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MIL-PRF-50884 Printed Wiring Board, Flexible Or Rigid-Flex, General Specification ForThis specification establishes the performance and qualification requirements for flexible and rigid-flex printed wiring boards with or without plated through holes \(see 6.1\). Verification is accomplished through the use of one of two methods of product assurance \(appendix A or appendix B\). Detail requirements, specific characteristics, and other provisions which are sensitive to the particular intended use are specified in the applicable master drawing.

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MIL�PRF�50884F

APPENDIX A

A.3.6.2.2 Conductor thickness. The conductor thickness shall be as specified (see A.3.1.1).

A.3.6.2.2.1 Conductors with copper plating (after processing). When a conductor thickness is specified, the

conductor thickness (metal foil and copper plating) shall be equal to or greater than the specified thickness. When a

conductor thickness with tolerance is specified, the conductor thickness (metal foil and copper plating) shall be within

the specified tolerance for the specified thickness. If only a starting metal foil weight requirement is specified, the

thickness limits for conductors with plating shall meet the requirements of table A�II. If only final metal foil weight

requirement is specified, the limits for minimum conductor thickness shall be as defined by the procuring activity.

Unless otherwise specified, the final conductor thickness of planarized layers will be less than the values in table A�II

due to the reduction allowance of A.3.6.4.2.

NOTE: Conductors with copper plating are typical of external layers of multilayer designs and internal layers of

sequential laminated multilayer designs.

TABLE A�II. Thickness of conductors with copper plating after processing (not planarized).

Starting

Processing

Minimum conductor thickness after processing

copper

reduction

Type 2

Types 2, 3, and 4

Type 3 and 4

foil weight

allowance

≤ .008 (0.2 mm)

> .008 and ≤ .030

> .030

(0.2 and 0.76 mm)

(0.76 mm)

inches (μm)

1/8

.00006 (1.5)

.000621 (15.78)

.001121 (28.473)

.001521 (38.633)

1/4

.00006 (1.5)

.000743 (18.87)

.001243 (31.572)

.001643 (41.732)

3/8

.00006 (1.5)

.000865 (21.97)

.001365 (34.671)

.001765 (44.831)

1/2

.00008 (2.0)

.001026 (26.06)

.001526 (38.760)

.001926 (48.920)

.00012 (3.0)

.001597 (40.56)

.002097 (53.263)

.002497 (63.423)

.00012 (3.0)

.002809 (71.35)

.003309 (84.048)

.003709 (94.208)

.00016 (4.0)

.003986 (101.2)

.004486 (113.944)

.004886 (124.104)

.00016 (4.0)

.005202 (132.1)

.005702 (144.830)

.006102 (154.990)

The starting copper foil weight is as specified on the master drawing.

The processing reduction allowance does not factor in any rework processing for copper foil weights

below 1/2. For weights of 1/2 and above, the processing reduction allowance accounts for one

rework process.

A.3.6.2.2.2 Conductors without copper plating (after processing). When a minimum conductor thickness is

specified, the conductor thickness (metal foil only) shall be equal to, or greater than, the specified thickness. When a

conductor thickness with tolerance is specified, the conductor thickness (metal foil only) shall be within the specified

tolerance for the specified thickness. For wrought or rolled metal foil types, if only a starting metal foil weight

requirement is specified, a reduction in thickness up to 5 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. For deposited metal foil types, if only a

starting metal foil weight requirement is specified, the limits for minimum internal layer foil thickness after processing

shall be in accordance with table A�III. If only final metal foil weight requirement is specified, the limits for minimum

conductor thickness shall be as defined by the procuring activity.