Testing Controlled Impedance Boards This paper presents the results of research into the process of testing controlled impedance circuit boards. It aims to provide a general introduction to the subject of controlled impedance circuit boards production for manufacturers wishing to make this type of board in the future and offers constructive suggestions for those who may want to improve on their current process. Consequently, in addition to describing test issues, there are also references to some of the main subject areas that require attention when the productiong of high quality controlled impedance circuit boards is to be considered namely; design, materials and fabrication. The content of this paper is based on production trials that were conducted by MEPD Met-Etch (Selkirk) Ltd. at their manufacturing facilities in Scotland as part of a UK Ministry of Defense research contract. The results of this research were included in a report for the UK Defense Research Agency (Electronics Division) and subsequently they were also detailed in an individual ,,Guidelines for Designers" document. In order to verify the test results separate comparison measurements were also conducted by other circuit board manufacturers using a range of suitable test instrumentation. There is growing requirement in the printed circuit board industry for a simple means of testing controlled impedance boards. This paper promotes the use of computer controlled test instrumentation so that accurate and repeatable measurements can be made by production staff in a manufacturing environment. If this is achieved, then it should be possible to close the quality loop on controlled impedance circuit board production using normal statistical process control techniques.
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