Background
Department of Defense Acquisition
Reform
The Department of Defense has adopted a vision of
becoming a world-class buyer of best value goods and services from a globally
competitive industrial base.
Navy Acquisition Reform
Principles
1.
Use
Commercial Products, Practices, and Processes to
the maximum extent practicable (e.g., EIA-JEDEC standards and committees,
automotive and communication products, and SPC and process controls instead of
screening).
2.
Reliability and Maintainability (R&M) establishes the basis for a
comprehensive effort designed to assure meeting mission needs and reducing
life-cycle ownership costs.
The Navy has attempted to minimize it’s reliance on
MILSPECs and STDs for R&M through the use of guideline documents developed
cooperatively with industry experts, based on sound engineering principles and
providing technical guidance.
The acquisition reform of the Navy developed the
following reliability and maintainability information to look for when preparing
a request for proposal (RFP) or statement of work (SOW).
a.
A
design-reference mission-profile to establish adequate and complete performance
requirements. This should include functional and environmental profiles
that:
1)
Define
the boundaries of the performance envelope.
2)
Provide
the timelines (i.e., environmental conditions and applied induced stresses over
time) typical of operations within the
envelope.
3)
Identify
all constraints (e.g., conditions of storage and maintenance).
b.
Requirements
for the contractor to identify mission or safety critical single point failures
and the steps he will take to avoid them.
c.
Requirements
for the performance of parts stress analysis and testing to verify compliance
with agreed to derating criteria under worst-case mission profile environments.
The parts derating criteria should be mutually agreed upon between the
contractor and the government, taking into consideration past component history,
environmental stresses, and component criticality.
d.
Requirements
for the contractor to show that commercial and nondevelopmental items will be
operationally suitable for their intended use and capable of meeting their
allocated reliability and maintainability requirements.
e.
Shown
below is exerts from the Navy’s sample RFP checklist.
Sample Reliability and
Maintainability
RFP Checklist
RELIABILITY AND
MAINTAINABILITY
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YES
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NO
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WAIVER
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REQUIREMENTS:
Reliability Program
Maintainability Program
Availability
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DESIGN DISCIPLINES:
Stress Analysis
Worst Case Analysis
FMEA
Thermal Survey
Parts Derating
TEOOO-AB-GTP-010
Predictions
MIL-HDBK-217
ESD Control
MIL-STD-1686
Commercial
Practice
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TESTING:
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MANUFACTURING:
Environmental Stress Screening
(ESS)
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3.
Warranties –
Acquisition reform principle of risk management and maximum use of commercial
processes suggests warranties should be limited to those already in use by
industry, and a cost/risk assessment be undertaken for any proposed “government
unique” requirement.
Look for:
a.
Use
of existing warranties offered by industry or other government customers instead
of unique government warranty.
b.
Specified
reliability requirements consistent with technology advances and determination
that state-of the-art reliability provides realistic objectives and thresholds
for specification requirements.
4.
Performance
Specifications –
Acquisition reform is striving to reduce Government risk by using performance
based specifications and standards. This makes the contractor responsible for
providing the item or service requested and assuming the risk for meeting
performance requirements. In addition, the contractor can seek innovations to
efficiently and effectively achieve performance objectives.
Look for requirements
derived from a higher level requirement, i.e., specific environment and
application requirements.
5.
Risk
Management –
Acquisition reform seeks to move from a risk adverse to a risk management
philosophy. This is to streamline processes, reduce oversight and control, and
seek to reduce cost.
It is the responsibility of
the contractor to control the manufacturing processes and verify conformance to
the detail design and technical requirements of the technical data package. The
quality assurance provisions in the technical data package serve to verify
conformance of the parts and components of the system.
6.
Testing–
Test and evaluation begins when a concept to fill a military need is first
identified and continues throughout the development and operational life of the
system.
Look for:
a.
Requirements
for sufficient testing on commercial and non-developmental items to ensure
performance, operational effectiveness, and operational suitability for the
military applications.
b.
Test
program tailoring to recognize previous commercial testing and
experience.
c.
Modeling,
simulation, and process control techniques instead of development and production
testing.
Microcircuit Usage in
Military Applications
The NAVSEA Part Requirement & Application Manual,
TE000-AB-GTP-010 Revision 2, complies with acquisition reform policies and
principles established by DoD.
DoD acquisition reform policy guided and directed these
positions stated herein.
1.
Selecting
Microcircuits
a.
DoD does not have a selection process (e.g., QML first, military SCD
second, industrial third and commercial fourth).
b.
The
policy is to use the best commercial products to get the best
value.
c.
The
application establishes performance and environmental requirements, a
reliability plan and then selects the best value microcircuit for the
application.
d.
