GUIDELINE FOR

HAND SOLDERING PRACTICES

Guideline for Hand Soldering Practices

First Edition

by

Paul. T. Vianco, Ph.D. Sandia National Laboratories Albuquerque, New Mexico

ISBN-13: 978-0-87171-846-4

© 2015 by American Welding Society

All rights reserved Printed in the United States of America

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Personnel

AWS C3 Committee on Brazing and Soldering

R. W. Smith, Chair S-Bond Technologies

G. L. Alexy, Vice Chair Alexy Metals

1. M. Volpe, 2nd Vice Chair Senior Aerospace—Metal Bellows Division

   1. N. Borrero, Secretary American Welding Society

      K. Allen Bellman-Melcor

      J. J. Bassindale Woodward, Incorporated

      D. E. Budinger General Electric Aviation

      W. M. Coughlan Metglas, Incorporated

      C. F. Darling Lucas-Milhaupt, Incorporated

      W. J. Engeron Engeron Technology Group, Incorporated

      S. L. Feldbauer Abbott Furnace Company

      Y. Flom NASA Goddard Space Flight Center

      D. Fortuna Sulzer Metco (U.S.), Incorporated

      B. Freund Millennium Industries

      Y. Gao Aerojet

      P. H. Gorman Sandia National Laboratories

      1. A. Gross Gourley Curtiss-Wright

         T. D. Grohoske General Electric

      2. R. Hazelbaker Consultant

      3. P. Hirthe Kru-Mar Manufacturing Services

K. Holko Holko Consulting

J. R. Jachna Modine Manufacturing Company

D. A. Javernick Los Alamos National Laboratory

D. J. Jossick Lucas-Milhaupt, Incorporated

G. F. Kayser Aerojet

E. Liguori Consultant

J. A. Liguori Space Exploration Technologies

J. Longabucco Lucas-Milhaupt, Incorporated

J. C. Madeni Johns Manville

1. P. McKinney J. W. Harris Products Group

   W. Miglietti Power Systems Manufacturing, LLC

   T. Oyama WESGO Metals

   M. Pohlman Honeywell Aerospace

   A. Rabinkin Brazing and Joining Consultant

   J. P. Sands Bellman-Melcor

   1. E. Shapiro Titanium Brazing, Incorporated

P. T. Vianco Sandia National Laboratories

C. Walker Sandia National Laboratories

1. Weinstein Wall Colmonoy Corporation

   R. R. Xu Rolls Royce Corporation

   H. Zhao Creative Thermal Solutions

   
   

