Wafer Storage & Management for Extending Product Lifecycle

Flexibility is achieved as die/wafer inventory can be used to satisfy many user requirements for such things as package type, screening level, and speed grades. With packaged devices, the flexibility is lost as these product choices must be made at assembly. The only costs immediately incurred are the wafer cost and the costs of maintaining the storage environment. Other costs such as assembly, test, screening, marking, and packaging are postponed until specific orders are received. Die and wafers stored in wafer storage containers or waffle packs also take up a fraction of the space of finished devices, providing the benefit of reduced space requirements and lower cost.

Finally, and most critically, storage in die/wafer form can reduce the potential failure mechanisms that are inherent in storage of finished devices, especially when compared to devices in plastic packaging. Mishandling of die/wafers can result in corrosion or scratching of the die or bond pads, while mishandling of ceramic packaged parts can result in package cracking, corrosion, or lead solderability issues. In addition to these package issues, plastic devices are also subject to other potential problems due to moisture issues, including delamination, outgassing, and the requirement for repeated testing and repacking. Overall, the risks to product damage are reduced when stored in die/wafer form.

The proper conditions include a controlled atmosphere (dry, nitrogen-purged storage is preferred), steady-state temperature conditions, cleanliness of the facility (low levels of gases and particulates), and careful handling and proper removal and replacement as wafers are pulled for builds.