Design Guidelines for Surface Mount Technology

Design Guidelines for Surface Mount Technology covers the basics and the mechanics of surface mounted design technology. Surface mount technology (SMT) embodies an automated circuit assembly process, using a generation of electronic components called surface mounted devices (SMDs). Organized into eight chapters, the book discusses the component selection, space planning, materials and processes, and total concept needed to ensure a manufacturable design. The opening chapters of the book examine the significant requirements and variables affecting SMT and SMDs. The book then deals with the substrate materials specifications, including fabrication and material planning, assembly, design rules, layout guidelines, package outlines, and bar code labeling. The next chapters describe the manufacturing and assembly processes in SMDs and process-proven footprint patterns for each of the component types used, as well as guidelines for creating a suitable pattern on future products. Other chapters discuss the component spacing requirements for SMT and the generation of footprint patterns for passive and active components of SMDs. The concluding chapter describes the design criteria for maximizing machine insertion of leaded electronic components into printed circuit boards (PCBs). These criteria aid the PCB designer by detailing the considerations and some of the trade-offs that will provide reliable insertion in a production environment. Supplementary texts on surface mount equipment, supplies, and services are also provided. Design engineers and researchers will find this book invaluable.

Preface

Chapter 1 SMD Essentials

Designing with SMD

Substrate Configurations

Mixed Prints

Automated SMD Placement Machines

Soldering Techniques

Footprint Definition

Footprints for Wave Soldering

The "Shadow Effect"

Footprint Orientation

Solder Thieves

Placement Inaccuracy

Dummy Tracks for Adhesive Application

Footprints for Reflow Soldering

Solder Cream Applications

Screen Printing

Floating

Footprint Dimensions

Layout Considerations

Component Pitch

Solder Land/Via Hole Relationship

Solder Land/Component Lead Relationship

Placemant Machine Restrictions

Substrate Population

Test Points

CAD Systems for SMD Substrate Layout

CAE/CAD/CAM Interaction

Chapter 2 Space Planning and Interface

Standards for SMT Components

Component Packaging Options

Component Selection Guidelines

Passive Devices: Monolithic Capacitors

Tantalum Capacitors

Resistors for SMT

Resistor Networks

Potentiometer for SMT

Active Devices

ICs for SMT

Small Outline (SO) ICs

Plastic Chip Carriers and Quad Packages

Ceramic ICs

Connectors and Interface for SMT Assembly

Heat Seal

Compression

Assembly Considerations

Estimating Total Component Area

Optimizing Component Placement

Component Orientation

Utilizing Both Sides of Substrate

Thermal Considerations

Power Dissipation

Thermal Resistance

Junction Temperature (Tj)

Factors Affecting θJA

Package Considerations

Thermal Resistance Measurements

Test Method

TSP Calibration

Thermal Resistance Measurement

Test Ambient

θJC Tests

Data Presentation

Thermal Calculations

System Considerations

Using Leaded Devices (SO, SOL, & PLCC)

