Design Guidelines For Surface Mount And Fine Pitch Technology

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Fine pitch high lead count integrated circuit packages represent a dramatic change from the conventional methods of assembling electronic components to a printed interconnect circuit board. To some, these FPTpackages appear to bean extension of the assembly technology called surface mount or SMT. Many of us who have spent a significant amount of time developing the process and design techniques for these fine pitchpackages haveconcluded that these techniquesgobeyondthose commonly useed for SMT. In 1987 the presentauthor, convincedofthe uniqueness ofthe assembly and design demands ofthese packages, chaired ajoint committee where the members agreed to use fine pitch technology (FPT) as the defining term for these demands. The committee was unique in several ways, one being that it was the first time three U. S. standards organizations, the IPC (Lincolnwood, IL), theEIA(Washington, D. C. ),and theASTM (Philadelphia),cametogether tocreate standards before a technology was in high demand. The term fine pitch technology and its acronym FPT have since become widely accepted in the electronics industry. The knowledge of the terms and demands of FPT currently exceed the usage of FPT packaged components, but this is changing rapidly because of the size, performance, and cost savings of FPT. I have resisted several past invitations to write other technical texts. However, I feel there are important advantages and significant difficulties to be encountered with FPT.

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.

Surface mount technology (SMT) is a mature technology. SMT allows placement of more surface mount components (SMC) into smaller and tighter printed circuit board (PCB) areas. This increased density means increased performance and power in smaller packaging systems, and allows manufacturing of smaller and higher performance products at lower cost. The advance of integrated circuit (IC) technology and the requirements of high density for high-speed circuity is driving the design of SM C to higher pin count and smaller package size. In general, the higher pin count and smaller package size are accomplished by reducing the bond pad size and spacing (pitch) on the chip level and the lead/pin/solder dimensions and pitch on the chip carrier (module) level. The last few years have witnessed an explosive growth in the research and development efforts devoted to FPT as a direct result of the rapid growth of SMT and miniaturization. Some examples are: hand held lightweight video recorders that can take sharp pictures, hand held lightweight devices that can track the worldwide package movements, and portable computers with tiny yet powerful microprocessors and large memory capability that can fit into a briefcase or into the palm of your hand.

A foreword is usually prepared by someone who knows the author or who knows enough to provide additional insight on the purpose of the work. When asked to write this foreword, I had no problem with what I wanted to say about the work or the author. I did, however, wonder why people read a foreword. It is probably of value to know the background of the writer of a book; it is probably also of value to know the background of the individual who is commenting on the work. I consider myself a good friend of the author, and when I was asked to write a few words I felt honored to provide my view of Ray Prasad, his expertise, and the contribution that he has made to our industry. This book is about the industry, its technology, and its struggle to learn and compete in a global market bursting with new ideas to satisfy a voracious appetite for new and innovative electronic products. I had the good fortune to be there at the beginning (or almost) and have witnessed the growth and excitement in the opportunities and challenges afforded the electronic industries' engineering and manufacturing talents. In a few years my involve ment will span half a century.

This is a state-of-the-art guide to SMT with fine pitch components intended for professionals in electronics manufacturing. The overriding objective is to equip manufacturing people in the electronics industry with a better understanding of the manufacturing processes involved.