Diagnosis of Malfunctions in Complex Electronic Assemblies. Final Report. Page: 45 of 66
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In the second evaluation, a group of 40 production units was randomly tested
and rejects were investigated. The units were visually and electrically in-
spected. Inspection personnel were not aware that special conditions existed.
Seven of the first 14 units failed because of a missing wire. Two failed be-
cause of out-of-tolerance capacitors, and one failure was not detected. The
undetected failure was not immediately rejected during the inspection tests.
That component was a reversed tantalum capacitor failure which was aggra-
vated by stress. Table 3 summarizes these results.
Table 3. Product Defects Detected During the Second Evaluation
Number Nature Inspection Tester Verifier
Faults Faults ot)ected Undetected Detected Uindetected
7 Missing 0 7 7 0
2 Out-of- 0 2 2 0
1' Misoriented 1 0 0 1
* This capacitor was a tantalum capacitor that was reversed. Neither
the verifier nor the inspection tester rejected this unit until after
continuous stress aggravated the unit.
Total Units Evaluated 40
Total Existing Faults 10
Rejects (percent) 25
The appropriate production operator was alerted to the missing wire over-
sight. Investigation reflected that the next three levels of inspection testing
did not check for the presence of this connection. Corrective rework and
reassembly time at the higher level was estimated at 2 hours. Reflow time
was estimated at 72 hours. This included retesting and visual inspection
The two capacitors had capacities reading slightly out of specification, but
did not cause any output parameters to be out of tolerance. They did cause
one parameter to shift significantly away from normal distribution.
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Losure, J. A. Diagnosis of Malfunctions in Complex Electronic Assemblies. Final Report., report, January 1, 1971; Kansas City, Missouri. (https://digital.library.unt.edu/ark:/67531/metadc1031893/m1/45/: accessed March 24, 2019), University of North Texas Libraries, Digital Library, https://digital.library.unt.edu; crediting UNT Libraries Government Documents Department.