There is nothing wrong with a healthy debate, whether it’s related to determining the best pizza topping or the most philanthropic celebrity. In the PCB world, a common debate that plagues designers and researcher alike revolves around deciding whether the copper tracks of a PCB should be routed at a 90-degree angle or a 45-degree angle to avoid acid traps and other design flaws.
With today’s equipment, however, it turns out that except in special circumstances, it doesn’t matter which angle you use. By utilizing modern PCB design software, routing tools can accommodate for whichever angle choice you stand behind or that is necessary for your device’s needs.
The Effect of Right-Angle Tracks on EMI Emission
Engineers are often concerned about having right-angle tracks on their PCB due to the possibility of Electromagnetic Interference (EMI) radiated at sharp corners. The popular theory is that high-frequency signals emit Radio Frequency radiation at every 90° turn of the copper track. This mere assumption is enough for most hardware designers to eliminate any right-angle tracks from their design.
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, of course, an exception when you’re designing ultra high-speed PCBs 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° corners. Otherwise, they should not present a major concern.
Only worry about right-angle 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° corners for high-frequency signal, 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° corners, within the testing limits.
Why Are 45° Corners So Widely Used?
The verdict is out and it’s safe to use right-angle tracks in your design, as long as you’re not working on ultra-high frequency microwave designs. The myth of 45° angle routing is finally put to rest. But if it was a misconception to start with, why does PCB design software continue to incorporate 45° angles in their routing strategy? Furthermore, why did people start routing with 45° 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 or any sharp angle corners presented a realistic 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 is properly etched, right-angle or not. Veteran engineers from the days of avoiding right-angle 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 used to cause manufacturability issues.
Why Do I Prefer 45° Angle Corners?
Despite the fact that there’s no harm in having right-angle corners in my design, I meticulously ensure that every single corner is 45° before sending my PCB for fabrication. This isn’t because I’m an RF designer - I’m not. My obsession with 45° corner is pretty simple. They look stylish and much nicer, in my opinion, compared to 90° 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 right-angles in your PCB design? Talk to an Altium expert for their opinion.
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