NEPCON West - Fiberoptic Expo Conference Proceedings


FLEXIBLE PRINTED CIRCUIT TECHNOLOGY - A VERSATILE INTERCONNECTION OPTION

Author: Joseph Fjelstad
Company: Silicon Pipe, Inc.
Date Published: 12/3/2002   Conference: NEPCON West - Fiberoptic Expo


Abstract: The definition of a flexible circuit found in the IPC-T-50 Terms and Definitions for Printed Boards is: "A patterned arrangement of printed wiring utilizing flexible base material with or without flexible coverlayers. It is a concise and functional definition; however it fails to adequately portray the depth and breadth of this extraordinarily versatile interconnection technology. Flexible circuits can be found in nearly every type of electronic product from simple toys and games on up to the highly sophisticated electronic instrumentation. They can be found in everything from modems to medical diagnostic and therapy equipment, from disk drives to dashboards, from cables to cameras, from printers to packages. The list is probably beyond accurate measure.

Flexible circuits have a long and fascinating history. A patent issued in 1898 to German inventor, Albert Hanson of Berlin, described the production of flat conductors on a sheet of paraffin coated paper. The concept was amenable to multilayer construction. It was clearly ahead of its time. Other notable inventors, including Thomas Edison weighed in with their concepts. While first viewed as a simple passive interconnection scheme and an alternative for some wire harnesses, flexible circuits soon were seen as having greater potential as a circuit board alternative and from there they captured the imagination of countless product engineers looking for ways to improve on their products.

While the collapse of the Internet Bubble in 2001 has left the interconnection industry a generally dismal state, one area of reasonable stability has been the flex circuit. According to a relatively recent report from Techsearch International, in year 2000, standard flex circuit technology was an approximately $3.4 billion market worldwide, (IPC TMRC had the number at $3.9 billion for the same period) However, The Techsearch report noted that there was perhaps another 2.5 billion dollar market for high density flex such as will be required for IC packages. At that time there was an anticipated average growth rate of about 15% per year. This seemed a reasonable number as flexible circuits has enjoyed double digit growth rates in the past. While the present situation still leaves much to be desired, the future of the technology still looks very bright. Japan still leads the world in both production and application of this versatile interconnection technology, however, flex manufacturing is rapidly spreading throughout Asia. The Techsearch International report notes that there are more than 40 top and mid-tier manufacturers of flex circuits in Asia.

Entry into the world of flex circuit manufacturing requires both care and capital. It is not a "drop in" replacement for rigid PCBs, either in fabrication or assembly. The difficulties have been recorded by many flex circuit novices who have been "beaten up" by hard lessons. The flex industry pioneers, both manufacturers and users alike, often lacked the specific design and production knowledge required to prevent the types of problems they encountered. Others repeated the mistakes many times over until the lessons learned came to the attention of a broader electronics manufacturing industry and the experience was formalized through standards, specifications and design guidelines. The common language of these documents enhances the possibilities for better communication, further improvements and continued growth of this vital technology. The IPC-2223 - Sectional Design Standard for Flexible Printed Boards is one of the most important products of that collected experience.



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