SAE GEIA-STD-0005-2A-2012 Standard for Mitigating the Effects of Tin Whiskers in Aerospace and High Performance Electronic Systems (Formerly TechAmerica GEIA-STD-0005-2 REV A).pdf

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4、0 (outside USA) Fax: 724-776-0790 Email: CustomerServicesae.org SAE WEB ADDRESS: http:/www.sae.org SAE values your input. To provide feedback on this Technical Report, please visit http:/www.sae.org/technical/standards/GEIASTD0005_2A TECHNICAL REPORT GEIA-STD-0005-2 REV. A Issued 2006-06 Revised 201

5、2-05 Standard for Mitigating the Effects of Tin Whiskers in Aerospace and High Performance Electronic Systems 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 with the publis

6、hing 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 provisions of the S

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8、of the existing specification or standard format. TechAmerica Standard Standard for Mitigating the Effects of Tin Whiskers in Aerospace and High Performance Electronic Systems GEIA-STD-0005-2 Revision A May 2012 GEIA-STD-0005-2NOTICE TechAmerica Engineering Standards and Publications are designed to

9、 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 particular need. Existence of such Stand

10、ards 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 voluntary use by those other than TechAme

11、rica 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 assume any liability to any patent ow

12、ner, 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 comparison between the TechAmerica Stand

13、ard 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 health practices and to determine the a

14、pplicability of regulatory limitations before its use. (Formulated under the cognizance of the TechAmerica (APMC) Avionics Process Management Committee and the (G-12) Solid State Devices Committee. This is a joint activity of the Aerospace Industries Association (AIA), Avionics Maintenance Conferenc

15、e (AMC), and TechAmerica, to address aerospace issues related to the global elimination of lead from electrical and electronic equipment put on the market after July 1, 2006. Formed in 2004, this coalition includes all stakeholders (market segments, supply chain, geographic regions.) Published by 20

16、12 TechAmerica Standards two Annexes added. May 2012 GEIA-STD-0005-2 Revision A i Contents Foreword . v Introduction . v 1 Scope 1 2 Terms and Definitions 1 3 Requirements 4 3.1 Control Level Selection . 4 3.1.1 Control Levels and Levels of Integration . 5 3.1.2 COTS and Control Level Selection 6 3.

17、2 Requirements for Control Levels . 6 3.2.1 Control Level 1 Requirements 6 3.2.1.1 Control Level 1 Requirements for Documentation of Uses of Pb-free Tin Finishes 6 3.2.1.2 Control Level 1 Requirements for Detecting and Controlling Pb-free Tin Finish Introduction 6 3.2.1.3 Control Level 1 Requirement

18、s for Tin Whisker Risk Mitigation 6 3.2.1.4 Control Level 1 Requirements for Parts Selection 6 3.2.1.5 Control Level 1 Requirements for Analysis and Documentation of Risk and Mitigation Effectiveness 6 3.2.2 Control Level 2A Requirements . 7 3.2.2.1 Control Level 2A Requirements for Documentation of

19、 Uses of Pb-free Tin Finishes 7 3.2.2.2 Control Level 2A Requirements for Detecting and Controlling Pb-free Tin Finish Introduction . 7 3.2.2.3 Control Level 2A Requirements for Tin Whisker Risk Mitigation . 7 3.2.2.4 Control Level 2A Requirements for Parts Selection 7 3.2.2.5 Control Level 2A Requi

20、rements for Analysis and Documentation of Risk and Mitigation Effectiveness . 7 3.2.2.6 Control Level 2A Exceptions . 7 3.2.3 Control Level 2B Requirements . 7 3.2.3.1 Control Level 2B Requirements for Documentation of Uses of Pb-free Tin Finishes 7 3.2.3.2 Control Level 2B Requirements for Detectin

21、g and Controlling Pb-free tin Finish Introduction 8 3.2.3.3 Control Level 2B Requirements for Tin Whisker Risk Mitigation . 8 3.2.3.4 Control Level 2B Requirements for Parts Selection 8 3.2.3.5 Control Level 2B Requirements for Assessment and Documentation of Risk and Mitigation Effectiveness . 9 GE

22、IA-STD-0005-2 Revision A ii 3.2.4 Control Level 2C Requirements . 9 3.2.4.1 Control Level 2C Requirements for Documentation of Uses of Pb-free Tin Finishes 9 3.2.4.2 Control Level 2C Requirements for Detecting and Controlling Pb-free Tin Finish Introduction . 10 3.2.4.3 Control Level 2C Requirements

