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.

Pages 1 - 2 - 3 - 4 - 5 - 6 - 7 - 8 - 9 - 10 - 11 - 12

MIL�PRF�50884F

CONTENTS

PARAGRAPH

PAGE

A.3.5.5 Solder mask........................................................................................................................................... 21

A.3.5.5.1 BGA lands ....................................................................................................................................... 21

A.3.5.5.2 Coverage ........................................................................................................................................ 21

A.3.5.5.3 Discoloration ................................................................................................................................... 22

A.3.5.5.4 Registration ..................................................................................................................................... 22

A.3.5.5.5 Soda straw voids............................................................................................................................. 22

A.3.5.5.6 Solder mask cure ............................................................................................................................ 22

A.3.5.5.7 Thickness ........................................................................................................................................ 22

A.3.5.6 Stiffeners ............................................................................................................................................... 22

A.3.5.6.1 Acceptability, design, and placement .............................................................................................. 22

A.3.5.6.2 Bonding ........................................................................................................................................... 22

A.3.5.6.3 Foreign material between the stiffener and printed wiring board surface ........................................ 23

A.3.5.6.4 Stiffener access hole registration .................................................................................................... 23

A.3.5.7 Via protection......................................................................................................................................... 23

A.3.5.7.1 Filled via, cap plating....................................................................................................................... 23

A.3.5.7.2 Unfilled via, solder mask tenting...................................................................................................... 23

A.3.5.8 Wicking of metallic conductor finish materials ....................................................................................... 23

A.3.6 Plated hole structural requirements.............................................................................................................. 23

A.3.6.1 Base material......................................................................................................................................... 23

A.3.6.1.1 Adhesive voids ................................................................................................................................ 23

A.3.6.1.1.1 Non-stressed specimens .......................................................................................................... 23

A.3.6.1.1.2 Stressed specimens ................................................................................................................. 23

A.3.6.1.2 Base material cracks and voids....................................................................................................... 24

A.3.6.1.2.1 Non-stressed specimens .......................................................................................................... 24

A.3.6.1.2.2 Stressed specimens ................................................................................................................. 24

A.3.6.1.3 Coverlayer thickness ....................................................................................................................... 24

A.3.6.1.4 Delamination ................................................................................................................................... 24

A.3.6.1.5 Dielectric layer thickness................................................................................................................. 24

A.3.6.1.6 Metal plane hole fill insulation material............................................................................................. 24

A.3.6.1.7 Hole wall to dielectric separation..................................................................................................... 24

A.3.6.1.7.1 Non-stressed specimens .......................................................................................................... 24

A.3.6.1.7.2 Stressed specimens ................................................................................................................. 24

A.3.6.1.8 Via fill of blind and buried vias......................................................................................................... 24

A.3.6.2 Conductor pattern .................................................................................................................................. 25

A.3.6.2.1 Conductor finish .............................................................................................................................. 25

A.3.6.2.1.1 Dewetting.................................................................................................................................. 25

A.3.6.2.1.2 Nonwetting................................................................................................................................ 25

A.3.6.2.1.3 Outgrowth and overhang .......................................................................................................... 25

A.3.6.2.1.4 Protective finishes for internal metal cores or metal backing .................................................... 25

A.3.6.2.1.5 Thickness ................................................................................................................................. 25

A.3.6.2.2 Conductor thickness........................................................................................................................ 26

A.3.6.2.2.1 Conductors with copper plating (after processing).................................................................... 26

A.3.6.2.2.2 Conductors without copper plating ........................................................................................... 26

A.3.6.2.3 Conductor width .............................................................................................................................. 27

A.3.6.2.4 Annular ring, internal ....................................................................................................................... 27

A.3.6.2.5 Bonding of conductor to base material and lifted lands................................................................... 27

A.3.6.2.5.1 Non-stressed specimens .......................................................................................................... 27

A.3.6.2.5.2 Stressed specimens ................................................................................................................. 27

A.3.6.2.6 Undercutting.................................................................................................................................... 27

A.3.6.3 Hole preparation prior to metallization ................................................................................................... 27

A.3.6.3.1 Desmear (hole cleaning) ................................................................................................................. 27

A.3.6.3.2 Etchback ......................................................................................................................................... 28