MIL-PRF-31032/1B
3.6 Microsection requirements. Printed board test specimens (production printed boards or test coupons) shall
conform to the requirements in 3.6.1 through 3.6.11, as applicable (see figure 1). Blind and buried vias shall meet the
requirements of plated-through holes.
3.6.1 Annular ring, internal. The minimum internal annular ring shall be as specified.
3.6.2 Conductor finish thickness (plating or coating). The plating or coating thickness of the conductor finish shall
be as specified.
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3.6.3 Conductor thickness. The conductor thickness shall be as specified (see 3.1).
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3.6.3.1 Minimum external thickness (type 3) and internal sequentially plated layer thickness (type 4). When a
conductor thickness is specified, the external conductor thickness (copper foil and copper plating) shall be equal to or
greater than the specified thickness. When a conductor thickness with tolerance is specified, the external conductor
thickness shall be within the specified tolerance for the specified thickness.
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3.6.3.2 Minimum internal thickness (multilayered). When the procurement documentation specifies a minimum
conductor thickness for internal conductors, the resulting conductor shall be equal to or within the specified tolerance
for the specified conductor thickness. If only a copper foil weight requirement is specified, a reduction in thickness up
to 10 percent below the minimum allowable foil thickness specified by the applicable material specification shall be
considered acceptable in order to accommodate a processing allowance for cleaning either by chemical or
mechanical means.
3.6.4 Hole wall plating.
3.6.4.1 Copper plating thickness. Unless otherwise specified, the copper plating thickness shall be in accordance
with the applicable design standard. Any copper plating thickness less than 80 percent of the specified thickness
shall be treated as a void.
3.6.4.1.1 Copper plating voids. The copper plating in the plated-through hole shall not exhibit any void in excess of
the following:
a.
There shall be no more than one plating void per panel, regardless of length or size.
b.
There shall be no plating void longer than five percent of the total printed board thickness.
c.
There shall be no plating voids evident at the interface of any conductive layer and plated hole wall.
Conductor finish plating or coating material between the base material and copper plating (i.e., behind the hole wall
copper plating) is evidence of a void. Any plated hole exhibiting this condition shall be counted as having one void for
panel acceptance purposes.
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3.6.4.2 Copper plating defects. Nodules, plating folds, plating inclusions, or plated reinforcement material
protrusions that project into the plated-through hole shall be acceptable provided that the hole diameter and the
copper thickness are not reduced below their specified limits.
3.6.4.3 Wicking. Wicking of copper plating extending 0.08 mm (.003 inch) into the base material shall be
acceptable provided it does not reduce the conductor spacing below the minimum clearance spacing requirements
specified.
3.6.5 Metallic cracks. There shall be no cracks in the platings, coatings, or internal conductive foils. Cracks are
permissible in the external layer (outer) copper foil provided they do not extend into the plated copper.
3.6.6 Dielectric layer thickness. The minimum dielectric thickness between conductor layers shall be as specified.
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