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The Board Authority

Advanced Technologies for Packaging, Flex, and Rigid-Flex (07/2006)

Eighteen original articles to help you build better boards in new technologies for Packaging and Flex.

Introduction by Karl H. Dietz

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Introductory Overview CircuiTree Live 2006 The Board Authority. Advanced Technologies for Packaging, Flex and Rigid-Flex

As the title implies, this year’s edition of The Board Authority focuses on a cluster of related topics, all of which are quite timely. IC packaging substrates have become very complex,
especially flip chip BGA packages and stacked packages that require new material
solutions for signal integrity and reliability. The links from IC packaging to flexible
circuit technologies are the familiar chipon- flex, roll-to-roll processing, and flex for
TAB applications. The thinness, chemical resistance, and high break-down voltage of
polyimides are very attractive properties in many packaging applications. Redistribution
layers in wafer-level packaging often use polyimide dielectrics for rerouting the wafer’s I/Os for area array packaging.

Flexible circuits and rigid-flex structures have seen a dramatic increase in recent years
due to their popularity in hand-held devices where thinness and form factors (bend to install, dynamic flex) are essential. But specialty applications for the medical and military markets have also steadily grown. Specialty medical applications of flexible circuits are covered in two of the papers. Flex and rigid-flex constructions require wet chemical processing steps and conditions that are different from standard FR-4 processing. For example, due to the better chemical resistance of polyimide, throughhole surface preparation (swell & etch) has to be modified, which is described in another presentation. Market growth projections for the next five years are offered in one of the presentations.

Flexible circuits present a special challenge in handling and fixturing. The industry uses
roll-to-roll processing, support frames and leaders to facilitate transport and handling
through processing and testing. The challenges of electrical testing of thin, highdensity
flex structures is the subject of one of the presentations. Singulation (cutting, routing) of flexible circuits with traditional techniques can produce undesirable stresses and burrs. Laser cutting offers a more suitable technology for flex substrates.

“Adhesiveless” (all-polyimide) base materials have gained share due to their superior
dimensional stability and chemical resistance. The traditional RA (rolled annealed)
copper, known for its superior flex properties, is being replaced in some applications
by ED (electro-deposited) copper. These developments are described in several presentations. The third-level packaging interconnections for flex boards have seen the
development of non-mainstream interconnects such as ACF (anisotropic conductive
films) that require thermo-compression. The relatively high processing temperatures
are a problem for very thin structures, and encouraged the development of alternatives
such as Thermosonic Low Temperature Interconnections, described in two papers. Electroplated via fill has become an important enabling technology for buildup microvia layers for flip chip BGAs, and is now being introduced to flex structures which is the subject of yet another paper.

Embedded passive components are beginning to make inroads in flex circuits and IC
packaging. This subject is covered by two more papers.

There are many more papers in this year’s edition of The Board Authority that will help you build better substrate packages, flexible circuits, and rigid-flex constructions. We hope it proves a valuable resource.

Karl H. Dietz
Technology Expert & Issue Editor of CircuiTree Magazine

The Board Authority is Sponsored by:

