In addition to RF interference, electromagnetic interference can also affect customized flex PCBs. As a result, this can have a wide variety of unintended effects. They can range from but are not restricted to higher error rates.
EMI shield is essential for protecting specialized flexible PCBs from this kind of interference. This is achievable in a number of ways. It includes silver ink, copper layers, and shielding coatings. Each of these has its own set of benefits and drawbacks.
Let’s take a closer look at the procedure and the criteria for making the final choice:
What Is Flex PCB EMI Shielding?
The circuits on flex PCBs, like those on any other electrical connection, are vulnerable to EMI. It can cause an increase in the rate of error or even data loss if it is not properly shielded. EMI protection on flexible PCBs is accomplishable with silver ink, copper layers, and specialized shielding sheets.
It is important to consider things like minimum bend radius and regulated impedance. When deciding on a shielded material. All the various shielding methods result in thicker PCBs. This is due to their varying levels of effectiveness. The capacity to bend a printed circuit board decreases as its thickness rises.
Consequently, it is essential to accurately specify and analyze the minimum bending radius. And also kind of bending requirements for shielded systems as part of the material and design selection procedure. Whether the required bending is static (a single bending motion to ensure a tight fit) or dynamic (repetitive bending to maintain a constant shape), additional limitations are considerable. When compared to a static bending design. The least bending capacity of dynamic bending flexible PCB applications is significantly greater.
The need for regulated impedance outputs further limits the possible shielding methods. The shield should possess electronic characteristics that are in accordance with the EMI criteria. Besides this, it serves as referenced planes to get the required regulated impedance values. Unfortunately, not all forms of protection from radiation are compatible with both of these conditions.
The circuit type and the operating frequency determine the type of shielding material needed to prevent electromagnetic interference.
Common Applications Of Flex PCB EMI Shielding
Many popular uses in the healthcare, telecommunications, and defense sectors necessitate EMI shielding, and they are listed below.
- Magnetic Resonance Imaging
- Monitoring System
- Infusion Pumps
- Radio-frequency communication systems
- Mobile phones
- Data transfer designs
- Communication method
- Radar Systems
FLEX PCB EMI SHIELDING Methods
To protect against electromagnetic interference (EMI). Designs must get encased in a shielding material. Any EMI is safely dissipated by connecting these shielding layers.
When deciding on a shielding technique and material. It is also important to keep in mind several other factors.
· Bend Requirements
Different shielding techniques increase the flexible circuit’s thickness by different amounts. A design’s flexibility will get constrained since the minimal bending capability is proportional to its thickness. In order to make an informed choice on the type of bending and minimal bend radius needed for shielded systems. Designers and engineers must carefully describe these parameters.
Additionally, limiting factors include whether the bending is dynamic (repetition bending) or static (bends only once for fitting). When compared to a static bending design. The minimum bending capability of a dynamically bent flexible PCB application is substantially greater.
· Controlled Impedance
Requirements for controlled impedance signals further restrict the available shielding options. To attain the necessary regulated values of impedance. There should be electrical properties. The properties should meet standards and those of the reference planes. In practice, however, not all strategies meet both requirements.
Flex PCB EMI Shielding Materials
The majority of shielding in the business world is one of three basic types. The effectiveness of each shielding method, the effect on mechanical bending, and the compatibility with regulated impedance layouts are all factors to consider.
The circuit designs get encapsulated in an overlay material. And the silver conducting ink shield consists of additional layers of ink applied selectively to the surface. In order to disclose the grounding circuit of the layout. Cover lays feature strategically placed openings that are sewn along the outer margins of the part’s length.
The ink adheres to the ground and runs into the carefully placed holes. Silk screening is the most popular technique used to apply ink. With this approach, the shield’s precision and coverage area may get compromised. The ink coatings are then encapsulated. And then electrically isolated by laminating further overlay on top of them.
Advantages of Conductive Ink:
- Economically viable
- Exhibiting a high degree of adaptability
- Capable of providing enough protection
- Does not fulfill the purpose of regulated impedance designs.
- Multiple overlays are necessary (procedure steps and added materials)
- Lower industrial demand
EMI Shielding Copper Layers
Shields made of copper layers require an increase in the number of design layers as they are made up of etched copper that must get placed to the outside of the structure. Layers of copper can be crosshatched or solid planes for greater adaptability. This is possible at the expense of some shielding effectiveness.
Copper Layer Benefits:
- Provides solutions for regulated impedance design.
- Excellent shielding
- It’s the costliest option available.
- The most detrimental effect on adaptability
- Mechanical bending stress devices can be formed by stitched vias, significantly reducing flexibility.
EMI Shielding Film
The shielding film is an extra lamination layer on top with a specific function. The need for the camcorder industries, digital cameras, and mobile phones inspired the creation of these films.
The barrier layer is non-stick and jet-black in hue. With the use of pressure, the layers are laminated together. The coverlay’s opening is flooded with conductive glue, which bonds to the underlay and completes the circuit to ground.
Shielding Films Advantages:
- Increase in popularity
- Excellent shielding ability
- Overall thinnest construction
- Greater flexibility
To sum up, shielding is an essential part of many flexible PCB designs. It guarantees the overall effectiveness of the finished product. Effective designs that meet all mechanical and electrical standards are possible. This is because of the wide range of material possibilities and shielding methods.