Surface Mount Technology

One Introduction to Surface Mounting.- 1 Introduction to Surface Mounting.- 1.0 Introduction.- 1.1 Types of Surface Mounting.- 1.2 Benefits of Surface Mounting.- 1.3 SMT Equipment Requiring Major Capital Investment.- 1.3.1 Pick-and-place equipment.- 1.3.2 Solder paste screen printer.- 1.3.3 Curing/baking oven.- 1.3.4 Reflow soldering equipment.- 1.3.5 Solvent cleaning.- 1.3.6 Wave soldering equipment.- 1.3.7 Repair and inspection equipment.- 1.4 When to Use Surface Mounting.- 1.5 Technical Issues in Surface Mounting.- 1.6 Trend in Surface Mounting.- 1.7 The Future.- 1.7.1 Chip-and-wire (chip-on-board) Technology.- 1.7.2 Tape-automated bonding (TAB).- 1.7.3 Flip chip or controlled collapse bonding:.- 1.8 Summary.- 2 Implementing Surface Mount Technology.- 2.0 Introduction.- 2.1 Setting the Implementation Strategy.- 2.2 Building the SMT Infrastructure.- 2.2.1 Developing internal SMT infrastructure.- 2.2.2 Influencing external SMT infrastructure.- 2.3 Setting In-House Manufacturing Strategy.- 2.4 Selecting an Outside SMT Assembly House.- 2.4.1 Evaluation and qualification of subcontractors.- 2.4.2 The various stages of subcontractor qualification.- 2.4.3 Questionnaires for rating of subcontractors.- 2.4.3.1 Technology questions.- 2.4.3.2 Manufacturing questions.- 2.4.3.3 Business questions.- 2.4.3.4 Quality assurance questions.- 2.5 Managing the Risk: Pilot to Production.- 2.6 Summary.- Two Designing with Surface Mounting.- 3 Surface Mount Components.- 3.0 Introduction.- 3.1 Surface Mount Component Characteristics.- 3.2 Passive Surface Mount Components.- 3.2.1 Surface mount discrete resistors.- 3.2.2 Surface mount resistor networks.- 3.2.3 Ceramic capacitors.- 3.2.4 Tantalum capacitors.- 3.2.5 Tubular passive components.- 3.3 Active Components: Ceramic Packages.- 3.3.1 Leadless ceramic chip carriers.- 3.3.2 Ceramic leaded chip carriers (preleaded and postleaded).- 3.4 Active Components: Plastic Packages.- 3.4.1 Small outline transistors.- 3.4.2 Small outline integrated circuits.- 3.4.3 Plastic leaded chip carriers.- 3.4.4 Small outline J packages.- 3.4.5 Fine pitch packages.- 3.5 Miscellaneous Components.- 3.6 Future Components.- 3.7 Major Issues in Components.- 3.7.1 Lead coplanarity.- 3.7.2 Lead configuration.- 3.7.3 Standardization.- 3.8 Component Procurement Guidelines.- 3.9 Summary.- 4 Substrates for Surface Mounting.- 4.0 Introduction.- 4.1 Glass Transition Temperature (Tg).- 4.2 X, Y, and Z Coefficients of Thermal Expansion.- 4.3 Selection of Substrate Material.- 4.3.1 CTE compatibility considerations in substrate selection.- 4.3.2 Process considerations in substrate selection.- 4.4 Ceramic Substrates.- 4.4.1 Porcelainized steel substrates.- 4.5 Constraining Core Substrates.- 4.5.1 Copper-invar-copper constraining core substrates.- 4.5.2 Graphite epoxy constraining core substrates.- 4.6 Compliant Layer Substrate.- 4.7 Glass-Epoxy Substrates.- 4.7.1 Types of glass epoxy substrate.- 4.7.2 Operating temperatures for glass epoxy boards.- 4.7.3 Fabrication of glass epoxy substrates.- 4.8 Plating Processes.- 4.8.1 Copper plating.- 4.8.2 Gold plating.- 4.8.3 Nickel plating.- 4.8.4 Lead-tin solder plating.- 4.9 Solder Mask Selection.- 4.9.1 Wet versus dry film solder masks.- 4.9.2 Photoimageable solder masks.- 4.10 Via Hole Cracking Problems in Substrates.- 4.11 Summary.- 5 Surface Mount Design Considerations.- 5.0 Introduction.- 5.1 System Design Considerations.- 5.2 Form, Fit, and Function.- 5.3 Real Estate Considerations.- 5.4 Manufacturing Considerations.- 5.5 Cost Considerations.- 5.5.1 Printed circuit board cost.- 5.5.2 Component cost.- 5.5.3 Assembly cost.- 5.6 Thermal Considerations.- 5.7 Package Reliability Considerations.- 5.7.1 Package cracking mechanism.- 5.7.2 Solutions to package cracking.- 5.7.3 Reliability tests for package cracking.- 5.8 Solder Joint Reliability Considerations.- 5.8.1 Solder joint reliability tests.- 5.9 Interconnect Considerations.- 5.10 CAD Layout Considerations.- 5.11 Summary.