3 New IEC 62647 Series Standards – Lead Free Aerospace Electronics

Lead-free electronic assemblies have really impacted the aerospace and defense industries.  With the adoption of the RoHS and WEEE Directives in Europe, the industry has been challenged to meet lead-free requirements.  Now 3 new IEC 62647 Series technical specifications have been released to help you meet your customer requirements:  IEC/TS 62647-21, IEC/TS 62647-22 and IEC/TS 62647-23.  These standards provide the guidance needed for an industry-wide transition to the use of lead-free solder and terminations for electronics.  We’ll review each separately.

IEC/TS 62647-21, Process management for avionics – Aerospace and defence electronic systems containing lead-free solder – Part 21: Program management – Systems engineering guidelines for managing the transition to lead-free electronics

This technical specification reflects the unique challenges faced by the high performance electronics market.  For aerospace and defense customers particularly, the reworking of electronic components can inadvertently introduce non-compliant hazardous material into parts.  Additionally, the transition period introduces it’s own set of risks as older non-compliant parts are mixed with newer lead-free ones.

Your standard starts with the usual sections on scope, referenced documents and terms.  Then there is a general discussion of engineering concerns, including the program manager’s role, how extensive the issue is within the organization, and associated risks.

Section 5 covers requirements, both customer generated and regulatory.  Section 6 provides guidance on how to review the usage requirements your parts must meet, and Section 7 covers basic decisions that will have to be made during your transition period.  For example, when you are reviewing your suppliers lead-free compliance, you’ve got Annex D to review with a checklist you can use for your program.

You’ll also need to determine how you can control these hazardous materials, so Section 8 gives you a plan to use.  And of course, Sections 9 and 10 cover requalification and rework/repair.  Risk management and cost are covered in Sections 11 and 12.

Annex A provides you with a great table reviewing the document clause by clause — with the level of detail you’ll need to address for each (piece part, assembly, unit or system).  Annex B links the standard to RoHS, RoHS 2, and WEEE as well as the U.S. Executive Order 13148.  Annex C is a checklist for the program manager to use in dealing with Pb-free issues.  Annex D is your supplier questionaire, and Annex E gives you the recommended language to use in your supplier contracts to define your lead-free requirements.  A bibliography rounds out the standard.

IEC/TS 62647-22Process management for avionics – Aerospace and defence electronic systems containing lead-free solder – Part 22: Technical guidelines

While the previous document provides the how of setting up your program, this Part 22 covers the technical details you’ll need to consider.  For example, when using lead-free solder, higher manufacturing temperatures are required.  Can your circuit boards handle this?

So you’ll use this specification to establish your guidelines for the actual usage of lead-free alloys while maintaining the high reliability standards required in the aerospace and defense industries.

There is also the acknowledgement that the use of these lead-free products is currently in the early stages.  The committee does state that they expect changes to the standard as more information on performance is gathered.  However, regulatory requirements mean that the use of the best information possible at this point is necessary.

Your IEC/TS 62647-22 guidelines are intended to be used with IEC/PAS 62647-3 and GEIA HB-0005-4 (not currently in distribution).   You’ll find the usual scope, referenced documents and definition sections, as well as a discussion of the approach taken by the committee in developing the standard.

Section 5 covers the behavior of lead-free solder alloy.  It reviews the 3 main lead-free solders, all based on tin.  After this detailed discussion of the new alloys performance traits, Section 6 discusses the various service level environments the materials must perform in.  This includes reliability, expected lifetime, ruggedness, and so on.  Various environmental tests are covered, such as humidity and vibration.  Section 7 covers high performance electronics testing.  Solder joint reliability considerations reside in Section 8.

The balance of the standard covers various component considerations.  They are:

  • Section 9  – Piece parts,
  • Section 10 – Printed circuit boards
  • Part 11 – Printed circuit board (PCB)/printed wiring board (PWB) assembly
  • Part 12 – Module assembly considerations
  • Part 13 – Manufacturing resources
  • Part 14  – Aerospace wiring/cabling considerations
  • Part 15 – Rework/repair
  • Part 16 – Generic life test
  • Part 17 – Similarity analysis

Annex A on equipment service environmental definitions and the Bibliography finish the document.

IEC/TS 62647-23Process management for avionics – Aerospace and defence electronic systems containing lead-free solder – Part 23: Rework and repair guidance to address the implications of lead-free electronics and mixed assemblies

If you’re an original equipment manufacturer (OEM), contract manufacturer (CM) or a commercial depot, this is the document you’ll want to review.  It’s to be used to develop your procedures and processes for rework and repair of electronics systems for aerospace, defense and high performance applications.

The need for higher temperatures when working with lead-free solder, PCB’s, etc., means a challenge for rework and repair personnel and processes.  Further, the dependence on tin as the replacement metal for the lead has led to increased problems with tin-whiskers.  And you’ll need to compensate for the generally poorer wetting ability of lead-free solders as well.

This technical specification reviews all these concerns and more.  It covers the various substitute materials replacing lead and the equipment used by your staff.  There is discussion of considerations for rework/repair, and the processes for pre-rework/repair, rework/repair itself and post-rework/repair.  Annex A on termination finishes, Annex B on tin whiskers, and the bibliography finish the 50-page technical specification.

Because these impacted industries are global in nature, the requirements within any of today’s major jurisdictions cannot be avoided.  Lead-free is here to stay.  Luckily, we now have well documented specifications from IEC to support the transition.

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Claudia Bach

Claudia Bach is the President of Document Center Inc. and a world-wide recognized expert on Standards and Standards Distribution. You can connect with her on Google+

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