What is EMI? How does it relate to the PCB World? And when is it important?

In the year 1873, the Scottish physicist James Clerk Maxwell published an article titled: A Treatise on Electricity and Magnetism. In the following years, Maxwell’s findings turned out to be a huge discovery because they had finally and successfully linked the phenomena of electricity and magnetism.

Today, the field of electromagnetics is governed by a set of four equations called the Maxwell laws. And everything ‘smart’ around us must obey these laws. That includes : CPU, ADC, sensors, power supplies, wireless and even car windshields.

If those laws were to be simplified to their bare essentials and then allowed to speak, they would say that electricity and magnetism are mostly decoupled in static applications. And that they’re strongly coupled when the electric or magnetic fields change over time.

In our case, this means that embedded systems will always showcase electromagnetic behavior when deployed because of operating ICs, clock signals, power source ripples ..

Now you might be tempted to say: Ok, my PCB components and traces are electromagnetic, so what?

Enter EMI. Also known as Electro-Magnetic Interference. All the D&D in the system design industry boils down to two basic principles: 1. The embedded system must operate correctly 2. It must continue to do so whatever else is happening around it.

The first principle doesn’t need explanation. The second however bares two fundamental meanings : Your system must not be disturbed by outside EMI, and must itself not radiate too much EMI that could cause OTHER systems to fail.

The first principle is an inhouse constraint because you’ll always make sure your system functions correctly. The second is an outside constraint called EMC or Electro-Magnetic Compliance. EMC is in certain cases a compulsory requirement for applications like : ECU in the car industry, home appliances or VFD for industrial motors.

In order to comply with the abovementioned prerequisites, tests should be conducted in real operating conditions to make sure your system is immune to EMI. And once your system is ready, samples should be sent to trusted laboratories to get the final EMC approval.

Expert Solution PCB offers to manufacture your PCB in small batches to help you get through your testing phases with remarkable speed. Contact us to know more.

Copyright © 2021 ExolPCB s.a.r.l