PCB Routing Angle Myths: 45-Degree Angle Vs 90-Degree Angle

There is nothing wrong with a healthy debate, whether it’s related to determining the worst pizza topping or the best solder mask. In the PCB editor world, a debate that plagues designers and researcher alike revolves around PCB routing angles. Should copper tracks of a PCB be routed at a 45-degree angle vs 90 degree angle PCB? ​

With today’s equipment, however, it turns out that it usually doesn’t matter which angle you use. By utilizing modern PCB design software, routing tools can accommodate whichever angle choice you stand behind or that is necessary for your device’s needs.

The Effect of Right-Angle PCB Tracks on EMI Emission

Engineers are often concerned about having right-angle PCB tracks on their circuit board shape due to the possibility of Electromagnetic Interference (EMI) radiating at sharp corners. The popular theory is that high-frequency signals emit Radio Frequency radiation at every 90 degree turn of the copper track. This mere assumption is enough for most hardware designers to eliminate any right-angle PCB routing from their track design or auto router software.

However, the theory that electrons in a high-speed signal are unable to make right-angle turns has been debunked by an experienced electrical engineer, Dr. Howard Johnson. As a matter of fact, electrons bounce billions of times in different directions even with a short length; they have minimal problems navigating right-angle corners.

There is an exception--when you’re designing ultra-high-speed PCB ground plane in the range of 10 GHz or more, or you’re involved in microwave designs that use traces with large widths of 100 mils. In such extreme applications, you actually need to worry about 90 degree corners. Otherwise, they should not present a major concern.

Only worry about right-angle PCB corners in ultra high-speed design.

To resolve this debate once and for all, a test was conducted to measure and compare radiated emission between right-angle and 45 degree corners for high-frequency signals, for signals up to 17ps rise pulse. The results confirm the argument of Dr. Howard Johnson that there is no difference in EMI emission levels between right-angle and 45 degree corners within the testing limits.

Why Are 45° Corners So Widely Used?

The verdict is out and it’s safe to use right-angle PCB tracks in your design, as long as you’re not working on ultra-high frequency microwave designs. The myth of 45 degree angle routing is finally put to rest. But if it was a misconception to start with, why does Printed Circuit Board design software continue to incorporate 45 degree angles in their routing strategy? Furthermore, why did people start routing with 45 degree in the first place?

Every myth has an origin. In the case of routing with 45° corners, the myth can be traced back to a time when PCB manufacturing wasn’t as advanced as it is today. Back then, right-angle PCB corners or anything with a sharp angle presented a real threat to manufacturability. Sharp corners could cause acid traps, where some of the acids used in etching linger and continue to corrode the copper at sharp corners. Back then, engineers were also concerned that right-angled corners aren’t as sturdy as 45° ones and could be peeled off easily.

Thankfully, these worries belong to the past, as new PCB manufacturing technology ensures that your PCB ground plane is properly etched, right-angle or not. Veteran engineers from the days of avoiding right-angle PCB corners often continue to frown on using 45° angles in today’s designs. However, for many of them, it’s more of a habit than a rule.

Sharp corners are used to cause manufacturability issues.

Why Do I Prefer 45° Angle Corners?

Despite the fact that there’s no harm in having right-angle PCB corners in my design, I meticulously ensure that every single corner is 45° before sending my PCB layout for fabrication. This isn’t because I’m an RF designer - I’m not. My obsession with the 45° corner is pretty simple. They look stylish and much nicer, in my opinion, compared to right-angle PCB corners.

Simply put, it’s a matter of personal preference. After all, Altium Designer^® is already configured to beautifully route 45° angle tracks and I didn’t see a pressing need to alter those default settings. Make sure you are using PCB design software that can enable any of your design preferences.

Are you bothered by the right-angle PCB design? Talk to an Altium Designer expert for their opinion.