MILPRF50884F
APPENDIX A
A.3.6.1.2 Base material cracks and voids (see figure G1).
A.3.6.1.2.1 Non-stressed specimens (as received condition). Laminate voids with the longest dimension of .003
inch (0.08 mm) or less shall be acceptable.
A.3.6.1.2.2 Stressed specimens (after rework simulation, resistance to soldering heat, or thermal shock). After
undergoing rework simulation, resistance to soldering heat, or thermal shock testing (see A.3.7.4.8, A.3.7.6.2, and
A.3.7.6.3), laminate cracks and voids are not evaluated in zone A. Laminate cracks located wholly in zone A shall be
acceptable. Laminate cracks and voids that originate in zone A and encroach into zone B shall not exceed a length
of .003 inch (0.08 mm). Laminate cracks and voids in zone B shall not exceed a length of .003 inch (0.08 mm), shall
not bridge adjacent uncommon conductors, and shall not reduce dielectric spacing, either laterally or vertically, below
the minimum specified spacing. Multiple laminate cracks and voids located between two adjacent plated-through
holes shall not have a combined length in excess of .003 inch (0.08 mm), shall not bridge adjacent uncommon
conductors, and shall not reduce dielectric spacing, either laterally or vertically, below the minimum specified spacing.
A.3.6.1.3 Coverlayer thickness. Unless otherwise specified (see A.3.1.1), the thickness of the coverlayer shall not
be measured.
A.3.6.1.4 Delamination. Printed wiring boards shall have no delaminations in excess of that allowed in A.3.5.1.3.
A.3.6.1.5 Dielectric layer thickness (see figure G3). The minimum dielectric thickness separating the conductor
layers of the printed wiring boards shall be as specified (see A.3.1.1). If not specified on the applicable master
drawing, the minimum dielectric spacing for rigid, or rigid and flex base materials, should not be less than the value
specified in the IPC's 2220 series of documents for the design of flexible or rigid-flex printed wiring boards. On the
date of publication of this document, the minimum dielectric spacing dimension for rigid base materials was listed as
.0035 inch (0.089 mm), and when the dielectric material between conductor layers is composed of both rigid and
flexible base materials, the minimum dielectric was listed as .0015 inch (0.038 mm).
A.3.6.1.6 Metal plane hole fill insulation material (see figures G4 and G5). Radial cracks, lateral spacing,
wicking, or voids in the dielectric material used to insulate the heat sink plane or metal core from circuitry and plated
through holes shall not reduce by 75 percent the specified lateral spacing between adjacent conductive surfaces.
Unless otherwise specified (see A.3.1.1), the minimum lateral spacing between adjacent conductive surfaces,
nonfunctional lands, or plated-through hole and the heat sink plane shall be .004 inch (0.102 mm) or 50 percent of the
specified spacing, whichever is less.
A.3.6.1.7 Hole wall to dielectric separation (resin recession) (see figure G1).
A.3.6.1.7.1 Non-stressed specimens (as received condition). Any separation between the vertical edge of the
dielectric material and the outer surface of the plated hole barrel wall shall be permitted provided the maximum depth
as measured from the barrel wall does not exceed .003 inch (0.08 mm) and the dielectric separation on any side of
the plated-through hole does not exceed 40 percent of the cumulative base material thickness (sum of the dielectric
layer thickness being evaluated) on the side of the plated-through hole being evaluated.
A.3.6.1.7.2 Stressed specimens (after rework simulation, resistance to soldering heat, or thermal shock). After
undergoing rework simulation, resistance to soldering heat, or thermal shock testing (see A.3.7.4.8, A.3.7.6.2, and
A.3.7.6.3), resin recession at the outer surface of the plated hole barrel shall be permitted and is not cause for
rejection.
A.3.6.1.8 Via fill of blind and buried vias. Unless otherwise specified (see A.3.1.1), blind vias shall be at least 75
percent filled with the via fill material (laminating resin or similar via filling material). Unless otherwise specified,
buried vias shall be at least 95 percent filled with the via fill material.
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