Compliant Layer

Matching TCE

Substrate Types

Conclusion

Chapter 3 Specifying Materials for Substrates

Common Substrate Materials

Fabrication and Material Planning

Providing for Assembly Automation

Design Rules and Layout Guidelines

Plated through-Holes

Multilayer and Fine Line Construction

Surface Mount and Via Holes

Computer Aided Design and Via Holes

Solder Mask on PC Boards Using SMT

Plating Process for SMT

High Tech Materials for Military Applications

Specifying Copper Clad Invar

Materials for Copper Clad Invar/Polyamide

Commercial SMD Packages

Military Packages

Special Package Outlines

Bar Code Labeling

Footprints

Chapter 4 SMD Assembly Process

Solders for SMD Applications

Fluxing and Cleaning

Types of Flux

Flux Types

Solder Applications

Curing Solder Paste

The Reflow Process

Cleaning after Reflow Soldering

Assembly Methods

Assembly Options for SMDs

Adhesive Applications and Curing

Physical Characteristics

Adhesive Application

Pin-Transfer

Screen-Printing

Pressure Syringe

Adhesive Dot Height Criteria

Dummy Tracks

Solder Land Contamination

MELF Component Placement

Adhesive Curing

Curing by Heat/Time Plus Catalyst

Curing by Catalytic Action Alone

Anaerobic and UV Assisted Curing

Fluxing and Cleaning

Fluxes

Types of Flux

Organic Soluble Fluxes

Non-Activated Rosin (R) Flux

Rosin, Mildly Activated (RMS) Flux

Rosin, Activated (RA) Flux

Water Soluble Fluxes

Water Soluble Fluxes with Inorganic Salts

Water Soluble Fluxes with Organic Salts

Water Soluble Fluxes with Organic Acids

Solder Creams

Flux Selection

Application of Flux

Foam Fluxing

Wave Fluxing

Spray Fluxing

Flux Density

Pre-Heating

Post-Soldering Cleaning

Polar Contaminants

Non-Polar Contaminants

Solvents

Solvent Cleaning

Aqueous Cleaning

Conformal Coatings

Conclusions

Solder Joint Criteria

Inspection

Defect Classification

Soldering Defects

Drawbridging

Adhesive Contamination

Blow Holes

General Solder Joint Criteria

Good Wetting

Sound Smooth Surface

Correct Amount of Solder

SMD Joint Assessment

Leadless SMDs

SMDs with Few Short Leads

SO IC Packages

VSO IC Packages

PLCC with J-Leads

Chip Carriers with Metallized Castellation

Inspection Systems

Component and Substrate Solderability

Aspects of Solderability

Protective Coatings

Fusible Coatings: Electro-Plated Tin/Lead

Solder Coating

Solder Land Contamination

Chapter 5 Contact (Footprint) Design

Designing for Producibility

Component Spacing

Discrete Component Contact Design

Preferred Component Orientation

Commercial IC Footprint Planning: SOIC, PCC, and QUAD Lead Packages

Ceramic IC Packages

Contact Design for Other SMT Products: DIP and SIP Module Design

Chip Carrier Design

Building Contact (Footprint) Libraries for SMT

Contact Geometry for Chip Components

Optional Wave Solder Contact Geometry for Chip Components

Tantalum Capacitor Contact Geometry

MELF Component Contact Geometry

SOT-23 Contact ACT Geometry

SOT-89 Contact Geometry

Plastic Chip Carrier (PCC) Contact Geometry

Small Outline Contact Geometry

Chapter 6 Component Spacing for SMT

Basic Considerations

Placement Accuracy Requirements

Placement Techniques

Trace-to-Trace Guidelines

Contact (Footprint) to Via Pad

Solder Mask for Solder Control

Automatic Assembly and Testing

Mixed Technology, Through-hole and Surface Mounted

Component-to-Board Edge Requirement

Chapter 7 Artwork Generation

Footprint (Contact) Pattern for Passive Devices

Footprint Planning for Active (IC) Components

Hand-Taped Artmaster Preparation

Tape and Reel

Computer-Aided Design

Autorouting SMT

Preparing for Future Assembly Methods

CAD Applications

Chapter 8 PCB Design Considerations

Printed Circuit Board Design

Board Considerations

Component Location Objectives

Component Selection

Lead Diameter Considerations

Board Holder Design

Workboard Holder Considerations

Rotary Workboard Holder Design

Automatic Board Handling Workboard Holders

Programming Considerations

Insertion Machine Pattern Program Format

Board Error Correction

Axial Lead Component Insertion

Component Input Taping Considerations

Axial Lead Sequencing

Insertion Center Considerations

Lead Form and Tooling

Printed Circuit Board Thickness Versus Body Diameter

Hole Diameter Requirements

Component Body Configuration

Location Considerations

Clinch Patterns

Pattern Program Considerations

Radial Lead Component Insertion

Taping Considerations

Tape Splicing Specification

Hole Diameter Requirements

Hole Span Considerations

Board Sizing Considerations

Location Considerations

Uninsertable Area

Cut and Clinch Patterns

Pattern Program Considerations

Insertion Reference Point

Optimum Pattern Programming

Special Programming Considerations

Appendix I Surface Mount Equipment, Supplies, and Services

Appendix II Surface Mount Device Bibliography

Index