jackscrews A means of
controlling the plugging together of
connectors and locking them in place.
Rotation of the screws jacks the
connectors together or apart. This is
particularly useful for connectors
having a large number of contacts and
therefore a high insertion and
withdrawal force.
JEDEC = Joint Electronic
Device Engineering Council
JEDEC is the semiconductor engineering
standardisation body of the Electronic
Industries Association (EIA), and
develops and publishes configuration
standards for semiconductor device
packages.
JIT = Just-In-Time
Minimizing inventory by supplying
material and components directly to the
manufacturing line just before
incorporating them into the product.
J-lead A lead
configuration typically used on plastic
chip carrier packages which have leads
that are bent underneath the package
body. A side view of the formed lead
resembles the shape of the letter ‘J’
The PLCC has J-leads on all four
sides, and the limiting factors regards
lead dimension is the need to form the
leads. In consequence, PLCCs typically
have a lead spacing of 1.25mm (0.05 in).
J-leads made with thinner material, and
on closer pitches, are generally only
found in the SOJ package, used for
memory devices, which has leads only on
the two shorter edges. Whilst the J-lead
configuration appears to conserve board
space, as opposed to the gull-wing
design, the high lower limit on lead
spacing means that J-lead packages are
generally substantially bigger than the
gull-wing equivalents
jumper A component
or wire that forms a discrete electrical
connection between conductive areas on
the external surface of a circuit board.
Some jumpers are added during normal
assembly, through-hole components using
formed wire, and surface mount
assemblies using zero-ohm chip
resistors. Others are pluggable
components.
Another use of the term ‘jumper’ is
for an electrical connection which is
added after fabrication, usually to
correct errors or to enable modification
of circuitry. Such jumpers are typically
made of wire (exceptionally of flexible
circuit board), soldered to the surface,
and thus referred to as “wire adds”. In
order to ensure a reliable joint, this
repair operation has to be conducted
with extreme care, An alternative way of
making jumpers uses wire-wrapping around
terminals
junction temperature
The operating temperature of the active
element of a circuit component.
