NANO Circuit Design

Nano-tech Introduction

You've designed your circuit, perhaps even bread boarded a working prototype, and now it's time to turn it into a
nice Printed Circuit Board (PCB) design. For some designers, the PCB design will be a natural and easy
extension of the design process. But for many others the process of designing and laying out a PCB can be a
very daunting task. There are even very experienced circuit designers who know very little about PCB design,
and as such leave it up to the "expert" specialist PCB designers. Many companies even have their own
dedicated PCB design departments. This is not surprising, considering that it often takes a great deal of
knowledge and talent to position hundreds of components and thousands of tracks into an intricate (some say
artistic) design that meets a whole host of physical and electrical requirements. Proper PCB design is very often
an integral part of a design. In many designs (high speed digital, low level analog and RF to name a few) the
PCB layout may make or break the operation and electrical performance of the design. It must be remembered
that PCB traces have resistance, inductance, and capacitance, just like your circuit does.
This article is presented to hopefully take some of the mystery out of PCB design. It gives some advice and
“rules of thumb” on how to design and lay out your PCBs in a professional manner. It is, however, quite difficult to
try and “teach” PCB design. There are many basic rules and good practices to follow, but apart from that PCB
design is a highly creative and individual process. It is like trying to teach someone how to paint a picture.
Everyone will have their own unique style, while some people may have no creative flair at all!
Indeed, many PCB designers like to think of PCB layouts as works of art, to be admired for their beauty and
elegance. “If it looks good, it’ll work good.” is an old catch phrase.
Lets have a go shall we...
The Old Days
Back in the pre-computer CAD days, PCBs were designed and laid out by hand using adhesive tapes and pads
on clear drafting film. Many hours were spent slouched over a fluorescent light box, cutting, placing, ripping up,
and routing tracks by hand. Bishop Graphics, Letraset, and even Dalo pens will be names that evoke fond, or not
so fond memories. Those days are well and truly gone, with computer based PCB design having replaced this
method completely in both hobbyist and professional electronics. Computer based CAD programs allow the
utmost in flexibility in board design and editing over the traditional techniques. What used to take hours can now
be done in seconds.

NANO CIRCUITARY

There are many PCB design packages available on the market, a few of which are freeware, shareware, or
limited component full versions. Protel is the defacto industry standard package in Australia. Professionals use
the expensive high end Windows based packages such as 99SE and DXP. Hobbyists use the excellent freeware
DOS based Protel AutoTrax program, which was, once upon a time, the high-end package of choice in Australia.
Confusingly, there is now another Windows based package also called AutoTrax EDA. This is in no way related
to the Protel software.
This article does not focus on the use of any one package, so the information can be applied to almost any PCB
package available. There is however, one distinct exception. Using a PCB only package, which does not have
schematic capability, greatly limits what you can do with the package in the professional sense. Many of the
more advanced techniques to be described later require access to a compatible schematic editor program. This
will be explained when required.
Standards
There are industry standards for almost every aspect of PCB design. These standards are controlled by the
former Institute for Interconnecting and Packaging Electronic Circuits, who are now known simply as the IPC
(www.ipc.org). There is an IPC standard for every aspect of PCB design, manufacture, testing, and anything else
that you could ever need. The major document that covers PCB design is IPC-2221,

Local countries also have their own various standards for many aspects of PCB design and manufacture, but by
and large the IPC standards are the accepted industry standard around the world.
Printed Circuit Boards are also known (some would say, more correctly known) as Printed Wiring Boards, or
simply Printed Boards. But we will settle on the more common term PCB for this article.