MILPRF50884F
APPENDIX A
d.
Plating and coatings that are less than .00005 inch (0.00125 mm) in thickness shall not be measured using
metallographic techniques. The plating and coating thickness shall be evaluated using the alternate
measurement techniques of A.4.8.1.6.
A.4.8.2.3 Evaluation of plated hole features by DPA (see A.3.6). When external and internal features and
structures of printed wiring board test specimens are inspected in accordance with A.4.8.2.2, the following details
shall apply:
Dielectric layer thickness (see A.3.6.1.5). The dielectric layer thickness shall be inspected between all
a.
conductor layers present in the printed wiring board test specimen.
b.
Thermal planes (see A.3.6.1.6). The lateral dielectric spacing between the heat sinking planes and adjacent
conducting surfaces (nonfunctional lands) or plated-through holes shall be measured at the closest point
between these surfaces or the plated-through hole.
c.
Plating and coating thickness (see A.3.6.2.1.5 and A.3.6.4). Isolated thick or thin sections shall not be used for
averaging. However, isolated areas of reduced copper thickness shall be measured for compliance with the
requirements of A.3.6.4.3.
Copper plating voids (see A.3.6.4.4). When a single plating void that is within the acceptable limits of A.3.6.4.4
d.
is present in a microsection, the sampling procedures of A.4.6.2.2.e shall apply for group A verifications. Any
plated hole structure in the microsection failing the plating void criteria specified in A.3.6.4.4 subparagraphs a,
b or c, shall be cause for the entire panel of printed wiring boards associated with the microsection to be
rejected. For group B inspections, see A.4.7.1.4.
Annular ring, internal (see A.3.6.2.4). This measurement shall apply to all internal lands for all plated hole
e.
structures in the cross section.
A.4.8.2.4 Registration (types 3 and 4). Layer-to-layer registration of multilayered printed wiring boards shall be
determined by either evaluating microsectioned test coupons (method II, see A.4.8.2.4.1) or by evaluating of special
registration coupons when provided (method III, see A.4.8.2.4.2).
A.4.8.2.4.1 By microsection (method II). Method II registration of printed wiring boards shall be satisfied if all
layers meet the annular ring and hole pattern accuracy requirements specified (see A.3.1.1). Registration shall be
evaluated using any combination of the non-stressed specimens (as received) (see A.3.7.2.1) and or the resistance
to soldering heat (see A.3.7.6.2) microsectioned printed wiring board test specimens taken from diagonal corners of
the panel. Both printed wiring board test specimens shall have been microsectioned in the vertical plane with one
printed wiring board test specimen representing the panel's length (X) direction and the other representing the panel's
width (Y) direction.
A.4.8.2.4.2 By registration test coupons (method III) (optional). Registration test coupons and techniques, when
provided by the printed wiring board fabricator, shall be evaluated in accordance with methods approved by the
qualifying activity and when applicable, the acquiring activity. Unapproved methods of measurement using
registration test coupons shall be backed up by method II of A.4.8.2.4.1 using the appropriate test coupons (see table
AVIII) from the same panel.
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