23、 for Tin Whisker Risk Mitigation . 10 3.2.4.4 Control Level 2C Requirements for Parts Selection 10 3.2.4.5 Control Level 2C Requirements for Assessment and Documentation of Risk and Mitigation Effectiveness . 10 3.2.5 Control Level 3 Requirements 11 3.2.5.1 Control Level 3 Requirements for Documenta

24、tion of Uses of Pb-free Tin Finishes 11 3.2.5.2 Control Level 3 Requirements for Detecting and Controlling Pb-free tin Finish Introduction 11 3.2.5.3 Control Level 3 Requirements for Mitigation of Tin Whisker Risk and Mitigation Effectiveness 11 3.2.5.4 Control Level 3 Requirements for Parts Selecti

25、on 11 3.2.5.5 Control Level 3 Requirements for Assessment and Documentation of Risk and Mitigation Effectiveness . 11 3.2.6 Requirements for Mitigating Tin Whisker Risk for Solder Joints 12 4 Implementation Methods 13 4.1 Flowing Requirements to Lower Level Suppliers (applies to Control Level 2B, Co

26、ntrol Level 2C, and Control Level 3) 13 4.2 High Voltage Applications 13 4.3 Detecting and Controlling Pb-free Tin Finish Introduction . 13 4.3.1 Sample Monitoring Plans (applies to Control Level 2B and Control Level 2C) 13 4.3.2 Lot Monitoring Requirements (applies to Control Level 3) . 14 4.4 Meth

27、ods for Mitigating Impact of Pb-free Tin Finishes (applies to Control Level 2B, Control Level 2C) . 14 4.4.1 Hard Potting and Encapsulation 14 4.4.2 Physical Barriers . 15 4.4.3 Conformal and Other Coats 15 4.4.4 SnPb Soldering Process with Validated Coverage . 16 4.4.5 Circuit and Design Analysis .

28、 16 4.5 Part Selection Process 17 4.6 Assessment and Documentation of Risk and Mitigation Effectiveness 17 4.6.1 Elements of Assessment . 18 GEIA-STD-0005-2 Revision A iii 4.6.2 Other Risk Analysis Issues . 18 Annex A Guidance on Control Levels, Risk Assessment, and Mitigation Evaluation . 19 A.1 In

29、troduction 19 A.2 Control Level Determination . 19 Annex B Technical Guide on Detection Methods, Mitigation Methods, and Methods for Limiting Impact of Pb-free Tin Finishes . 26 B.1 Hard Potting, Encapsulation, and Physical Barriers 26 B.2 Conformal and Other Coats 26 B.3 Pb-free Tin Finish Replacem

30、ent and SnPb Soldering Processes . 30 B.3.1 Solder Dip Pb-free Tin-finished Surfaces . 30 B.3.2 Re-plate Whisker Prone Areas 30 B.3.3 Pb Over-plating . 31 B.3.4 Soldering with SnPb Solder 31 B.4 Circuit Design and Analysis 31 B.5 Whisker Lengths and Derivation for Gap Distance Rules without Conforma

31、l Coating . 32 B.6 Part Level Strategies to Be Considered in Part Selection 34 B.6.1 Annealing, Fusing, and other Heat Treatments 34 B.6.2 Plated vs. “Hot Dipped” Tin . 34 B.6.3 Immersion Tin for Boards . 34 B.6.4 Nickel Underplate . 35 B.6.5 SnAg Finishes . 35 B.6.6 SnBi Finishes 35 B.6.7 Non-compl

32、iant SnPb (1% to 3% Pb) 36 B.6.8 Successful passage of JESD201 testing at Class 2 level. 36 B.7 Part Level Strategies with Less ADHP Industry Support or Consensus . 37 B.7.1 “Matte” Tin 37 B.7.2 Choice of Substrate Material 38 B.7.3 SAC Finishes 38 B.7.4 Thick Tin . 38 B.8 Pb-free Tin Detection . 39

33、 Annex C Tin Whisker Inspection . 41 C.1 General Inspection Guidance . 41 C.2 Inspection of Installed Hardware . 41 C.3 Inspection of Removed Units and/or Inspection During Failure Analysis or in Other Laboratory Situations. 41 GEIA-STD-0005-2 Revision A iv C.3.1 Inspection Using Stereomicroscope 41

