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PD IEC/TS 62647-2:2012 Process management for avionics. Aerospace and defence electronic systems containing lead-free solder - Mitigation of deleterious effects of tin, 2013
- 30276310-VOR.pdf [Go to Page]
- CONTENTS
- FOREWORD
- INTRODUCTION
- 1 Scope
- 2 Normative references
- 3 Terms, definitions and abbreviations [Go to Page]
- 3.1 Terms and definitions
- 3.2 Abbreviations
- 4 Technical requirement [Go to Page]
- 4.1 Control level requirements [Go to Page]
- 4.1.1 General
- 4.1.2 Control levels and levels of integration
- 4.1.3 COTS and level selection
- 4.1.4 Other level selection information
- 4.2 Requirements for control levels [Go to Page]
- 4.2.1 Control level 1 requirements
- 4.2.2 Control level 2A requirements
- 4.2.3 Control level 2B requirements
- 4.2.4 Control level 2C requirements
- 4.2.5 Control level 3 requirements
- 4.2.6 Requirements for mitigating tin whisker risk for solder joints
- 4.3 Implementation methods [Go to Page]
- 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)
- 4.4 Methods for mitigating impact of Pb-free tin (applies to control level 2B, control level 2C) [Go to Page]
- 4.4.1 General
- 4.4.2 Hard potting and encapsulation
- 4.4.3 Physical barriers
- 4.4.4 Conformal and other coats
- 4.4.5 SnPb soldering process with validated coverage
- 4.4.6 Circuit and design analysis
- 4.5 Part selection process
- 4.6 Assessment and documentation of risk and mitigation effectiveness [Go to Page]
- 4.6.1 General
- 4.6.2 Elements of assessment
- 4.6.3 Other risk analysis issues
- Annex A (informative) Guidance on control levels, risk assessment, and mitigation evaluation
- Annex B (informative) Technical guide on detection methods, mitigation methods, and methods for limiting impact of tin
- Annex C (informative) Tin whisker inspection
- Annex D (informative) Analysis and risk assessment guidance
- Annex E (informative) Whiskers growing from solder joint fillets and bulk solder
- Bibliography
- Figures [Go to Page]
- Figure A.1 – Decision tree
- Figure A.2 – Decision tree, sub-tree 1
- Figure A.3 – Decision tree, sub-tree 2
- Figure B.1 – Insufficient solder flow
- Figure C.1 – Equipment setup for whisker examination
- 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
- Figure C.5 – Comparisons between whisker observations by microscope and SEM
- Figure C.6 – Limitation of microscope observation
- Figure C.7 – Preliminary whisker examination in non-coated test specimens
- 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
- Figure E.2 – Long whisker growing from SAC405 no-clean assembly reported by Terry Munson (Foresite)
- Figure E.3 – Whiskers and hillocks protruding through flux residueand growing from solder free of the flux residue [87]
- Figure E.4 – Tin whisker length impact by ionic cleanliness
- Figure E.5 – Tin whisker density impact by ionic cleanliness
- Figure E.6 – Whisker length depending on component and assembly cleanliness
- 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
- Figure E.9 – SAC105 bulk solder at ambient T in nitrogen chamber [34]
- Tables [Go to Page]
- Table A.1 – Control level summary table (1 of 2)
- Table B.1 – Conformal coating material physical properties from S. Meschter [10]
- Table B.2 – Conformal coating physical properties from T. Woodrow [12]
- Table B.3 – Conformal coating physical properties from R. Kumar [13] [Go to Page]