MILPRF50884F
APPENDIX A
A.3.5.1.2.1 Exposed or disrupted fibers. Exposed or disrupted reinforcement fibers on the horizontal surface of the
printed board shall not bridge conductors and shall not reduce the conductor spacing below the minimum conductor
spacing requirements. Unless otherwise specified, weave texture (reinforcement texture) or weave exposure
(exposed reinforcement material fibers) by mechanical fabrication operations shall be acceptable provided they meet
the exposed or disrupted reinforcement fiber requirements.
A.3.5.1.2.2 Surface pits and voids. Surface pits and voids in the base material shall be acceptable providing the
following conditions are met:
a.
Surface pits or voids are no bigger than .031 inch (0.8 mm) in the longest dimension.
b.
The surface pits or voids do not bridge conductors.
c.
The total area of all surface pits or voids does not exceed five percent of the total printed board area.
d.
The surface pit or void does not affect the performance of the base material.
A.3.5.1.3 Subsurface imperfections. Subsurface imperfections (such as blistering, haloing, and delamination) shall
be acceptable providing the imperfection meets the following:
a.
The imperfection is translucent.
b.
The imperfection does not bridge more than 25 percent of the distance between conductors or plated-
through holes. No more than two percent of the printed wiring board area on each side shall be affected.
c.
The imperfection does not reduce conductor spacing between adjacent conductors below the minimum
requirements specified (see A.3.1.1).
d.
The imperfection does not propagate as a result of testing (such as rework simulation, resistance to
soldering hear, or thermal shock).
e.
Color variations or mottled appearance in bond enhancement treatments shall be acceptable. Random
areas of missing bond enhancement treatment shall not exceed 10 percent of the total conductor surface
area of the affected layer.
A.3.5.1.3.1 Foreign inclusions. Foreign inclusions shall be acceptable provided they comply with the following:
a.
The inclusion is trapped within the flexible portion of the printed wiring board.
b.
The inclusion does not reduce the spacing between conductors below the minimum conductor spacing
specified (see A.3.1.1). If not specified, the inclusion shall not reduce the conductor spacing by more than
20 percent.
c.
The inclusions longest dimension is no greater than .032 inch (0.81 mm) in circuitry areas. Inclusions in
non-circuitry areas have no maximum dimension requirement.
d.
When the base material specification allows for more or larger inclusions, those inclusions are allowed in the
finished printed wiring board, up to the size and quantity defined by the base material specification provided
that the inclusion does not violate the conductor spacing requirements of A.3.5.1.3.c.
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