All About Flex: Flex Circuit Specifications for Commercial and Military Applications


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Applications across the various markets for printed circuit boards can have significantly different specifications and performance requirements. Circuits for toys and games logically have lower performance requirements than those used in medical devices. IPC-6013 is an industry-driven specification that defines the performance requirements and acceptance features for flexible printed circuit boards.
 
This specification was drafted to recognize the differences in performance requirements for different applications. Three classes of performance and acceptance requirements have been created in it:  Class 1, Class 2 and Class 3. Class 3 specifies the most stringent set of requirements and is used to specify quality requirements for products requiring the highest level of reliability. Class 3 requirements are often specified in applications for the Department of Defense (DoD), aerospace, and medical devices.
 
While IPC 6013 Class 3 is often used to specify flex circuits for military applications, MILP-50884 and MIL-PRF-31032 are two military documents also being used. These three different specifications define performance requirements for essentially the same applications and, in fact, there is significant redundancy and often confusion regarding how to properly specify product for military applications. To understand how things got to where they are today requires a review of some history.
 
Background The evolution of flexible circuit military specifications can be associated with the legendary story about the $600 toilet seat. In the 1980s during Reagan’s presidency, the U.S. was embarking on a major expansion in the size  and capabilities of the U.S. forces. Defense spending increased dramatically, which had some political ramifications. In the mid-1980s, the Project on Government Oversight reported the Pentagon was dramatically overpaying for commercially available items. Notable examples used were a $435 hammer and a $600 toilet seat.
 
In response, President Reagan created a commission, headed by David Packard, to study the procurement practices of the DoD. The basic findings of the commission were that there was no rational system for specifying and procuring products. Extremely high costs were due to overly rigid specifications created by overly complicated organizations (Source). The results of these findings drove a number of efforts to simplify government procurement processes. One of these efforts was to specify commercial off-the-shelf products (COTS) when possible. Specifically, the military started to look at specifications used for commercial product as at least a guide in developing procurement specifications.
 
 
Editor's Note: This article originally appeared in the September 2016 issue of The PCB Magazine.

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