IEC 62435-7:2020 pdf free download – Electronic components – Long-term storage of electronic semiconductordevices
4.1overview of MEMS applications
MEMS (Micro-electromechanical Systems) are miniaturized mechanical or electromechanicalelements that typically vary in size from 1 micron to 1 000 microns that are used to mechanicallymeasure or manipulate matter，light or create electric signals from environmental inputs.Storage of MEMS devices should consider different sensitivities and risks compared to othersemiconductor devices due to the mechanical nature of the devices.MEMS may be subject toadditional mechanical related performance and failure mechanisms in addition traditionalsemiconductor performance mechanisms.The storage program should consider the end useand failure mechanisms related to the function of the MEMS device. Typical uses are listed forinitial consideration and risk assessment.
– Actuator mechanical movement related to electrostatics, thermal changes or piezoelectric
effects.
– Physical sensors related to acceleration, vibration, field/flux, force, magnetic field, electro-static, optical stimulus or radiation effects, pressure, temperature.
– Chemisensors related to gas or liquid induced mechanical response changes (may alsohave requirements for moisture or solvent which also have shelf life).
– Biosensors liquid,mechanical or fluidic induced mechanical response changes (may alsohave requirements for moisture or solvent which also have shelf ife).
4.2Failure mechanisms
4.2.1occurrence of failure and driving force
Failures during long-term storage may be mitigated by control of the stimuli driving given failuremodes of interest as defined by risk assessment toois,for example, failure modes and effectsanalysis (FMEA).Storage related failures are often detected as modes of non-operation, visualquality, reduced life time or other non-conformance.The modes of failure during storage aretypically related to a failure mechanism that is driven by a physical stimuli or condition. Examplefailure stimuli are given in Table 1.Additional examples of deterioration mechanisms are foundin lEC 62435-2.Successful long-term storage is accomplished by mitigating failures throughcontrol of the stimuli or driving force.
4.2.2Storage environment and mitigation for stimuli to prevent failure
Mitigation of failures during and after long-term storage occurs by directly controlling or limitingthe stimulus for failure by a number of means.Common requirements for sustained long-termstorage are given in Tabie 2.Knowledge and control of the storage environment is of primaryimportance to identify the risk of failure occurrence and to control or eliminate failure stimuliduring storage. Examples of the storage environment are contained in IEC 62435-4.Otherstorage environment parameters related to long-term storage that could be important forproducts or devices with certain sensitivities are presented in Annex A. lt is the responsibilityof the end customer to maintain the storage environment, as well as to ensure that terms andconditions are in place successful long-term storage at the time of product purchase.
The full component thermal and environmental chain should be considered in planning reliabilitycharacterization evaluation and for estimation of reliability after storage,and added to the usereliability estimates.
4.5Documentation/paper lot identifiers
Lot information and documentation can be stored with units in LTS as a method to ensure unitlevel and lot level identification during storage and prior to use.Lot information recorded onpaper and electronic devices are subject to the same restrictions for absorbed or adsorbedmoisture,chemical contaminants or oils that may provide stimuli for failure of parts upon finalassembly.