Table Of ContentElectroless Plating:
Fundamentals
And Applications
Glenn 0. Mallory
Juan B. Hajdu
Edftors
Reprint Edition
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ABOUT THE EDITORS
Glenn 0. Mallory
Glenn 0. Mallory has more than 30 years' experience in the surface finishing
industry, with specialization in electroless deposition processes. In 1986, Mr.
Mallory formed the Electroless Technologies Corporation (ETC) in Los Angeles,
CA. ETC is an independent R&D organization which licenses its technical
developments. Prior to that he was vice president of R&D for electroless nickel
development for the Allied-Kelite Division of Witco Chemical Corporation in Los
Angeles.
Mr. Mallory is the author of many papers and patents on electroless
deposition. He was elected a fellow of the Institute of Metal Finishing in 1974,
and received the AES Silver Medal for a paper published in Plating and Surface
Finishing in 1975. Mr. Mallory received his BS degree from UCLA and his MS
from California State University, Los Angeles.
Juan B. Hajdu
Juan B. Hajdu has extensive experience in surface treatments and electroless
plating. During his30-yearcareer he has been affiliated with ENTHONE, Inc., in
New Haven, CT. He joined ENTHONE in 1961 as a research chemist and is
currently Vice President, Technology, for ENTHONE-OMI, Inc., a subsidiary of
Asarco Inc.
Mr. Hajdu obtained his PhD at the University of Buenos Aires, Argentina, then
joined Pantoquimica, S.A., an affiliate of ENTHONE. He has written many
papers on electroless deposition and electrodeposition, and is the inventor or
co-inventor on some 20 patents. In 1966, Mr. Hajdu received the AES Gold Medal
for work published in Plating concerning plating on plastics, and in 1970, the
Eugene Chapdelaine Memorial Award for his work in zinc plating.
539
viii
CONTRIBUTORS
MICHAEL J. ALEKSINAS, Fidelity Chemical Products Co., Newark, NJ
DONALD W. BAUDRAND, CEF, Allied-Kelite Division, Witco Chemical Corp.,
Melrose Park, IL
PETER BERKENKOTTER, Western Digital Corp., Santa Clara, CA
DR. PERMINDER BINDRA, International Business Machines Corp., Endicott,
NY
ROBERT CAPACCIO, P.E., Mabbett, Capaccio & Associates, Boston, MA
DR. JOSEPH COLARUOTOLO, Occidental Chemical Corp., Berwyn, PA
JOHN G. DONALDSON, CEF, Surface Finishing Engineering, Tustin, CA
DR. E.F. DUFFEK, Adion Engineering Co., Cupertino, CA
DR. NATHAN FELDSTEIN, Surface Technology Inc., Trenton, NJ
DR. JUAN B. HAJDU, Enthone-OM1 International, Inc., West Haven, CT
DR. N. KOURA, Science University of Tokyo, Machida City, Japan
JOHN J. KUCZMA, JR., Elnic, Inc., Nashville, TN
DAVID KUNCES, CEF, Fidelity Chemical Products Corp., Newark, NJ
JOHN KUZMIK, MacDermid, Inc., Waterbury, CT
HARRY J. LITSCH, CEF-SE, Litsch Consultants, Bethlehem, PA
GLENN 0. MALLORY, Electroless Technologies Corporation, Los Angeles,
CA
DR. YUTAKA OKINAKA, AT&T Bell Laboratories, Murray Hill, NJ
KONRAD PARKER, Consultant, Park Ridge, IL
FRED PEARLSTEIN, CEF, Temple University, Philadelphia, PA
W.H. SAFRANEK, CEF, American Electroplaters and Surface Finishers
Society, Orlando, FL
PHILLIP D. STAPLETON, The Stapleton Co., Long Beach, CA
DR. DONALD STEPHENS, Consultant, Westlake Village, CA
FRANK E. STONE, Inland Specialty Chemical Corporation, Tustin, CA
DIANE M. TRAMONTANA, Occidental Chemical Corp., Grand Island, NY
DR. ROLF WEIL, Stevens Institute of Technology, Hoboken, NJ
DR. JAMES R. WHITE, International Business Machines Corp., Austin, TX
CATHERINE WOLOWODIUK, AT&T Bell Laboratories, Murray Hill, NJ
PREFACE
The term "electroless plating" describes the methods of depositing metals and alloys
by means of electrochemical reactions. However, chemical plating is the more
accurate term that can be used to denote the several means of metal deposition
without the application of electric current from an external source. Hence,
immersion deposition, as well as electroless deposition, covered in this book, are two
forms of chemical plating. In usage, the term "electroless plating," as coined by
Abner Brenner, has come to be synonymous with autocatalytic plating. In this
process, the chemical reaction proceeds continuously on selected surfaces,
providing the means to produce uniform coatings with unique properties on a wide
variety of substrates.
