Clearance and insulation

• Calculating Creepage and Clearance Early Avoids Design Problems Later
• The Evaluation of Spacings in Electronic Product Design
• Calculating spacing between PCB traces for various voltage levels
• European standard: EN60065:2002 "Audio, video and similar electronic apparatus. Safety requirements"
• IPC standard: IPC-2221A "Generic Standard on Printed Board Design"
• Saturn PCB Design Toolkit A free download tool for calculating conductor spacing and other parameters

Current carrying capacity

• Articles on Trace Current/Temperature/Power/Resistance
• IPC standard: IPC-2152 "Standard for Determining Current Carrying Capacity in Printed Board Design"
• Saturn PCB Design Toolkit A free download tool for calculating current carrying capacity and other parameters
• Online ANSI IPC-2221A PCB Trace Width Calculator

High-Density BGA

• Designing With High-Density BGA Packages for Altera Devices
• High-Density Design With MicroStar BGAs
• 96 and 114 Ball Low-Profile Fine-Pitch BGA Packages
• Xilinx Device Package User Guide Board Routability Guidelines with Xilinx Fine-Pitch BGA Packages section of the Recommended PCB Design Rules chapter.

Miscellaneous topics

• Guidelines for flex boards
• PCB Design and Fabrication School
• Electronics Topics Library, University of Bolton
• Articles by Doug Brooks, UltraCAD Design

Dielectric materials datasheets
Standard FR-4 materials

• Isola DE104
• Nan Ya Plastics NP-140TL
• Panasonic R1755C
• Panasonic R1566W (Halogen free)
• Taiwan-Leader

High-Tg FR-4 materials

• Isola HR370
• ITEQ IT-180A (Low CTE)
• Kingboard KB-6168
• Panasonic R1755V

Other materials

• Arlon 25FR (Low-Er)
• Rogers 4003C and 4350B (Low-Er)
• Taconic RF-35P (Low-Er)
• Arlon 85N (Polyimide)
• Thinflex-A (flexible polyimide)