Sealing and Shielding

Not long ago in hospitals and other critical care facilities, you were greeted with a large, ominous warning sign the moment you walked through the entrance doors to refrain from cell phone use due to possible medical equipment malfunction or interruption.

Today, patients and visitors are free to use mobile phones and devices without fear of interfering with medical equipment, but there’s still a long way to go to reduce electromagnetic emissions and electromagnetic compatibility (EMI/EMC) issues in medical devices.

Medical devices require complex analysis of the EMI/EMC regulations used for medical equipment and system certification. There are many new aspects that need to be addressed since medical devices are no longer used in just a hospital setting. With the increase of wearable medical tech, patients can theoretically be anywhere in the world. Therefore, EMI/EMC compliance testing needs to address the location of “end use” such as in the home healthcare environment and transportation considerations – trains, planes and automobiles.

The primary EMI/EMC standard for medical electrical equipment and systems is IEC 60601-1-2. Developed by the International Electrotechnical Commission, this global standard applies to the basic safety and essential performance of medical equipment and systems in the presence of electromagnetic disturbances, and to electromagnetic disturbances emitted by equipment and systems. 

It also recognizes that RF wireless radio communications equipment (mobile phones, Wi-Fi and biotelemetry) can no longer be prohibited from the patient environment and medical equipment and systems.

However, the standard falls short of defining EMI/EMC test requirements for special environments and points to manufacturers addressing special environments in the risk assessment.

Remember, the difference between emissions and immunity tests are that the emissions requirement is concerned with the amount of electromagnetic energy emitted from your device, while the immunity requirement is concerned with how susceptible your device is to electromagnetic energy existing in the location of end use. This includes energy being emitted from surrounding devices.

• IEC 60601-1-2 – The basic document addresses emissions requirements for professional health care and home healthcare environments. Requirements are determined based on CISPR 11, IEC 61000-3-2 and IEC 61000-3-3 based on the environments of intended use.
• IEC 60601-1-2 – The basic document addresses immunity requirements for professional health care and home healthcare environments
• IEC 60601-1-2 – The basic document addresses immunity only in the automotive environment by including test requirements to ISO 7637-02 on direct current power inputs. This is being applied for both general automobile and ambulatory use.
• IEC 60601-1-2 – The basic document addresses immunity testing for environments near RF wireless radio communications equipment.
• Manufacturers should consider applying the emissions requirements of CISPR 25 and ISO 7637-2 for automotive environments. This is being used for both general automobile and ambulatory use.
• Manufacturers should consider applying the emissions requirements of ISO 7137, RTCA DO-160 and EUROCAE ED-14 for aircraft environments. This is being used for both general aviation and medical helicopter use.
• Manufacturers should consider applying the emissions and immunity requirements of IEC 62236-1 for railway environments.
• Manufactures should consider applying ANSI C63.27 for coexistence of wireless systems equipment (cell phones, Wi-Fi and biotelemetry). This is being used to ensure that medical devices which incorporate an RF transmitter AND are used near each other operate correctly in any environment.
• Product specific standards exist for specific types of medical electrical equipment and systems (endoscopic, infusion pumps, electrocardiograph, ultrasonic equipment etc.) that must be considered. In many cases these standards alter the basic requirements within IEC 60601-1-2.

Key takeaways

The world of medical devices is dramatically changing how medical electrical equipment and systems are being used in various environments. Many different EMI/EMC standards need to be considered to address all environments of intended use.

Parker Chomerics Test Services, in association with Parker Chomerics Applications Engineering can assist in determining what standards should be applied to your medical electrical equipment and systems and help ensure compliance to the requirements. Our extensive experience in solving EMI/EMC test failures will result in manufacturable solutions which will reduce your time to market.

This blog was contributed by Jarrod Cohen, marketing communications manager, Parker Chomerics Division.

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You are working on a new design and want to incorporate the sealing system directly – in 3D including a design space proposal? In Parker Prädifa´s CAD library, 3D step files are available for you to download.

CAD models as 3D Step files for numerous standard products are available on our product pages at www.parker.com/praedifa (or via the “CAD Library” quick link).

This makes it possible for design engineers to import Parker Prädifa seals and the matching design spaces as models directly into CAD designs for a full representation of the system. The CAD bill of materials then automatically includes the seal’s part number. This creates greater transparency and allows the parts to be traced in the system.

As a special benefit the sketch of the design space proposed by Parker Prädifa for the selected profile already exists in the model. This precludes the risk of mistakes in dimensioning the design space and further facilitates the concept design of the total system for the design engineer.

This blog was contributed by Michael Pavlou, market unit manager fluidpower, Engineered Materials Group Europe, Prädifa Technology Division

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We’re rounding up the most popular posts of the year on the Parker Chomerics EMI shielding blog in an effort to bid adieu to 2018 and give you our most useful, popular content in one spot.