   Advisors to the AWS C3 Committee on Brazing and Soldering

   1. Aluru Progress Energy

      1. Barten Delphi Thermal & Interior

         1. Belohlav Lucas-Milhaupt, Incorporated

1. S. Bhargava American Axle & Manufacturing Company

D. W. Bucholz General Electric

S. Christy Pratt and Whitney

N. C. Cole NCC Engineering

L. H. Flasche Foresite, Incorporated

1. E. Fuerstenau Lucas-Milhaupt, Incorporated

   P. K. Gupta Honeywell Aerospace

   1. M. Hosking Consultant

      1. N. Jain Lucas-Milhaupt, Incorporated

         1. Kay Kay & Associates

            M. J. Kuta Lucas-Milhaupt, Incorporated

         2. Lugscheider Aachen University of Technology

W. D. Rupert Lucas-Milhaupt, Incorporated

AWS C3B Subcommittee on Soldering

C. F. Darling, Chair Lucas-Milhaupt, Incorporated

S. N. Borrero, Secretary American Welding Society

G. L. Alexy Alexy Metals

W. M. Coughlan Metglas, Incorporated

S. L. Feldbauer Abbott Furnace Company

D. J. Jossick Lucas-Milhaupt, Incorporated

J. Longabucco Lucas-Milhaupt, Incorporated

J. C. Madeni Johns Manville

A. Rabinkin Brazing and Joining Consultant

J. Sands Bellman-Melcor

A. E. Shapiro Titanium Brazing, Incorporated

R. W. Smith S-Bond Technologies

P. T. Vianco Sandia National Laboratories

C. Volpe Senior Aerospace—Metal Bellows Division

C. Walker Sandia National Laboratories

H. Zhao Creative Thermal Solutions

Advisors to the AWS C3B Subcommittee on Soldering

N. C. Cole NCC Engineering

L. H. Flasche Foresite, Incorporated

C. E. Fuerstenau Lucas-Milhaupt, Incorporated

P. K. Gupta Honeywell Aerospace

T. P. Hirthe Kru-Mar Manufacturing Services

F. M. Hosking Consultant

M. J. Pohlman Honeywell Aerospace

R. R. Xu Rolls-Royce Corporation

Preface

The origins of soldering can be traced back several thousands of years to Middle Eastern cultures that used it to construct a variety of utensils and elaborate jewelry items. Today, it is recognized that soldering extends well beyond the artisan community; in fact, it has become a technology in its own right. Soldering forms the basis for the manufacturing of elec- tronic products ranging from highly functional, Personal Digital Assistants (PDAs) and cell phones to high-reliability military, space, and satellite systems. Such achievements are the result of advances that have been made in understand- ing the materials science and engineering of solder alloys, wetting-and-spreading behavior of base material surfaces, interface reactions, as well as monotonic and cyclic deformation modes in assembled solder joints. Concurrently, there have been new developments in assembly automation, process control, and inspection that have allowed for the low-cost manufacturing of a wide range of soldered products.

It is important to realize that there are still a large number of applications—many structural in nature—whereby an oper- ator performs the soldering process manually. That person may be an artisan fabricating expensive jewelry; a plumber constructing a critical piping system in a chemical plant; or an operator repairing life-saving medical electronics. As an important manufacturing process in the electronics community, hand soldering has been supported by a large number of instructional resources, certification programs, and standards that are a resource for operators as well as process develop- ment engineers.

Unfortunately, there is a gap in the depth of resources such as guidelines, specifications or standards that address, specif- ically, hand soldering. The third edition of the Soldering Handbook (AWS) contains a wealth of fundamental as well as applied materials, processing, and reliability data for soldering as a technology. However, there remains to be a need to provide operators and process engineers with a “jumping-off point” to develop, and subsequently optimize, hand soldering processes for structural applications.

The objective of this Guideline for Hand Soldering Practices is to provide an information resource for developing viable, cost-effective hand soldering processes. This book is not intended to provide in-depth treatises on the fundamental prin- ciples of soldering; the reader is referred to the Soldering Handbook for those detailed discussions. Rather, the guideline’s chapters and sections provide sufficient information that allows the operator and process engineer to develop a hand sol- dering process that meets the performance and reliability requirements of the final product.

Chapter 1 (Fundamental Understanding) is a brief introduction into the definitions of wettability and solderability. Also, the role of the heating process is described in order to understand its impact on the hand soldering process.

Chapter 2 (Base Materials) discusses the hand soldering of metallic and nonmetallic materials. Supporting information is provided regarding the synergism between base materials and coatings with respect to achieving the desired solderabil- ity behavior. Also, given the fact that hand soldering uses electric irons and torches that are very high-temperature heat sources, there are discussions of the need to consider the temperature sensitivity of base materials, especially the effects of heating and cooling rates.

Chapter 3 (Filler Metals) describes filler metals (solder alloys). There are a large number of filler metals available today and the list continues to grow as manufacturers address the need to build ever-more complex parts, as well as changing alloy availability due to environmental regulations in both the United States and abroad (e.g., Pb- and Cd-free solders). The solder can be available in the form of wire, preforms, or paste. The form of the solder will significantly impact the choice of hand soldering technique and process parameters. The final section in this chapter discusses the importance of selecting filler metals that are listed in approved standards and specifications.

Chapter 4 (Fluxes and Controlled Atmospheres) touches on fluxes and their uniqueness to the soldering process. Unfortunately, there remains a great deal of “mystery” behind their role in soldering. The goal of this chapter is to provide an accurate resource describing the selection and utilization of fluxes in a hand soldering process.

