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From the Hill: Sampling Plan Language in MIL-PRF-31032

What’s the Sample?

Conformance to military standards is all about using the correct sample specimen and testing the proper quantity. That, of course, sounds too simple to warrant an entire column. However, military specifications have numerous tests with various sample specimen types that all require different quantities for test or inspection. The complexity greatly increases by the fact these specifications contain 35–40 pages and cross-references to many more documents.

Specifically, the MIL-PRF-31032 series of specifications is composed of 12 Department of Defense (DoD) documents. In addition, within the main documents, there are at least 20 more commercial specifications related to board testing, inspection, and design. Therefore, listing every sampling combination in every document is not possible in this summary column. Therefore, the focus will be limited to MIL-PRF-31032/1C WAM 2 dated July 11, 2018, for rigid multilayer boards. This information is not meant to be a replacement for reading the specification but a learning guide that should make understanding the key parts of compliance straightforward.

To start, here is some sample terminology specific to MIL-PRF-31032:

• B/P or B: A production board from the lot
• T: Test coupon (A, B, AB, D, S, G, E, C, M, N, P, etc.)
• SMT: Surface-mount test coupon
• THM: Through-hole test coupon
• MIX: Boards with through-holes and surface-mount features
• Sample Plan Frequency Series Table E-I Options: H, J, and N (most frequently used)

To read this entire column, which appeared in the January 2020 issue of PCB007 Magazine, click here.