Advanced Technologies for Packaging, Flex, and Rigid-Flex
Table of Content

Section	Article
4	Metallization of Packaging Substrates: MHC Beyond the Rigid PCB Rikiya Shimizu, Dennis Yee —The required characteristics of semiconductor package design with Rohm and Haas Electronic Materials adhesion promotion and electroless copper deposition processes.
10	Decoupling of High Performance Semiconductors Using Embedded Capacitor Technology William Borland, Daniel Amey, and Karl H. Dietz —Results and discussion of an investigation by a joint program, initiated and sponsored by DuPont with the Georgia Institute of Technology Packaging Research Center (PRC), of the integration of embedded Thick Film capacitors and HiK polyimide-based planar capacitor materials in IC packages.
16	Industry Direction in Implementing Embedded Components Dr. Richard Ulrich —An overview to help electronics manufacturers become familiar with the state of the art, its current applications, and what can be done to more easily implement embedded components into their products.
19	Thermosonic Low Temperature COF Interconnection Yoshikazu Hirayama —An innovative flip chip technology “Thermosonic Low Temperature Interconnection” has been developed as the next generation COF packaging process with less than 30 microns pitch.
22	A Novel IC Packaging Approach Anna Fontanelli —SiP is a modular design approach offering unprecedented flexibility in the development of systems. An intelligent partitioning of all the components of the electronic system is key to achieving greater functionality in a smaller area, combining dissimilar device types and high-yielding memory devices with similar size and wiring requirements.
26	Dynamic Applications of Adhesiveless Electro-Deposited Copper/Polyimide Laminates Matthew Heim —Traditionally, Actuator Flex Circuits (AFCs) in hard disc and tape drives have been fabricated using a KaptonHN polyimide/adhesive/ Rolled-Annealed Copper (RACu) base laminate. Switching to an adhesiveless KaptonE polyimide/Electro-Deposited Copper (EDCu) base laminate can often provide a solution path with equal or improved performance.
32	Reliable Flip Chip Assembly on Flexible Boards by Tin/Gold Bonding for Display Modules Sung-Woong Choi — Flip chip packaging is rapidly replacing wire bonding because it can meet high speed requirements. Are you ready?
35	Blind Micro Via and Through Hole Filling for Thin Core and Flexible Base Materials Stephen Kenny —The latest results obtained from horizontal conveyorized equipment ideally suited for the production of thin core and flexible materials.
38	Ultra-Smooth Copper Foil for Fine Pitch COF and FPC Takuya Yamamoto, John Andresakis, Naomitsu Inoue, and Masayuki Misawa —Polyimide casting base FCCL has had several critical performance issues that allow sputtered base FCCL to lead the market in substrate for COF. With the newly developed, ultra-smooth copper foil, DFF®, it has opened a door for polyimide casting and laminate base FCCL to compete with sputtered base FCCL.
42	A Future In Flex Merle Tingelstad —The combination of high density surface mount technology (SMT), micro-electromechanical systems (MEMS) and nano-scale construction enables a new wave of medical devices that benefit from increased use of flexible circuits.
44	Adhesiveless Copper on Polyimide Substrates for Medical Applications Tad Bergstresser, J. Mestdagh, and S. Storme —An in-depth discussion of adhesiveless copper-on-polyimide laminate properties, as they pertain to ultrasound interconnect requirements.
50	Burr and Stress-Free Cutting of Flexible Printed Circuits Using UV-laser Technology Dr. Marc Hüske, Dr. Dieter Meier —Laser cutting has already proven to be a technology well suited to complement conventional cutting technologies in prototyping, pre-series and low-volume production. By reducing product changeover time, increasing accuracy and eliminating tooling costs these systems produce a better product at a lower cost.
54	Staying Flexible: Utilizing Flying Probe Testers for Flexible Circuit Boards Jeff Hagopian —What are the challenges of flexible circuit tests? We evaluate the use of flying probe testers as a preferable solution for flexible circuit board electrical test.
60	Five-Year Projection of the Global Flexible Circuit Market Robert Turunen, Dominique Numakura and James J. Hickman —An investigation into the future of the flex industry to 2010 has been conducted. A new market research process has been developed to estimate the global market size of all kinds of flexible circuits in the next five years. Conventional flex circuits and advanced flex circuits are studied individually and reported on separately.
64	Evaluating New FR4 Laminates for Reliability in Rigid-Flex and Substrates Happy Holden —An investigation of the reliability of the newer higher-temperature resistant FR-4s used for a 0.034” eight (8)–layer, all FR-4 rigid-flex subjected to lead-free, RoHS compliant assembly temperatures and rework.
70	Rigid-Flex Comes of Age Michael Schumacher —Technical and commercial reasons to deploy flexible circuit interconnect solutions in the military/aerospace industries.
74	Pre-Treatment and PTH Solutions for Flex-Rigid PCBs Colin Devenny, Lars-Eric Pribyl —A discussion of some of the difficulties faced by flex and flex-rigid PCB manufacturers: desmearing different lay-ups of flex-rigid, electroless copper pre-treatment concepts, as well as a direct concept will be discussed showing the benefits and results for even the most demanding of board layouts and materials.
78	Understanding and Accelerating the UL Certifi cation process for Rigid-Flex PCBsCrystal Vanderpan —An overview of the material, process, and certification parameters to consider when moving to a flexible or rigid-flex PCB, providing guidance for accelerating the UL certification process.