DD IEC/PAS 62435:2005

FOREWORD
INTRODUCTION
1 Scope
2 Normative references
3 Storage decision criteria
  3.1 Advantages
      3.1.1 Technical simplicity - Rapidity
      3.1.2 Solution durability
      3.1.3 Preventive storage
  3.2 Hazards - Drawbacks
      3.2.1 Generic aging hazard
      3.2.2 Poor stock dimensioning
      3.2.3 Incorrect control of reliability during storage
      3.2.4 Freezing equipment functionalities
  3.3 Storage cost
  3.4 Decision criteria
4 Purchasing - Procurement
  4.1 List of components
  4.2 Quantity of components to be stored
      4.2.1 Production stock
      4.2.2 Field service stock
  4.3 When is it worth keeping in stock?
  4.4 Procurement recommendations
5 Technical validation of the components
  5.1 Purpose
  5.2 Relevant field
  5.3 Test selection criteria
  5.4 Measurements and tests
      5.4.1 Sampling
      5.4.2 Visual examination, sealing, solderability
      5.4.3 Compliance with the electrical specifications
      5.4.4 Assessment of the supplied batch reliability
      5.4.5 Manufacturing control check (technological analysis)
  5.5 Sanction
6 Conditioning and storage
  6.1 Type of environment
  6.2 Elementary storage unit
  6.3 Stock management
  6.4 Redundancy
  6.5 Identification - Traceability
  6.6 Initial packaging
  6.7 Stabilization bake
  6.8 Storage conditions
      6.8.1 Storage area
      6.8.2 Temperature
      6.8.3 Temperature variations
      6.8.4 Relative humidity - Chemical attacks - Contamination
      6.8.5 Pressure
      6.8.6 Electrostatic discharges
      6.8.7 Vibration - Mechanical impacts
      6.8.8 Electromagnetic field - Radiation
      6.8.9 Light
  6.9 Maintaining storage conditions
7 Periodic check of the components
  7.1 Objectives
  7.2 Periodicity
  7.3 Tests during periodic check
8 Destocking
  8.1 Precautions
      8.1.1 Electrostatic discharges
      8.1.2 Mechanical impacts
  8.2 Inspection
9 Feedback
Annex A (informative) Example of a component list
Annex B (informative) Examples of periodic and/or destocking
                      tests (1/3)
Annex C (informative) Parameters influencing the final price
                      of the component storage
Annex D (informative) Parameters influencing the quantity of
                      components to be stored
Annex E (normative) Failure mechanisms: Encapsulated and
                    non-encapsulated active components
Annex F (normative) Failure mechanisms: GaAs components

Describes practical guide to methods of long-duration storage (more than five years) which summarizes the existing practices in the industry.

This PAS applies to the long-duration storage of electronic components. Although it has always existed to some extent, obsolescence of electronic components, and particularly integrated circuits, has become increasingly intense over the last few years. Indeed, with the existing technological boom, the commercial life of a component has become very short compared with the life of industrial equipment such as those encountered in the aeronautical field, the railway industry or the energy sector. The many solutions enabling obsolescence to be resolved are now identified. However, selecting one of these solutions must be preceded by a case-by-case technical and economic feasibility study, depending on whether storage is envisaged for field service or production, for example: - remedial storage as soon as components are no longer marketed - preventive storage anticipating declaration of obsolescence Taking into account the expected life of some installations, sometimes covering several decades, the qualification times, and the unavailability costs, which can also be very high, the solution to be adopted to resolve obsolescence must often be rapidly implemented. This is why the solution retained in most cases consists in systematically storing components which are in the process of becoming obsolescent. The technical risks of this solution are, a priori, fairly low. However, it requires the perfect mastery of the implemented process, and especially of the storage environment, although this mastery becomes critical when it comes to long-term storage. All handling, protection, storage and test operations must be performed according to the state of the art.