BSI PD IEC/TS 62647-2:2012:2013 Edition
$215.11
Process management for avionics. Aerospace and defence electronic systems containing lead-free solder – Mitigation of deleterious effects of tin
| Published By | Publication Date | Number of Pages |
| BSI | 2013 | 72 |
This Technical Specification establishes processes for documenting the mitigating steps taken to reduce the harmful effects of Pb-free tin in electronic systems.
This Technical Specification is applicable to aerospace, defence, and high performance (ADHP) electronic applications which procure equipment that may contain Pb-free tin finishes.
This document may be used by other high-performance and high-reliability industries, at their discretion.
PDF Catalog
| PDF Pages | PDF Title |
|---|---|
| 4 | CONTENTS |
| 6 | FOREWORD |
| 8 | INTRODUCTION |
| 9 | 1 Scope 2 Normative references |
| 10 | 3 Terms, definitions and abbreviations 3.1 Terms and definitions |
| 13 | 3.2 Abbreviations |
| 14 | 4 Technical requirement 4.1 Control level requirements 4.1.1 General |
| 16 | 4.1.2 Control levels and levels of integration 4.1.3 COTS and level selection 4.1.4 Other level selection information |
| 17 | 4.2 Requirements for control levels 4.2.1 Control level 1 requirements 4.2.2 Control level 2A requirements |
| 18 | 4.2.3 Control level 2B requirements |
| 19 | 4.2.4 Control level 2C requirements |
| 21 | 4.2.5 Control level 3 requirements 4.2.6 Requirements for mitigating tin whisker risk for solder joints |
| 22 | 4.3 Implementation methods 4.3.1 Flowing requirements to lower level suppliers (applies to control level 2B, control level 2C, and control level 3) 4.3.2 Detecting and controlling Pb-free tin finish introduction 4.3.3 Sample monitoring plans (applies to control level 2B and control level 2C) 4.3.4 Lot monitoring requirements (applies to control level 3) |
| 23 | 4.4 Methods for mitigating impact of Pb-free tin (applies to control level 2B, control level 2C) 4.4.1 General 4.4.2 Hard potting and encapsulation 4.4.3 Physical barriers 4.4.4 Conformal and other coats |
| 24 | 4.4.5 SnPb soldering process with validated coverage 4.4.6 Circuit and design analysis |
| 25 | 4.5 Part selection process 4.6 Assessment and documentation of risk and mitigation effectiveness 4.6.1 General |
| 26 | 4.6.2 Elements of assessment 4.6.3 Other risk analysis issues |
| 27 | Annex A (informative) Guidance on control levels, risk assessment, and mitigation evaluation |
| 28 | Figures Figure A.1 – Decision tree |
| 29 | Figure A.2 – Decision tree, sub-tree 1 |
| 30 | Figure A.3 – Decision tree, sub-tree 2 |
| 33 | Tables Table A.1 – Control level summary table (1 of 2) |
| 35 | Annex B (informative) Technical guide on detection methods, mitigation methods, and methods for limiting impact of tin |
| 36 | Table B.1 – Conformal coating material physical properties from S. Meschter [10] |
| 37 | Table B.2 – Conformal coating physical properties from T. Woodrow [12] |
| 38 | Table B.3 – Conformal coating physical properties from R. Kumar [13] |
| 41 | Figure B.1 – Insufficient solder flow |
| 47 | Annex C (informative) Tin whisker inspection |
| 48 | Figure C.1 – Equipment setup for whisker examination |
| 49 | Figure C.2 – Whiskers examination areas and direction Figure C.3 – Side-illumination by flexible light Figure C.4 – Coating residuals and dusts attached on lead-frame with conformal coating |
| 50 | Figure C.5 – Comparisons between whisker observations by microscope and SEM Figure C.6 – Limitation of microscope observation |
| 53 | Figure C.7 – Preliminary whisker examination in non-coated test specimens |
| 54 | Annex D (informative) Analysis and risk assessment guidance |
| 58 | Annex E (informative) Whiskers growing from solder joint fillets and bulk solder Figure E.1 – Whiskers and hillocks formed after 500 hours of storage at 85 °C / 85 % RH followed by –55 °C to 85 °C air to air cycling, 1 000 cycles |
| 59 | Figure E.2 – Long whisker growing from SAC405 no-clean assembly reported by Terry Munson (Foresite) |
| 60 | Figure E.3 – Whiskers and hillocks protruding through flux residueand growing from solder free of the flux residue [87] |
| 61 | Figure E.4 – Tin whisker length impact by ionic cleanliness Figure E.5 – Tin whisker density impact by ionic cleanliness |
| 62 | Figure E.6 – Whisker length depending on component and assembly cleanliness |
| 63 | Figure E.7 – Microstructures of solder fillet with 0,8 % HBr activated flux assembled in air after 1 000 hours at 85 °C / 85 % RH Figure E.8 – The mechanism of Sn whisker formation on solder fillet induced by oxidation |
| 64 | Figure E.9 – SAC105 bulk solder at ambient T in nitrogen chamber [34] |
| 65 | Bibliography |
Related products
-
BSI PD IEC/TS 62647-2:2012:2013 Edition
Process management for avionics. Aerospace and defence electronic systems containing lead-free solder – Mitigation of…
