It's easy for new PCB designers to be overwhelmed. But organization and education can help you get started right.

So you're becoming a PCB designer. You're new to the field, and you have lots of questions about how to take a design from concept to reality. There are no magic formulas, but there are some areas that should be given special attention along the way. We will discuss them in the order of the design process.

Get Organized

First of all, get organized. You will need every bit of organizational skill you can muster. The job we do can be extremely complex and any little piece of information forgotten can spell disaster. Designers are often asked to manage more than one project at a time. Anything that can be done to break your work down into more manageably-sized pieces should be considered. One way to organize your work is with project documents and checklists that keep all the relevant pieces of information together and give everyone involved something to check their progress against. Another way is to set standards for the way you and your co-workers work.

It takes a little extra time to get organized in the beginning, but the effort pays off dramatically in good documentation and transition. After all, when you do a project right the first time, people notice. Get ready to work with a team of (usually) great people. They'll need you to provide input into the project and to check the results. As a board designer, you will need to understand the circuit design engineer's ideas and priorities and how to implement them. You will also interact with representatives of the mechanical, fabrication, assembly, and test teams regarding information like clearances, impedances, placement, panelization, and test procedures. You need to be sure that the information you send at data handoff can actually be implemented.

Get Started

When a new project comes in, you will need to gather and understand the data sheets for the required parts. The engineer is going to talk in terms of memory, processors, switches and buffers and you will want to know which parts he's talking about. Get into the habit of looking carefully at all data sheets and understanding the standard information vs. what is specific to this part. You'll need to immerse yourself in function, footprint, gates, speed, voltage and suggested layout, and more. One thing you don't want to know about is long lead time!

Early in the design process you must check for parts and symbols in your company's library. Some companies ask their PCB designers to implement the schematic, but others delegate this to the design engineer. Assuming that the designer is responsible for the schematic, you will need to build any new symbols and be sure that they will translate properly into parts for the board. The symbols should be built so that they have enough of the same appearance that they can easily be placed together into a schematic, and have a consistent flow and appearance. Symbols should show all pins, to help clarify that a pin is not connected or forgotten. The design group should decide which footprint standard will be used for building the parts, and deviation should only occur when absolutely required. All PCB footprints should be checked for size and connection accuracy by comparing them to the symbols as well. When designing for multiple projects, it can become confusing remembering which parts worked properly and which did not. Setting up a separate library for parts that have been used successfully can be very helpful in precluding the re-use of bad parts.

If you are asked to do the schematic, you'll need to work within some basic guidelines. If a block diagram is not provided, it may be very helpful to create one; block diagrams can break down a project into pieces that are more manageably sized.

Set up the schematic's design flow from left to right, with inputs on the left and outputs on the right. Use off-page ports to supply information about the signal's destination, information that may not be readily available to someone who does not completely understand the circuit. Understand the the required electronic groupings by working with the data sheets and talking with the design engineers. Minimize the crossing of signal lines for readability and clarity. And lastly, limit the amount of information on a page to what is easily readable. More pages are better than one page that is too stuffed with information to be followed easily.

The transfer of information is the truth serum of the design! It tells us how well we have done our work, because this is where the translation between the symbol and part will or will not work as planned. It is also the place where those pesky single pin nets and unused gates will be discovered. The engineer may have hooked up something with two different net names on two different parts of the schematic when he meant to use only one, so check the netlist information before you move on.

Next, your design software takes all this information and throws all the parts and connections into one big chaotic mess on the board. Now is the time for breaking everything into those small pieces. Group the parts according to the block diagram and schematic groupings. Place the groups that function together near each other. Inside the board outline, the I/O connections and fixed location parts go down first, followed by the best combinations of parts grouped according to speed, logic family, voltage, function and flow. Additional grouping considerations might be grid, routing channels, noise, heat and potential trace length. Parts can also be grouped by their location on the top side or bottom side of the board.

