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How to Design Your Next Printed Circuit Board Like a Pro

Sam Sattel

pcb-professional

How to Design Your Next Printed Circuit Board Like a Pro

There’s a ton of work that goes into designing a PCB, but not all of the pieces to this puzzle are treated equally. Are you guilty of not giving your PCB layout the love it deserves? You likely invest a lot of your time making the perfect schematic or choosing the best parts, but if you can’t get all of that data and theory down into something that functions in the real world, then what’s the point? Before you end up giving both yourself and your manufacturer a headache with a board that’s a nightmare to make, be sure to follow the tips below to design your next PCB like a pro.

Drop Those Components Like It’s Hot

Before you ever place down one of those lightning hot copper traces, your components need to find their homes. This process requires a designer to become a puzzle master, wearing both the hats of an artist and a scientist. This balancing act can be made easier with these tips:

Keep your parts in the same direction

Be sure to orient all of your components of a similar type in the same direction. This will help your soldering process go off without a hitch as your board rolls through the soldering oven. If you place your components haphazardly, don’t be surprised when you have a bunch of unsoldered connections on your PCB and your board just doesn’t work.

proper-pcb-component-placement

Here’s the preferred orientation for your top and bottom components that align with the PCB soldering process.

Place like parts together

 

If you plan on working with Surface Mount (SMT) components, be sure to place all of them on the same side of your board. As for Through-Hole (TH) components, those need to all be placed on the top of your board. Why the placement preferences?

  • This will allow your surface mount components to be placed in one go with the help of a pick-and-place machine without requiring another step.
  • This will also help you to save money by reducing the time spent assembling your through-hole components by hand.
  • And of course, it just keeps your board easier to review and manufacture when parts of similar intent are on the same layer.
xbox-motherboard

Here’s the motherboard for an Xbox One – they’ve done a good job of grouping all linked-minded components together for an easy soldering process. (Image Source)

Look one step ahead

When placing your components always be mindful of how long your traces are going to need to be to connect your pins together. By putting relevant parts next to each other, you can make your routing process a whole lot easier and efficient by keeping similar routing jobs in one area on your board.

It’s Getting Hot in Here

Heat dissipation is a concern for any electronics device when all of your very active components and traces are throwing up loads of heat. As enclosures get smaller and PCBs get even more densely packed, turn down the heat with these tips:

Use extra copper

If you’re planning to have some heat dissipation on your board, do yourself a favor and place extra copper around your surface mount pads. This will provide an additional surface area to dissipate heat from. Check out your component datasheets to find all the info you need use your pad surface area as a heatsink.

Channel heat with vias

Did you know that you can use vias to move heat from one side of your PCB to the other? This can come in handy when you need to lower the operating temperature of your components by pushing some heat to the other side of your board.

via-channel-heat

Use your vias to channel away some of that heat from larger components. (Image Source)

Keep those hot parts separate

Many parts pump out some serious heat including bridge rectifiers, diodes, MOSFETs, inductors, and resistors. You’ll want to keep these components away from other parts that are heat sensitive, such thermocouples and electrolytic capacitors. If those capacitors get too hot, they’ll start to lose their ability to retain a charge.

Just Integrate It

Integrated Circuits (ICs) offer a ton of advanced functionality in one small, compact package. But they also come with their own set of challenges, with some having hundreds of pins that all need to be routed. Here are some tips to make your IC placement and routing easier:

Give em’ some space

ICs with a ton of pins, or any IC for that matter, needs to be given plenty of space between other ICs on your board for easy routing. Many beginner designers will make the mistake of packing their ICs too close together, leaving little to no room to route all the required pins. As a general guideline, try to allow 0.350” – 0.500” of spacing between each of your ICs, and even more space for larger parts.

large-bga

This IC is going to need some serious space to connect all of those pads!

Keep them in line

To keep your ICs organized and in order try placing them in an up/down or left/right orientation. By doing this, you’ll be able to align the first pin of each IC in the same direction, which will make your job just that much easier come routing and design review time.

same-component-orientation

Keep all of your ICs in the same orientation to line up pin numbers and make routing easy.

Power with common rails

To properly power your ICs, we recommend using common rails for each supply. Also, be sure to use solid and wide traces to let that power easily flow through to your energy-hungry ICs, and avoid daisy-chaining power lines between parts to prevent any voltage drop issues.

Route Like a Boss

Signal traces are your go-to route for connecting all of the components on your PCB layout. And if you’re like every other engineer, routing your signal traces also offers a fun opportunity for some organized artistry. Before you go diving into routing your PCB layout, remember these tips:

Take the sharpness out of angles

Avoid using any sharp 90° angles in any of your signal traces. This makes it a huge pain to keep the width of your traces consistent, especially as they get narrower. Instead, opt for 45° bends to keep everything flowing smoothly.

A great example of what not to do when routing your PCB, keep those traces at 45 degrees! (Image Source)

Figure out those trace widths

Before laying down any of your traces, be sure to use a trace width calculator (thanks, Advanced Circuits). Using this calculator will help you to easily determine how thick and wide all of your traces will need to be based on your specific design requirements. And if you end up having extra space on your board, go ahead and use traces with wider widths, as this won’t cost extra from your manufacturer.

Remember where your heat goes

If you’re planning to design a multilayer PCB, remember that the all of the traces on your external layers have way better cooling capabilities than traces on internal layers. Those internal traces have a lot farther to travel through layers of copper and other materials before they can get their heat radiated away, so place them on the top and bottom if possible.

Power It Up, Power it Down

With all of your signal traces placed, you still have to worry about getting everything powered up, with your power and ground traces. These power rails will send the current you need to power all of that PCB magic, and can be completed easily with these tips:

Current capacity matters

Traces that are carrying a lot of current will need to be wider than your standard signal traces to accommodate the heavier load. Here are some values that can provide guidance on how wide to make your traces for distinct currents:

Trace Width and Currents Reference

  • 0.010″      0.3 Amps
  • 0.015″      0.4 Amps
  • 0.020″     0.7 Amps
  • 0.025″      1.0 Amps
  • 0.050″      2.0 Amps
  • 0.100″      4.0 Amps
  • 0.150″      6.0 Amps

Keep that noise away

When routing any noisy ground traces, be sure to keep them as far away as possible from signals that need some peace and quiet. You can also place a ground plane directly under noisy signal traces to lower the impedance for high-speed designs.

Houston, We Have Liftoff

Once your PCB layout is fully designed, you’re now ready to move on to an even more important step – the design review! At this stage, make sure you double check that the routing of every signal trace is properly connected. You can do this by running through your schematic wire-by-wire, and compare those with the path of the traces on your PCB layout. Everything looking good? Then it’s time for manufacturing.

Ready to design your next PCB like a pro? Autodesk EAGLE has a brand spankin’ new routing engine that makes it easy. Try Autodesk EAGLE for free today.

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