MIL-PRF-19500P
APPENDIX C
C.8.1.1.1 General elements of a design qualification program. A design qualification program is a qualification of
the design and the manufacturing process, more commonly referred to as PDQ. These tests are usually performed
as part of the quality design process for determining the long-term reliability of the design and the manufacturing
process. Once performed and acceptable, these tests are not repeated unless a major design change is made which
would require a new PDQ.
a.
Product failures: Perform step stress testing in order to generate failures, not produce the absence of
failures.
b.
Failure analysis: Once failure occurs, perform failure analysis (if needed) to ascertain the mechanisms
and failure rates or time to wearout.
c.
Engineering evaluations: Evaluate to constantly improve the final product quality and reliability.
d.
Failure mechanism identification: Identify and focus on failure mechanisms typical for the technology
(assembly, packages, and die-level failures).
C.8.1.2 Detailed elements of a design qualification program. Defining a device family: In order to provide
acceptable coverage during representative reliability assessment testing, all devices shall first be grouped into their
respective device families. Device families may be selected based on characteristics from the following three
categories:
a.
Package grouping based on: Package profile, volume, complexity of package construction, and number
of pins or wire bonds.
b.
Overall construction grouping based on: Die attach method, interconnect construction techniques (e.g.,
spring contact), or category of bond.
c.
Die grouping based on: Overall dimensions, aspect ratio, thickness, number of bonds, voltage,
frequency, or power rating.
When selecting device families, consideration shall also be given to differences due to the use of different production
facilities, variations in fabrication procedures, and differing design techniques. Differences or variations, which may
influence device reliability, imply that a separate device family should be established. Ignoring these factors in
creating device families shall be justified to the qualifying activity.
Identification of worst case devices: Once device families have been established, worst case device types from
within those families shall be selected which will provide coverage for the reliability assessment of all other devices
within the family. Worst case parameters (or combinations of parameters) from within the three categories listed
above (i.e., packaging, overall construction, and die) shall be identified in order to establish which devices are worst
case.
C.8.2 Process optimization. Process optimization is the mechanism to provide for continuous improvement as
equipment and materials technology changes. Following process characterization, it is necessary to optimize the
process parameters. Optimization is accomplished through identification of optimal targets and continual reduction of
variation around those targets. Process characterization should be conducted on the entire process (i.e., design
through delivery). A matrix should be developed that identifies failure mechanisms and their controls (see C.5.2
FMEA). The ability to maintain control of key process points will determine process capability.
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