LNP™ FARADEX™ COMPOUNDS FOR EMI SHIELDING

WHERE DOES EMI COME FROM?

Ever since Marconi raised the first radio antenna, the broadcasted electrical noise from lightning storms could be heard. This phenomenon is known as radio frequency interference (RFI). Today’s frequencies at which electronic equipment operates are much higher, typically in the range of 30 Mhz to 10 Ghz. Electromagnetic Interference (EMI) is the newer term for the undesired negative effects caused by electromagnetic radiation.

EMI occurs when the electromagnetic field or transmission of one device disrupts, impedes or degrades the operation of another electronic device.

Electromagnetic disturbances can be conducted or radiated and originate from low or high frequency sources in the circuits, components and wires of electronic equipment.

The skyrocketing use and ever increasing portability of electronics has brought these devices even closer to one another, aggravating the issue. moreover, as devices become smaller, faster and more complex, their sensitivity increases, making them more vulnerable to interference. not surprisingly, regulatory standards have become more stringent, increasing the challenge faced by electronics, packaging and compliance engineers.

The optimally dispersed conductive fibers in the polymer matrix form a mesh that, through its bulk electrical conductivity, creates a Faraday Cage effect and provides EMI shielding performance. In many applications, a welcome side effect is the low surface resistivity achieved with LNP™ FARADEX™ compounds providing excellent protection against electrical discharge (ESD).

That performance comes with the principal advantages that set LNP™ FARADEX™ compounds apart.

DESIGN FREEDOM

The complex geometries of many devices require materials with optimal moldability. LNP™ FARADEX™ compounds work efficiently with injection molding equipment, filling even small seams and openings in a way metal cannot match. This design freedom gives opportunities for further component integration/part consolidation in a mass production environment.

LIGHT WEIGHT

Shielding components made from LNP™ FARADEX™ compounds are typically 40-70% lighter than their metal counterparts.

COST SAVINGS

By eliminating processing steps, which are essential to other shielding approaches, LNP™ FARADEX™ compounds streamline your operations, potentially generating cost savings.

EASE OF PROCESSING

no electroplating, painting or metallization is required to create the shielding effect. This not only eliminates certain traditional challenges, like the difficulty of coating some thermoplastics, but also brings parts made from LNP™ FARADEX™ compounds in compliance with stringent environmental requirements covering recyclability and disposal.

COLORABILITY

LNP™ FARADEX™ compounds can be custom-colored, thus secondary finishing steps can be eliminated. LNP™ FARADEX™ compounds come fully compounded and pre-colored in a broad range of base polymers,

enhancing their versatility – and your design freedom – even further.

JOINT DESIGN

Ideally, joints should maintain electrical continuity to avoid acting as “slot antenna” that leak electromagnetic radiation. Unfortunately, the resin rich surface is reducing the electrical conductivity across the joint. To minimize this “slot antenna” effect, using a tongue-in-groove, or lap joint design should be used. Such designs increase the joint surface area and contact pressure, improving electrical continuity across the joint and reducing the capacity impedance. Overlap length of 1.5 to 2.5 x wall thickness should be sufficient. An environmentally responsible method to improve the electrical contact between joining surfaces is laser ablation. This technique brings stainless steel fibers to the surface based on evaporation of the resin rich skin on a molded part, using high intensity, nanosecond laser pulses.

APERTURE DESIGN

The size of vent and access holes has substantial impact on electromagnetic radiation leakage. narrow, short, deep slots deliver better performance than long, wide, shallow slots. Provided the electromagnetic field direction is known the slots are best placed perpendicular. Similarly, the use of many smaller holes minimizes the disruption of induced current flows in the shield, and reduces escape and ingress of electromagnetic waves better than a large hole of the same area. Typical sizes are in the range below λ/6 (λ = wavelength).

