Printed circuit boards have become common in the electrical and electronic components we utilize daily. That might include gadgets such as televisions, smartphones, smart watches, wearables, and so on. However, PCBs are not indestructible and sometimes get damaged by certain things, including vibrations and heat. However, out of the many things that lower the performance or ultimately make a printed circuit board fail, radio frequency tends to dominate the list.
Radiofrequency electromagnetic signals disrupt the normal functioning of a printed circuit board by messing with its electrical circuit. However, you can deal with this issue via RF shielding. But what does radio frequency shielding entail? What are the benefits of RF shielding? And should you apply RF shielding to your printed circuit board?
Radio Frequency Shielding
RF shielding or Radiofrequency shielding is basically blocking off harmful radiofrequency EM signals which tend to cause RFI. Generally, RFI can mess with the electrical circuitry of a PCB hence altering how it usually functions. Doing so lowers the performance of the PCB or ultimately makes it fail.
To accomplish RF shielding, technicians install barriers encompassing conductive and magnetic components around the electronic device’s cable lines, circuitry, and potential sources and victims of EM fields. Doing so isolates this component hence shielding the board from RFI.
However, how effective the RF shield is in regards to reducing RFI on the PCB depends upon a couple of factors which include:
- Shielding materials
- The thickness of the RF shield
- The shield’s design
- Electromagnetic frequency
- And lastly, discontinuities that exist on the radio frequency shield
Radiofrequency interference has the potential to affect the performance of electronic and communication gadgets in a negative manner. Moreover, various electrical components have distinct responses when you expose them to RFI. For starters, some gadgets might result in system and information losses, while others might result in data and security breaches. However, if the RFI is intense, it might result in the device failing.
Even though radio frequency interference is harmful to electrical gadgets, it is inevitable. Actually, it is pretty widespread in various electronic gadgets, and you can’t eliminate it. The main reason why RFI is unavoidable is the simple fact that electrical circuits can emit radio frequency electromagnetic signals. However, after emitting these signals, they become susceptible to them since they affect them in a negative manner. Therefore, the use of various RF shields is a great measure that you can utilize to shield your devices and equipment from RFI and its harmful effects.
Nature of Radio Frequency Interference
Electromagnetic (EM) waves generally carry energy. Furthermore, these waves encompass electric and magnetic wave that oscillates at 900 of each other. EM waves have two significant characteristics, which are the following:
- Frequency
- Wavelength
Moreover, you can visualize the continuum of EM waves in the EM spectrum.
RFI and EMI
EMI or electromagnetic interference occurs whenever unwanted EM waves or signals disrupt the normal functioning of any electronic device. The disruption that EMI causes is normally called noise or EM noise. The explanation of RFI and EMI tends to leave most people wondering whether or not RFI and EMI are the same things. However, this is not the case.
EM radiations at any particular frequency can lead to EMI. On the flip side, radio frequency interruption is a variation of EMI since the waves that cause RFI tend to fall under the EM spectrum. Moreover, the frequency of radio waves can range in between three hundred gigaHertz and three kilohertz. Therefore, even though most people tend to utilize the terms EMI and RFI interchangeably, they are different.
Types of RFI
Radiofrequency interference or RFI be classified according to various factors, which include bandwidth, duration, and source as follows:
Source
Man-Made
Electronic and electrical gadgets can emit EM radiation which can affect other gadgets and equipment that are near them and cause them to underperform.
You can further break down the man-made source of radiofrequency interference into the following categories:
Unintentional Sources
Gadgets such as transmission lines, satellites, inverters, rectifiers, lightning, generators, and motors tend to disrupt nearby gadgets when they switch large quantities of electrical current. But, even though the gadgets cause RFI, it is entirely incidental and not intentional.
Moreover, electronic devices that use wireless signals, such as cellphones, laptops, bluetooth mice and speakers, wireless routers and controls, can be sources of radiofrequency interference. That is because, as these devices become faster, they tend to emit more electromagnetic radiation into the environment, which could cause adverse effects to nearby gadgets. Simply put, the EM radiation leaking from these gadgets can lead to RFI.
Intentional Sources
Intentional sources of RFI are the gadgets that technician design to emit electromagnetic energy to the environment. These sources include:
- Radar
- Jamming gadgets
- Radio transmitters
Natural Sources
RFI that occurs naturally tends to be generated by some astronomical phenomena, which include the following:
- Snowstorms
- Dust storms
- Cosmic noise
- Static electricity
- Solar flares
- Lightning strikes
Duration
C-RFI or continuous RFI simply refers to radiofrequency interference that is emitted continuously by specific sources via conduction or radiation. On the flip side, I-RFI or impulse RFI is the RFI that occurs intermittently or for a short period.
Lightning and switches commonly cause I-RFI, which disrupts the voltage and current equilibrium of nearby devices.
Moreover, you should note that both man-made and natural sources can generate both C-RFI and I-RFI.
Bandwidth
Frequency range within which an electronic component experiences RFI is what technicians refer to as bandwidth. Under this category, we can group RFI into the following classes:
Narrowband
When components emit RFI that feature a single frequency, we refer to this RFI as narrowband. Generally, narrowband RFI can be produced by various forms of oscillators. Furthermore, spurious signals can also generate narrowband RFIs since they cause various kinds of disruptions in transmitters.