The key content of this book resides in Chapter 5 (Process Development). After a brief introductory section, the follow- ing two sections address preassembly cleaning and fixture techniques. The next five sections describe specific types of

hand soldering processes as distinguished by the heating technique: (electric) iron, torch (flame), hot gas, resistance, and induction. Within each section, there is an introduction that is then followed by a brief overview of the equipment. Next, there is the detailed description of the soldering procedures (e.g., soldering with filler metal wire, preforms, butt joints, lap joints, etc.). The ninth section considers two less-common hand soldering processes: laser soldering and infrared sol- dering. The chapter draws to a close with two sections, the first of which, examines post-assembly cleaning steps. The final section provides information related to the use of hand soldering for the rework and repair of solder joints.

Finally, Chapter 6 (Environmental Safety and Health) offers a brief synopsis of the environmental, safety, and health con- cerns specific to hand soldering operations. The chapter does not provide a complete listing of federal, state, or local reg- ulations and directives. Besides the ungainly number of such statutes, environmental and safety regulations change on an almost daily basis thereby quickly rendering them obsolete. Rather, the intent of this chapter is to describe “common sense” procedures that should be implemented by the operator or process engineer in order to minimize the likelihood of accidents and/or environmental contamination when using hand soldering procedures.

An important feature of this guideline is the illustrations. The author is all too familiar with the fact that solder joints are not well presented using standard light photography. Shiny surfaces and extraneous shadows cause misleading visual artifacts. Therefore, photographic images are used sparingly. Rather, greater use is made of schematic illustrations to show fixtures as well as solder flow behavior and fillet geometries.

The author would like to express his sincere gratitude to the following individuals who have contributed to this piece. First, I would like to thank Sara Sokolowski, Don Susan, Brian Wroblewski, Edwin Lopez, Mike Hosking, as well as the members of the AWS C3B Subcommittee on Soldering (Chairperson Creed Darling) for their painstaking review of the manuscript. Secondly, I want to acknowledge those folks at Sandia National Laboratories who have worked alongside of me and who have taught me “a-thing-or-two” about soldering materials, processes, and reliability. Jerry (JR) Rejent, together with Mark Grazier and Peter Duran, have performed the experiments and data analysis that is the heart of the research and development successes in Sandia’s soldering technology program. Alice Kilgo, Dick Grant, Gary Zender, and Paul Hlava (ret.) are the metallography and microanalysis “talents” that provided valuable insight into properties of solder alloys and the performance of soldered assemblies.

My extreme gratitude goes to Steve Borrero, AWS Secretary to the C3 Committee on Brazing and Soldering, who assisted the author with the proofing as well as publication logistics of this book from its inception. His diligence and attention to detail were absolutely crucial to the completion of this work.

Lastly, I would like to thank my wife, Karen, and daughters Maria, Sara, and Ana for their patience and love throughout this effort. Without their support and encouragement, this book would not have been possible.

Paul T. Vianco, Ph.D.,

Sandia National Laboratories and the

C3 Committee on Brazing and Soldering,

American Welding Society

Table of Contents

Page No.

