MILPRF50884F
APPENDIX A
A.4.8.2 Microsection inspection. Microsection inspections (to evaluate characteristics such as plated hole
structures, plating thickness, or foil thickness) shall be accomplished by using the following preparation and
inspection methods.
A.4.8.2.1 Microsection preparation. Microsection preparation shall be accomplished by using methods in
accordance with either test method numbers 2.1.1 or 2.1.1.2 of IPCTM650. Automatic microsectioning techniques
may be used in lieu of test methods 2.1.1 or 2.1.1.2 of IPC-TM-650. The following details shall apply:
a.
Number of holes for each specimen. A minimum of three plated hole structures cross sectioned vertically
shall be made for each printed wiring board test specimen required. Each side of the three plated hole
structures shall be viewed independently.
b.
Accuracy.
(1) Through holes. All three plated hole structures of each printed wiring board test specimen shall be
sectioned, ground, and polished to within ±10 percent of the center of the drilled diameter of the hole.
(2) Microvias. For non-copper filled microvias, at least three microvias of each printed wiring board test
specimen shall the be sectioned, ground, and polished to within ±10 percent of thier center. For copper
filled microvias, the grinding and polishing accuracy is not required.
c.
Premicroetch evaluations. The three plated hole structures of the printed wiring board test specimens shall
be evaluated for plating separations, superfluous copper, and wicking prior to microetching (see A.6.11).
d.
When more than two printed wiring board test specimens are contained in a mount (couponstacking or
gang mounting), the following shall apply:
(1) The printed wiring board test specimens shall not be in direct contact with any other printed wiring board
test specimen in the mount. The recommended minimum distance between printed wiring board test
specimens in a mount is .010 inch (0.25 mm).
(2) The traceability requirements of A.3.9.1 shall apply.
A.4.8.2.2 Microsection examination and inspection. Microsection examination and inspection shall be
accomplished in accordance with test method number 2.2.5 of IPCTM650 to evaluate characteristics such as
dielectric spacing, etchback, plating thickness, foil thickness, and other characteristics, in plated holes. If more than
three plated holes are on a printed wiring board test specimen (as with test coupon "ABR"), all holes of the same
size shall be evaluated. The following details shall apply:
a.
Magnifications. The printed wiring board test specimens shall be inspected at the magnifications specified in
test method number 2.2.5 of IPCTM650.
b.
Evaluations. Pre and postmicroetch evaluations for the criteria of A.3.6 shall be accomplished at
magnifications specified above. The printed wiring board test specimens shall be evaluated for plating
separations, superfluous copper, and wicking both prior to and after microetching.
c.
Measurements. Specified thickness measurements shall be averaged from at least three determinations for
each side of each plated hole of each test specimen. Isolated thick or thin sections shall not be used for
averaging; however, isolated areas of reduced copper thickness shall be measured and evaluated to the
copper plating void rejection criteria specified in A.3.6.4.4.
EXAMPLE: The copper plating thickness of the plated hole wall shall be determined from the average of
three measurements, approximately equally spaced, taken on each side of the plated-through hole.
Conductor thickness shall be determined by an average of three measurements on each layer and each
side of the hole.
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