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Wafer Storage & Management for Extending Product Lifecycle

The key stages of semiconductor lifecycle management (SLiM) were presented in my previous blogs, so now we will delve into more specific details of a successful SLiM program. (See: Nuts & Bolts of Semiconductor Lifecycle Management, Part 1 and Nuts & Bolts of Semiconductor Lifecycle Management, Part 2.)

In this article we will take a look at device storage and wafer management issues, methodologies, and proper management of inventory levels. Here are the critical issues and steps to consider in wafer storage for extending the lifecycles of semiconductor products.

  • Device storage issues:
  • Many military contractors procure semiconductor devices in advance of project needs once end-of-life notices have been received. This technique puts the burden of cost and storage on the user but requires a crystal ball to determine the project needs far into the future. By working with a strategic SLiM supplier, contractors can avoid a last-time-buy purchase and can postpone the cost outlays until the budget year of the project build.

  • Device storage methodology:
  • The first determining factor for device storage is the storage method. Devices can be stored in die/wafer form or as packaged units. There are several advantages to storing devices in die/wafer form, including flexibility, lower cost, more compact storage, and potentially higher reliability.

    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.

  • Critical wafer storage factors:
  • Now that the decision has been made that die/wafer storage is the preferred method, the second critical factor is to develop proper storage facilities that maintain the necessary environment to ensure long-term viability. Successful wafer storage over 10 to 20 years is possible without product degradation.

    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.

  • Beyond wafer storage:
  • With all the proper controls in place to maintain and build from the wafer bank, the remaining issue is planning for the time when the wafer supply runs out. A prepared SLiM provider can anticipate the lowering levels of inventory and undertake product redesign to continue the availability of critical devices for as long as key military and aerospace programs need the devices.

    9 comments on “Wafer Storage & Management for Extending Product Lifecycle

    1. Ms. Daisy
      March 31, 2011

      Joseph:

      Considering the pace of evolution of the semiconductors, would focus on wafer storage to extend product life cycle be a cost-effective management strategy? Or is it better for product designers to take a look at product design for either portability of the product or cost-beneficial half-life of the products, therefore not worrying about the end-of-life management hassels? 

    2. Backorder
      March 31, 2011

      I cant help but point out the reports which mentioned damage to wafers inside the fabs. Now, since we are talking about wafer storage and management, and from my experience of visits to a few high tech fabs in the states, I believe the fabs are actually very well insulated from the vibrations and shocks. And given that the wafers are actually handled veyr carefully, like you mention, how is it that the quake in japan was able to damage the wafers in process?

    3. Ms. Daisy
      March 31, 2011

      Any experience with non-military equipments, such as medical equipments? The pace of change with medical electronic equipments is my point of reference.

    4. Parser
      March 31, 2011

      Semiconductor fabrication sites are protected from vibration coming through building foundations. Earthquakes however are too strong and even micro-movements can destroy nano-meter process. Japanese fabs did not report any major damage to the sites, but I am sure that any production at time of quakes and aftershocks are damaged or they have very low yield. I think this a really good idea to store ICs in wafer specifically for military needs and for spare parts in case of major production irruptions due to many reasons. Unfortunately it would be an additional cost and these runs have to be recycled just like medical emergency supplies. 

    5. SP
      March 31, 2011

      Nice article

    6. Anand
      April 3, 2011

       Nice article joseph. You said “Successful wafer storage over 10 to 20 years is possible without product degradation”. What happens after 20 years, what factors degrade the wafers ? what are the main challenges to store it safely beyond 20 years ?

       

       

    7. prabhakar_deosthali
      April 5, 2011

      Even if the wafers are stored properly for the 20 year expected life-cycle of the products in which they will be required, the associated tools for packaing these wafers , testing the packaged ICs , may not exist 10years down the line. How is this situation going to be handled?  With the current pace of the semiconductor industry , such scenario is quite possible.

    8. KarenQ
      December 19, 2013

      Have you visited this website?  www.rocelec.com

      Rochester Electronics in Massachusetts is the world leader in semiconductor obsolete material.  We are the Leaders on the Trailing Edge of Technology!  

       

       

    9. MarkSindone
      July 23, 2018

      It's probably harder to look at the control of storage and management issues from a large business perspective, but if we are talking about small companies, I'm sure that it may be a little easier to invest in a small storage unit with climate control and protection to ensure the components are well taken care of perhaps?

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