GENERAL REQUIREMENTS

The printed wiring board is clean and damage-free, with sharply defined conductive patterns. Plated-Through Holes (PTH) and vias are properly located, clean and unfilled, and exhibit smooth and uniform plating. Electrical termination areas are bright and shiny. Solder mask exhibits proper registration.

Best Workmanship Practice

PREFERRED

GOLD/PRECIOUS METAL CONTACTS

Contact surfaces are clean and bright, with a uniform and smooth finish.

Best Workmanship Practice

PREFERRED

HOLE LOCATION/REGISTRATION

Holes (supported/unsupported) shall be centered in the lands and located per engineering documentation. Annular ring shall be concentric to the pad.

Best Workmanship Practice

PREFERRED

INTERFACIAL CONNECTIONS (VIAS)
DOUBLE-SIDED PWBs

Vias in double-sided PWBs require the use of filler wire (Z-wire) for support if the PWB coupon has not been evaluated by construction analysis (micro-section).

NASA-STD-8739.3 [11.2.4.a]

PREFERRED

INTERFACIAL CONNECTIONS (VIAS)
MULTI-LAYER PWBs

Vias in multi-layer PWBs do not require the use of filler wire (Z-wire), nor shall they be solder-filled. No dedicated effort shall be made to remove solder in unused holes.

NASA-STD-8739.3 [11.2.4.b]

PREFERRED

ETCHED LEGENDS/MARKINGS

Legends/Markings are sharply defined, of uniform size and density, correct alignment and polarity, and meet minimum electrical spacing requirements. Markings do not touch or cross over solderable surfaces.

Best Workmanship Practice

PREFERRED

SOLDER MASK/RESIST COATING

Coating is uniform in color and finish. Registration is correct. No blisters, scratches, voids, waves, ripples, wrinkling, bubbles, haziness, tackiness or entrapped particles.

Best Workmanship Practice

PREFERRED

SUPPORTED HOLES

Supported/Plated Through Holes (PTH) designated for lead insertion exhibit a smooth/even bore and plating, proper diameter, are free of resist and have symmetrical annular rings.

Best Workmanship Practice

PREFERRED

UNSUPPORTED HOLES

Unsupported/Non-Plated-Through Holes (NPTH) exhibit smooth/even walls, proper diameter, are free of plating and have symmetrical annular rings.

Best Workmanship Practice

ACCEPTABLE

DISCOLORED CONDUCTORS

Slight dulling of clean metallic surfaces is acceptable, provided the surface conductivity or solderability is not affected.

Best Workmanship Practice

ACCEPTABLE

ANNULAR RING

The hole is not centered in the land, however it is acceptable providing the minimum annular ring requirement is not violated.

Best Workmanship Practice

UNACCEPTABLE

INSUFFICIENT ANNULAR RING

The lower hole is improperly located, causing the annular ring dimension to be less than minimum requirements.

Best Workmanship Practice

ACCEPTABLE

CRAZING

Crazing (whitish, discrete spots or crosses below the laminate surface) which does not bridge uncommon conductors is acceptable.

NASA-STD-8739.2 [12.8.2.c.3]

UNACCEPTABLE

CRAZING

Crazing which bridges uncommon conductors is unacceptable.

NASA-STD-8739.2 [12.8.2.c.3]

ACCEPTABLE

EPOXY/SOLDER FILLED VIAS/PTH

Vias and plated-through holes, not intended for lead insertion, may be plugged by epoxy resin or solder, if documented on the engineering drawings.

Best Workmanship Practice

ACCEPTABLE

TENTED VIAS/PTH

Vias and plated-through holes not intended for lead insertion may be tented by solder mask, if documented on the engineering documentation.

Best Workmanship Practice

ACCEPTABLE

ETCHED LEGENDS/MARKINGS

Legends/markings may exhibit slightly irregular definition, broken letters/lines, size or density, provided they are legible and/or their intent is clear.

Best Workmanship Practice

UNACCEPTABLE

ETCHED MARKINGS/LEGENDS

Poor definition, improper alignment/polarity, missing characters, smudged, smeared, multiple-imaged, touch or cross over solderable surfaces, exposed copper, delamination, violate electrical spacing requirements.

Best Workmanship Practice

ACCEPTABLE

EXPOSED BASE METAL

Exposed base metal on the vertical edge of printed wiring conductors, lands and pads is acceptable.

NASA-STD-8739.2 [12.8.2.c.5]
NASA-STD-8739.3 [13.6.2.c.5]

UNACCEPTABLE

EXPOSED BASE METAL

Defects or damage (cuts, nicks, gouges, scrapes, etc.) that result in exposed base metal (except for the vertical edges of circuit traces, lands and pads) shall be rejectable.