- 6 Surface Mount Land Pattern Design.- 6.0 Introduction.- 6.1 General Considerations for Land Pattern Design.- 6.2 Land Patterns for Passive Components.- 6.2.1 Land pattern design for rectangular passive components.- 6.2.2 Land pattern design for tantalum capacitors.- 6.3 Land Patterns for Cylindrical Passive (MELF) Devices.- 6.4 Land Patterns for Transistors.- 6.5 Land Patterns for Plastic Leaded Chip Carriers.- 6.6 Land Patterns for Leadless Ceramic Chip Carriers.- 6.7 Land Patterns for Small Outline Integrated Circuits and R-Packs.- 6.8 Land Patterns for SOJ (Memory) Packages.- 6.9 Land Patterns for DIP (Butt Mount) Packages.- 6.10 Land Patterns for Fine Pitch, Gull Wing Packages.- 6.11 Land Patterns for Solder Paste and Solder Mask Screens.- 6.12 Summary.- 7 Design for Manufacturability, Testing, and Repair.- 7.0 Introduction.- 7.1 Design Guidelines, Rules, the Role of the Designer.- 7.2 Standard Form Factor Considerations.- 7.3 Component Selection Considerations for Manufacturability.- 7.4 Soldering Considerations.- 7.5 Component Orientation Consideration.- 7.6 Interpackage Spacing Considerations.- 7.6.1 Assumptions in interpackaging spacing requirements.- 7.6.2 Interpackage spacing requirements.- 7.7 Via Hole Considerations.- 7.8 Solder Mask Considerations.- 7.9 Repairability Considerations.- 7.10 Cleanliness Considerations.- 7.11 Testability Considerations.- 7.11.1 Guidelines for ATE testing.- 7.12 Summary.- Three Manufacturing with Surface Mounting.- 8 Adhesive and Its Application.- 8.0 Introduction.- 8.1 Ideal Adhesive for Surface Mounting.- 8.1.1 Precure properties.- 8.1.2 Cure properties.- 8.1.3 Postcure properties.- 8.2 General Classification of Adhesives.- 8.3 Adhesives for Surface Mounting.- 8.3.1 Epoxy adhesives.- 8.3.2 Acrylic adhesives.- 8.3.3 Other adhesives for surface mounting.- 8.4 Conductive Adhesives for Surface Mounting.- 8.5 Adhesive Application Methods.- 8.5.1 Screening.- 8.5.2 Pin transfer.- 8.5.3 Syringing.- 8.6 Curing of Adhesives.- 8.6.1 Thermal cure.- 8.6.1.1 Thermal cure profile and bond strength.- 8.6.1.2 Adhesive cure profile and flux entrapment.- 8.6.2 UV/Thermal cure.- 8.7 Evaluation of Adhesives with Differential Scanning Calorimetry.- 8.7.1 Basic principles of DSC analysis.- 8.7.2 DSC characterization of an epoxy adhesive.- 8.7.3 DSC characterization of an acrylic adhesive.- 8.8 Summary.- 9 Solder Paste and Its Application.- 9.0 Introduction.- 9.1 Solder Paste Properties.- 9.1.1 Metal composition.- 9.1.2 Metal content.- 9.1.3 Particle size and shape.- 9.1.4 Flux activators and wetting action.- 9.1.5 Solvent and void formation.- 9.1.6 Rheological properties.- 9.1.6.1 Viscosity.- 9.1.6.2 Slump.- 9.1.6.3 Working life and tackiness.- 9.1.7 Solder balls.- 9.1.8 Printability.- 9.2 Solder Paste Printing Equipment.- 9.3 Solder Paste Printing Processes.- 9.3.1 Screen printing.- 9.3.2 Stencil printing.- 9.3.3 Screen printing versus stencil printing.- 9.3.4 Dispensing.- 9.4 Paste Printing Defects.- 9.5 Paste Printing Variables.- 9.5.1 Solder paste viscosity.- 9.5.2 Print thickness.- 9.5.3 Squeegee wear, pressure, and hardness.- 9.5.4 Print speed.- 9.5.5 Mesh tension.- 9.5.6 Board warpage.- 9.6 Summary.- 10 Metallurgy of Soldering and Solderability.- 10.0 Introduction.- 10.1 Phase Diagrams.- 10.2 Metallization Leaching in Passive Surface Mount Components.- 10.3 Solder Alloys and Their Properties.- 10.4 Solderability.- 10.4.1 Wetting.- 10.4.2 Nonwetting.- 10.4.3 Dewetting.- 10.5 Various Approaches for Ensuring Solderability.- 10.6 Solderability Test Methods and Requirements.- 10.7 Recommendations for Solderability Test Methods and Requirements.- 10.8 Effect of Substrate Surface Finish on Solderability.- 10.9 Effect of Component Lead or Termination Finish on Solderability.- 10.10 Summary.- 11 Component Placement.- 11.0 Component Placement.- 11.1 Manual Placement of Parts.- 11.2 Automated Placement of Parts.- 11.3 Selection Criteria for Placement Equipment.- 11.3.1 Maximum substrate size handling capacity.