This book is for PCB designers who are designing boards with multiple very large Ball Grid Array (BGA) packages. It explores the impact of dense BGAs with high pin-count on PCB design and provides solutions for the inherent design challenges. Though you may not yet have been confronted with the difficulties of routing BGAs and the impact on fabrication costs and signal integrity, this book will reveal these potential pitfalls as well as methods to mitigate these problems
Author(s): Charles Pfeil
Edition: 2
Publisher: CreateSpace
Year: 2010
Language: English
Pages: 192
Preface – Second Edition ....................................................................... v
Chapter One - Introduction ................................................................... 1
Expedition PCB ............................................................................... 2
Figures ............................................................................................ 2
Definitions ...................................................................................... 2
Via Types ........................................................................................ 6
Stackup Types................................................................................. 6
The Problem ................................................................................. 12
Solutions ....................................................................................... 15
Chapter Two - BGA Packages .............................................................. 17
High Pin Counts ............................................................................ 17
Impact on Routing, Performance and Cost .................................. 20
Off-Matrix Ball Pads ..................................................................... 22
0.8mm Pin-Pitch ........................................................................... 23
The Near Future ........................................................................... 24
Chapter Three - HDI Layer Stackups .................................................... 25
Fabrication Vendors ..................................................................... 25
Dependencies ............................................................................... 26
Overview of Stackup Types .......................................................... 27
HDI Stackup Details ...................................................................... 31
Via Models .................................................................................... 36
Plane Layer Assignments.............................................................. 39
Layer Count .................................................................................. 42
Design Rules ................................................................................. 43
Fanout Patterns ............................................................................ 43
Signal Integrity ............................................................................. 44
Recommended HDI Stackups ....................................................... 44
Secondary HDI Stackups............................................................... 48
Any-Layer-Via Stackups ................................................................ 52
Summary ...................................................................................... 53
Chapter Four - Fanout Patterns ........................................................... 55
Theoretical Breakout Methods .................................................... 56
Signal Integrity Concerns.............................................................. 60
Minimizing the Variables .............................................................. 61
Fanout Pattern Goals and Approach ............................................ 64
Through-Vias ................................................................................ 65
Drilled Blind and Buried-vias ........................................................ 78
HDI Micro-Vias.............................................................................. 89
Summary ...................................................................................... 94
Chapter Five - Layer Biased Breakouts ................................................ 95
Board Description ......................................................................... 95
General Assessment of Original Board......................................... 95
Recommendations and Solutions ................................................ 96
Using Layer Biased Breakouts ...................................................... 97
Fanouts for Micro-Via Layers ..................................................... 101
Route Results.............................................................................. 119
Summary .................................................................................... 120
Chapter Six - 0.8mm Pin-Pitch BGA Tests .......................................... 121
Test Scenario .............................................................................. 121
Test 1: Through-Vias ................................................................... 124
Test 2: Micro-Vias and Through-Vias ......................................... 134
Test 3: Any-Layer-Vias ................................................................ 149
Summary .................................................................................... 163
Chapter Seven - Software for Generating BGA Fanouts ..................... 165
Method ....................................................................................... 166
Regions ....................................................................................... 167
Adding Blind and Through-Vias .................................................. 168
Adding Buried Vias ..................................................................... 170
Additional Example .................................................................... 173
Conclusion ........................................................................................ 175
About the Author .............................................................................. 177