NASA-STD-8739.2 [12.8.2.c.5]
NASA-STD-8739.3 [13.6.2.c.5]

ACCEPTABLE

LABELS

Labels shall exhibit a flat, smooth profile, legible graphics, proper placement and adhesion. Labels shall be non-conductive and shall not be placed over components, exposed circuit traces, vias or solder terminations.

Best Workmanship Practice

UNACCEPTABLE

LABELS

Labels which exhibit damage, improper placement, improper adhesion are conductive and/or placed over components, exposed circuit traces, vias or solder terminations etc., shall be rejectable.

Best Workmanship Practice

ACCEPTABLE

LAMINATE SCRATCHES

Scratches, scrapes, gouges, nicks and/or cuts to the laminate that do not expose glass fiber or reduce electrical spacing are acceptable.

NASA-STD-8739.2 [8.7.4.c], [12.8.2.c.6]

UNACCEPTABLE

LAMINATE SCRATCHES

Scratches that expose glass fiber are an indication of improper process control and/or handling.

NASA-STD-8739.2 [8.7.4.c], [12.8.2.c.6]

ACCEPTABLE

LAMINATE VOIDS

Laminate voids located a minimum of 0.003 inch (0.080 mm) from the periphery of a plated-through hole, and sized less than 0.003 inch (0.080 mm) in any dimension, are allowable.

Best Workmanship Practice

UNACCEPTABLE

LAMINATE VOIDS

Laminate voids located less than 0.003 inch (0.080 mm) from the periphery of a plated-through hole, and sized greater than 0.003 inch (0.080 mm) in any dimension, are not allowed.

Best Workmanship Practice

ACCEPTABLE

PLATING

Plating is uniform and smooth. Luster may vary from bright to slightly dull. Minor scratches, scuffing and solder on non-contact areas of fingers are allowable.

Best Workmanship Practice

UNACCEPTABLE

IRREGULAR PLATING

Irregular or skipped plating is an indicator of improper process control and/or contamination.

Best Workmanship Practice

ACCEPTABLE

MEASLING

Measling (whitish, discrete spots or crosses) below the laminate surface that do not bridge uncommon conductors is acceptable.

NASA-STD-8739.2 [12.8.2.c.3]

UNACCEPTABLE

MEASLING

Measling (whitish, discrete spots or crosses below the laminate surface) which bridges uncommon conductors is unacceptable.

NASA-STD-8739.2 [12.8.2.c.3]

ACCEPTABLE

SMOOTH TOOL IMPRESSION MARKS

Scratches, scrapes, gouges, nicks and/or cuts to the printed wiring pattern that do not expose base metal or reduce cross-sectional area are acceptable.

NASA-STD-8739.2 [12.8.2.c.5]

UNACCEPTABLE

SCRATCHES (PRINTED WIRING)

Scratches that expose base metal are an indication of improper process control and/or handling.

NASA-STD-8739.2 [12.8.2.c.5]

ACCEPTABLE

SOLDER MASK

Minor waves, ripples or wrinkling which do not reduce the coating below minimum thickness requirements. Isolated bubbles or void, which do not bridge conductive patterns or reduce electrical spacing requirements.

Best Workmanship Practice

UNACCEPTABLE

SOLDER MASK DEFECTS

Solder masik tackiness, cracking, flaking or separation from the substrate or conductors.

NASA-STD-8739.2 [12.8.2.c.8]
NASA-STD-8739.3 [13.6.2.c.8]

ACCEPTABLE

WEAVE TEXTURE

Weave textue is a visual condiction in which a weave pattern is apparent, but where the glass cloth is completely covered by resin and not exposed.

Best Workmanship Practice

UNACCEPTABLE

EXPOSED WEAVE

Weave exposure reduces the dielectric properties between conductive patterns to less than the minimum electrical clearance.

NASA-STD-8739.2 [12.8.2.c.3]

UNACCEPTABLE

BLISTERS

Blitering betwen any of the laminate layers, or between the laminate and the metallization, is not allowed.

NASA-STD-8739.2 [128.2.c.10]
NASA-STD-8739.3 [13.6.2.c.10]

UNACCEPTABLE

BREAK-OUT

Break-out of the annular ring is caused by misregistration during the drilling process.

Best Workmanship Practice

UNACCEPTABLE

BRIDGING

Bridging of conductive surfaces is an indication of improper process control.

NASA-STD-8739.2 [12.8.2.c.4]
NASA-STD-8739.3 [13.6.2.c.4]

UNACCEPTABLE

CONTAMINATION

Contamination is a reliability concern.

NASA-STD-8739.2 [12.8.2.b.9]

UNACCEPTABLE

CONTAMINATED PLATING

Plating is not uniform, smooth, bright and/or shiny. Solder or other contamination on the contact area shall be cause for rejection.

