MILPRF50884F
APPENDIX A
A.3.5 External visual and dimensional requirements. When examined in accordance with A.4.8.1, the
finished printed wiring board shall meet the dimensional requirements specified in A.3.5.1 through A.3.5.8.
Unless otherwise specified (see A.3.1.1), design related dimensional requirements specified in A.3.3, such as
cutouts, overall thickness, periphery, and other features specified, shall be examined in accordance with
A.4.8.1. Scratches, dents, and tool marks shall not bridge or expose signal conductors, expose base metal,
expose or disrupt reinforcement fibers, reduce dielectric properties, and reduce spacing below the minimum
requirements herein. Appendix F contains figures, illustrations, and photographs that can aid in the
visualization of externally observable accept/reject conditions of printed wiring board test specimens.
A.3.5.1 Base material (flexible and rigid).
A.3.5.1.1 Edges of base materials. Base material edges include the external edge of the printed board, the edges
of cutouts, and the edges of nonplatedthrough holes. Loose metallic burrs shall not be acceptable.
A.3.5.1.1.1 Edges of flexible sections. Defects such as burrs, nicks, tears, or delamination, along the trimmed
edges of flexible sections of printed wiring boards shall be acceptable provided the penetration does not reduce the
edge spacing by more than 50 percent of the edge spacing specified (see A.3.1.1). Discoloration or resin recession
along the trimmed edges of the flexible sections following the solderability or resistance to soldering heat test is
acceptable providing the discoloration or resin recession dimension does not exceed the thickness of the adhesive
material in the bonding area (when applicable) or reduce the edge spacing below the requirements of the master
drawing.
A.3.5.1.1.2 Edges of rigid sections (types 4 and 5). Defects such as burrs, crazing, nicks, and haloing along the
edges of printed wiring boards, including edges of cutouts and edges of non-plated-though holes, shall be acceptable
provided the penetration does not reduce the edge spacing by more than 50 percent of the edge spacing specified
(see A.3.1.1) or .10 inch (2.5 mm), whichever is smaller. If no requirement for edge spacing is specified (see
A.3.1.1), the penetration shall not exceed .10 inch (2.5 mm). Inspection panels that are scored or partially routed with
breakaway tabs for printed wiring board or test coupon removal shall meet the de-panelization requirements specified
(see A.3.1.1).
A.3.5.1.1.3 Edges between flexible and rigid sections (see figure F1). The edge of the rigid portion of a flexible to
rigid junction shall define the transition between flexible and rigid portions of a printed wiring board. Unless otherwise
specified (see A.3.1.1), the inspection range for a flexible to rigid junction shall be limited to .060 inch (1.52 mm) on
either side of the transition. Imperfections along the flexible to rigid transition such as adhesive squeeze out,
localized deformation of dielectric and conductors, protruding dielectric materials, crazing, or haloing not extending
past the inspection range shall be acceptable.
A.3.5.1.2 Surface imperfections. Imperfections in the surface of the base material such as blistering, burrs, cuts,
dents, foreign materials, gouges, nicks, pits, resin scorched areas, resin starved areas, scratches, tool marks,
variations in color such as white spots or black spots, or other visual defects detrimental to the performance of the
base material shall be acceptable in localized concentrations providing the following conditions are met:
a.
The imperfection does not bridge between conductors (weave texture may bridge conductors).
b.
The dielectric spacing between the imperfection and conductors does not reduce conductor spacing below
the specified minimum requirements (see A.3.1.1).
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