Circuit boards shielding

U.S. market is about 20 million pounds per year. The applications are those where one needs very high flame resistance (clothing for firefighters and welders, welder s protective shield, upholstery and drapes), heat resistance (ironing board covers, insulation film for electrical motors and transformers, aerospace and military), dimensional stability (fire hose, V- and conveyor belts), or strength and modulus (circuit boards, bulletproof vests, fiber optic and power lines, ship mooring ropes, automobile tire cord, puncture-resistant bicycle tires). 

Electrical Conductivity. Unmodified polymeric resins are natural insulators and do not exhibit electrical conductivity. There are certain applications, however, where electrically conductive adhesives provide a significant value. One such application is the use of conductive adhesives as an alternative for wire or circuit board soldering. Another application, with less of a requirement for conductivity, is the assembly of components that are shields or protection from electromagnetic interference. 

For document handling applications, there are several components for which PAB s are suited. These include bases and chassis, which require high modulus pen bodies and optical devices, which require excellent dimensional stability moving parts that require lubricity and wear resistance and paper paths that require electrostatic dissipation (BSD). Similar requirements occur for related components in computers. Electromagnetic Interference (EMI) shielding is required for computer enclosures and printed circuit boards. Among the more common PAB s specified for these applications are PC/ABS and PPE/PS. 

Polyarylates are used in automotive applications such as door handles, brackets, and headlamp and mirror housings. Polyarylates are also used in electrical applications for connectors and fuses. The polymer can be used in circuit board applications, because its high temperature resistance allows the part to survive exposure to the temperatures generated during soldering. The excellent UV resistance of these polymers allows them to be used as a coating for other thermoplastics for improved UV resistance of the part. The good heat resistance of polyarylates allows them to be used in applications such as fire helmets and shields. ... 

The material developed by these authors consists of two polyolefin copolymers with different melt flow rates and filled with electrically conductive fillers and other additives. Two of the resins used are propylene/ethylene copolymers with different flow rates and flow ratios ranging from 2 3 to 1 90. The conductive filler particles include copper, silver, iron, or carbon black. These conductive resins can be molded or extruded, and applicatirais range from circuit boards to shielding to implants. 

Inorganic lead compounds were used in paints and organic compoimds in fuel to increase octane number, until concerns about lead s toxic properties arose. Lead is relatively opaque to ionizing radiation and is a valuable shielding material in X-ray applications and nuclear facilities. Another market for lead is in alloys that are used as solders in applications ranging from circuit boards to heat exchangers. Lead is also used in acoustic barrier panel, glassware and ceramic, and fiber optic cables. 

Polpmides have excellent thermal stability, solvent resistance, radiation resistance, wear resistance, hydrolytic stability, low dielectric constant, high mechanical properties, good chemical resistance and a low dielectric constant. Due to these superior properties, the application field of polyimide has generally been enlarged from printed circuit boards and electrical insulation layers in microelectronics to functional layers of humidity sensors, shielding layers for sensor surfaces and novel platforms for thermal sensor devices, temperature sensor arrays, micro-hotplates integrated into gas sensors and biosensors. 

Conductive Adhesives. Isotropically electrically conductive adhesives (ICAs) are widely used in the electronics industry when high-temperature soldering processes are unsuitable. Typical applications include silicon die attachment, component attachment in multi-chip modules (MCMs), surface mounted printed circuit board repair, and elec-tromagnetic/radio frequency (EMI/RFI) shielding. 

Specialty products for the electronics industry include aluminum foil-backed tapes for antistatic shielding and copper foil tapes for electrostatic shielding of circuit boards and microwave components. 

A potential alternative to plastic shielded wires is to replace them with electrically conductive fibers. Conductive yams twisted from fibers form a soft cable that naturally integrates in the clothing s stmeture keeping the system as clothing-like as possible. Fiber yams provide durable, flexible and washable solutions. Also lightweight optical fibers are used in wearable applications, but their function has been closer to a sensor than a communication medium [60, 61], The problem of conductive fibers is due to the reliable connections of them. Ordinary wires can be soldered directly to printed circuit boards, but the stmeture of the fiber yam is more sensitive to breakage near the solder connections. 

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