The plane setup and board stack-up come next; these must be considered for power distribution and return current. If plane setup and board stack-up are not addressed early, the board could suffer power problems, signal integrity issues and EMI failure. With the speeds of today's parts, even the slower signals must be no more than one dielectric layer away from a plane for return purposes, and the signals should not cross splits in those planes. A good power and ground plane pair also provides extra high-frequency capacitance for those high-speed parts. Other items to consider are the number of routing layers needed, the impedance needed, material, construction and balance. Now may be a good time to add design constraints to the board. Some software systems take this step in the schematic, some at the board level. At the board level you may want to call out certain elements, such as trace widths and clearances, classes to keep certain groups away from other groups, sizes of vias for classes, and layer-restricted routing. Design constraints are always a good idea, but use as few as necessary to do the job correctly to keep the DRC check from bogging down.

Man or Machine?

A decision must be made whether to hand-route or autoroute the board. Signal integrity is almost always better with hand-routing, but autorouting has the benefit of speed. No matter how the routing will be done, use both to help determine what is best for any particular board. Autorouting can help with fanout, as well as determining layer count and identifying areas of difficulty in the placement. Hand-routing can help with layer-paired routing, critical signals, and following the data sheet design rules. Now you are actually going to route the board. This is not about connecting the ratsnest, but knowing and implementing the principles that govern this portion of the job. There are several types of routing, and you need to understand how they're used. For instance, memory must be daisy chain-routed, but clock signals are usually star-routed. You absolutely must know the reasoning behind decoupling and power distribution on a board in order to understand the placement and routing needs of the planes and different value capacitors. Fanout factors include allowing room between the antipads for return current and knowing whether the fanout vias will also be used as testpoints. The issues that affect impedance must be clear for a designer to understand how the signals will perform – and how they can be controlled – within the board structure. Trace width and distance to the nearest plane are key. The order of routing will be determined by circumstances such as whether the signal is considered critical and whether it is part of a bus or an I/O signal. Also to be considered before routing are the following: routing the "hardest" areas of the board first, the presence of repeating circuits, matched length routing and differential trace matching.

You have finished routing the board. Don't stop now! Any finishing and checking scenario will give you a few more steps to complete. The parts should be resequenced to make it easier for the people who must test, use and repair the board. After back-annotation to the schematic, importing the netlist one last time verifies that the board and schematic are completely in sync. A last visual and DRC check should be performed to ensure all problems have been cleared up. Have the engineer check the board a final time against a checklist of potential problems. Create output files and check them thoroughly for anything unexpected. And finally, save only one copy of the board in a safe place, so that there is only one place to retrieve a database to start any engineering change orders (ECOs).

The Business

Don't forget that there's more to being a designer than actually designing boards. To stay employed, you'll need to keep current on a whole raft of evolving, everchanging technologies and techniques. A great way to keep informed is by networking. Get to know people in every segment of the business, so that you'll have sources to turn to when you have questions or ideas that you'd like to bounce off other designers (you will). This requires getting out of your darkened office and actually talking to people. We designers tend to be solitary, but trying to do things on our own can lead to wasted time and effort, bad habits and few allies.

There are numerous networking opportunities in this business. Get on the design-related user forums, including the ones sponsored by PCD&M (PCDList), the IPC Designers Council (DC List and Technet), and the EDA software vendors. These forums allow designers to talk about issues and ask questions, and all can be helpful, even if you just "listen in" to the regulars. Also, join the local chapters of professional organizations such as the Designers Council and the Surface Mount Technology Association (SMTA). The meetings present great topics and it's easy to get to know other designers. Be nice to these people; they represent a future source of jobs.

You'll need to get every bit of education and training that you can. The most obvious sources for design education are conferences such as the PCB Design Conferences. Training can include anything from classes and workshops at conferences to Webinars and courses held at your local community college. Read magazines, books, Internet articles and PCB standards. If you have questions, go to your network of friends and teachers and talk things over with them. Remember that the educated, informed designer is more likely to keep his job when the chips are down.

Volunteer! The Designers Council and SMTA are always looking for help, and members can influence the selection of speakers and presentations. Get involved. You'll never regret volunteering. The above information is not meant to be a comprehensive list of everything that needs to be done to design a board. There are hundreds of variables to be considered on any design, variables that make it unique from every other design. But this should help get you started, or fill in a few blanks if you're already working.

I encourage you to always keep reading and learning about PCB design throughout your design career. PCD&M

Susy Webb is a senior PCB designer at Suntron Corp. She has 26 years of design experience and is scheduled to teach a PCB basics class at PCB West 2006. She can be reached at This email address is being protected from spambots. You need JavaScript enabled to view it..