The practice of electroless plating is a relatively young art, developed over the past
fifty years for a large number of applications. Several major industries, such as
printed circuit boards, hard memory disks and electroplated plastics were made
possible by the development of electroless technology. This book describes the
chemical principles of the major electroless processes and the practical applications
of these techniques in industry. Of the different electroless processes available,
electroless nickel and electroless copper have gained the largest industrial use and
are discussed extensively. Other electroless plating processes and related subjects
are discussed in individual chapters. A limited number of techniques, mentioned in
the literature, that have no experimental proof or applications background were not
included. It is important to note here that electroless plating is a fast-growing field
and the references should be updated continuously.
Two points should be made on editorial decisions. As a result of our intention to
cover both principles and applications of electroless plating, some subjects required
a theoretical approach, while other subjects demanded pragmatic and descriptive
treatment. For this reason, the authors had very few constraints on style, format,
units and the general outlay of their chapters.
In addition to electroless plating, immersion plating is reviewed. While this process
is not based strictly on chemical reduction, it is closely related to electroless plating
in industrial applications.
The editors would like to express their gratitude to the many persons who have
made this book a reality: First of all to the authors for their cooperation and patience;
to the staff and authorities of the American Electroplaters and Surface Finishers
Society for their help and support; and to the members of the Electroless Finishing
Committee, eSpeCiallY to our colleagues, Michael Aleksinas, Dr. Moe El-Shazly,
David Kunces, CEF, and Fred Pearlstein, CEF, in reviewing the manuscripts. Special
thanks are also due Harry Litsch, CEF-SE, for preparing the index.
No work on the subject of electroless plating should be published without
acknowledging the industry's lasting debt to the pioneering work of Dr. Abner
Brenner.
We hope this book will fill the void which has existed for a complete reference on
electroless deposition, and that you will find it a most useful addition to your library.
Glenn 0. Mallory Juan B. Hajdu
Editor Editor
vii
CONTENTS
Preface vii
Contributors viii
Chapter 1 1
The Fundamental Aspects of Electroless Nickel Plating
Glenn 0. Mallory
Chapter 2 57
Composition and Kinetics of Electroless Nickel Plating
Glenn 0. Mallory
Chapter 3 101
Troubleshooting Electroless Nickel Plating Solutions
Michael J. Aleksinas
Chapter 4 111
Properties of Electroless Nickel Plating
Rolf Weil and Konrad Parker
Chapter 5 139
Equipment for Electroless Nickel
John Kuczma, Jr.