Personnel iii

Preface v

List of Tables ix

List of Figures ix

1. Fundamental Understanding 1

   1. Hand Soldering 1

   2. Wettability and Solderability 2

   3. Heating Process 7

2. Base Materials 10

   1. Solderability 10

   2. Temperature Sensitivity 11

   3. Metallic Base Materials 15

   4. Coatings 18

   5. Nonmetallic Base Materials—Ceramics and Glasses 20

3. Filler Metals 23

   1. Materials Technology 23

   2. Processing Effects 25

   3. Standards and Specifications 26

4. Fluxes and Controlled Atmospheres 29

   1. Function of the Flux 29

   2. Flux Compositions 30

      1. Inorganic Fluxes 31

      2. Organic Acid Fluxes 31

      3. Rosin-Based Fluxes 31

      4. No-Clean and Low-Solids Fluxes 33

      5. Other Fluxes 33

   3. Standards and Specifications 33

   4. Proper Use of a Flux 35

      1. Applying Flux at the Beginning of the Soldering Process 36

      2. Applying Flux during the Soldering Process 36

   5. Controlled Atmospheres 37

5. Process Development 38

   1. Introduction 38

   2. Preassembly Cleaning 38

      1. Organic Contaminants 39

      2. Inorganic Contaminants 39

      3. Mechanical Abrasion 40

   3. Fixtures 41

   4. Soldering with an Iron 44

      1. Equipment 44

      2. Soldering Procedures—Tip Conditioning 50

      3. Soldering Procedures—Solder Wire 51

      4. Soldering Procedures—Preplaced Solder Preforms or Paste 54

   5. Soldering with a Torch (Flame) 57

      1. Equipment 57

      2. Soldering Procedures—Solder Wire 60

      3. Soldering Procedures—Preplaced Solder Preforms or Paste 63

      4. Butt Joints: Cylinder-to-Cylinder, Cylinder-to-Plate, and Plate-to-Plate 65

      5. Lap Joints: Cylinder-to-Cylinder, Plate-to-Plate, and Cylinder-to-Plate 70

   6. Soldering with Hot Air or Hot Inert Gas 76

      1. Equipment 78

      2. Soldering Procedures—Solder Wire, Preplaced Solder Preforms, or Paste 79

   7. Resistance Soldering 79

      1. Equipment 80

      2. Soldering Procedures—Solder Wire 83

      3. Soldering Procedures—Preplaced Solder Preforms or Paste 85

   8. Induction Soldering 86

      1. Equipment 88

      2. Soldering Procedures—Preplaced Solder Preforms or Paste 94

   9. Other Hand Soldering Techniques: Laser Soldering and Infrared Soldering 95

      1. Equipment 96

      2. Soldering Procedures—Solder Wire 97

      3. Soldering Procedures—Preplaced Solder Preforms or Paste 98

   10. Post-assembly Cleaning 99

       1. Introduction 99

       2. Equipment 100

       3. Postsoldering Cleaning Processes 100

   11. Rework and Repair 103

6. Environmental Safety and Health 108

   1. Hand Soldering Hazards 108

   2. Regulations and Guidelines 108

      1. AWS Safety and Health References 109

      2. AWS Safety and Health Fact Sheets 109

      3. Government and Industrial Resources 109

7. List of AWS Technical Documents on Brazing and Soldering 111

List of Tables

Table Page No.

2.1 Common Solutions for Removing Inorganic Surface Contaminants 18

1. Forms of Solder Materials 23

2. Partial Listing of Sn-Pb, Sn-Pb-Sb, Sn-Pb-Ag, and Pb-Ag Solder Compositions from ASTM B32,

   Standard Specification for Solder Metal 27

3. Partial Listing of Solder Compositions from ISO/DIS 9453, Soft solder alloys—Chemical

composition and forms 28

1. Activation and Decomposition Temperatures for Commonly-Used Flux Types 30

2. Flux Designations per ANSI/IPS J-STD-004, Requirements for Soldering Fluxes 32

3. List of ASTM, IPC, and ISO Specifications on Solder Pastes and Flux Core Solder Wire 35

1. Precleaning Solutions for Typical Metal Alloys 40

2. Guidelines of Soldering Iron Power Ratings and Tip Sizes for General Applications 47

3. Properties of Common Fuel Gases 58

4. Electrical Resistivity, Product of Heat Capacity and Density, and Thermal Conductivity of

   Mild Steel, Stainless Steel, Copper, and Aluminum 82

5. Values of Relative Magnetic Permeability, Absolute Magnetic Permeability, and Resistivity of Nonmagnetic Copper (Cu), Moderately Magnetic Steel, and Highly Magnetic Iron (Fe). 88

6. Penetration Depths for Several Common Metals as a Function of Frequency (f ) 90

List of Figures

Figure Page No.