WALL THICKNESS

Recommended wall thickness is a minimum of 1.5 mm and as uniform as possible. This allows adequate formation of the conductive network in the polymer matrix and helps minimize fiber attrition. Consider generous radii when designing corners, to minimize fiber attrition during filling phase of the mold cavity, thus preserving the shielding performance. For similar reasons, transition in wall thickness should be gradual.

BOSSES, RIBS AND GUSSETS

LNP FARADEX compound products have the right balance of mechanical properties and flow characteristics, allowing them to form complex features such as ribs, gussets and bosses. When properly designed such features can significantly improve part stiffness, strength and stability and improve design for assembly.

Design bosses and ribs following design standards for plastic materials to minimize sinking and void formation. For details, see the SABIC Engineering Thermoplastics Design Guide.

SPRUES, RUNNERS, GATING

Best practices to minimize fiber attrition are seen when sprue bushings and full round tool runner systems with generous dimensions and no sharp corners are used. This will also help to minimize pressure drop through the gating systems, provided low shear gating systems are considered. For LNP™ FARADEX™ compounds we advise the use of minimum 1.8 mm gate openings; pinpoint gating is because of high shear forces during filling not recommended. Hot runner systems can be used, provided they are externally heated with open nozzles, or equipped with needle shut-off valves. Torpedo-shaped hot runners should not be used in combination with LNP™ FARADEX™, as fiber attrition will be very high and EMI shielding effectiveness will suffer.

For specific recommendations on gating designs and sizing, please contact your local SABIC Technical Service Engineer. 

REGRIND USAGE

Although LNP™ FARADEX™ compounds can be recycled and reprocessed, care must be taken when incorporating regrind. Sprue regrind can be used to a level of 5 %. larger quantities will lead to reducing shielding effectiveness in the molded parts, due to too high fiber attrition resulting from additional stainless steel fiber breakage during reprocessing step.

Customers should always conduct their individual, application related regrind studies to confirm EMI shielding performance.

TOOL MATERIALS

Generally for engineering resins and LNP™ FARADEX™ compounds a hardened tool steel, like 1.2344/1.2738, or h-13, is recommended. The effect of stainless steel fibers on tool wear is minimal, similar to the unfilled base polymer. E.g. glass fibers are found more abrasive than stainless steel fibers.

The hardness for stainless steel is approximately 4.4 Mohs. Typical hardness of many other fillers and additives used in thermoplastic compounds is in the range of 3.5 to 5.5 Mohs. The volumetric loading of stainless steel fibers in LNP™ FARADEX™ compounds is low. Additionally the very high aspect ratio of the stainless steel fibers ensures there are fewer abrasive fiber ends present in the compound.

Predictive wear results of LNP™ FARADEX™ compounds versus other reinforced and unfilled thermoplastic materials are shown in the table below. Processing stainless steel fiber filled compounds does not result in significant wear on tooling, or molding equipment.

KEY BENEFITS

• Method is non-destructive
• The measurement is fast (15 sec.) and requires no sample preparation
• Eddy-Current Method shows good correlation with standardized method (ASTM D4935)
• Method does not require flat surfaces, so it is suitable for application testing
• Equipment is mobile, so it can be used at injection molding trials
• An effective way to monitor Shielding Effectiveness as a quality assurance tool or for application development

TEST METHODS FOR ESD PROTECTION

• Surface resistivity (IEC 93, ASTM D257, ASTM D4496)
• Measures of the ability to conduct an electrical current across a surface
• Typical performance Sr < 1012 Ω/sq

Static decay (IEC 61000-4-2, FTMS101B, Mil-B-81750B)

• Measure of the ability to discharge a specified electro static load
• Typical requirement is bleed-off time from 5000v to 0v in less than 2 seconds at 23°C and 15% rh (relative humidity)

First, SABIC is focused on continuously reducing the intensity of our global operational footprint, including reducing carbon intensity, improving energy and water use, and increasing material efficiency – benefits that also ultimately flow to our customers.

