DISCRETE WIRING
DEADBUGS
printed wiring board with deadbugs added
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.

axial-leaded components glass-bodied components

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

dual inline package radial leaded component

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

NASA WORKMANSHIP STANDARDS
NASA logo Released:
05.31.2002
Revision:
Revision Date:
Book:
3
Section:
3.03
Page:
1




DISCRETE WIRING
DEADBUGS (cont.)
component properly mounted and terminated component properly mounted and terminated

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

to can component axial component piggyback

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

chip metallized terminal stacked chip components

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
NASA logo Released:
05.31.2002
Revision:
Revision Date:
Book:
3
Section:
3.03
Page:
2




DISCRETE WIRING
DEADBUGS (cont.)
stacked components improper lead dress

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

conductor with improper mounting orientation improper mounting of surface mount termination components mounted on leads

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

leaded devices with improper solder termination improper staking

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 be secured with an adhesive material, per engineering documentation.

Best Workmanship Practice

NASA WORKMANSHIP STANDARDS
NASA logo Released:
05.31.2002
Revision:
Revision Date:
Book:
3
Section:
3.03
Page:
3




DISCRETE WIRING
DEADBUGS (cont.)
improper termination wrap stacking of MELF components

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 CONPONENTS

The piggy-backing/stacking of cylindrical/glass-bodied/MELF components is not recommeneded.

Best Workmanship Practice

tombstoned termination

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











NASA WORKMANSHIP STANDARDS
NASA logo Released:
05.31.2002
Revision:
Revision Date:
Book:
3
Section:
3.03
Page:
4





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