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DISCRETE WIRING
DEADBUGS
DEADBUGS
The term “Deadbugs” is an industry nickname
for the discrete components added and wired
into a printed wiring assembly (PWA) to
facilitate active circuit modifications, rather
than redesign and manufacture a new board.
The nickname comes from their general
appearance on the board: upside down, with
their termination leads (legs) up in the air – like
a dead bug.
While their use is an accepted practice, the
customer must grant approval prior to their use
and installation.
DISCRETE WIRING
DEADBUGS (cont.)
ACCEPTABLE
PIGGYBACKING / STACKING TO ICs
AXIAL / RADIAL / SMT COMPONENTS
IC piggybacking is acceptable when space and/or
noise requirements prohibit more traditional
placement methods. Component leads / jumper
wires shall meet minimum bend requirements.
Best Workmanship Practice
UNACCEPTABLE
IMPROPER LEAD DRESS
Dead-bugged components shall be mounted and
dressed in a manner that prevents shorting of the
leads to the component case (pictured) or to
other conductors.
Best Workmanship Practice
PREFERRED
AXIAL-LEADED COMPONENT
Component is properly mounted. Lead bends are
within limits. Terminations are properly wrapped.
The solder joints meet all minimum requirements.
Jumper wires have appropriate stress relief.
Best Workmanship Practice
PREFERRED
GLASS-BODIED COMPONENT
Component is covered with a transparent resilient
sleeving, and properly mounted. Lead bends are
within limits. Terminations are properly wrapped.
The solder joints meet all minimum requirements.
Jumper wires have appropriate stress relief.
Best Workmanship Practice
UNACCEPTABLE
IMPROPER MOUNTING ORIENTATION
Components shall be mounted with the leads in
an orientation that ensures the terminations meet
minimum electrical spacing requirements. As
pictured, the component terminals are resting on
exposed circuitry and vias.
Best Workmanship Practice
UNACCEPTABLE
IMPROPER MOUNTING
SMT COMPONENTS MOUNTED ON LEADS
Chip and MELF devices shall not be directly
mounted on component leads of integrated circuit
(chip) packages.
Best Workmanship Practice
PREFERRED
DUAL-INLINE PACKAGE (DIP)
Component is properly mounted and terminated.
Jumper wires are properly terminated, with
appropriate stress relief. The solder joints meet
all minimum requirements.
Best Workmanship Practice
PREFERRED
RADIAL-LEADED COMPONENT
Component is properly mounted and terminated.
Lead bends are within limits. Terminations are
properly wrapped. The solder joints meet all
minimum requirements. Jumper wires have
appropriate stress relief.
Best Workmanship Practice
UNACCEPTABLE
IMPROPER SOLDER TERMINATION
LEADED DEVICES
Jumper wires shall be lap soldered to the device
leads. Wrapped terminations place stress on the
component lead, and may violate minimum lead-to-
lead electrical spacing requirements.
Best Workmanship Practice
UNACCEPTABLE
IMPROPER STAKING
The component shall
adhesive
material,
documentation.
Best Workmanship Practice
be secured with an
per
engineering
NASA WORKMANSHIP STANDARDS
Released:
Revision:
Revision Date:
NASA WORKMANSHIP STANDARDS
Released:
Revision:
Revision Date:
05.31.2002
Book:
Section:
Page:
05.31.2002
Book:
Section:
Page:
3
3.03
1
3
3.03
3
DISCRETE WIRING
DEADBUGS (cont.)
DISCRETE WIRING
DEADBUGS (cont.)
UNACCEPTABLE
IMPROPER TERMINATION WRAP
Jumper wires shall be wrapped at least 180° to
270° around the component lead prior to
soldering, and shall not be located closer than
one (1) lead diameter to end of the component
lead.
Best Workmanship Practice
UNACCEPTABLE
PIGGY-BACK / STACKING
CYLINDRICAL / MELF COMPONENTS
The piggy-backing / stacking of cylindrical / glass-
bodied / MELF components is not recommended.
Best Workmanship Practice
PREFERRED
SURFACE MOUNT TECHNOLOGY
CHIP / MELF / METALLIZED TERMINALS
Component is properly mounted and terminated.
Jumper wires are properly terminated, with
appropriate stress relief. The solder joints meet
all minimum requirements.
Best Workmanship Practice
PREFERRED
SURFACE MOUNT TECHNOLOGY
GULL-WING / J-LEAD / LEADED DEVICES
Component is properly mounted and terminated.
Jumper wires are properly terminated, with
appropriate stress relief. The solder joints meet
all minimum requirements.
Best Workmanship Practice
UNACCEPTABLE
TOMBSTONED TERMINATION
Deadbugged components shall be mounted parallel
to and in contact with the base laminate, or base
component (if applicable). Tombstoning places
unacceptable stress on the component/solder pad
termination.
Best Workmanship Practice
PREFERRED
TO-CAN COMPONENT
Component is properly mounted and terminated.
Lead bends are within limits. Terminations are
properly wrapped. The solder joints meet all
minimum requirements. Jumper wires have
appropriate stress relief.
Best Workmanship Practice
ACCEPTABLE
AXIAL COMPONENT PIGGYBACK
Axial components may be piggybacked to axial
components in a vertical or horizontal orientation,
but shall be staked. Terminations shall meet
minimum lead seal spacing, lead bend, wrap, and
solder fillet requirements.
Best Workmanship Practice
ACCEPTABLE
CHIP / MELF / METALLIZED TERMINALS
ALTERNATE MOUNT
Chip component mounting to a single pad is
acceptable, provided the component is properly
staked to prevent stress to the solder joints or the
component body.
Best Workmanship Practice
ACCEPTABLE
PIGGYBACKING / STACKING
SMT (3-5 SIDE) CHIP COMPONENTS
The components are in vertical alignment, with no
overhang. The terminations exhibit fully wetted
solder fillets and the stack does not exceed two
(2) components high.
Best Workmanship Practice
NASA WORKMANSHIP STANDARDS
Released:
Revision:
Revision Date:
NASA WORKMANSHIP STANDARDS
Released:
Revision:
Revision Date:
05.31.2002
Book:
Section:
Page:
05.31.2002
Book:
Section:
Page:
3
3.03
4
3
3.03
2

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