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PRINTED WIRING BOARD FLEXIBLE LAMINATE | |
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The thin films used in flexible circuitry offer significant width and space savings over traditional rigid designs and allow the development of printed boards that can be bent and folded in three-dimensional (3-D) configurations. Flexible boards may be single, double or multi-layer; may contain through-hole, surface mount or mixed technology; and, can be constructed wholly of flex or a combination of both flex and rigid (see rigid-flex, section 5.04). |
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PREFERRED GENERAL Flexible circuit is clean, smooth, of uniform thickness and free of damage. Solderable surfaces are clean and bright. Markings are legible and properly oriented. |
PREFERRED COVERFILM The coverfilm is smooth, clean and of uniform thickness. There is no evidence of bubbles, creases, delamination, entrapped particles, gouges, tears or ripples. Alignment and registration are correct. Best Workmanship Practice |
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PREFERRED TRIMMED EDGE The trimmed edge shall be free of burrs, nicks, delamination or tears. Minimum edge to conductor spacing shall be maintained. Best Workmanship Practice |
ACCEPTABLE COVERFILM REGISTRATION The coverfilm is aligned and registered within engineering specification. All annular ring cutouts are centered, and there is no evidence of unwanted material on land areas. Best Workmanship Practice |
| NASA WORKMANSHIP STANDARDS | |||
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Released: 04.05.2002 |
Revision: |
Revision
Date: |
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Book: 5 |
Section: 5.03 |
Page: 1 |
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PRINTED WIRING BOARD FLEXIBLE LAMINATE (cont.) | |
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ACCEPTABLE EDGE NICKS Nicks along the edges of the flexible printed wiring, cutouts and unsupported holes are acceptable, provided minimum edge to conductor spacing is maintained and damage is within agreed-upon limits. Best Workmanship Practice |
ACCEPTABLE PLATED SURFACES Plating is uniform, smooth and shiny. Holes are smooth and clean. No evidence of solder wicking/plating migration. Best Workmanship Practice |
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ACCEPTABLE SURFACE ROUGHNESS/SCUFFING Minor roughness or scuffing of the laminate surface is acceptable, provided the damage does not reduce reliability or interfere with the design of service/operability. Best Workmanship Practice |
ACCEPTABLE TIE-IN TAB TEARS Minor nicks and tears that result from the use of tie-in tab design are acceptable, provided the damage does not reduce edge to conductor spacing below minimum requirements, or exceed the damage requirement agreement. Best Workmanship Practice |
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UNACCEPTABLE CREASES Creases reduce the current carrying capability and reliability of the printed conductors and the bond integrity of the laminate. Flexible circuits shall exhibit proper bend radius and strain relief. Best Workmanship Practice |
UNACCEPTABLE EDGE NICKS Nicks along the edges of the flexible printed wiring, cutouts and unsupported holes which reduce minimum edge to conductor spacing below minimum requirements or expose conductive surfaces, are unacceptable. Best Workmanship Practice |
| NASA WORKMANSHIP STANDARDS | |||
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Released: 04.05.2002 |
Revision: |
Revision
Date: |
|
Book: 5 |
Section: 5.03 |
Page: 2 |
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PRINTED WIRING BOARD FLEXIBLE LAMINATE (cont.) | |
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UNACCEPTABLE FOREIGN MATERIAL IN COVERCOAT Foreign material under the covercoat represents a contamination and reliability concern. Best Workmanship Practice |
UNACCEPTABLE PHYSICAL DAMAGE Cuts, nicks, gouges, tears or other physical damage that result in exposed circuitry or reduce electrical separation below minimum requirements are unacceptable. Best Workmanship Practice |
| NASA WORKMANSHIP STANDARDS | |||
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Released: 04.05.2002 |
Revision: |
Revision
Date: |
|
Book: 5 |
Section: 5.03 |
Page: 3 |
|
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