PREFERRED

The component is properly centered between the lands and exhibits acceptable solder thickness and tilt. No mechanical or heat damage is evident.

NASA-STD-8739.2 [12.9.1]

PREFERRED

END JOINT WIDTH (C)

The width of the end joint is equal to the width of the compoenent (W), and extends to the width of the land (P).

Best Workmanship Practice

ACCEPTABLE

END JOINT WIDTH (C)

End joint width shall not be less than 75% of the component termination width (W) or less than 75% of the land width (P).

Best Workmanship Practice

UNACCEPTABLE

INSUFFICIENT END JOINT WIDTH (C)

An end joint of insufficient width indicates that there may be solderability problems that may adverely impact the long-term reliability and integrity of the solder termination.

Best Workmanship Practice

ACCEPTABLE

MINIMUM FILLET HEIGHT (F)

There shall be evidence of a properly wetted fillet on the exposed sides of the termination.

NASA-STD-8739.2 [12.9.1.a]

PREFERRED

MAXIMUM FILLET HEIGHT (E)

The fillet shall exhibit a positive wetting angle and shall not contact the component body.

NASA-STD-8739.2 [12.8.1], [12.8.2.b.12], [12.9.1.a]

PREFERRED

INSIDE OVERHANG

The target condiction is the component centered between the termination pads, without the inside edges of the metallized pads overhanging the edges of the termination pads.

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

ACCEPTABLE

INSIDE OVERHANG (X)

Inside overhang (X) 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]

UNACCEPTABLE

EXCESS INSIDE OVERHANG (X)

Inside overhang shall not exceed 50% of the end termination width (T) and the minimum end joint width (C) requirements shall be met.

NASA-STD-8739.2 [12.6.2.a.2]

UNACCEPTABLE

END OVERHANG (B)

Overhang of the chip's metallization (pad) beyond the outside edge of the termination pad is not permitted.

Best Workmanship Practice

PREFERRED

SIDE JOINT LENGTH (D)

The length of the side joint fillet equals or exceeds the component terminatio pad length (T).

Best Workmanship Practice

ACCEPTABLE

SIDE JOINT LENGTH (D)

Any side joint length is acceptable, provided there is evidence of a side joint, and all other joint parameters are met.

Best Workmanship Practice

PREFERRED

SIDE/LATERAL OVERHANG (A)

The component is centered on the pads, with no side/lateral overhang (A).

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

ACCEPTABLE

SIDE/LATERAL OVERHANG (A)

Side overhang shall not exceed 25% of the part width (W) and the minimum end joint width (C) requirements shall be met.

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

UNACCEPTABLE

EXCESS SIDE/LATERAL OVERHANG (A)

Side overhang in excess of 25% of the part width (W) and/or the minimum end joint width (C) may impact the long-term reliability and integrity of the solder termination.

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

ACCEPTABLE

MINIMUM SOLDER THICKNESS (G)

The solder quantity shall be sufficient to form a properly wetted, concave fillet on the vertical surfaces of the chip, and which exhibits good wetting tot he chip metallization and termination 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 be less than or equal to 25% of the part thickness, and shall not interfere with the proper placement of adjacent parts.

NASA-STD-8739.2 [12.6.2], [12.9.1]

UNACCEPTABLE

EXCESS TILT

Part tilt in excess of 25% of the part thickness may impact the long-term reliability and integrity of the solder termination, and may interfere with the proper placement and thermal profile of adjacent parts.

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