34、 C.3.2 Inspection Using Scanning Electron Microscope . 49 Annex D Analysis and Risk Assessment Guidance 50 D.1 Data Relevant to Tin Whisker Risk Assessment . 51 D.2 The Role of Whisker Propensity Tests 52 D.3 Analyses of Field Data . 53 D.4 Risk of Plasma Events . 53 Annex E Whiskers Growing from So

35、lder Joint Fillets and Bulk Solder 55 E.1 General Phenomenon of Sn Whisker Formation in Sn-Pb and Pb-free Solder . 55 E.2 Long Sn Whiskers in Pb-free Solder . 56 E.2.1 Long Sn Whiskers in Pb-free Solder with Ionic Contamination 56 E.2.2 Long Sn Whiskers in Pb-free Solder with Rare Earth Elements 60

36、Annex F Bibliography 62 GEIA-STD-0005-2 Revision A v Foreword This Standard is intended for use by those procuring, designing, building or repairing electronic assemblies that could use items with Pb-free tin finishes to document processes they use to assure performance, reliability, airworthiness,

37、safety, and certifiability of those assemblies. It provides a framework to communicate and agree on the processes to be used to control and mitigate the use of Pb-free tin finishes in these applications. The Aerospace Industries Association (AIA), the Avionics Maintenance Conference (AMC), and TechA

38、merica, formerly Government Electronics and Information Technology Association (GEIA) formed a joint working group with the express purpose of generating a series of industry standards documents for the use and handling of Pb-free solder, piece parts, and boards in aerospace, defense, and high perfo

39、rmance applications. This Standard was prepared by that group. It was balloted and approved by TechAmerica G-12 (Solid State Subcommittee) and TechAmerica Avionics Management Conference (AMC Subcommittee). This Standard is intended to work in concert with GEIA-STD-0005-1, GEIA-HB-0005-1, and GEIA-HB

40、-0005-2. This Standard may be referenced in proposals, requests for proposals, work statements, contracts, and other documents. It may be used as a stand-alone standard or as part of compliance with GEIA-STD-0005-1. This Standard addresses the risk of tin whiskers forming on Pb-free tin finishes. Ho

41、wever, the state of research into tin whisker risk still does not allow accurate quantitative estimates of the risk and reliability. It defines three baseline Control Levels that detail the amount of attention that should be paid to the risk of tin whiskers: no restrictions on Pb-free tin finish use

42、, some restrictions on Pb-free tin finish use, and prohibition of Pb-free tin finish use. There are six informative annexes in this Standard: Annex A provides guidance on selecting Control Levels and performing risk assessments. Annex B provides some background on various mitigation methods. Annex C

43、 provides guidelines for performing tin whisker inspections Annex D provides some additional guidance on tin whisker risk analyses Annex E provides information on whiskers growing from bulk solder and joints Annex F provides a bibliography Introduction Many constituent materials used in the producti

44、on of electronic products have come under scrutiny. The European Union (EU) has enacted two directives; 2002/95/EC Restriction of Hazardous Substances (RoHS) and 2002/96/EC Waste Electrical and Electronic Equipment (WEEE) that restrict or eliminate the use of various substances in a variety of produ

45、cts produced after July 2006. One of the key materials restricted is lead (Pb), which is widely used in electronic solder and electronic piece part terminations, and printed wiring boards. While these regulations only directly affect products for sale in the EU, due to the reduced market share of th

46、e Aerospace, Defense, and High Performance Industry in electronics, many suppliers are changing their products because their primary market is world-wide consumer electronics. Additionally, several Asian countries and GEIA-STD-0005-2 Revision A vi U.S. states have enacted similar “green” laws. Many

47、Asian electronics manufacturers have recently announced completely “green” product lines. The restriction of Pb use has generated a transition by many piece part and board suppliers from tin-lead (Sn-Pb) finishes to pure tin or other Pb-free finishes. Lead-free tin finishes can be susceptible to the

48、 spontaneous growth of crystal structures known as “tin whiskers” which can cause electrical failures, ranging from parametric deviations to short circuits to catastrophic arcing events, and may interfere with sensitive optical surfaces or the movement of Micro-ElectroMechanical Systems (MEMS) struc

49、tures. Though studied and reported for decades, the mechanism behind their growth is not well understood, and tin whiskers remain a potential reliability hazard. Furthermore, the growing number of piece parts with pure tin finishes means there are more opportunities for whiskers to grow and to produce failures. The nature and meaning of risk posed by tin whiskers may vary considerably across the range of users of this Standard.