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Posted by Sealing & Shielding Team on 28 Nov 2018
Mobile electronic devices such as smartphones and tablets require highly populated printed circuit boards (PCBs) to support their functionality and performance requirements in an increasingly competitive market space. Consumers demand faster processing, high resolutions, and a longer battery life all in the palm of their hand.
To deliver advanced functionality and performance, board and semiconductor package designers must work together to tightly pack semiconductor devices on PCBs in the most efficient ways possible without causing EMI issues. Mobile electronic device OEMs have no tolerance for EMI issues since performance and reliability drive consumer demand in this market.
To eliminate potential EMI issues caused by densely populated PCBs, PCB and semiconductor designers are investigating novel new ways of shielding semiconductor devices and printed circuit boards. Traditional metal EMI shields are no longer an option, as they take up too much board space and therefore reduce the overall competitive functionality of the mobile electronic device.
One possible solution is an integrated EMI shield: a semiconductor device which has an electrically conductive layer applied over the top and sides of the semiconductor package, which grounds the device to the printed circuit board internally. Integrating the EMI shield into the semiconductor package this way has two main advantages: first, it saves PCB space by incorporating the EMI shield into the semiconductor device itself, reducing the overall size of the final product, and, secondly, it simplifies the board design and shortens product cycles.
The two most common ways to create an integrated EMI shield are applying a metallization layer using some form of physical vapor deposition (PVD) or spraying an electrically conductive coating directly on the semiconductor package. Both technologies provide effective EMI shields, reduce the PCB footprint of the semiconductor device, and simplify the PCB design. Using a PVD process to create an integrated EMI shield can be a high risk and costly option.
In contrast, Chomerics advanced conductive coatings can be applied to semiconductor devices with minimal capital equipment investment in a continuous high volume application process. By applying a conductive coating in a continuous high volume application process, semiconductor manufacturers can minimize their risk and achieve the lowest overall cost/integrated EMI shield. Also, organic conductive coatings are more flexible than typical metallized PVD coatings, resulting in fewer adhesion issues following environmental exposure.
Another method to resolving EMI issues in electronic mobile devices is by applying an organic absorber coating to the semiconductor package or PCB to absorb surplus electromagnetic waves. Chomerics’ absorber coatings are formulated to absorb electromagnetic waves at customer specific frequencies, and because they are non-conductive - can be applied directly to PCBs already populated with semiconductor packages. These absorber coatings can be applied to the PCBs or sections of the PCBs to reduce unwanted EMI noise after board assembly.
The challenges of suppressing board level EMI are not going away. On the contrary, as consumers continue to demand more and more functionality from their mobile electronic devices, OEMs must continue to find novel approaches to solve these ever growing board level EMI issues without impacting product design cycles and manufacturing costs.
Learn more about Chomerics advanced paints and coatings for EMI shielding.
This blog was contributed by Jarrod Cohen, marketing communications manager, Parker Chomerics Division.
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You’ve probably heard a bit about microwave absorbers and how they are used to reduce or absorb the energy that is present in a microwave. But what are they exactly? And how do they work? Go ahead, read on.
Simply put, microwave absorbers are special materials, often elastomer or rubber based, which are designed to offer a user-friendly approach to the reduction of unwanted electromagnetic radiation from electronic equipment. They also work well to minimize cavity to cavity cross-coupling, and microwave cavity resonances. When comprised of a silicone elastomer matrix with ferrous filler material, microwave absorbers provide RF absorption performance over a broadband frequency range from 500 MHz to 18 GHz.
The microwave absorber itself is considered a dielectric medium, which is an electrical insulator that can be polarized by an applied electric field. When such a material is placed in an electric field, electric charges do not flow through the material as they do in a conductor, but instead, the charges shift equilibrium positions causing dielectric polarization. This creates an internal electric field.
An EMI microwave absorber is filled with dielectric ferromagnetic materials. As a microwave strikes these materials, the wave becomes attenuated and loses energy. The energy loss is due to a conversion from EMI energy to heat energy via phase cancellation.
The amount of attenuation of the microwave is dependent on the frequency and the electrical permittivit, (dielectric constant) and magnetic permeability of the material. The amount attenuation varies by frequency.
There are two general classes of microwave absorbing materials, and they have to do with the frequency range that the products can effectively attenuate.
There are two general scenarios for microwave absorbing materials:
At the end of the day, there are many theoretical factors that will determine how well a particular absorber will attenuate in an application.
However the typical approach to an absorber solution is to narrow down the selection of a product and a thickness, and then evaluate these samples in the customer’s specific application through trial and success. Ultimately, it really only matters if the product works for the customer in their application and not what theory says.
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