To this end, SABIC embraces Responsible Care®, the chemical industry’s global voluntary initiative to continuously improve safety, health, and environmental performance, as a framework for sustainability. We are building upon our strong management systems and history of responsible manufacturing to create an even safer, cleaner environment.

Second, our sustainability program focuses on the marketplace, where we are committed to sharing our expertise and working even more closely with our customers to develop products, applications and solutions that respond to their sustainability needs. Our product portfolio, coupled with our technological expertise and history of innovation, gives us the opportunity to develop materials that can help our customers tackle a wide variety of environmental issues. 

“We commend SABIC for its proactive efforts to provide new alternatives to traditional materials across the spectrum of sustainability. The key to this initiative is the verification of environmental benefits using established standards and rigorous validation and testing processes. Our work in independently evaluating SABIC’s materials helps ensure that they fulfill their eco claims and deliver proven, measurable value to customers.”
Truman Semans, Principal, greenOrder

SUSTAINABILITY SOLUTIONS PORTFOLIO

The Sustainability Solutions portfolio makes it easy for customers to identify, evaluate and select the right SABIC materials. This portfolio encompasses five broad categories that address today’s most important environmental initiatives:

• Post-consumer recycled (PCr) content
• Automotive weight-out
• Advanced flame retardance
• Energy efficiency
• Bio-based materials

The properties, performance and/or content of these materials can make a significant contribution to reduced environmental impact, from lowering carbon emissions to maximizing use of the earth’s limited resources.

To support our customers’ environmental objectives, SABIC plans to expand the Sustainability Solutions portfolio as we innovate in new technologies, improve our manufacturing processes and develop a deeper understanding of how our products and their uses contribute to sustainability.

For a significant number of products in the portfolio, there are third-party standards defining sustainability features, such as halogen-free flame retardance or post-consumer recycled content.

For a number of other solutions, such as automotive lightweight design or footprint reductions, there are no widely recognized industry or third- party standards defining sustainability. For these solutions, it is necessary to verify the environmental benefits over incumbent alternatives using life Cycle Assessment (lCA) methods for estimating the environmental footprint of products and processes. SABIC incorporated these LCA methods into its new Sustainable Product Scorecard to ensure that the verification process is done in a rigorous and credible way. 

This scorecard has two components:

LIFE CYCLE ASSESSMENT

LCA and life Cycle Inventory (LCI) methodologies, based on the ISO 14040 and ISO 14044 standards, are used to build the first component of the scorecard. The carbon and energy footprints of the products or applications are estimated across the life cycle. The results of the assessment are summarized in the Environmental Product Datasheet.

GREEN CHEMISTRY SCREEN (GCS)

This component of the scorecard guides the assessment of the chemical composition of the product, including impurities, byproducts and catalysts, against well-established toxicological, regulatory and industry standard criteria.

The output of the scorecard is used to develop well-substantiated environmental claims that undergo third-party verification. These validated claims enable our customers to differentiate their products and showcase the results of their sustainability efforts. 

Environmental standards for electronic devices are covered under two broad standards:

RESTRICTION OF HAZARDOUS SUBSTANCES (ROHS)

This EU legislation requires the elimination of lead, cadmium, mercury, hexavalent chromium, polybrominated biphenyl (PBB) and certain polybrominated diphenyl ether (PBDE) flame retardants.

WASTE FROM ELECTRICAL AND ELECTRONIC EQUIPMENT (WEEE)

The WEEE standard raises the required recycling level for electrical and electronic equipment. hardware manufacturers are responsible for recycling costs at the end of the devices’ life.

LNP FARADEX COMPOUNDS CAN HELP

All LNP™ FARADEX™ compounds are RohS compliant, and grades based on non- brominated, non chlorinated flame retardant systems are available.

