PREFERRED

The part is properly oriented to the land pattern, with each lead centered across the width of the land. Leads are planar. Fillets are shiny, concave and evident on the front and back faces of the lead.

NASA-STD-8739.2 [12.8.1], [12.9.5]

PREFERRED

COPLANARITY

The preferred planarity of the lead to the land pattern area is with the component feet parallel to, and in full contact with, the pad.

NASA-STD-8739.2 [7.1]

ACCEPTABLE

COPLANARITY

The maximum acceptable non-planarity between any portion of the lead foot and the pad shall not exceed 0.26 mm (0.010").

NASA-STD-8739.2 [7.1], [12.9.2.b.3]

UNACCEPTABLE

IMPROPER COPLANARITY

Excessive non-planarity results in open or mechanically weak solder joint. Improper component lead coplanarity can produce solder bridging and open terminations.

NASA-STD-8739.2 [7.1], [12.9.2.b.3]

ACCEPTABLE

END JOINT WIDTH (C)

The width of the end joint (C) should be greater than the lead width (W), but shall not be less than 75% of lead width (W).

Best Workmanship Practice

UNACCEPTABLE

INSUFFICIENT END JOINT WIDTH (C)

The width of the end joint is less than 75% of the lead width (W).

Best Workmanship Practice

MANDATORY

HEEL FILLET

There shall be evidence of complete wetting and a positive wetting angle. The heel fillet shall extend across the entire width of the contact area.

NASA-STD-8739.2 [12.9.5.b.2]

UNACCEPTABLE

MISSING HEEL FILLET

There shall be evidence of complete wetting and a positive wetting angle.

NASA-STD-8739.2 [12.9.2.b.2]

MANDATORY

HEEL OVERHANG

Heel overhang is prohibited, as it will prevent the formation of the heel fillet (mandatory).

NASA-STD-8739.2 [8.8.4], [12.9.5]

ACCEPTABLE

HEEL/TOE FILLET HEIGHT

The fillet height shall not exceed 75% of the lead height. The fillet shall be the full width of the contact area, exhibit a positive wetting angle, and the lead contour shall be visible.

NASA-STD-8739.2 [12.9.5.a], [12.9.5.b.3]

UNACCEPTABLE

EXCESSIVE HEEL/TOE FILLET HEIGHT

The fillet height shall not exceed 75% of the lead height. The fillet shall be the full width of the contact area, exhibit a positive wetting angle, and the lead contour shall be visible.

NASA-STD-8739.2 [12.9.5.b.3]

UNACCEPTABLE

INSUFFICIENT HEEL/TOE FILLET HEIGHT

The fillet height shall be sufficient to exhibit evidence of complete wetting.

NASA-STD-8739.2 [12.9.5.a.1]

ACCEPTABLE

LATERAL/SIDE OVERHANG (A)

Lateral/side overhang shall not exceed 25% of lead width.

NASA-STD-8739.2 [8.7.4.k]

UNACCEPTABLE

IMPROPER LATERAL/SIDE OVERHANG

The lead is overhanging the termination pad in excess of 25% of the lead width.

NASA-STD-8739.2 [12.6.2.a.7], [12.9.5.b.1]

PREFERRED

SIDE JOINT FILLET*

The side joint fillet shall exhibit proper wetting to the component lead, a positive contour, and shall extend to the edges of the termination pad. (*See Nonwetting for special exclusion.>

NASA-STD-8739.2 [12.8.1.b], [12.9.5.a.1]

UNACCEPTABLE

INSUFFICIENT SIDE JOINT FILLET (D)*

The side joint fillet does not exhibit proper wetting, or a positive contour. (*See Nonwetting for exclusion.)

NASA-STD-8739.2 [12.8.2.b.4]

ACCEPTABLE

NONWETTING
(SPECIAL EXCLUSION)

Leads not having wettable sides (edges) by design (such as leads stamped from pre-plated stock) are not required to exhibit side fillets.

Best Workmanship Practice

UNACCEPTABLE

IMPROPER WETTING

The solder fillet shall exhibit a positive wetting angle, wet all elements of the connection with smooth flow lines, and shall extend to the edge of the pad.

NASA-STD-8739.2 [12.9.5.a.1], [12.9.5.b.4]

PREFERRED

SOLDER THICKNESS (G)

The solder thickness shall be sufficient to form a properly wetted, concave fillet which extends over the complete periphery of the connection.

NASA-STD-8739.2 [12.8.1.b], [12.9.5.a]

UNACCEPTABLE

INSUFFICIENT SOLDER QUANTITY

The solder quantity shall be sufficient to form a properly wetted, concave fillet.

NASA-STD-8739.2 [12.9.5.a.1], [12.9.5.b.4]

UNACCEPTABLE

EXCESS SOLDER

The solder fillet may be convex, but shall exhibit a positive wetting angle, and the lead contour shall be visible.

NASA-STD-8739.2 [12.9.5.a.2]

UNACCEPTABLE

INCOMPLETE SOLDER FILLET

The solder fillet shall exhibit complete wetting and extend over the complete periphery of the connection.

NASA-STD-8739.2 [12.9.5.b.4]

MANDATORY

TOE OVERHANG

Toe overhang is prohibited.

NASA-STD-8739.2 [8.8.4], [12.9.5]

PREFERRED

TOE FILLET

There shall be evidence of complete wetting and a positive wetting angle.

NASA-STD-8739.2 [12.9.5.a.1]

UNACCEPTABLE

MISSING TOE FILLET

There shall be evidence of complete wetting and a positive wetting angle that extends over the complete periphery of the connection.

NASA-STD-8739.2 [12.8.1.b], [12.9.5]