance Electronic Interconnects Containing Pb-free Solder and Finishes NOTICE This document has been taken directly from the original TechAmerica document and contains only minor editorial and format changes required to bring it into conformance w
6、ith the publishing requirements of SAE Technical Standards. The release of this document is intended to replace the original with the SAE International document. Any numbers established by the original document remain unchanged. The original document was adopted as an SAE publication under the provi
7、sions of the SAE Technical Standards Board (TSB) Rules and Regulations (TSB 001) pertaining to accelerated adoption of specifications and standards. TSB rules provide for (a) the publication of portions of unrevised specifications and standards without consensus voting at the SAE committee level, an
8、d (b) the use of the existing specification or standard format. TechAmerica Standard Performance Testing for Aerospace and High Performance Electronic Interconnects Containing Pb-free Solder and Finishes GEIA-STD-0005-3-REV A December 2012 GEIA-STD-0005-3-REV ANOTICE TechAmerica Engineering Standard
9、s and Publications are designed to serve the public interest by eliminating misunderstandings between manufacturers and purchasers, facilitating interchangeability and improvement of products, and assisting the purchaser in selecting and obtaining with minimum delay the proper product for his partic
10、ular need. Existence of such Standards and Publications shall not in any respect preclude any member or nonmember of TechAmerica from manufacturing or selling products not conforming to such Standards and Publications, nor shall the existence of such Standards and Publications preclude their volunta
11、ry use by those other than TechAmerica members, whether the standard is to be used either domestically or internationally. Standards and Publications are adopted by TechAmerica in accordance with the American National Standards Institute (ANSI) patent policy. By such action, TechAmerica does not ass
12、ume any liability to any patent owner, nor does it assume any obligation whatever to parties adopting the Standard or Publication. This TechAmerica Standard is considered to have International Standardization implications, but the ISO/IEC activity has not progressed to the point where a valid compar
13、ison between the TechAmerica Standard and the ISO/IEC document can be made. This Standard does not purport to address all safety problems associated with its use or all applicable regulatory requirements. It is the responsibility of the user of this Standard to establish appropriate safety and healt
14、h practices and to determine the applicability of regulatory limitations before its use. (Formulated under the cognizance of the TechAmerica (APMC) Avionics Process Management Committee. This document was prepared by the LEAP working group, a multi-association group consisting of the AIA, TechAmeric
15、a, and the AMC.) Published by 2012 TechAmerica Standards and it is especially disruptive to aerospace and other industries that produce electronic equipment for high performance applications. These applications, hereinafter described as AHP (Aerospace and High Performance), are characterized by seve
16、re or harsh operating environments, long service lifetimes, and high consequences of failure. In many cases, AHP electronics must be repairable at the soldered assembly level. Typically, AHP industry production volumes may be low and, due to low market share, they may not be able to resist the chang
17、e to Pb-free. Furthermore, the reliability tests conducted by suppliers of solder materials, components, and sub-assemblies cannot be assumed to assure reliability in AHP applications. This document provides guidance (and in some cases direction) to designers, manufacturers, and maintainers of AHP e
18、lectronics in assessing performance of Pb-free interconnections. GEIA-STD-0005-3-REV A v Over the past several decades, electronics manufacturers have developed methods to conduct and interpret results from reliability tests for lead-bearing solder alloys. Since these alloys have been used almost un
19、iversally in all segments of the electronics industry, and since a large body of data, knowledge, and experience has been assembled, the reliability tests for Pb-bearing solder alloys are well-understood and widely accepted. When it became apparent that the use of Pb-bearing alloys would decline rap
20、idly, programs were implemented to evaluate the reliability of the Pb-free replacement alloys. Those programs have generated a considerable database. To date, however, there is no reliability test method that is widely accepted in the AHP industries. Reasons for this include: 1. No single Pb-free so
21、lder alloy has emerged as a replacement for lead-bearing alloys; instead, a number of alloys are being used in various segments of the electronics industry. 2. The physical, chemical, and metallurgical properties of the various Pb-free replacement alloys vary significantly. 3. Due to the many source
22、s of solder alloys used in electronic component termination materials or finishes, assembly processes, and repair processes; the potential number of combinations of alloy compositions is nearly unlimited. It is an enormous task to collect data for all these combinations. 4. The test methods develope
23、d by other segments (References 1 and 2) are directed toward shorter service lives and more benign environments. Also, there is still a question of suitable dwell times and acceleration factors. (However, the intent of this document is to provide a means of coordinating the information from Referenc
24、es 1 and 2 into a basic approach for AHP suppliers.) 5. The data from reliability tests that have been conducted are subject to a variety of interpretations. In view of the above facts, it would be desirable for high-reliability users of Pb-free solder alloys to wait until a larger body of data has
25、been collected, and methods for conducting reliability tests and interpreting the results have gained wide acceptance for high-reliability products. In the long run, this will indeed occur. However, the transition to Pb-free solder is well under way and there is an urgent need for a reliability test
26、 method, or set of methods, based on industry consensus. While acknowledging the uncertainties mentioned above, this document provides necessary information for designing and conducting performance tests for aerospace products. In addition, when developing test approaches, the material in question n