1. Hand Soldering Processes 1

2. An Optical Micrograph of the Intermetallic Compound (IMC) Layer that is Formed Between the

   63Sn-37Pb Solder and Copper (Cu) Base Material. 3

3. Images of the Edge of the Sn-Ag-Cu Solder Layer on Silver (Ag) Showing Different Degrees

   of Base Metal (Ag) Dissolution. 4

4. Wetting and Spreading of a Molten Solder 5

5. Capillary Action of Molten Solder within Confined Geometry of a (Horizontal) Gap Between

   Base Materials 5

6. Schematic Diagrams and Photographs Illustrate the Three Solderability Conditions 6

7. Dewetting Phenomenon caused by Local Nonwettable Areas on a Generally Wettable Base

Material Surface 7

1. Chamfers Used on Base Material Corners to Assist Solder Wetting and Spreading Around

   Corners into Gaps 11

2. Flow of Molten Solder through a Gap having a Bend in the Pathway 12

3. Soldering of a Blind Gap Joint 13

4. Development of Residual Stresses during Solder Joint Cooling caused by a Mismatch of

   Thermal Expansion Coefficients Between Dissimilar Base Materials 1 and 2 14

5. Optical Micrograph Showing the Dissolution of Copper (Cu) Base Metal by Molten 100Sn 15

6. Graph of Dissolution Rate as a Function of Molten Solder Temperature Showing Effect

   of Tin (Sn) Content in the Tin (Sn)-based Filler Metals 16

7. Graph of Dissolution Rate as a Function of 60Sn-40Pb (wt.%) Solder Temperature Showing

   Effect of Base Metal Composition 17

8. Molten Solder Wetting and Spreading Over a Base Material with a Solderable and

   Protective Finishes 19

9. SEM images Showing Solder Joints made to a Au-Pt-Pd Thick Film Layer bonded on an

Alumina Ceramic Base Material 22

1. Solder Wetting and Spreading on a Horizontal Surface 29

2. Reactive Flux Process 34

3. Application of a Gas Blanket to Exclude the Air Atmosphere from Around Base Material

during Soldering of Joint 37

1. Surface Tension Effect by Molten Solder 38

2. Self-Alignment Designs of Base Material Parts 43

3. Range of Fixture Complexity 45

4. Soldering Irons Having the Tip Heated 46

5. Geometry of Two Copper (Cu) Rods Soldered Together by a Butt Joint 47

6. Four Basic Geometries of Soldering Iron Tips 49

7. Contact Between Tip Geometry and Base Material Geometry 49

8. Soldering of a Pin-in-Hole Joint using a Soldering Iron and the Placement of Flux prior to

   the Heat-Up Step 52

9. Manual Soldering of a Pin-in-Hole Joint using a Soldering Iron and the Placement of Flux

   after the Heat-Up Step 53

10. Two Approaches for the Preplacement of a Solder Preform. 55

11. Steps for Soldering a Joint with a Soldering Iron and a Preplaced Filler Metal Preform

    Located at Gap Entry Point 56

12. Images of the Four Combustion Conditions for a Fuel Gas (Acetylene) 59

13. Images showing the Sequence of Steps used to Solder a Fitting to a Tube 61

14. Process for Soldering a Horizontally Oriented Tube-to-Fitting Solder Joint Prone to

    Filler Metal Run-out at the Bottom (e.g., Too Wide of a Gap) 63

15. Solder Joints Typically Soldered with a Torch Flame 66

16. Procedure for Making Butt Joints 68

17. Preplacement of a Solder Preform for the Torch Soldering of Tube-to-Tube Butt Joints 70

18. Torch Soldering of Common Lap Joints: Tube-to-Tube, Plate-to-Plate, and Tube-to-Plate 71

19. Tube-to-Plate and Tube-to-Tube Lap Joints 74

20. Complicated Lap Solder Joints 77

21. Hot Air (Gas) Nozzle Geometries Controlling Flow Volume and Direction 78

22. Two Techniques for Heating the Base Material in Resistance Soldering 80

23. Methods to Make Butt Joints by Resistance Soldering 83

24. Resistance Soldering Steps (Lap Joint) when the Operator Manually Feeds Solder Wire 84

25. Resistance Soldering Steps (Lap Joint) when using a Preplaced Solder Preform. 85

26. Magnetic Field Resulting from a Current passed through a Coiled Conductor 87

27. Formation of Eddy Currents in a Conductive Material due to an Alternating Magnetic Field 88

28. Effects of Coil Proximity and Coil Pitch on Heated Thickness of Base Material 90

29. Various Coil Geometries and Part Configurations 91

30. Use of Coil/Base Material Separation, x, and Coil Pitch, N/L, to Alter Heat Distribution

    Along the Flat Surface of the Base Material [(A)—(C)] 92

31. Use of a Metal Shield to Block the Magnetic Field from Induction Heating the Base Material

    Behind It 93

32. Percentage of Light Reflected from several Metal Base Material Surfaces as a Function of the

Light’s Wavelength. 97