PCB007 Magazine

PCB-Sept2016

Issue link: http://iconnect007.uberflip.com/i/723195

Contents of this Issue

Navigation

Page 25 of 83

26 The PCB Magazine • September 2016 some political ramifications. In the mid-1980s, the Project on Government Oversight reported the Pentagon was dramatically overpaying for commercially available items. Notable exam- ples used were a $435 hammer and a $600 toilet seat. In response, President Reagan created a com- mission, headed by David Packard, to study the procurement practices of the U.S. Department of Defense. The basic findings of the commis- sion 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 pro- curement 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 com- mercial product as at least a guide in developing procurement specifications. Specifications for flexible printed circuits Previous to the 1990s, MIL-P-50884, "Print- ed Wiring Board, Flexible or Rigid-Flex, General Specification For" was used to define sampling plans and quality requirements for the procure- ment and specification of flexible circuits for DOD applications. Among other things, circuit fabricators were required to periodically submit coupons from fabricated panels for testing at a certified independent laboratory. A supplier also had to be certified as capable to build to this specification. This was accomplished by pe- riodically producing test coupons and submit- ting them for examination and test for specific quality metrics. As with many specifications created before the 1990s, MIL-P-50884 was rigid and complex. The DOD decided to look at the commercial world for developing a more practi- cal specification. During the 1990s, IPC developed a pair of specifications intended to set universal stan- dards for circuitry performance in known ap- plications. Those documents were IPC-6013, "Qualification and Performance Specification For Flexible Printed Boards" and IPC-6012, "Qualification and Performance Specification For Rigid Printed Boards." The IPC is a trade association of material suppliers, circuit fabri- cators and OEMs. The military worked closely with this consortium in creating requirements that could be used for military applications. They did this with the knowledge that the exist- ing MIL-P-50884 was going to be discontinued. These IPC documents specified requirements for the three classes of circuit application as de- fined in IPC-6011: • Class 1: General Electronic Products • Class 2: Dedicated Service Electronic Products • Class 3: High-Reliability Electronic Products IPC 6013 Class 3 describes the most stringent quality requirements and it was the intention of the military to use this document to procure flexible circuits for military applications. This specification was also intended to replace MIL- P-50884. Unfortunately, an additional specifica- tion evolved as the DOD decided to create its own replacement specification for MIL-P-50884 (the new specification is MIL-PRF-31032) that incorporated the principles of commercial prod- ucts. Further adding some confusion, there was no documentation or guidance given on what should happen to drawings specifying the dis- continued MIL-P-50884 specification. In effect, the industry was left in limbo regarding what documentation should be used when draw- ings called out MIL-P-50884. This has generally resulted in a default to continue using MIL- P-50884 as the quality specification for legacy parts. Flexible circuit fabricators continue build- ing product to and are certified to MIL-P-50884. This only applies to programs designed and specified before 1999. MIL-P-50884 can no lon- ger be used for designs specified after February 1999. Most large OEMS are procuring military and aerospace products to IPC-6013 and speci- fying Class 3 quality requirements but some new military documentation specifies MIL- PRF-31032. Consequently, it is possible that a circuit fabricator may be required to produce similar products/applications for three different specification requirements. FLEX CIRCUIT SPECIFICATIONS FOR COMMERCIAL AND MILITARY APPLICATIONS

Articles in this issue

Links on this page

Archives of this issue

view archives of PCB007 Magazine - PCB-Sept2016