Susan/Alcon:
- Mil-Spec's always prohibited bending the leads inward (toward the
centerline or longitudinal axis) of the component due to the high probability
of component failure due to entrained stress.  USN had many negative
experiences, typically the tops being separated from the body of ceramic
DIP's due to catastrophic failure of the glass frit.  The failure occurred on
both PTH assemblies when the leads were bent/clinched (partial clinch)
inward, and on SMT assemblies when the leads were  formed inward (like
J-leads, only ending up as "L" leads).  The failure mechanism (not difficult
to envision) was that stress entrained in the leads (Kovar or Alloy 42) was
communicated to the glass frit and/or the component top (upper section of the
package) in an arc which tended to lift the top off of the component.
Temperature cycling accelerated the failure rate.  Fellow named Bob Reuter
(retired) had quite a collection of photo's showing pwa's littered with DIP
tops after a relatively brief time in Fleet service.  Photos and data are
probably in a landfill somewhere as little was saved when the Naval Air
Warfare Center was shut down via BRAC (Base Realignment And Closing).
- Leads bent outward did not evidence the failure and consequently were of no
concern to DOD.  When Mil-Std-2000 was originated the requirement that DIP
leads not be bent "inward" was limited to leads which were formed manually
(since lead bending machines had no idea which way was in or out, and were
not sufficiently sophisticated (then) to be programed to such a level of
discrimination.
- Since Mil-Specs have gone away, so (for the most part) have the high
reliability  hermetically sealed components.  No hermetically sealed
components, no ceramic bodies - no glass frits, no glass frits - no
Kovar/Alloy-42 leads, no Kovar/Alloy -42 leads - no failure (plastic
components use copper leads and retain no stress after even improper lead
forming).  Nooo Problem, Be Happy.
- Hope the above helps explain why the requirement existed (once upon a time).
Regards, Jim Moffitt

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