MIL-PRF-19500P
APPENDIX A
A.3.15 Engineering evaluation. An engineering evaluation is an in-depth scientific investigation of anomalies or
potential problems to determine root cause and provide solutions. An analysis of a possible non-conformance or
quality defect will be performed by appropriate engineers or applicable technical experts. An assessment of the
damage or non-conformance will be documented and corrective action will be implemented. Conclusions can be
based on visual inspection, data, past history, failure analysis, destructive physical analysis (DPA), delidding, step
stress testing, electric screening, or any reasonable tool or combinations of tools. A detailed report shall be
documented and made available to the qualifying activity.
A.3.16 Failure analysis. Failure analysis (FA) is the discipline incorporating all techniques of physical, chemical
and electro-magnetic (EM) characterization of product and materials to isolate the mode of failure and define the
mechanism of occurrence. FA is used as an integral tool in root cause determination and process-segment targeting
in the corrective action procedure.
A.3.17 Forward bias. The bias which tends to produce current flow in the forward direction (p-type semiconductor
region at a positive potential relative to n-type region).
A.3.18 Failure mode and effects analysis (FMEA). A FMEA is an analytical technique used as a means to assure
potential failure modes and their associated causes/mechanisms have been considered and addressed. The process
and design FMEAs should identify process and design failure modes, and identify process and design variables on
which to focus controls for detection and occurrence reduction. It develops a list of potential failure modes and
establishes a priority system for corrective action considerations. Creation of the FMEA should start with the process
flow. A potential failure mode is defined as the manner in which the process could potentially fail to meet the process
requirements or design intent. FMEAs also include information on potential effects of failure, severity level, potential
causes, current process controls, as well as other information.
A.3.19 Metallurgical bond, diode construction, and thermal matching. Metallurgical bonds as used in JAN-brand
semiconductor devices will be identified by one of the following categories. The listing of the three types of
metallurgical bonds is for clarification and may not necessarily be listed in order of merit.
A.3.19.1 Double plug construction. Double plug construction is one where the terminal plugs have equal nominal
diameters. Plug contact with the semiconductor die may be achieved either through direct contact with the die
metallization materials or via brazing or solder preform metallization. The use of a point contact whisker or other wire
conductors is not allowed.
A.3.19.2 Dash-one construction. Dash-one diodes shall be of double plug construction utilizing high temperature
metallurgical bonding between both sides of the silicon die and attach preform or terminal pins.
A.3.19.3 Category I metallurgical bond. A category I metallurgical bond is formed when the bond between the
semiconductor element (such as silicon or germanium) and the package consists of a phase which melts during the
bonding process and which includes in the solidified melt both a portion of the semiconductor element and a portion
of the metallization layer which is on the package mounting surface. Category I bonds between adjacent
semiconductor elements (as in stacks) shall include portions of both semiconductor elements in the solidified melt.
Unless otherwise specified in the specification sheet, category I metallurgical bonds are typically required for all axial
leaded diodes, equal to and greater than 1 watt or 1 amp.
A.3.19.4 Category II metallurgical bond. A category II metallurgical bond is formed utilizing a brazing or soldering
alloy which melts during the bonding process and bonds to a metallization layer on each of the surfaces being joined.
Dissolution of the semiconductor element or any of the wetted surface layers is not required.
A.3.19.5 Category III metallurgical bond. A category III metallurgical bond is formed when the surfaces to be
bonded are brought together under conditions of temperature and pressure such that a diffusion bond is formed
between the outermost metallization layer of the elements being joined. This bond is characterized by having species
from both sides of the original interface diffused across the interface without any molten phase having been present.
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