DD IEC-PAS 62435:2005 pdf download Electronic components — Long-duration storage of electronic components — Guidance for implementation
Scope
This Publicly Available Specification (PAS) is, first of all, a practical guide to methods of longduration storage (more than five years) which summarizes the existing practices in the industry.
Unless otherwise specified, the approach, as well as the methods presented, apply to all familiesof electronic components,such as
passive components, including quartz crystals, connectors and relays. Howevercomponents with “manufacturer’s” specifications showing an expiry date or specific storageconditions are excluded from this document (for example, primary cells, storage cells, etc.);
encapsulated or non-encapsulated active components of a silicon (Si] or gallium arsenide[GaAs] technology;
micro-electronic assemblies
2Normative references
The following referenced documents are indispensable for the application of this document. Fordated references, only the edition cited applies. For undated references, the latest edition of thereferenced document (including any amendments) applies.
EC 60068-2-17:1994Basic environmental test procedures – Part 2: Tests – Test Q: Sealing
IEC 60068-2-20:1979，Environmental testing – Part 2: Tests – Test T: Soldering
EC 60410:1973,Sampling plans and procedures for inspection by attributes
EC 61340-5-1:1998, Electrostatics – Part 5-1: Protection of electronic devices from electrostaticphenomena-Generalrequirements
IEC 61340-5-2:1999, Electrostatics – Part 5-2: Protection of electronic devices from electrostaticphenomena -User guide
EC 61945, Integrated circuits – Manufacturing line approval – Methodology for technology andfailure analysis
IEC 62380: Reliability data handbook – Universal model for reliability prediction of electronicscomponents.PCBs and equipment
EN 190 000:1995,Generic specification – Integrated monolithic circuits
3Storage decision criteria
Any creation of an electronic component inventory should be carried out
on the one hand, after having compared with the following additional solutions:
modification to the printed board by adding a “backpack” macro-component
3.1Advantages
Technical simplicity – Rapidity3,1.1
When the various steps of the storage process are finalized and validated, the creation of astock is a simpler, faster and technically less hazardous solution than developing or modifyingelectronic boards.
Storage can also be a temporary solution enabling equipment maintenance during modificationor development of electronic boards.
3.1.2Solution durability
Any equipment changes based on the use of new electronic components will be facedeventually, with the obsolescence of these new components. Storage can resolve obsolescenceproblems until the end of the operating life of the equipment.
3.1.3Preventive storage
Preventive storage (i.e., before the component becomes obsolete) presents several additionaadvantages compared with remedial storage (i.e, when the component has already becomeobsolete), for example, when
the component price has not become prohibitive as in the case of specific obsoletecomponents which have become very rare;
the quality level is ensured if the component can be purchased direct from the manufacturelor approved distributor. When a component has been obsolete for a long time, it can only befound at specialists in purchasing, storage and resale of obsolete components (“brokers”). lnthis case,no component reliability guarantee will apply.
3.2Hazards – Drawbacks
3.2.1Generic aging hazard
Stock dimensioning is based on the assumption of a constant component failure rate. Theproblem of generic aging of the components (“bath-tub curve”) cannot be easily taken intoaccount and quantified. However, the existing electronic components seem to have extremelyong lives provided that they are manufactured with all quality guarantees and that they are usecin accordance with their specifications.
3.2.2Poor stock dimensioning
The calculation of the volume o components to be stored may be based on teedback (operational failure rate) and/or on theoretical models (predictive failure rate). Calculation using feed.back is only valid if the sample is big enough (significant population of components installedoperation for several years, high number of failures evidenced). Predictive calculations do notgenerally take into account the extrinsic parameters of the components (defects caused byprinted-board handling and repair, systematic replacement of the components (includingunctional components) during repairs, improper use of the components, etc.). Therefore, thestock volume may be improperly assessed.
DD IEC-PAS 62435:2005 pdf download
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