- 11.3.2 Maximum feeder input or slot capacity.- 11.3.3 Placement rate and flexibility.- 11.3.4 Placement accuracy/repeatability.- 11.3.5 Vision capability.- 11.3.6 Adhesive dispensing capability.- 11.3.7 Other important selection criteria.- 11.4 Selection of Feeders for Placement Equipment.- 11.4.1 Tape and reel feeders.- 11.4.2 Bulk feeders:.- 11.4.3 Tube or stick feeders.- 11.4.4 Waffle packs.- 11.5 Available Placement Equipment.- 11.5.1 Equipment with low flexibility and high throughput.- 11.5.2 Equipment with high flexibility and low throughput.- 11.5.3 Equipment with medium flexibility and throughput.- 11.5.4 Equipment with low cost and throughput but high flexibility.- 11.6 Summary.- 12 Soldering of Surface Mounted Components.- 12.0 Introduction.- 12.1 Wave Soldering.- 12.1.1 Design and process variables in wave soldering.- 12.1.2 Process and equipment variables in wave soldering.- 12.2 Types of Wave Soldering for Surface Mounting.- 12.2.1 Dual-wave soldering.- 12.2.2 Vibrating wave soldering.- 12.2.3 Modified wave soldering.- 12.3 Wave Versus Reflow Soldering.- 12.4 Single-Step Soldering of Mixed Assemblies.- 12.5 Single-Step Soldering of Double-Sided SMT Assemblies.- 12.6 Vapor Phase Soldering.- 12.6.1 The Heat transfer mechanism in vapor phase soldering.- 12.7 Infrared Reflow Soldering.- 12.7.1 The Heat transfer mechanism in infrared soldering.- 12.7.2 Convection/IR versus near IR.- 12.8 Vapor Phase Versus Infrared Reflow Soldering.- 12.8.1 Cost and flexibility.- 12.8.2 Solder profile development.- 12.8.2.1 Heating rate.- 12.8.2.2 Peak temperature in preheat zone.- 12.8.2.3 Time above solder melting point.- 12.8.2.4 Peak reflow temperature.- 12.8.2.5 Cooling rate and duration above glass transition temperature.- 12.8.3 Solder defects.- 12.8.4 Solder opens (wicking).- 12.8.5 Tombstoning and part movement.- 12.8.6 Thermal shock on components.- 12.8.7 Solder mask discoloration.- 12.9 Laser Reflow Soldering.- 12.10 Miscellaneous Reflow Soldering Methods.- 12.11 Selecting The Appropriate Soldering Method.- 12.12 Summary.- 13 Flux and Cleaning.- 13.0 Introduction.- 13.1 Concerns in Surface Mount Cleaning.- 13.2 The Function of Flux.- 13.3 Considerations in Flux Selection.- 13.4 Flux Classification.- 13.4.1 Inorganic fluxes.- 13.4.2 Organic acid fluxes.- 13.4.3 Superactivated fluxes (SRA and SA).- 13.4.4 Rosin fluxes.- 13.5 Contaminants and Their Effects.- 13.5.1 Particulate contaminants.- 13.5.2 Nonpolar contaminants.- 13.5.3 Polar contaminants.- 13.6 Major Considerations in Solvent Selection.- 13.7 Commonly Used Solvent Types.- 13.8 Solvent Cleaning Equipment.- 13.8.1 Batch solvent cleaning equipment.- 13.8.2 In-line solvent cleaning equipment.- 13.8.3 Ultrasonic cleaning equipment.- 13.9 Aqueous Cleaning.- 13.9.1 Aqueous cleaning equipment.- 13.10 Cleanliness Test Methods and Requirements.- 13.10.1 Visual examination.- 13.10.2 Solvent extraction.- 13.10.3 Surface Insulation Resistance (SIR).- 13.10.3.1 SIR measurement test conditions.- 13.10.3.2 Application of the SIR test.- 13.11 Designing for Cleaning.- 13.12 Summary.- 14 Quality Control, Repair, and Testing.- 14.0 Introduction.- 14.1 Statistical Quality Control.- 14.2 Application of SQC: A Case History.- 14.2.1 Implementing statistical process control.- 14.3 Defects Related to Materials and Process Defects.- 14.3.1 Substrate-related defects.- 14.3.2 Component-related defects.- 14.3.3 Adhesive-related defects.- 14.3.4 Defects related to solder paste.- 14.3.5 Process-related defects.- 14.4 Solder Joint Quality Requirements.- 14.5 Solder Joint Inspection.- 14.6 Repair Equipment and Processes.- 14.6.1 Repair requirements.- 14.6.2 Soldering irons for surface mount repair.- 14.6.3 Hot air systems for surface mount repair.- 14.6.4 Rework profiles.- 14.7 Assembly Testing.- 14.7.1 Fixtures for ATE testing.- 14.7.2 Issues in ATE testing.- 14.8 Summary.- Appendix A Surface Mount Standards.- Appendix B Detailed Questionnaire for Evaluating Pick-and-Place Equipment for Surface Mounting.- Appendix C Glossary.