As electronic products get smaller, faster, stronger, and cheaper, can engineering thermoplastics keep up? The engineers at GE Advanced Materials have been hard at work to make sure their materials can keep pace. The company last month introduced a host of new plastics aimed at demanding electrical and electronic applications. Here's a closer look at them:
PEI flexes its muscles in circuitry
As a lower cost alternative to polyimide in flex circuitry applications, GE has developed a trio of polyetherimide (PEI) films that combine thermal and electrical performance with chemical resistance, adhesion to metals, heat-seal capabilities, and good tear strength. ULTEM EXSP0023 has the best heat performance of the three with a glass-transition (Tg) temperature of 245C. It also has a dielectric strength of 4,700 V/mil and a dielectric constant of 2.9 at 10 GHz. Next in line is ULTEM 500B film, which has a Tg of 225C and a dielectric strength of 5,300 V/mil, and a dielectric constant of 3.3. ULTEM 1000B has a Tg of 217 C and electrical properties slightly above those of the 500B. Aside from flex circuitry, applications for the new films include bar code labels, flexible heaters, stiffeners, insulative tapes, motor insulations, speaker cones, and wire wrapping. These films can also be »thermoformed into a variety of products. All three products are available in thicknesses from 2 to 28 mils and in widths up to 48 inches.
Tough in the cold
For electronics enclosures needing good low-temperature impact performance, GE added two new grades to its LEXAN EXL polycarbonate-siloxane copolymer. The siloxane improves the cold temperature impact, allowing the material to remain ductile down to –80C. One of the new grades, LEXAN EXL 9112, has the best flow properties of any flame-resistant (UL 94-5VA) polycarbonate-based material in GE's portfolio, making it a good fit for thin-wall electronics enclosures. The other new grade, ELX 1434, has been formulated to endure long-term UV exposure. It targets stationary outdoor electronics and portable devices that see lots of sunlight.
Get the lead out
Two new THERMOCOMP glass-reinforced composites from LNP Engineering Plastics, a GE Advanced Materials Company, have been formulated to stand up to thermal demands of lead-free soldering methods, such as infrared reflow soldering. One new grade, HT Solder UF-1006, is based on polyphthalamide (PPA). The other, HT Solder ZF-1006, employs a matrix of modified polyphenylene ether (PPE). Both grades have a 30-percent glass filling, offer heat distortion temperatures in excess of 260C, and feature a halogen-free eco-compliant flame retardant package. They also have mold shrinkage values similar to those of the polyester materials, possibly allowing them to serve as a drop-in replacement for incumbent materials.
Usually dc cords and plugs use vinyl, thermoplastic urethanes (TPU), or flame-retardant polyethylene (PE) as their wire-coating material. GE has come up with an alternative to these materials in the form of modified polyphenylene ether (PPE) resins. Unlike vinyl, these new modified PPE grades contain no halogens. And they offer a lower specific gravity than TPUs or flame-retardant PE, potentially reducing the weight reductions. Two new grades are available that have passed OEM bending-strength tests. NORYL WCD910 has been developed for use in dc cords, and NORYL WCP has been formulated for use in plugs.
For LCD diffusers, GE has developed a film that uses an optical quality
polycarbonate with built-in diffusion properties to take the place of polyester
films that get their optical properties from coatings. These ILLUMINEX films get
their optical properties from two proprietary technologies. The first uses
additives to incorporate diffusion properties into the resin itself. The second
involves a surface modification to the films as part of the melt-calendaring
process. This texturing process creates a "random surface profile" that helps
distribute light evenly, one of the primary functions of diffuser films.
Circuit Substrate: Polyetherimide films
could serve as an alternative to costlier polymide films in flexible