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Just like any other industry segment within the circuit board world, the military sector has its own share of documents…and likely many more than most! These documents have been developed over the years to guide, shape, and test anything and everything that might go into a jet fighter, a radar system, a warship, a weapons system, etc. Even though military technology and equipment has certainly become more dependent on electronics over the more recent years, this industry has always been at the forefront of technological breakthroughs and thus their testing protocols have been around for decades. Believe it or not, for example, MIL-I-46058, mentioned in more detail later, has been around for more than 50 years! In this column, a brief taste is supplied of the common military testing documents that guide PCBs, printed circuit assemblies, and some electrical components in this most complicated of industries. The summaries below give you a short description of these common documents in respect to their focus and structure.
This military detail specification covers four series of electrical connectors that are capable of operation from -65°C to +200°C. The series includes connectors containing pin & socket contacts with the document providing information pertaining to orientation guides, hermetical sealing, and EMI shielding. Additionally, guidance is presented with respect to the various mechanical, environmental, and electrical tests that are required, including specific test requirements for different classification ratings.
This military specification was established for the qualification of electrically insulative compounds used for coating printed circuit assemblies. These compounds are commonly referred to as conformal coatings within the circuit board industry. The document, although officially inactive since 1998, is still widely used throughout the printed circuit board/assembly industry to this day and contains various visual, electrical, and environmental test methods, pertaining to the analysis of the coating material itself.
This military performance specification was established to test printed circuit boards and printed wiring boards in a manner that would certify they meet the necessary requirements for military use. Successful completion of the certification/qualification process results in a company being listed on the qualified manufacturer’s list (QML)—a resource that others can use for various other aspects of the marketplace. As for the document itself, requirements for obtaining the QML listing are obviously included, along with appendices that address various requirements/methods grouped by technology and specific end use.
MIL-PRF-50884 and MIL-PRF-55110
These military performance specifications were established to test flexible and rigid-flex printed wiring boards (MIL-PRF-50884) and rigid single-sided, double-sided, and multilayer printed wiring boards (MIL-PRF-55110), as they pertain to military use. The main document contains general information about the qualification process, with various appendices dedicated to topics such as: the qualified products list (QPL), the QML (as mentioned in the MIL-PRF-31032 section above), testing products to superseded design standards, as well as requirements for this qualification specifically.
This military test method standard was established for the testing of electronic and electrical component parts. The methods contained within the document set guidelines for environmental, physical, and electrical tests, in line with conditions expected for military operation. The test methods are grouped in the following way: environmental tests (100 class), physical
characteristics tests (200 class), and electrical characteristics tests (300 class).
This military test method standard is not so much a collection of test methods, although it does have some, but more so a document to help engineers, analysts, and managers with material selection. Specifically, the direction of the document is to marry an environmental test screening process with expected design and end use environment.
This military test method standard was established for the testing of microelectronic devices that are destined for use within military and aerospace systems. The document as a whole is comprised of environmental, mechanical and electrical tests, as well as workmanship and training procedures that have been shown to ensure a specific level of quality and reliability. The test methods are grouped in the following way: environmental tests (1000 series), mechanical tests (2000 series), electrical tests—digital (3000 series), electrical tests—linear (4000 series), and test procedures (5000 series).
The above descriptions are general in nature and by no means cover all of the documents that govern the military electronics world. That being said, the list is a good representation of common documents that are typically associated with a PCB or a printed circuit assembly’s place in the military market. At the same time, it is not uncommon for those desiring high levels of quality and reliability to test to these same documents even if the end use of the specific product is not military in nature. After all, the military realm is one sector of the market always looking for the best products and the most dependable equipment.
Editor's Note: This column originally appeared in the September 2016 issue of The PCB Magazine.