<< BACK

The Board Authority

Flexible Circuitry Issue
(03/2001)

Introduction by William Jacobi

Cost: $65.00 per entire issue OR
$7.50 per individual article

You may order the entire issue here, or individual articles below.
CLICK HERE to jump to Table of Contents

When I was young (I didn't say "younger"), Charles Atlas had a series of cartoon ads. The scene was a beach where a skinny boy got sand kicked in his face. Most episodes depicted this skinny boy enrolling in a body building course and, soon thereafter, returning to the beach to be the kicker instead of the kickee. The ad was successful for Charles Atlas, and played well in the cities with or without beaches.

This issue of The Board Authority has been devoted to a form of interconnect that relies on its "skinniness" to provide many salient features to the world of electronics. Indeed, the flexible circuit would not be very flexible if not for its thinness. It would not be a space or weight saver if it were thicker. Beyond the dimensional aspects of this special form of printed wiring, its thinness brings processing advantages: aspect ratios in the plated vias are always small, making the reliability of layer-to-layer connections reliable; and the vias or pathways between circuit layers are short, allowing mechanical punching and lasing to be viable techniques. So, unlike me and my childhood brethren, these "skinny" circuits didn't have to bulk up to be sand kickers.

Flexible circuits came into favor early because of their foldability and knack of being tucked in the electronic enclosure with ease. As electronic packages shrank in size and mass, flex became an acceptable platform.

Designers—who had to slake the consumers appetite for smaller yet more powerful, lighter yet more feature packed electronics—turned to flexible circuitry in ever-increasing numbers. The caveats are many to working with this skinny flexible circuit. But as the industry matured, it departed from the old fiefdoms where each manufacturer had "special" design features. Through the efforts of organizations such as IPC and JPCA, standards for design and performance have emerged.

To be sure, each flex manufacturer has carved out certain niches of expertise and can provide cost reducing efficiencies. Through all of this, the industry has become more viable and geared to respond to its growing customer base. It is hard to stay away from this skinny circuit. The applications for the flexible circuit range from your automobiles to portable phones to computers to cameras to a myriad of electronic devices known only by their acronyms. The robust growth attesting the flexible circuit's success is tied to its functionality and not its ability to kick sand. Sorry, Chuck.

WILLIAM JACOBI

Flexible Circuitry
Table of Contents

6	Flexible Printed Circuits...a Technology on the Move by JOSEPH FJELSTAD AND BILL JACOBI The limiting factors in the advance of electronic packaging with flexible circuits rest in the imagination of those assigned the task. Hopefully, this issue of The Board Authority will provide the reader with a better appreciation of flexible circuit technology and, just perhaps, spark a few new ideas of how it might be used.
12	Market Trends in High Density Flex Circuits by E. JAN VARDAMAN Demand for HDI flex in IC packages is expected to continue, especially with increased demand for low cost, small form factor packages. In addition, performance advantages gained with the use of flex-based packages make the technology an attractive option for many high-end applications.
14	Meeting the Flex HDI Challenge with Materials Technology by PETE KACZMAREK There are some important new flexible materials choices which may allow the fabricator to stretch existing processes further in the pursuit for new business in flex HDI circuitry.
22	All-Polyimide Flexible Laminates for Displays by KURT D. ROBERTS Consumer electronic applications demand flexible circuits with fine pitch for chip on flex (COF) attachment and high-density interconnection capability. All-Polyimide flexible laminates are ideally suited for producing these dense, high-performance flexible circuits.
26	Coverlay Selections for Reliable High Density Flex Circuits by DOMINIQUE NUMAKURA Many new coverlay technologies have been developed to satisfy the requirement of high density interconnects of flex circuits in the last ten years. Which is the right solution for you?
34	Flexible Manufacturing—How Design and Cost Can Influence Processing by KEITH NETTING, PETER TAYLOR, AND PAUL THOMAS Designers should involve fabricators and assemblers as early as possible to produce the most cost effective and successful interconnect solution.
38	Finite Element Modeling: An Important Design Tool for Flexible Circuits by JOSEPH FJELSTAD Finite element analysis is a method well-suited to the needs of the flexible circuit designer.
44	Cutting-Edge of Flex-Processing Laser Technology by SRI VENKAT New developments in laser technology increase flex manufacturing speed.
48	Plasma Processed Flexible and Rigid-Flexible HDIs by MICHELE STAMPANONI AND DR. WALTER SCHMIDT A general overview of the plasma processing technology and build-up structures.
54	Laser Cutting of Flex Circuits by JENS BAENSCH Why has it become necessary to cut flex circuits by laser?
56	Roll-to-Roll by THOMAS STEARNS Roll-to-roll process is the Holy Grail of high-volume flexible printed wiring (FPW) production. While not practical for short runs, it is the only way to make high volumes of product at lowest cost in a form which facilitates other automated processes such as component stuffing and tape automated bonding (TAB).
64	Automobile Applications of Double-Sided Flex Circuits Produced by RTR Processes by STEVE DEAN, DARRYL MCKENNEY, AND DOMINIQUE NUMAKURA PalFlex: An examination of one process.
66	Flexible Circuit Testing Challenges by MARK J. DRAGAN AND BRIAN WALKER Testing of flexible circuits is challenging—but it is possible to get accurate testing results by looking carefully at all elements of the testing system and testing approach. A creative approach to meeting the challenge of future high density flex circuits by applying the right tools and methods for each given job will be imperative.
70	Flexible Testing: Don't be a Test Dummy by BOB NEVES A look at "non-point to point" testing of flexible circuits.