ECMA has released a new standard that specifies an accelerated aging test method for estimating the life expectancy of recordable or rewritable optical disks.
The property referred to as the archival life of
data recorded to optical media plays an increasingly important role for the intended applications.
ECMA's new standard provides a methodology for applying an accelerated aging test method for estimating the life expectancy for the retrievability of information stored on DVD-R/-RW/-RAM, +R/+RW optical discs.
The methodology includes the effects of temperature (T) and relative humidity (RH) in the degradation of the readability of an optical disc. In brief, optical media samples are stored special ovens under different high-stress environments of temperature and relative humidity, for an extended period of time. The disks were tested periodically to monitor the effect of temperature and humidity on the error rate (PISum8, BER). Each disk has its initial error rates measured before their exposure to "stress conditions". The stress conditions are used to accelerate the chemical reaction rate from what would occur normally at ambient or usage conditions. The chemical reaction is considered degradation in desired material property that eventually leads to disc failure. Thereafter, each disk is measured for its error rates after each stress condition time interval. For all those unfamiliar with the optical stroage quality measurements, we should mention that "error rate" is the rate of errors on a disc measured before error correction is applied.
The results are then applied to the Arrhenius and the Eyring acceleration models, a set of mathematical procedures and computations for accelerated aging, which assume that temperature and relatively humidity are the crucial variables that over time affect the longevity of optical media.
The results are used to determine if an optical disc will or will not exceed a life expectancy of X-years.
ECMA's approach does not attempt to model degradation due to complex failure mechanism kinetics, nor does it test for exposure to light, corrosive gases, contaminants, handling, and variations in playback subsystems. Disks exposed to these additional sources of stress or higher levels of T and RH are expected to experience shorter usable lifetimes.
The project was initiated by the Optical Storage Technology Association (OSTA) and developed the initial
drafts. Following that development, the project was moved to Ecma International TC31 for further development and finalization. NIST, CDs21 Solutions, and DCAj have also supported the development of the standard.