PREFERRED

COMPONENT LEADS

The component's leads have been tinned, formed and cleaned per engineering requirements. Gold plating has been removed. The spacing and radius of bends are within requirements. There is no mechanical damage to the component leads or body.

PREFERRED

CONDUCTORS/WIRE

The conductors have been stripped, tinned, formed and cleaned per engineering requirements. There is no mechanical damage to the conductor or insulation, no reduced cross-section and individual strands are discernable.

PREFERRED

TERMINATION AREAS/PWB

Termination areas have been tinned with hot-coated tin-lead solder or hot reflowed electro-deposited tin-lead solder prior to mounting of the parts. Gold plating has been removed.

PREFERRED

TERMINATIONS/MISCELLANEOUS

The terminations have been properly tinned, formed and cleaned in preparation of solder termination. The preparation of simple terminations, such as the hook and conductor termination shown, is just as important as more complex terminations.

PREFERRED

COMPONENT CENTERING

The component leads shall be bent such that the distance from the bend to the end seal shall be approximately equal at each end of the part, resulting in the centering of the part between the mounting holes.

NASA-STD-8739.3 [8.1.6.a]

UNACCEPTABLE

IMPROPER CENTERING

The component leads shall be bent such that the distance from the bend to the end seal shall be approximately equal at each end of the part, resulting in the centering of the part between the mounting holes.

NASA-STD-8739.3 [8.1.6.a], [13.6.2.a.5]

ACCEPTABLE

LEAD FORMING-BEND RADIUS

The radiius of bends in the conductor shall not be less than the lead diameter or lead thickness.

NASA-STD-8739.3 [8.1.6.a]

UNACCEPTABLE

IMPROPER BEND RADIUS

The radius of bends in the conductor shall not be less than the lead diameter or lead thickness.

NASA-STD-8739.3 [8.1.6.a], [13.6.2.a.10]

ACCEPTABLE

LEAD FORMING-BEND SPACING

The minimum distance from the part body or seal to the start of the bend in a part lead shall be a minimum of 2 lead diameters for round leads, and 0.5 mm (0.020 in.) for ribbon leads.

NASA-STD-8739.3 [8.1.6.a]

UNACCEPTABLE

IMPROPER LEAD/BEND SPACING

The minimum distance from the part body, seal or weld bead to the start of the bend in a part lead shall be a minimum of 2 lead diameters for round leads, and 0.5 mm (0.020 in.) for ribbon leads.

NASA-STD-8739.3 [8.1.6.a], [13.6.2.a.15]

ACCEPTABLE

LEAD FORMING-SMOOTH TOOL MARKS

Smooth tool impression marks resulting from tool holding forces are acceptable, provided they do not expose base metal or reduce cross-sectional area.

NASA-STD-8739.3 [7.2.3], [8.1.6.d]

UNACCEPTABLE

REDUCED CROSS-SECTIONAL AREA

Part leads and other conductors that have deformation/damage resulting in a reduced cross-sectional area shall not be used.

NASA-STD-8739.3 [7.2.3], [8.1.6.d]
NASA-STD-8739.4 [10.1.3]

ACCEPTABLE

PREFORMING/SIZING

Part leads shall be formed so that they may be installed into the holes in the PWB without excessive deformation that can stress the part body or end seals. All leads should be tinned and formed prior to mounting.

NASA-STD-8739.3 [8.1.6.b], [8.1.6.c]

UNACCEPTABLE

IMPROPER PREFORMING/SIZING

Part leads shall be formed so that they may be installed into the holes in the PWB without excessive deformation that can stress the part body or end seals.

NASA-STD-8739.3 [8.1.6.b], [8.1.6.c]

ACCEPTABLE

TINNING-COVERAGE

The portion of stranded or solid conductors, or part leads shall be solder tinned and cleaned prior to attachment. The solder shall completely wet the conductor and exhibit 100% coverage.

NASA-STD-8739.3 [7.2.5], [7.2.6]
NASA-STD-8739.4 [10.1.5]

UNACCEPTABLE

IMPROPER TINNING (COVERAGE)

The solder shall completely wet the conductor and shall exhibit 100% coverage.

NASA-STD-8739.3 [7.2.5], [7.2.6], [13.6.2.a.3]
NASA-STD-8739.4 [10.1.5]

ACCEPTABLE

TINNING-DIMENSIONS

Hot tinning of solid conductors and part leads shall not extend closer than 0.5 mm (0.020 in.) to part bodies, end seals or insulation, unless the part configuration and mounting configuration dictate.

NASA-STD-8739.3 [7.2.5.a]

UNACCEPTABLE

IMPROPER TINNING (SPACING)

The tinning has extended closer than 0.5 mm (0.020 in.) to the part body/lead seals, and may have compromised the hermetic seal.

NASA-STD-8739.3 [7.2.5.a], [13.6.2.a.3]

ACCEPTABLE

TINNING-DIMENSIONS
(SPECIAL EXEMPTION)

In instances where conductor tinning is required to be closer than 0.5 mm (0.20 in.), the part body, end seals, or insulation shall be inspected for damage and results recorded.

NASA-STD-8739.3 [7.2.5.a]

ACCEPTABLE

TINNING-GOLD REMOVAL

Gold plating on all surfaces that become part of finished solder connection shall be removed by two successive tinning operations, or by other approved processes.

NASA-STD-8739.3 [7.2.5.c]

ACCEPTABLE

TINNING-STRANDED WIRE

The solder shall completely wet the conductor, penetrate to the inner strands, and exhibit 100% coverage. Wire strands shall be distinguishable. Wicking of flux or solder shall be minimized.

NASA-STD-8739.3 [7.2.5], [7.2.6]
NASA-STD-8739.4 [10.1.5]

UNACCEPTABLE

DAMAGED INSULATION

After stripping and tinning, the conductor insulation shall not exhibit any damage, such as nicks, cuts or charring. Conductors with damaged insulation shall not be used.

NASA-STD-8739.3 [13.6.2.a.1]
NASA-STD-8739.4 [19.6.2.a.2]

ACCEPTABLE

TINNING-TERMINALS/SOLDER CUPS

Terminals and solder cups shall be solder tinned, examined for damage, and cleaned prior to the attachment of conductors.

NASA-STD-8739.3 [7.2,5], [7.3.1], [7.3.2]

UNACCEPTABLE

DAMAGED CONDUCTOR-GENERAL

After removal of the conductor insulation and/or lead forming, the conductor shall not be nicked, cut or scraped to the point that base metal is exposed.

NASA-STD-8739.3 [13.6.2.a.8]
NASA-STD-8739.4 [19.6.2.a.1]

UNACCEPTABLE

EXCESSIVE WICKING

The use of flux and the solder-tinning operation shall be controlled to limit wicking under the insulation.

NASA-STD-8739.3 [7.2.5]
NASA-STD-8739.4 [10.1.5]