Novel compound resists interference and impact

A LNP Engineering Plastics Europe product story

Edited by the Engineeringtalk editorial team Jul 26, 2004

A novel compound combines the toughness, high impact strength and excellent flow characteristics of Lexan EXL resin with the EMI shielding properties of stainless steel fibres.

LNP Engineering Plastics has added a new grade to its growing family of electroconductive Faradex compounds.

The new product - Faradex DS-1003 FR HI compound - combines the toughness, high impact strength, and excellent flow characteristics of Lexan EXL resin with the EMI shielding properties of stainless steel fibres, in a custom-colourable, halogen-free flame-retardant package.

It is available from the company worldwide.

Faradex DS-1003 FR HI compound offers both EMI shielding and electrostatic dissipative (ESD) properties.

It is highly effective against electromagnetic radiation sources, providing EMI attenuation between 20 and 60dB, a range that satisfies most electronics and telecommunications applications.

The new grade is specially formulated to achieve balanced dispersion of the steel fibres - which make up 1-2% by volume and 10-20% by weight - during plasticisation to help maintain the fibre length/diameter (L/D) ratio for an optimal conductive network for shielding effectiveness.

Excellent impact resistance has been achieved by using GE Advanced Materials' Lexan EXL polycarbonate (PC) resin as the new Faradex compound's base resin.

This tough PC material maintains impact strength at both elevated and low temperatures (9KJ/m2 at -45C), offering high flow and a good balance of high-performance properties.

It has been formulated with a halogen-free flame retardant in compliance with Blue Angel and TCO'98 green requirements resulting in a UL94V0 flammability listing at thicknesses of 2.1mm.

Traditionally, electronic devices have been shielded from EMI energy by installing thin metal shields or by using conductive paint, electroless plating, or vacuum metallisation.

However, each of these approaches has had its challenges.

Metal shields are often difficult to use in complex configurations and add weight and thickness at a time when the trend is toward lighter, smaller, thinner devices.

Although paint, plating and metallisation add minimal weight and thickness, they are applied via secondary operations that can be costly.

Because the new Faradex DS-1003 FR HI compounds use stainless steel, the new product not only deflects but also conducts electromagnetic waves, providing more effective and permanent shielding.

It can offer weight reduction compared with metal shields, cost reduction compared with surface treatments, plus greater effectiveness in complex designs - all in a single moulding step.

Faradex DS-1003 FR HI compound is targeted at a variety of electrical and electronics applications, such as local-area-network (LAN) connection boxes, traffic-control systems, credit-card payment devices, cash dispenser components, and smoke detector housings.

The new grade is also an excellent candidate for chassis and enclosures for notebook and desktop computers, servers, workstations, and flat-panel displays.

Compared with other conductive compounds that use carbon black or carbon fibre, the stainless steel fibre used in Faradex DS-1003 FR HI compound can deliver superior aesthetics to such applications and is less abrasive to tooling.

The new product also meets the chemical resistance requirements of Telecordia, NEBS and ETSI.

As a world leader in the development and manufacture of specialty polymer compounds, GE offers a number of conductive polymer lines.

Its lead brand is the fully compounded, precoloured Faradex family of compounds.

Products in this family are generally isotropic compounds, reducing warpage concerns, with a shrinkage rate similar to their unfilled base resins.

Other properties are dependent on the base resin used.

"With Faradex DS-1003 FR HI compound, we've solved two challenges with one product", said Nitin Apte, Global Product Manager, GE Advanced Materials.

"EMI is effectively shielded thanks to the stainless steel fibres, and Lexan EXL resin has given us the impact strength our customers require.

The chemical resistance, conductivity, excellent flow, non-halogen flame resistance, and other outstanding properties this new product provides are icing on the cake".