22.214.171.124 Part Obsolescence and
Diminishing Manufacturer Sources (DMS)
Obsolescence occurs when parts that are required for system
support are no longer manufactured (usually due to insufficient market
demand). It is a common occurrence within the DoD for systems to have
lifetimes greater than the life cycle of their supporting part technologies.
Hence, part obsolescence is typically more of a problem for military systems
than for commercial systems. Also, parts qualified for military use have
historically represented more mature technologies relative to those used in
non-military applications. The potential for diminishing manufacturing
sources, causing parts that are not yet obsolete to become unavailable, must
also be considered. This unavailability can be the result of the manufacturer
experiencing limited orders, downsizing, market instability, or the result of
other business decisions to exit the market for a particular technology or
device. Regardless of the reason, the part is unavailable, and the effect is
essentially the same as if the part had become obsolete.
Part and vendor obsolescence management should be a basic part
of a companyís operating, design, and manufacturing procedures (i.e., best
commercial practices) and be substantially product independent, evolve around
needed components, operating environments and package styles. Implementation
of an effective PMP requires diligent management in maintaining part
availability for system support, including taking the actions necessary to
maintain availability of parts that are, or will be, obsolete during the
equipment life cycle. Such actions can be grouped into two categories:
management and technical.
Management solutions to part availability problems include
preventive measures to alleviate the use of potentially obsolete parts,
detection of the use of potentially unavailable parts, and identification of
the need to procure an adequate quantity of parts to support the equipment
throughout its life cycle. Management solutions include the use of a PPL and
the lifetime purchase of parts to ensure part availability in the event that
they become obsolete. This latter solution carries its own risks and burdens
(for example, provisions for storing the parts in a sufficiently benign
environment that precludes the occurrence of storage-related failure
Technical solutions include replacement of the unavailable part
with an equivalent part, device emulation, and system redesign. If there is a
direct replacement available, substitution is usually the easiest and least
costly solution. There are several semiconductor information sources that can
assist in the identification of equivalent parts. These include the IC Master
and Part Master (available from International Handling Services), and Computer
Aided Product Selection (CAPS) (available from Cahners Publishing).
Early notification of part/vendor end-of-life status provides
time to select an acceptable solution that will minimize the identified
problemís impact on manufacturing. External sources such as the Defense
Logistics Agency/Defense Supply Center Columbus (DLA/DSCC), Government
Industry Data Exchange Program (GIDEP) and vendors, as well as management of
the companyís internal PPL, can be used to provide early notification. Figure
7.2-2 illustrates a process flow for short and long term solutions that takes
place when obsolete part notification is received. The major difference
between short and long term solutions is that, in the long term solution, even
when a part or vendor exists or another solution is found, the effort does not
stop. As mentioned, it is critical that the solution is not just a stop gap
and that long term support issues are addressed. Therefore, a trade study
using the factors indicated in Figure 7.2-2 is performed to ensure a long term
solution is not required in the future. (This concept is further described in
"767 AWACS Strategies For Reducing DMS Risk").
When a device has been identified as needed but unprocurable,
the most practical solution is emulation. Device emulation is a process by
which a direct replacement is designed and fabricated for an unavailable part.
The design task may include reverse engineering, simulation, or direct design
and fabrication (if original schematics and drawings are available). The
Defense Logistics Agency (DLA) currently leads such an emulation program,
referred to as the Generalized Emulation of Microcircuits (GEM).
System redesign is also a possible technical solution to
alleviate the dependence on unavailable parts. Device emulation and system
redesign can be very costly solutions to the unavailability problem.
Implementation of preventive measures early in the part selection process can
provide significant cost savings as the system reaches end-of-life.
The VHSIC Hardware Description Language (VHDL) is a valuable
tool that can assist in the emulation or redesign of devices. VHDL is fast
becoming the hardware description language of choice because it is an
IEEE standard and has technology process and vendor independence, CAD tool
support, and top-down design methodology capability. What is required is a
VHDL behavioral description of the obsolete device or printed wiring assembly.
The next step is to produce a structural VHDL description of the design to be
emulated, which can then be processed by logic and layout synthesis tools of
choice. This emulated design can then be processed by a compatible wafer
foundry processing capability and packaged appropriately for