Choosing a Die and Wafer Banking Partner? Pay Attention to Recovery Times

By Logan Wamsley

As the use of ASICs in product designs continues to grow – and die and wafer banking becomes more prominent in OEM obsolescence management strategies – it is important for OEMs to consider the new variables necessary to package, store, and handle such sensitive raw material successfully.

Of these variables, arguably the most important is relative humidity. Nearly all electronic components are sensitive to moisture — but when stored in basic die and wafer form prior to assembly, even the humidity levels of climate-controlled ambient storage (typically averaging between 30% and 60% relative humidity) are enough to corrode the silicon-based compound that die is composed of. To account for this, companies who wish to create a long-term storage infrastructure suitable for die and wafer banking require highly specialized desiccant dry cabinets designed specifically to absorb excess moisture and create a suitable climate.

Most dry cabinets on the market accomplish this through the use of nitrogen, which is capable of reducing relative humidity to between 5% and 10%. While this is a suitable level, maintaining such a low relative humidity over an extended period of time is contingent on other factors as well, such as the frequency the interior of the cabinet is exposed to the outside environment. Ideally, wafers would only be taken out of their highly regulated cabinet at the time of assembly – but, of course, OEMs do not assemble a product at a single specified time, but periodically throughout the course of a product’s life cycle.

The recovery time of a dry cabinet is the time a dry cabinet must remain sealed from the outside environment before the relative humidity once again reaches an appropriate level. For example, a standard nitrogen-enriched dry cabinet can take as long as 20-30 minutes to return to a 5%-10% relative humidity. Repeated exposure within this window could potentially compromise the functionality of the die. To account for this limitation, handlers can only afford to interact with the raw material a single time within this window. Such a tight restriction obviously can have a significant impact on the timetable of a product’s assembly, and if mismanaged, it can result in a substantial decrease in output.

Bank Die and Wafer “Smarter”

The ECD SmartDRY™ Dry Cabinets offered as part of the Partstat Custom Storage & Fulfillment Solution is the next evolution in die and wafer banking technology. Instead of coping with a 30-minute recovery time in between the handling of the moisture-sensitive material, SmartyDRY™ has reduced that window to less than three minutes. As a result, wafers can be safely retrieved and prepped for assembly up to an industry-leading 10-12 times per hour.

Such a drastic decrease in recovery time is made possible through our use of a naturally-occurring, clay-like, volcanic compound called zeolite that exhibits humidity control qualities far superior to nitrogen. As the cornerstone of SmartDRY™ technology, not only is zeolite capable of absorbing moisture quickly, but it can also intelligently maintain a relative humidity of 0.5 percent – far below the IPC standard.

Adding such flexibility to the handling of a critical component – even one as sensitive as a silicon wafer – not only has been proven to help the resulting product function as intended, for as long as intended, but it also gives our customers the ability to adapt to any unforeseen changes in their supply chain projections. If consumer demand suddenly increases, for example, and they wish to increase product output, Partstat will be able to fulfill the necessary die and wafer at a rate more than double that of a competitor who uses standard nitrogen-enriched cabinets.

We like to look at our use of ECD SmartDRY™ Dry Cabinets as innovation without compromise. Technology that can do something better, safer, and more efficiently than any other offering on the market — without any drawbacks— should be technology no OEM should have to live without. If you are considering incorporating die and wafer banking into your obsolescence management strategy, the Partstat Custom Storage & Fulfillment Solution should be the only place you need to look.