The narrowband radiofrequency interference tends to have minor effects on electrical and electronic gadgets. However, you should handle them appropriately. Otherwise, they might exceed acceptable levels and cause problems for your device. Narrowband RFI is emitted by multiple gadgets, which include:
- Mobile phones
- Wi-Fi routers
Broadband
Generally, broadband RF interference can occurs in multiple frequency ranges, which can encompass a large area of the electromagnetic spectrum. Moreover, the broadband RFI doesn’t occur in single or discrete signals.
Broadband RFI generally occurs in multiple forms and it can happen due to man-made and natural RFI sources. For example, the sun is a type of broadband RFI since it masks or blocks satellite signals.
Broadband RFI can also occur due to the following:
- Faulty brushes that occur in generators and motors
- Arc welding
- Defective lines of power
Coupling Mechanism
Coupling mechanisms seek to describe how EM signals or waves from various sources reach receivers and affect various devices. Generally, the coupling mechanism encompasses the following features:
- A capacitive
- The victim (which is generally the receiving gadgets that get hit by the RF)
- The source (which transmits the RF causing RFI)
- An inductive
Radiation Coupling
Out of the many radiofrequency interference mechanisms that exist, you are more likely to encounter radiation coupling. In radiation coupling, the EM waves move from the gadgets that transmit the EM waves to the device receiving the waves via the air. Simply put, in this type of coupling mechanism, the EM signal moves through the air from one medium to another.
Moreover, in this type of coupling mechanism, the receiver and the sender don’t come into physical contact with each other. Actually, the distance between the receiver and the sender can be significant.
Conduction Coupling
Conduction coupling generally occurs when radiofrequency interference travels across various conductors, for example, cables and wires connecting the receiver and the source. This coupling mechanism is popular in PSL (power supply lines). Moreover, this mechanism relies heavily on the electromagnetic wave’s magnetic components.
To mitigate this variation of RFIs, you should install RFI shields on the electrical wiring of your gadget.
Capacitive Coupling
Generally, capacitive coupling tends to occur whenever electrical charges from the source pass to the circuit of the receiver due to a difference in charge. Therefore, capacitive coupling typically occurs between two electrical circuits in the same system that are close to each other. Actually, for this RFI to occur, the circuits have to be less than one wavelength apart.
Magnetic Coupling
Induction coupling, which also goes by the name magnetic coupling, generally occurs when varying magnetic fields are present between conductor loops of a receiver and a source. These magnetic fields consequently lead to a transfer of RFI to the receiving side due to EM induction. However, this type of coupling mechanism tends to occur when the conductors are pretty close to each other.
Radio Frequency Shielding Materials
Generally, the effectiveness of a shield will mainly depend on four factors which are the following:
- The shield’s geometry
- The EM’s frequency
- The material’s permeability
- And the electrical conductivity
Impeccable conductivity helps the materials effectively block or reflect the electromagnetic wave’s electric components. On the other hand, a great magnetic permeability will allow the component to provide low reluctance paths for magnetic fluxes, which is pretty beneficial in drawing and absorbing magnetic fluxes around shielding areas.
When selecting the best materials for RF shielding, you should significantly consider the strength of the magnetic and electric components of the EM field. Doing so will help you select the perfect materials to generate your RF shield.
However, when it comes to the materials that generate RFI shields, you will find that they are so many. But the most common ones are the following:
Nickel Silver
Nickel silver which also goes by the name copper alloy 770 (cu alloy 770), encompasses an alloy of the following component:
- Zinc
- Copper
- Nickel
Technicians primarily utilize this component to generate RF shields for application in environments that are highly corrosive. Generally, Nickel silver is pretty effective in terms of attenuating radiofrequency interference from mid-kilohertz to the gigahertz frequency range. Moreover, this component bears a permeability of one, making it outstanding in generating radio frequency shields for MRI gadgets where magnetic waves tend to be prohibited.
Moreover, copper alloy 770 doesn’t need post-plating for it to become solderable and resistant to corrosion. Additionally, it is highly aesthetic since it bears a pretty bright silver appearance even though it doesn’t encompass silver on its alloy.
Copper
Out of the many RF shielding materials that exist, copper tends to be the most reliable. That is because copper is pretty effective in terms of attenuating and absorbing the magnetic and electric components of EM waves. Moreover, this component has impeccable electrical conductivity.
CU (copper) is pretty easy to produce. Moreover, you can form this material into your preferred shape during the production phase. Additionally, due to their flexibility, you can install copper RF shields in various electronic components with relative ease.
Copper is also naturally corrosion-resistant and resists oxidation more effectively than other components that technicians utilize to make RF shields.
You can also utilize various copper alloys, for example, bronze, brass, beryllium copper, and phosphorus bronze, to generate RF shields. In addition, the elasticity of beryllium copper and phosphorus bronze tends to make them pretty useful in various contact applications for springs and batteries. However, despite all these advantages of copper as an RF shielding material, it has one downside: it is relatively more expensive when compared with other RF shielding materials.
Aluminum
Aluminum (Al) has an impeccable strength-to-weight ratio and excellent electrical conductivity. Moreover, it also falls under the non-ferrous category of metals, which makes it great for RF shielding.
You can utilize thin aluminum sheets to block radio waves with low frequencies. They work impeccably. Moreover, you can also utilize aluminum enclosures for your electronic gadgets to provide a built-in shield that protects the device against RFI.
Generally, aluminum has about 60% of copper’s conductivity. Therefore to achieve an RF shield that rivals that of copper, you have to make the Al RF shield thicker.
However, on the flip side, aluminum is pretty prone to oxidation and corrosion. And it also bears poor solderability.
Conclusion
For a printed circuit board to be effective and reliable, it must fu
