MILPRF50884F
APPENDIX A
A.2.4 Order of precedence. Unless otherwise noted herein or in the contract, in the event of a conflict between the
text of this document and the references cited herein, the text of this document takes precedence. Nothing in this
document, however, supersedes applicable laws and regulations unless a specific exemption has been obtained.
A.3 REQUIREMENTS
A.3.1 General. The performance requirements contained in this section, although sometimes determined by
examination of sampled printed wiring boards or test coupons, apply to all deliverable printed wiring boards.
A.3.1.1 Master drawing (see A.6.2.1.d). Printed wiring boards delivered under this specification shall be of the
material, design, and construction specified on the applicable master drawing. For the purposes of this appendix,
when the term "specified" is used without additional reference to a specific location or document, the intended
reference shall be to the applicable master drawing. If individual design details are not specified on the applicable
master drawing, then the baseline design parameters shall be as detailed in the design standard that was used to
design the printed wiring board (see A.3.3).
A.3.2 Qualification. Printed wiring boards furnished under this appendix shall be products that are authorized by
the qualifying activity for listing on the applicable QPL at the time of award of contract (see A.4.5 and A.6.3).
A.3.3 Design (see A.6.2.1.e). Printed wiring boards shall be of the design as specified. Unless otherwise specified
(see A.3.1.1), if individual design details are not specified on the applicable master drawing, then the baseline design
parameters to be used for acceptability of finished product requirements shall be as detailed in the design standard
that was used to design the printed wiring board. If no design standard is specified on the master drawing or the
appropriate design standard cannot be determined, then the default design shall be performance class 3 of IPC2221
and IPC2223.
A.3.3.1 Test coupons. Test coupon design shall be in accordance with the applicable design standard specified
(see A.3.1.1) and herein. Test coupon placement and quantity on a production panel shall be in accordance with the
requirements of appendix H. Test coupon selection and usage shall be determined by the manufacturer in order to
meet the in-process, groups A, B, and C inspection requirements herein. NOTE: Test coupon design shall be as
specified in the applicable design standard or herein, and shall reflect worst case design conditions of the printed
wiring board(s) they represent.
A.3.4 Materials. The printed wiring boards shall be constructed of materials as specified (see A.3.1.1). When a
definite material is not specified on the applicable master drawing, a material shall be used that will enable the printed
wiring board to meet the performance requirements of this specification. Acceptance or approval of any material shall
not be construed as a guaranty of the acceptance of the finished printed wiring board.
A.3.4.1 Pure tin. Unless otherwise specified (see A.3.1.1), the use of pure tin, as an underplate or final finish, is
prohibited both internally and externally. Tin content of printed wiring board finishes and solder shall not exceed 97
percent, by mass. Tin shall be alloyed with a minimum of three percent lead, by mass (see A.6.8).
A.3.4.2 Recycled, recovered, or environmentally preferable materials. Recycled, recovered, or environmentally
preferable materials should be used to the maximum extent possible, provided that the material meets or exceeds the
operational and maintenance requirements, and promotes economically advantageous life cycle costs.
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