27、eeds to be suitably characterized. Such material properties as ultimate tensile strength, yield strength, Poissons ratio, creep rate, and stress relaxation have been shown to be key attributes in evaluating fatigue characteristics of Pb-free solders. Because of the dynamic nature of the transition t
28、o Pb-free electronics, this and other similar documents must be considered provisional. While this document is based on the best information and expertise available, it must be updated as future knowledge and data are obtained. GEIA-STD-0005-1-REV A vi The intent of the document is not to prescribe
29、a certain method, but to aid avionics/defense suppliers in satisfying the reliability and/or performance requirements of GEIA-STD-0005-1 5 as well as support the expectations in GEIA-HB-0005-1 6. Accordingly, it includes: 1. A default method for those companies that require a pre-defined approach an
30、d 2. A protocol for those companies that wish to develop their own test methods. Also, this document will focus on testing the Pb-free interconnections, i.e., the “system” comprised of the solder alloy as well as the component and board finishes. While the bulk of this introduction has discussed rel
31、iability testing of Pb-free assemblies, this document will direct attention to test guidelines to evaluate the performance of the Pb-free interconnection. The guidelines presented in this document do not suggest methods for reliability testing of product. That is left to each individual user. What t
32、he document does is provide insight as to what approaches should be used as part of a performance test when Pb-free interconnection is of prime interest. Given the current state of the industry, gaps do exist in the knowledge base especially in some recently disclosed phenomenon such as effects of r
33、oom temperature aging as well as issues in COTS testing and accelerated test. Subsequently, the user is advised to corroborate/validate information provided in the associated references. In summary, the purpose of this document is threefold: 1. It is meant to provide a means to acquire sound, accura
34、te data regarding the performance of a Pb-free interconnection under harsh conditions (aerospace, military, medical, etc.,) 2. It is usable for further design assessment and operation of a product, and 3. It is usable as part of a process development study. Finally, any portion of this document may
35、be used to develop a Pb-free assembly test program, i.e., THIS DOCUMENT IS TAILORABLE and provides room for flexibility. For those situations in which results are used for reliability, verification, or qualification, it is strongly recommended that stakeholder concurrence be sought and documented so
36、 that expectations are understood and concerns are addressed. GEIA-STD-0005-3-REV A 1 1.0 SCOPE This document defines: 1. A default method for those companies that require a pre-defined approach and 2. A protocol for those companies that wish to develop their own test methods. The default method (Se
37、ction 4 of the document) is intended for use by electronic equipment manufacturers, repair facilities, or programs which, for a variety of reasons, may be unable to develop methods specific to their own products and applications. It is to be used when little or no other information is available to d
38、efine, conduct, and interpret results from reliability, qualification, or other tests for electronic equipment containing Pb-free solder. The default method is intended to be conservative, i.e., it is biased toward minimizing the risk to users of AHP electronic equipment. The protocol (Section 5 of
39、the document) is intended for use by manufacturers or repair facilities which 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 wil
40、l 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 Pb-free material in question as well as knowledge of package-
41、 and board-level attributes as described in Section 4.1.1. As an example, research has shown that the mechanisms for creep are very different between SnPb and Tin-Silver-Copper (SAC) solders. Understanding these mechanisms is key to determining critical test parameters such as dwell time for thermal
42、 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. Reference 7 provides a comprehensive overv
43、iew of those technical considerations necessary in implementing a test protocol. This document addresses the evaluation of failure mechanisms, through performance testing, expected in electronic products containing Pb-free solder. One failure mode, fatigue-failure through the solder-joint, is consid
44、ered a primary failure mode in AHP electronics and can be understood in terms of physics-of-failure and life-projections. Understanding the all potential failure modes caused by Pb-free solder of AHP electronics is a critical element in defining early field-failures/reliability issues. Grouping of d
45、ifferent 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 enabling the correct application of reliability assessments and life-projection efforts. When properly used, the meth
46、ods or protocol defined in this document may be used along with the processes documented in compliance to Reference 3, to satisfy, at least in part, the reliability requirements of References 3 and 4. GEIA-STD-0005-1-REV A 2 This document may be used for products in all stages of the transition to P
47、b-free solder, including: Products that have been designed and qualified with traditional SnPb electronic components, materials, and assembly processes, and are being re-qualified with use of Pb-free components Products with SnPb designs transitioning to Pb-free solder; and Products newly-designed w
48、ith Pb-free solder. For programs that were designed with SnPb solder, and are currently not using any Pb-free solder, the traditional methods may be used. It is important, however, for those programs to have processes in place to maintain the SnPb configuration including those outsourced or manufact
49、ured by subcontractors. With respect to products as mentioned above, the methods presented in this document are intended to be applied at the level of assembly at which soldering occurs, i.e., circuit-card assembly level. For those users interested in COTS (commercial-off-the-shelf) testing, some guidance at box-level (e.g., power suppliers, module assemblies, etc.) is provided in Section 6.0. IMPORTANT TO NOTE:
