MILPRF50884F
APPENDIX A
A.3.5.3.2.1 Wrinkles or creases. Wrinkles or creases in the coverlayer shall be acceptable provided the
requirements of A.3.5.3.2 are met.
A.3.5.3.2.2 Continuous flex designs (installation use B). After exposure to the flexibility endurance test (see
A.3.7.4.7 and A.4.8.4.7), there shall be no propagation of any coverlayer separation or delamination in the continuous
flex area for installation use B designs.
A.3.5.3.3 Cover coat cure. The cured cover coat shall not exhibit tackiness and blistering or delamination shall not
A.3.5.3.4 Registration (access holes) (see figure F9). The coverlayer shall be registered to the land or terminal
patterns in such a manner as to meet the requirements specified (see A.3.1.1) and herein. If a clearance is specified,
no encroachment of the coverlayer on the land is allowed, except at the conductor attachment. The misregistration of
a coverlayer defined feature shall not expose adjacent isolated conductors or lands. If no registration requirements
are specified, the following shall apply:
a.
For plated-through holes and vias, the following shall apply:
(1)
Coverlayer misregistration (including squeeze-out or ooze-out) onto plated-through component hole
lands shall not reduce the external annular ring below the specified minimum requirements. The
(2)
Coverlayer shall not encroach into plated-through hole barrels or onto lands of unsupported holes to
which solder connections will be made.
(3)
Unless specified to be solder filled, coverlayer is permitted in plated holes or vias in which no lead is to
be soldered.
b.
For surface mount lands with no plated-through holes, the following shall apply:
(1)
For lands with a pitch of .050 inch (1.27 mm) or greater, coverlayer encroachment is on one side of land
only and does not exceed .002 inch (0.050 mm).
(2)
For lands with a pitch less than .050 inch (1.27 mm), coverlayer encroachment shall not exceed .001
inch (0.025 mm). The encroachment can occur on adjacent sides, but not on opposite sides of the land.
c.
For ball grid array lands, the following shall apply:
(1)
If the BGA land is coverlayer (or solder mask) defined, allowable misregistration of the coverlayer
causes breakout of the land of not more than 90 degrees.
(2)
If the BGA land is copper defined, the coverlayer shall not encroach onto the land. Coverlayer on the
land-to-via connecting conductor shall be acceptable.
(3)
If the BGA land is connected to a via and a coverlayer dam is specified, the dam shall remain in place
and be continuous over the conductor to the via (no cracked, peeling, or missing coverlayer).
d.
Edge-board contacts and test points which are intended for assembly testing shall be free of coverlayer
unless a partial coverage allowance is specified.
e.
Coverlayer shall not encroach into plated-through hole barrels or onto other surface features such as
connector fingers, test points, or lands of unsupported holes to which solder connections will be made.
f.
Covercoat need not be flush with the surface of the land. Misregistration of a covercoat-defined feature shall
not expose adjacent isolated lands or conductors.
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