BY Dean Frazier
Unlike typical commercial product lifetimes of a few years, most aerospace and defense program lifetimes are measured in decades. A significant dichotomy exists between the short lifetimes and large volumes of commercial products and the long lifetimes and smaller volumes of aerospace and defense programs. Semiconductor suppliers typically target the commercial market windows, and when this market slows, the products are discontinued, creating problems for aerospace and defense contractors dependent on continuous product availability throughout the program lifetime.
Traditionally, these suppliers have not been interested in providing a path to extend the lifetimes of critical ICs. Roughly three percent of the global pool of electronic components is made obsolete every month, and on many aerospace and defense projects, a majority of the semiconductor Bill of Materials are out of production before the program is even commissioned.
Obsolescence mitigation, typically not implemented until the end-of-life or last-time-buy announcements, has been the default approach to this problem. Obsolescence mitigation has focused primarily on either buying enough components to supply the total program requirements or undertaking a major system redesign.
The first option depends on the unlikely circumstance of perfectly forecasting lifetime component needs, and does not offer a long-term solution for extending program lifetimes beyond the original plan.
The second option is very costly, and is dependent on the essential resources being available well after the original design effort. Obsolescence mitigation is reactive and error-prone due to the lack of long-term strategic planning in the face of normal supply-and-demand realities. "Mitigation" accurately connotes only a partial fix to mil-aero supply chain challenges. Aerospace and defense contractors need a new methodology providing the integrated services essential to securing long-term continuity and quality of supply at a predictable cost.
Semiconductor life cycle
A new approach is essential to the design, manufacture, and long-term support of aerospace and defense systems. Preparing for component obsolescence effects is essential to the semiconductor life cycle management (SLiM) concept, a process which plans for the obsolescence of semiconductors at introduction, rather than waiting until the end-of-life announcement.
SLiM anticipates and prepares for known obsolescence problems and provides an approach to sustaining long-term support. Unlike obsolescence mitigation, SLiM doesn't merely "mitigate" obsolescence, it anticipates and eliminates it.
Suppliers providing semiconductor life cycle management understand that strategic foresight and preparation are essential to meeting the market needs. The adoption of a SLiM approach anticipates the uncertainties and disruptive conditions rampant in markets where extended lifetimes are required to meet program requirements. A solid SLiM approach includes long-term supply plans throughout the introduction, volume production, and eventual demand reduction phases in the life of semiconductor devices.
An effective SLiM program integrates many critical aspects in three key phases.
Phase 1: introduction
- Selecting semiconductor partners who have the capability to support long-term production of a variety of components
- Collaborating with key wafer fabrication, assembly, and test subcontractors
- Managing lifetime supply of key components from introduction and production release to end of life
- Working with aerospace and defense contractors to understand and manage critical component Bill of Materials
- Controlling costs by anticipating requirements and cost-effectively providing ongoing supply
Phase 2: volume production
- Banking of wafers with contained unit cost, build-out flexibility, nitrogen storage for reliability, and inventory management
- Offering a full complement of hi-rel test and packaging services
- Working with aerospace and defense contractors to review current build plans and determine which devices need on-going support
- Providing a secure supply chain delivering reduced risk and proven quality compliance
- Offering DSCC-qualified manufacturer listings and obtaining new approvals in a timely manner
Phase 3: demand reduction
- Migrating between compatible foundry sources, as needed
- Extending product life by redesigning products when fabrication and assembly resources become unavailable
- Redeveloping test programs, guaranteeing conformance with original device specifications
- Providing a domestic source of supply to meet classified program requirements
- Protecting against counterfeit risks by supplying qualified material
An effective SLiM program is valuable to commercial semiconductor manufacturers and aerospace and defense contractors. For commercial semiconductor manufacturers, the SLiM provider creates near-term revenue and cost-effectively addresses market requirements by creating a long-term revenue stream. The SLiM provider fully supports the aerospace and defense market; this allows the commercial manufacturer to focus on developing new products and permits earlier commercial product line discontinuance once demand slows.
For aerospace and defense contractors, SLiM provides even greater benefits. SLiM programs effectively plan for and manage secure continuity of supply for as long as the components are required, allowing extended production on mission-critical programs. This is its singular market value to aerospace and defense contractors. SLiM puts a process in place so program managers can be assured that devices continue flowing securely, without disruption or unforeseen financial or logistic nightmares, even after the devices are discontinued by the original manufacturers.
How is SLiM provided?
The SLiM process depends on five key aspects: partnerships, wafer supply, packaging, test programs, and quality assurance. A successful SLiM provider must be able to meet all these requirements throughout the product life cycle.
Key partnerships with commercial and military semiconductor suppliers are vital for any SLiM provider, and increase the value to the aerospace and defense contractor. A SLiM provider works with the original supplier to plan for the lifetime of semiconductors, guaranteeing continuous product availability. Unforeseen commercial product end-of-life/last-time buy announcements no longer affect the aerospace and defense contractor since the military devices will continue in production beyond the life of the commercial products.
Sourcing wafers from multiple foundry partners using a variety of processes to securely handle and store the wafers, and to verify the quality using wafer probe techniques is critical. Additionally, a SLiM provider must have capabilities in redesign and redirection to alternate fabrication facilities if the original are no longer available.
The SLiM provider must also have the capabilities in building, handling, and testing a myriad of semiconductor packages. The packages must meet all form, fit, solderability, coplanarity, and other design requirements. The supplier must also be able to redesign packages to accommodate redesigned die while meeting all of the original specifications.
Test programs are critical to all semiconductor devices and must be accurate and thorough to meet exacting standards. A SLiM provider must be able to modify test programs to use multiple testers and to conform to different platform requirements, while guaranteeing that the product meets every specification. Also, the supplier must be able to develop new test programs for re-designed die/packages while maintaining backward compatibility.
Finally, it is imperative that all the above processes meet the stringent quality requirements of the major certification agencies, such as the U.S. Department of Defense and the European Space Agency. Providing guaranteed products that meet DSCC and MIL-M-38510 specifications and comply with QML Class Q and V standards is critical. Certification to quality standards, such as the AS9100 and ISO9000 series, is also essential to guaranteeing the quality levels that aerospace and defense contractors demand.
A recent agreement with Free- scale Semiconductor provides a model for successful SLiM. The agreement extends the useful life of industry-standard 68K-series microprocessors, by planning for the extended lifetime requirements of the aerospace and defense contractors. As production of the 68020, 68882, and 68C000 processors decreases, a portfolio of high-reliability and commercial-grade products is created in both plastic and ceramic packages to meet the customer demand, and to provide availability for 10 years or longer.
Die is wafer banked based on forecasted customer requirements to ensure the continued supply following the commercial discontinuance. Licensing of the design allows the SLiM provider to continue to deliver high-reliability versions of its products, allowing building of products by sourcing commercial wafers and repackaging, screening, characterizing, and testing at extended temperatures for aerospace and defense requirements.
Another example of SLiM was identified and implemented in mid-2010. In this case, re-engineered versions of operational amplifiers, manufactured on a bipolar process, were released as drop-in replacements for the National/Fairchild LM741 used in aerospace and defense applications.
Market forecasts indicated that inventories of these military-grade devices would be depleted in the near term, and the SLiM provider is continuing production delivery of these devices.
DEAN FRAZIER is a corporate vice president of engineering with e2v Aerospace and Defense (formerly QP Semiconductor) in Santa Clara, Calif. (www.e2v.com/qp).