Best Workmanship Practice

UNACCEPTABLE

CORROSION

Corrosion is a reliability concern.

NASA-STD-8739.2 [7.4.1.d]

UNACCEPTABLE

CRACKED/RINGED BARREL

Cracks or ringing in the barrel are cause for rejection.

Best Workmanship Practice

UNACCEPTABLE

CUT/DAMAGED PATTERN

Repaired or damaged printed wiring conductor pattern shall be cause for rejection.

NASA-STD-8739.2 [12.8.2.c.9]
NASA-STD-8739.3 [13.6.2.c.9]

UNACCEPTABLE

DEMETALLIZATION/LEACHING

Boards exhibiting leaching or loss of metallization shall be rejected.

Best Workmanship Practice

UNACCEPTABLE

DISCOLORATION

Contamination or improper drying typically causes discoloration of the laminate or solder mask in the patterns depicted. Re-cleaning/Demoisturizing may correct this problem, provided no other damage is apparent.

Best Workmanship Practice

UNACCEPTABLE

EDGE DELAMINATION

Edge delamination is an indicator of improper tooling, process control or handling.

NASA-STD-8739.2 [12.8.2.c.7]

UNACCEPTABLE

EDGE PROJECTIONS

Edge projections that reduce electrical separation below minimum requirements are rejectable.

Best Workmanship Practice

UNACCEPTABLE

EXCESSIVE BOW/TWIST

Excessive bow or twist may inhibit proper mounting and may result in mechanical interference or shorting to adjacent assemblies or chassis.

Best Workmanship Practice

UNACCEPTABLE

EXPOSED/PROTRUDING GLASS FIBERS

Exposed glass fiber in the laminate indicates a process control problem and is a long-term reliability concern.

NASA-STD-8739.2 [12.8.2.c.6]

UNACCEPTABLE

HALO EFFECT

A lightened area around a hole or via, typically induced by mechanical stress. Haloing which bridges uncommon conductors is unacceptable.

NASA-STD-8739.2 [12.8.2.c.3]

UNACCEPTABLE

IMPROPER HOLE LOCATION

The improper location of holes (i.e.: component lead, via, mounting, etc.) is caused by misregistration during the drilling process.

Best Workmanship Practice

UNACCEPTABLE

IMPROPER PUNCH-OUT/NOTCH/ROUTING

The improper location of punch-out, notching or routing is caused by misregistration or improper process control.

Best Workmanship Practice

UNACCEPTABLE

LAMINATE CRACKS

Cracks in the laminate are cause for rejection.

NASA-STD-8739.2 [12.8.2.c.6]

UNACCEPTABLE

LAYER DELAMINATION

Delamination between any of the laminate layers, or between the laminate and the metallization, is not allowed.

NASA-STD-8739.2 [12.8.2.c.7]

UNACCEPTABLE

NON-WETTING

Tin, tin/lead reflowed or solder coated surfaces, exhibitng non-wetting on any conductive surface where a solder connection will be required shall be rejected.

Best Workmanship Practice

UNACCEPTABLE

OVER-ETCH

Conductors that are over-etched are incapable of carrying the designed current load, and are susceptible to reduced reliability.

Best Workmanship Practice

UNACCEPTABLE

PINK RING

Pink ring is caused by a thinning of the oxide coating on the copper layer in the through-hole/inner-layer interface zone, and is considered an indicator of a process control problem.

Best Workmanship Practice

UNACCEPTABLE

REDUCED CROSS-SECTIONAL AREA

Conductors that exhibit reductions in cross-sectional area are incapable of carrying the designated current load and are susceptible to reduced reliability.

Best Workmanship Practice

UNACCEPTABLE

REPAIRED CONDUCTOR PATTERN

Repairs to damaged printed wiring conductor pattern shall only be made after authorization, and by approval process.

NASA-STD-8739.2 [12.8.2.c.9]
NASA-STD-8739.3 [13.6.2.c.9]

UNACCEPTABLE

ROUGH/UNEVEN EDGES (LAMINATE)

Edges which are rough or uneven present a handling or sharp edge/protrusion hazard. Additionally, the presence of a rough or uneven edge may increase the potential for delamination of multi-layer boards.

Best Workmanship Practice

UNACCEPTABLE

SOLDER MASK MISREGISTRATION

Solder mask misregistration violating minimum annular ring requirements. Presence of mask material in plated-through holes designated to be soldered.

Best Workmanship Practice

UNACCEPTABLE

SOLDER SPLATTER/WEBBING

Solder splatter and webbing is typically caused by moisture, contamination or improper laminate bake-out, and is a reliability and short-circuit concern.

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

UNACCEPTABLE

UNDER-ETCH

Under-etch is an indicator of improper process control/improper chemistry during etching. Under-etch can result in bridging between traces, resulting in short circuits.

Best Workmanship Practice