A manufacturer may assign a date code based on date of assembly, date of seal or encapsulation, date of the marking operation, date of electrical test, or the date of any other important step in the manufacturing process. There is no standardized methodology for date code assignment. It is determined solely by the individual manufacturer. For most manufacturers, a four digit date code followed by alpha or alpha-numeric characters is a traceability indicator that the manufacturer can use for lot control in the factory. For the Distributor, the date code provides no benefit.
Inventory is maintained and replenished on a date of receipt basis.
There are some views in the purchasing and engineering community that after a two year shelf life, a semiconductor product has somehow 'aged' and is no longer 'fresh'. Twenty years ago, there may have been some truth to this perception. Twenty years ago, solderability problems were much more common than today and certain metallurgical problems worsened over time, to the extent that quality or reliability could have been compromised. Those failure mechanisms and effects are now well understood and permanent process improvements, universally adopted by a now mature industry, have eliminated the root causes of these types of problems. The three year rule was adopted for commercial procurement but is now irrelevant because of the technological advances that the industry has made in the intervening years.