PREFERRED

Device is centered on the termination pads, with proper end overlap and no inside overhang. The solder termination exhibits a full concave fillet on ther vertical terminal faces, with evidence of good wetting to the chip metallization and extends to the periphery of the land.

NASA-STD-8739.2 [8.7.4.g], [12.9.1.a]

PREFERRED

END JOINT WIDTH (C)

The End Joint Width (C) shall be equal to or greater than the component width (W) or width of the land (P), whichever is less.

Best Workmanship Practice

ACCEPTABLE

END JOINT WIDTH (C)

The End Joint Width (C) shall be 75% of the component width (W) or width of the land (P), whichever is less.

Best Workmanship Practice

UNACCEPTABLE

END JOINT WIDTH (C)

The width of the end joint shall not be less than 75% of the component termination width (W), or 75% of the land width (P), whichever is less.

Best Workmanship Practice

ACCEPTABLE

END OVERLAP (J)

There shall be end overlap (J) between the component termination cap and the termination pad. Preferntially, the end overlpa (J) should equal the termination cap length, with the component centered between the pads.

Best Workmanship Practice

UNACCEPTABLE

INSUFFICIENT END OVERLAP (J)

There shall be end overlap (J) between the component termination cap and the termination pad to ensure the proper formation of the solder fillet.

Best Workmanship Practice

PREFERRED

INSIDE OVERHANG

The target condiction is the component centered between the termination pads, without the indside edge(s) of the metallization pads overhanging the termination pad(s).

NASA-STD-8739.2 [8.7.4.g.2]

ACCEPTABLE

INSIDE OVERHANG

Inside overhang of the ship's metallization pad shall be less than or equal to 50% of the end termination width (T) and the minimum end joint width (C) requirements shall be met.

NASA-STD-8739.2 [8.7.4.g.2]

PREFERRED

LATERAL/SIDE OVERHANG (A)

The target condition is no lateral/side overhang, with the component centered on the land.

NASA-STD-8739.2 [8.7.4.g.1]

ACCEPTABLE

LATERAL/SIDE OVERHANG (A)

Lateral/side overhang (A) shall not exceed 25% of the component termination area (W) or land width (P), whichever is smaller.

NASA-STD-8739.2 [8.7.4.g.1]

UNACCEPTABLE

EXCESS LATERAL/SIDE OVERHANG (A)

The component shall not hang over the edge of the termination land by more than 25% of the component termination area (W), or 25% of the land width (P), whichever is less.

NASA-STD-8739.2 [12.9.1.b.7]

PREFERRED

MAXIMUM FILLET HEIGHT (E)

The maximum fillet height shall be the solder thickness (G) >u>plus the component termination height (H).

NASA-STD-8739.2 [12.9.1.a]

ACCEPTABLE

MAXIMUM FILLET HEIGHT (E)

The fillet may extend over the top of the end cap metallization, provided the fillet exhibits a positive wetting angle, and does not contact the component body.

NASA-STD-8739.2 [12.9.1.a]

ACCEPTABLE

MINIMUM FILLET HEIGHT (F)

The minimum fillet height shall be equal to or greater than the minimum solder thickness (G), plus 50% of the component termination height (H).

NASA-STD-8739.2 [12.9.1.b.3]

UNACCEPTABLE

INSUFFICIENT FILLET HEIGHT (F)

There shall be evidence of a properly wetted fillet between the chip and the land.

NASA-STD-8739.2 [12.9.1.b.3], [12.9.1.b.5]

ACCEPTABLE

SIDE JOINT LENGTH (D)

The side joint length should be equal to the End Termination Length (T) and should extend to the periphery of the termination pad (P).

Best Workmanship Practice

UNACCEPTABLE

SIDE JOINT LENGTH (D)

Although the solder fillet exhibits good wetting, the side joint length (D) is less than the End Termination Length (T), and does not extend to the periphery of the termination pad (P).

Best Workmanship Practice

UNACCEPTABLE

SIDE MOUNT

The mounting of chip components on their side is prohibited.

NASA-STD-8739.2 [12.8.2.a.2]

ACCEPTABLE

SOLDER THICKNESS (G)

The solder quantity shall be sufficient to form a properly wetted, concave fillet on the vertical surfacews of the chip, and which exhibits good wetting to the chip metallization and terminatio pad.

NASA-STD-8739.2 [12.8.1.b], [12.9.1.a]

UNACCEPTABLE

INSUFFICIENT SOLDER THICKNESS (G)

The solder quantity is insufficient to form a properly wetted, concave fillet which exhibits good wetting to the chip metallization and termination pad.

NASA-STD-8739.2 [12.9.1.b.5]

ACCEPTABLE

TILT

Part tilt shall not exceed 25% of the part thickness (H), and shall not interfere with the proper placement of adjacent parts.

NASA-STD-8739.2 [12.6.2.a.3]

UNACCEPTABLE

EXCESS TILT

Part tilt shall not exceed 25% of the component thickness (H), and shall not interfere with the proper placement of adjacent parts, or violate minimum electrical spacing requirements.

NASA-STD-8739.2 [12.9.1.b.1], [12.9.1.b.2]

UNACCEPTABLE

END OVERHANG (B)

End overhang is not permitted.

Best Workmanship Practice

UNACCEPTABLE

EXCESS INSIDE OVERLAP (X)

Inside overlap (X) shall not exceed 50% of the End Termination Length (T).

NASA-STD-8739.2 [12.9.1.b.8]