Keep reading to see what made the cut!

5. Design Decisions Relating to EMC Shielding

When approaching the problem of electromagnetic compatibility (EMC), design engineers often consider it to be a secondary issue that can be dealt with once the device is working and, after all, it can be dealt with by putting a metal box around it! But that places mechanical engineers in a tough position as they deal with constraints such as weight, cost, performance and corrosion. Discover our best design tips to help with EMI shielding DURING the design stage! Read now.

4. Best Conductive Plastics: Five Things to Look For

Can electrically conductive plastics really replace traditional metal electronics enclosures? The answer is a resounding yes! There are very effective electrically conductive plastics available today that provide excellent electromechanical properties that help shield portable electronics from the electromagnetic interference (EMI) noise that is proliferating our daily life.

Smart phones, Bluetooth, Wi-Fi, radio, even your television are all susceptible to EMI. Discover the key points you may want to consider when evaluating electrically conductive plastics for your application. Read now.

3. The Difference Between Thermal Conductivity and Thermal Impedance

While not technically a blog about EMI shielding, thermal interface materials and EMI shielding generally go hand in hand. Thermal Interface Materials (TIMs) are useful for thermal management in electronic components, as they enhance heat transfer from a heat-generating component to a heat dissipater, or heat sink.

Across the industry, manufacturers often publish thermal conductivity in units of Watts / meter-Kelvin as well as thermal impedance in units of °C – inches2 / Watt on their datasheets. So, what is the difference between these two, and how should you consider them when selecting a TIM? Read on to find out!

2. Five Ways to Maximize Performance of Electric Vehicle Batteries 

As the days get shorter and fall gives way to winter, Jim Bradley knows it’s time to reach for his trusty socket set and get to work. The annual Bikes for Kids charity is nearly upon him, and Bradley, a 32 year veteran of Parker Chomerics, has been instrumental in spearheading the fundraiser for the past five years.

Bikes for Kids solicits generous donations from Chomerics employees and their families and builds and delivers bicycles to the Toys for Tots, a program run by the United States Marine Corps Reserve which distributes toys to less fortunate children, allowing them to share in the magic of the holidays.

“Oftentimes, these are first-time bicycle riders who have dreamed of their first bike. There’s nothing better than seeing the face of a child who has been given the freedom to ride,” explains Bradley.

And this year, there’s truly something else to celebrate. Right on the heels of his retirement at the end of the year, Bradley and the Parker Chomerics Bikes for Kids program have surpassed 1,000 built and donated bikes over the past five years.

“It is truly an astounding accomplishment and we’re so happy to be able to give a child the thrill of receiving a brand new bike,” said David Hill, global general manager of Parker Chomerics. “I cannot thank Jim enough for his 32 years at Parker Chomerics and his tireless efforts managing Bikes for Kids. He’s going to be a hard guy to replace,” he added.

For Bradley’s sake, he’s excited to be able to spend more time with his grown children and grandchildren in retirement. “Something tells me I might not be done with Bikes for Kids in the future,” he hinted.

Every Parker location is focused on local community support and fundraising activities. In addition to donations, many employees also volunteer their time; dedicating countless hours in support of organizations that appeal to a personal connection.

Company sponsored fundraising drives include everything from holiday gifts, coats and backpack collections; to funds for education, the arts, medical research, community support organizations, and much more.

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.

• Dielectric types, in which the absorbing filler acts on the electric field
• Magnetic absorbers, in which the absorbing fillers act on the magnetic field

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.

• Broad band: these microwave absorbers, such as Parker Chomerics CHO-MUTETM, operate over a large frequency spectrum, but generally have only low to moderate attenuation.
• Narrow band or tuned: these microwave absorbers operate over a much smaller frequency spectrum, however in that range, their attenuation is better than Broad Band absorbers.

There are two general scenarios for microwave absorbing materials:

• Cavity resonance is in the near field, very close to the EMI field source. This occurs when signals are trapped / contained within a metal enclosure or compartment. Not only is energy absorbed but induced currents from the field itself are impeded by the absorber.
• Near field absorption can take place right on the radiating element. In order to avoid shorting, the absorber must have a very high resistance. Absorber thickness plays heavily in this condition.

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.  

This blog was contributed by Jarrod Cohen, marketing communications manager, Parker Chomerics Division.

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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.

1. They are non-conductive and don’t need to be electrically grounded to the PCB, simplifying or eliminating masking.
2. The coatings can address EMI issues on the PCB, in-between tightly packed semiconductor devices.
3. They can be tuned to absorb EMI at customer specific frequencies.
4. The coatings can be applied at the end of a product design cycle to solve EMI issues without having to go through another re-design cycle.
5. They can be applied in a continuous high volume manufacturing environment with minimal capital equipment investment, making them a low cost, low risk solution for board or component level EMI issues.

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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