DMS,
legacy and maintenance part selection should be done somewhat differently than
with new design. The government usually owns this legacy equipment, the
configuration is set and the product is mature or diminishing. By contrast, a
contractor controls the new design and has broad flexibility in selecting
product. DoD needs to develop a road map so these selection processes come
together as one. Logistic support is
essential in developing this road map which balances commercial concepts with
application life needs.
2.
Uprating
Microcircuits
a.
DoD
acquisition reform says to use the best commercial practices. For the
design-discipline of characterizing for a specific application, derating the microcircuit within the
application is the best practice.
b.
The
acquisition reform reliability-principles of the Navy require part derating,
stress analysis and a thermal survey. Uprating is not required and adds no
value. There will be an added cost to uprate - screen and a risk of
over-stressing the parts. In addition, the acquisition reform risk management
principle requires an added cost
justification.
c.
A
microcircuit manufacturer lists ratings, characteristics, and temperature
limitations by technology and package style. The manufacturers, for application
usage, list derating curves. They do not address uprating for application
selection.
d.
The
equipment manufacturer industry (e.g., military, automotive, and computer)
design by derating microcircuits to
applications. They do not design or establish reliability by uprating.
e.
No
scientific body recognizes the term uprating.
f.
The
definition of uprating “a process to
assess the capability of a component to meet the performance requirements of the
application in which the component is used outside the manufacturer’s
specification range” is broad and vague.
3.
Using
a microcircuit in a higher temperature application than its data sheet
range.
a.
This
had been unacceptable. It breaks design disciplines, the part’s data sheet
temperature ranges, and reliability and maintainability
requirements.
b.
This
is beginning to be done in the design-selection process. The way to do it is to
maintain strict commercial best practice
principles.
c.
When
design selecting, do so to the part’s true-characteristics, not the data sheet
limitations.
d.
A
part’s data sheet range may be exceeded, as long as the part’s junction
temperature and maximum parameter characteristics are never exceeded. Derating
the part’s power dissipating parameters is the best practice to control the
junction temperature.
4.
Screening microcircuits to be used outside their designated data sheet
range.
a.
This
breaks many of the acquisition reform principles (e.g., best commercial
practices, products, and processes, and reliability and maintainability
principles).
b.
Thermal
– characterization, to JEDEC Standard 51 Thermal Test Method, is the best
commercial practice to characterize parts. The application temperature with the
part’s junction temperature can easily be calculated to determine the part
derating. This test method is precise
and repeatable in measuring a part’s junction temperature at different airflow
temperature conditions. The test equipment can easily be setup at a lab to
assess a part’s thermal characteristics.
c.
Whatever
screen is used, it has to be a repeatable measurement of the part’s junction
temperature and a non-destructive test. The information gathered combined with
the application temperature is used to calculate the part’s derating factor.
d.
It
is unacceptable to use a part just because it passed screening to temperature
extremes. Furthermore, these kinds of screens will probably over-stress the
parts.
Conclusion
Military applications use
commercial microcircuits with no restrictions other than design and performance
requirements.
Commercial microcircuits are
beginning to be designed into military applications beyond the microcircuit data
sheet ambient temperature range.
Functional
design for
an application will not automatically give a system acceptable reliability and maintainability. In some
cases such as a high-speed CPU, the
reliability or maintainability is also tied to the reliability and maintainability of the
cooling fan attached to its surface. Something besides the function is required
to assure operation through a critical mission and for the entire life
cycle.
When using commercial parts in military applications
NAVSEA – Crane recommends:
1.
First,
define the environment (i.e., application temperature, moisture, salt,
etc.).
2.
Design
to the part’s true-characteristics; not the data sheet range, unless that is
acceptable.
3.
Select
by junction temperature not ambient range.
4.
Use
JEDEC 51 Test Method to verify the part’s temperature characteristics.
5.
When
screening for a part’s temperature characteristic use JEDEC 51 Test
Method.
6.
DSCC
should control lab suitability of test labs that screen commercial parts for
military applications.
7.
Only
select parts that meet the application ambient and part junction temperature
calculated with the application’s airflow
volume.
8.
Derate
parts to meet application and part junction-temperature limit.
9.
Control
parts used beyond their recommended boundaries through a government IPT and/or
DSCC. In addition, establish a risk assessment for the application.
10.
Use the term uprating as a general concept not a
specific requirement. Use the terms re-characterize or derate when specifically
required. Re-characterization is a good term to use in place of uprating when stated as a
requirement.
11.
The contractor, not the government, is
responsible for parts designed and used beyond their warranty in an application.
The government’s concern is managing risk, logistic support and getting the best
value product.
12.
Military, QML and SMD parts need to be
available, for logistic support, with no required screening or quality
conformance inspection (QCI) other than for process control. The same as with
commercial parts. This would change and establish a new logistic support
practice, similar to commercial practices, for DoD. The part manufacturer should
control the Military, QML and SMD part manufacturing process. Required tests or
screens should be imposed only for an application reason or manufacturing
control.
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