IEC 62435-4:2018 pdf download

IEC 62435-4:2018 pdf download.Electronic components – Long-term storage of electronic semiconductor devices
1 Scope
This part of IEC 62435 specifies long-term storage methods and recommended conditions for long-term storage of electronic components including logistics, controls and security related to the storage facility. Long-term storage refers to a duration that may be more than 1 2 months for products scheduled for long duration storage. The philosophy of such storage, good working practices and general means to facilitate the successful long-term storage of electronic components are also addressed.
3 Terms and definitions
For the purposes of this document, the following terms and definitions apply. ISO and IEC maintain terminological databases for use in standardization at the following addresses: • IEC Electropedia: available at http://www.electropedia.org/ • ISO Online browsing platform: available at http://www.iso.org/obp 3.1 storage environment specially controlled storage area, with particular control of temperature, humidity, atmosphere and any other conditions depending on the product requirements 3.2 moisture sensitivity level MSL rated and verified moisture sensitivity level assigned to a component that defines the maximum safe equilibrium moisture exposure for a specific encapsulated device prior to reflow assembly or rework 3.3 long-term storage LTS planned storage of components to extend the life-cycle for a duration with the intention of supporting future use 3.4 LTS storeroom area containing components that have additional packaging for storage to protect from moisture or from mechanical impact or for ease of identification or handling 3.5 moisture-sensitive device MSD device that has moisture absorption or moisture retention and whose quality or reliability is affected by moisture 3.6 electronic device packaged electrical, electronic, electro-mechanical (EEE) item, or assemblies using such items [SOURCE: IEC 60050-551 :1 998, 551 -1 4-01 , modified] 3.7 desiccant hygroscopic substance used to remove moisture from an atmosphere 3.8 moisture barrier bag MBB storage bag manufactured with a flexible laminated vapour barrier film that restricts the transmission of water vapour Note 1 to entry: Refer to IEC 60749-20-1 for packaging of moisture sensitive products. 3.9 humidity indicator card HIC card printed with a moisture sensitive chemical that changes from blue to pink in the presence of water vapour 3.1 0 water vapour transmission rate WVTR measure of permeability of MBBs to water vapour 3.1 1 electrostatic discharge ESD transfer of electric charge between bodies of different electrostatic potentials in proximity or through direct contact [SOURCE: IEC 60050-561 :201 4, 561 -03-06]
4 Purpose of storage (facility)
4.1 General Successful long-term storage is dependent upon sustained control of the environment and its physical and data security. Costs associated with handling, maintaining traceability, physical accounting and environmental conditions should be accounted for from the outset of long-term storage. 4.2 Cost of ownership Cost will be determined by type of storage facility, cabinet, continuous nitrogen flow or inert gas flow and periodical examination on a representative sample. 4.3 Security Access to controlled areas should be limited to a small number of persons to ensure adequate security. Controlled areas shall be secure from theft, tampering and environmental disturbances.4.4 Location and ambient environment The LTS storeroom should be located away from any vibration, electromagnetic fields, ultraviolet rays and other strong light. Consideration should be given to any catastrophic events likely to occur near or at the physical locale of the storage facility. For example, seismically active locations may have building safety and control mitigation measures in place. 4.5 Incorrect control of reliability during storage Storage conditions should be precisely defined and controlled, to ensure the reliability of the components (see Clause 5). Component integrity may be reduced by improper storage conditions. Potential causes of storage risk are related to poor control of environmental conditions. Proper control should consider temperature, humidity, moisture, pressure, atmospheric gases, electrostatic field charge, applied physical forces, handling (shock, vibration, impacts, etc.), contamination or other applied stress factors. Degradation mechanisms that are induced with moisture may occur if the integrity of the dry storage (cabinet or MBB) is violated. Verification of moisture exposure includes, but is not limited to, examination of the HIC for any change in colour, chamber humidity monitoring and the use of recording devices that indicate moisture exposure. Different materials can absorb moisture at different rates and should be evaluated based upon exposure time. For other degradation mechanisms that require oxygen, radiation, electrical exposure or mechanical impact, the LTS environment should be evaluated to prevent contributing to failure concerns.