Chapter 6 169
Test Methods for Electroless Nickel
Phillip Stapleton
Chapter 7 193
Surface Preparation for Electroless Nickel Plating
Juan Hajdu
Chapter 8 207
Engineering Applications of E!ectroless Nickel
Joseph Colaruotolo and Diane Tramontana
Chapter 9 229
Electronic Applications of Electroless Nickel
E.F. Duffek, D. W. Baudrand, CEF, and J.G. Donaldson, CEF
Chapter 10 261
Electroless Deposition of Alloys
Fred Pearlstein, CEF
Chapter 11 269
Composite Electroless Plating
Nathan Feldstein
Chapter 12 289
Fundamental Aspects of Electroless Copper Plating
Perminder Bindra and James R. White
Chapter 13 331
Electroless Copper in Printed Circuit Fabrication
Frank E. Stone
Chapter 14 377
Plating on Plastics
John J. Kuzmik
Chapter 15 401
Electroless Plating of Gold and Gold Alloys
Yutaka Okinaka
Chapter 16 421
Electroless Plating of Platinum Group Metals
Yutaka Okinaka and Catherine Wolowodiuk
Chapter 17 441
Electroless Plating of Silver
N. Koura
Chapter 18 463
Electroless Cobalt and Cobalt Alloys
Section I
W.H. Safranek, CEF
Section II
Peter Berkenkotter and Donald Stephens
Chapter 19 511
Chemical Deposition of Metallic Films from Aqueous Solutions
David Kunces, CEF
Chapter 20 519
Waste Treatment of Electroless Plating Solutions
Robert Capaccio, P.E.
Index 529
About the Editors 539
Chapter 1
The Fundamental Aspects
Of Electroless Nickel Plating
Glenn 0.M allory
The chemical deposition of a metal from an aqueous solution of a salt of said
metal has an electrochemical mechanism, both oxidation and reduction (redox),
reactions involving the transfer of electrons between reacting chemical species.
The oxidation of a substance is characterized by the loss of electrons, while
reduction is distinguished by a gain of electrons. Further, oxidation describes an
anodic process, whereas reduction indicates a cathodic action. The simplest
form of chemical plating is the so-called metal displacement reaction. For
example, when zinc metal is immersed in a copper sulfate solution, the zinc
metal atoms (less noble) dissolve and are spontaneously replaced by copper
atoms from the solution. The two reactions can be represented as follows:
-
Oxidation: Zno Zn” -+ 2e-, anodic, Eo= 0.76 V
Reduction: Cu” + 2e- Cuo,c athodic, Eo= 0.34 V
-
Owera// reaction: ZnO + Cu” Zn” + Cuo, Eo= 1.1 V
As soon as the displacement reaction begins, the surface of the zinc substrate
becomes a mosaic of anodic (zinc) and cathodic (copper) sites. The
displacement process continues until almost the entire substrate iscovered with
copper. At this point, oxidation (dissolution) of thezincanodevirtually stops and
copper deposition ceases. Chemical plating by displacement yields deposits
limited to only a few microns in thickness, usually 1 to 3 pm. Hence, chemical
plating via the displacement process has few applications.
In order to continuously build thick deposits by chemical means without
consuming the substrate, it is essential that a sustainable oxidation reaction be
employed as an alternative to the dissolution of the substrate. The deposition
reaction must occur initially and exclusively on the substrate and subsequently
continue to deposit on the initial deposit. The redox potential for this chemical
process is usually more positive than that for a metal being deposited by
immersion. The chemical deposition of nickel metal by hypophosphite meets
both the oxidation and redox potential criteria without changing the mass of the
substrate:
1
2 ELECTROLESS PLATING
-
Reduction: Nit' + 2e- N-i" E" = -25 mV
Oxidation: H2PO; + H?O HpO; + 2H' + 2e- E" = +50 mV
-
Ni'* + H2PO; + H?O Ni" + H2PO; + 2H' E" = +25 mV
which is the sum of the oxidation and reduction equations. This reaction does
not represent the true electroless plating reaction, since EN deposition is
accompanied by hydrogen evolution. Figure 1.1 shows the difference between
immersion and electroless deposition by comparing deposit thickness vs. time.
The term electrolessplating was originally adopted by Brenner and Riddell (1)
to describe a method of plating metallic substrates with nickel or cobalt alloys
without the benefit of an external source of electric current. Over the years, the
term has been subsequently broadened to encompass any process that
continuously deposits metal from an aqueous medium.
In general, electroless plating is characterized by the selective reduction of
metal ions only at the surface of a catalytic substrate immersed into an aqueous
solution of said metal ions, with continued deposition on the substrate through
the catalytic action of the deposit itself. Since the deposit catalyzes the reduction
reaction, the term autocatalytic is also used to describe the plating process.
Fig. 1.1-Thickness vs. time-comparison between electroless and immersion deposition.
