THROUGH-HOLE SOLDERING
DISCRETE WIRES
discrete wire
DISCRETE WIRES

Designs ofter require the termination of discrete conductors directly to the printed wiring board, rather than to terminal posts or through a connector. Terminations are typically through-hole, but lap terminations are also possible.

All discrete wires are considered to be components - with the same bending, soldering and stress relief requirements seen for other discrete axial/radial devices.

See Section 6.01 "Through-Hole Soldering, General Requirements", for common accept/reject criteria.
interim assembly through hole termination of discrete wire final assembly through hole termination of discrete wire

PREFERRED

THROUGH-HOLE TERMINATION
INTERIM ASSEMBLY

The conductor enters the hole, perpendicular to the board surface, and exhibits proper insulation clearance and lead protrusion. The wire end may be clinched to aid assembly.

NASA-STD-8739.3 [8.4]

PREFERRED

THROUGH-HOLE TERMINATION
FINAL ASSEMBLY

The termination exhibits proper insulation clearance and lead protrusion. The termination is fully wetted, with complete fillet formation on both sides of the board.

NASA-STD-8739.3 [8.4]
insulation gap excessive insulation gap

ACCEPTABLE

INSULATION GAP

The insulation gap (referenced from the first point of contact of the conductor to the terminal) shall be less than two (2) wire diameters, but shall not be imbedded in the solder joint. The wire contour shall be visible at the end of the insulation.

NASA-STD-8739.3 [9.1.1], [9.1.2]

UNACCEPTABLE

EXCESSIVE INSULATION GAP

The insulation gap exceeds the maximum of two (2) insulated wire diameters, and may present a shorting or birdcaging potential.

NASA-STD-8739.3 [9.1.1], [13.6.2.a.2]
NASA WORKMANSHIP STANDARDS
NASA logo Released:
06.27.2002 		Revision:
 		Revision Date:
Book:
6 		Section:
6.15 		Page:
1




THROUGH-HOLE SOLDERING
DISCRETE WIRES (cont.)
insufficient insulation gap multiple conductors

UNACCEPTABLE

INSUFFICIENT INSULATION GAP

The insulation is imbedded in the solder joint and the contour of the conductor is not visible.

NASA-STD-8739.3 [9.1.1], [13.6.2.a.2]

UNACCEPTABLE

MULTIPLE CONDUCTORS

No more than one conductor shall be inserted into any one hole, unless specified on the engineering documentation.

Best Workmanship Practice
lapped termination improper lap termination

ACCEPTABLE

LAPPED TERMINATION

The termination shall be parallel to the longest dimesnion of the pad, and exhibit a complete solder fillet around all sides of the lead. The conducotr shall not exhibit end overhang. A heel fillet is mandatory.

NASA-STD-8739.3 [11.2.5]

UNACCEPTABLE

IMPROPER LAP TERMINATION

The lap termination shall not overhang the land edge and/or violate minimum electrical spacing.

Best Workmanship Practice
strain relief improper strain relief

ACCEPTABLE

STRAIN RELIEF

Stress relief shall be incorporated, wherever possible, into all leads and conductors terminating in solder connections to provide freedom of movement of part leads or conductors between points of constraint.

NASA-STD-8739.3 [8.1.1], [8.1.5]

UNACCEPTABLE

IMPROPER STRAIN RELIEF

The termination does not exhibit an acceptable strain relief bend and is not properly staked. There is a potential for any pulling stress to transfer to the solder joint (note the termination is lightly bent) and eventual fracture fatigue.

NASA-STD-8739.3 [8.1.1], [13.6.2.a.10]
NASA WORKMANSHIP STANDARDS
NASA logo Released:
06.27.2002 		Revision:
 		Revision Date:
Book:
6 		Section:
6.15 		Page:
2






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