PCB DESIGN GUIDE



PRINTED CIRCUIT BOARD LAYOUT GUIDELINES, SOFTWARE,
TRACE CALCULATORS, AND TUTORIALS


<------------------------------------------------------------------------------------------------------------------------------------------------------------------------>

Let's begin with the basics. Printed circuit board (PCB) in general is a structure made of one or more layers of insulating material with electrical conductors. The insulator is typically made on the base of fiber reinforced resins, ceramics, plastic, or some other dielectric materials. During manufacturing, the portions of conductors that are not needed are etched off, leaving desired tracks that connect electronic components.



FIND PCB SOFTWARE AND SERVICES BY SPEC.


Alternatively, the conductors can be added by an electroplating process.

PCB Currently, the main generic standard for PCB design, regardless of materials, is IPC-2221B. It provides rules for manufacturability and quality, such as requirements for material properties, criteria for surface plating, conductor thickness, component placement, dimensioning and tolerance rules, and more. This standard applies to all printed circuit board types including single-sided, double-sided and multilayer. For a specific technology, a designer can then choose an appropriate sectional standard from the IPC-2220 series. For SMPS power conversion designs, additional parameters are recommended by IPC-9592B.

Before you start your project, you obviously need to make a schematic and footprints of all the components. Then you need to set design rules. The width and thickness of the conductors should be chosen based on maximum allowable temperature rise at the rated current per IPC-2152 and an acceptable impedance. There is another criterion that is often overlooked. The trace should not melt during short surge currents that can develop in the circuit. This requires sufficient cross-sectional area of copper as a function of overload amp-seconds. The spacing between the PCB traces is determined by peak working voltage, the coating, location of the circuit, and the product application. The minimum possible widths of the traces and of the spacing between them are both limited by the manufacturing capabilities of your fabricator. In any case, the width should not be less than 4 mils. Typical guidelines for minimum values are 6/6 mils. Depending on the application and product end use, other standards may also apply. For example, for mains-powered or battery-powered information technology equipment, the creepage and clearance requirements of IEC/UL 60950-1 take precedence over IPC.

Once you set the design rules you can place the parts and do the routing. IPC and other standards do not tell you how to properly route the board. Good PCB layout techniques require an understanding of the effects of non-zero trace impedance and the coupling of signals from one circuit to another through parasitic capacitances and radio transmission, as well as a basic understanding of circuit operation. Auto placement software may be used for most parts of control circuits, but power, ground and high di/dt circuits should be routed by hand. At the end, the design information has to be transferred into the form that can be sent to a fabricator. The set of the data that describes the board normally includes Gerber files as well as files in Excellon and other formats.

Below you will find more guidelines for designing PCB, links to software downloads, trace calculators, tools and other online resources.

PCB DESIGN GUIDELINES,
RULES AND TIPS
FREE DESIGN SOFTWARE, TOOLS, DEMOs DOWNLOADS PRINTED CIRCUIT BOARD TRACE CALCULATORS

Basic guide and tips to design PCB for SMPS power supply

IPC-2221B electrical clearance table and recommendations

Books on power electronics and circuit board layout

EMI and layout fundamentals for SMPS switched-mode circuits

Printed circuit board designing and layout guidelines for switching power supplies and regulators

PCB design tutorial and references- process, footprints, guidelines


PADS schematics capture & free PCB design software (working evaluation for small designs)

Free OrCAD program with PSPICE (functional limited size demo)

Free printed circuit board layout software download. Includes autorouter and trace optimizer

PRINTED BOARD PROTOTYPING, MANUFACTURING, ASSEMBLY

IPC-A-610E preview- acceptability of printed circuit board assembly

SchmartBOARD - prototyping blocks with footprints for most smt parts


Trace width calculator for external and internal layers per IPC-2152

A calculator of the spacing between the PC traces based on voltage levels

Creepage calculation per UL60950-1 2nd Edition

PC trace fusing current






<------------------------------------------------------------------------------------------------------------------------------------------------------------------------>