Furthermore, because LNP™ FARADEX™ grades are available in precolored versions, they can eliminate the need for metallization and/or conductive paint treatments. lnP FArADEx compounds therefore offer OEms the potential to eliminate volatile organic compounds (vOCs) emitted by these coating processes. Such processes have shown to negatively impact air quality. Using LNP™ FARADEX™ compounds can help manufacturers increase overall productivity by eliminating the painting/plating step, minimizing or eliminating costs from emission- permitting and disposal fees, all while providing an effective EMI shielding solution. At the end of their life cycle, they can be recycled without the need to have paints or plating removed. 

PROCESS ELIMINATION

LNP™ FARADEX™ compounds deliver similar performance without the need of a secondary, conductive painting process, which is required when using a standard PC/ABS resin. This eliminates associated volatile organic compound (VOC) emissions and permit fees, and increases overall productivity.

GREENHOUSE GAS EMISSIONS

On a component basis, LNP™ FARADEX™ compounds have significantly lower GHG emissions compared to conductive painted PC/ABS resin over the full product life.

A PCB enclosure made from LNP™ FARADEX™ compounds has a greenhouse gas footprint of 4.0 kg during its sourcing, manufacturing, fabrication, use and disposal versus 5.1 kg for one made from conductive painted PC/ABS resin, resulting in a 21% lower impact. Making 200,000 PCB enclosures with LNP™ FARADEX™ compounds instead of conductive painted PC/ABS resin could avoid as much GHG as would be absorbed annually by a UK forest the size of 117 soccer fields.

ENERGY EFFICIENCY

On a component basis, LNP™ FARADEX™ compounds have a significantly lower energy footprint compared to conductive painted PC/ABS resins over the full product life.

A PCB enclosure made from LNP™ FARADEX™ compounds consumes 72MJ of energy during its sourcing, manufacturing, fabrication, use and disposal versus 116 MJ for one made from conductive painted PC/ABS resin, resulting in a 38% lower impact. Making 200,000 PCB enclosures with LNP™ FARADEX™ compounds instead of conductive painted PC/ABS resin could save enough energy to power 708 European homes for a year.

LOWER COMPONENT COSTS

LNP™ FARADEX™ compounds are capable of meeting electronics compatibility regulations and part design requirements, while reducing the overall weight by up to 50% compared to aluminum alloys used in typical automotive electronics enclosure applications. The lower mass and system costs of LNP™ FARADEX™ compounds may contribute to total cost savings

GREENHOUSE GAS EMISSIONS

On a component basis, LNP™ FARADEX™ compounds have significantly lower GHG emissions compared to aluminum alloy over the full product life.

During its sourcing, manufacturing, fabrication, use and disposal, an aluminum alloy PCB enclosure has a GHG footprint of 7.6 kg. In comparison, a similar PCB enclosure made from LNP™ FARADEX™ compounds has a GHG footprint of 4.0 kg – a 47% lower impact. Making 200,000 PCB enclosures5 with LNP™ FARADEX™ compounds instead of aluminum could avoid as much GHG as would be absorbed annually by a UK forest the size of 384 soccer fields.6

ENERGY EFFICIENCY

On a component basis, LNP™ FARADEX™ compounds have a significantly lower energy footprint to aluminum alloy over the full product life. A typical PCB enclosure made from LNP™ FARADEX™ compound consumes 72 MJ of energy during its sourcing, manufacturing, fabrication, use and disposal versus 135 MJ for one made from aluminum alloy, which results in a 46% lower impact. Making 200,000 PCB enclosures with lnP FArADEx resin instead of aluminum could save enough energy to power 1,014 European homes7 for a year.

GREEN CHEMISTRY

LNP™ FARADEX™ compounds are designed to comply with the rohS Directive (2002/95/EC), the Joint Industry guide and the IEC “halogen-free” standard (IEC 61249-2-21), and eco-labels such as Ecoflower, TCO, Blue Angel and nordic Swan. In addition, its formulation does not include any of the substances of very high concern as specified under the rEACh regulation (EC 1907/2006) as verified on Oct 31, 2011.