Global legislation, technology drive electronic device trends
By Don Rosato

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Note: This is the first article of a four-part series covering electrical and electronic (E/E) device (1) trends, (2) material advances, (3) process technologies and (4) applications.

INDUSTRY PULSE

What are the key trends in electronic devices?
  • 1. RoHS2
  • 2. E-waste recycling
  • 3. Miniaturization
  • 4. LDS technology

The electrical/electronics (E/E) market is the world's third-largest plastics market, after packaging and building/construction. Depending on the electronic application, plastics are chosen for rigidity or flexibility, toughness/durability, resistance to low or high voltage and their electrical insulation or conductive qualities. To understand where this market is headed, we must understand two driving trends: recent global regulations and technological advancements.

The Restriction of Hazardous Substances 2 update or RoHS2 recast directive (2011/65/EU) that incorporates all 10 E/E equipment categories — including medical devices and monitoring/control equipment previously excluded from the original RoHS — took effect in January. The recast RoHS2 Directive also adds an additional 11th "catch-all" category for any E/E equipment not covered by the other 10 categories. The result is to extend RoHS coverage to all E/E devices unless specifically exempted.

Electronic devices legislation and performance requirements.

While the recast directive does not expand the list of substances subject to the directive's restrictions, a nonbinding recital directs the European Commission to study four substances, namely the flame retardant hexabromocyclododecane (HBCDD) and the phthalate plasticizers: bis 2-ethylhexyl phthalate (DEHP), butyl benzyl phthalate (BBP) and dibutylphthalate (DBP).

In China, new regulations to better manage the recycle and disposal of waste E/E products went into effect in 2011. Sales of electronic devices are surging in China, and the country generates as much as 2.3 million tonnes of electronic waste domestically each year, second only to the U.S., which produces 3 million tonnes annually.

Much of the American waste ends up in China, where imports of e-waste are banned but largely tolerated. Under the new regulations, the Chinese government has established a treatment fund for e-waste, which will be used to grant subsidies for the recovery and disposal of electronic products. In southern China, there are now more than 100,000 people employed to recycle discarded computers and other electronic waste.

A Chinese worker dismantles electronic waste for recycling.

Demand for more compact, lighter-weight electronic devices, especially in LED lighting, consumer electronics, automobiles and medical devices requiring thinner wall design is driving development of flame-retarded (FR) materials. Electronic device miniaturization is also driving plastic and process development. One example is the use of electronics printed on polycarbonate film that is back-molded into a cellphone housing to allow incorporation of additional antennae into the smartphone while maintaining or reducing phone housing size.

Other plastic compounds are also being developed for the productivity advantages plastic injection molding offers over metal forming in many E/E applications. Plastics also offer design flexibility to create complex shapes and the ability to achieve parts integration and elimination of secondary finishing steps typically required by metals.

Many of today's new technical developments in the E/E sector capitalize on the latest "new generation" plastics. Development of electronic devices fosters plastics innovation and the optimization of plastics materials, namely:
  • High-heat and high-flow plastics — miniaturization of electronic devices and the convergence of electronic product features lead to product wall thinning and increased operating temperatures.
  • Growing use of high-temperature, lead-free solder to comply with the EU's RoHS directive also adds to this demand, as does the increased use of plastics in under-the-hood automotive electronics applications.
  • Flame retardants
  • E-waste recycling — the growing mountain of scrapped electronic devices is prompting advances in e-waste recycle.
  • Thermally conductive plastic compounds — electronic devices (such as LED lamps) can lose efficiency, experience reduced service life or fail if they overheat.

Amorphous (left) and crystalline (right) plastics temperature/performance grid.
New processing developments are also changing the way in which plastics are used in electronics
  • Metal replacementónew plastics to replace metal parts enable injection molding process efficiencies in the manufacture of electronic devices.
  • Laser Direct Structuring (LDS) applied to three-dimensional partsóLDS technology and specially developed plastic compounds allows the electronic device plastic housing to take over the function of conventional antennas or circuit boards.
  • LDS technology also makes smaller, more powerful, and lower cost electronic devices possible.
In using plastics for electronic applications apart from mechanical properties, their electrical behavior is a decisive factor. A quick review of properties of plastics important for electronics devices is as follows:

Insulation properties are often of primary importance. Most plastics are good to excellent insulators with specific resistance around 1013 Ohm meter.

Dielectric strength is of special importance for plastics in high-tension applications, such as automotive ignition systems. At very high field strengths, insulation strength may suddenly break down; the current then forms sparks, which tunnel their way through the plastic.
  • Typical dielectric strength values are about 30,000 Volt/meter
  • For nylons, it may drop by 10-20 percent due to absorption of humidity
  • With static charges, surface resistivity is the determining factor
Tracking and arcing resistance:
  • Electrical tension may cause a tracking current to flow on plastics surfaces, especially if they are contaminated with humidity, dirt or chemicals. Small arcs can be generated at irregular interruptions along the current path causing a thermo-mechanical effect that erodes the material's surface. Tracking resistance indicates how well a plastic surface resists damage caused this way.
  • Arc resistance is closely connected with tracking resistance. Under the influence of an arc (such as generated by a short circuit) the plastic should not form a conductive bridge and should, if possible vaporize, so as to extinguish the arc.
Dielectric properties:
  • Dielectric properties must be taken into account when working in alternating current (AC) and high-frequency applications, such as data-processing and information technology.
  • The charges and dipoles of a plastic material change orientation in time with the AC's cycles.
Glow-wire test provides information about whether an object such as an overheating conductor could be a fire hazard in an electrical device.

Flame retardants are used to slow down combustion or prevent it altogether as nearly all plastics are inherently flammable, an important consideration in electronics.

Flow characteristics are important in E/E device miniaturization.
  • The many different connectors used in data technology and telecommunications are typical miniaturization examples.
  • In multipin connectors, good flow characteristics are required so high-quality, thin parts can be molded without displacing pins and sockets.
In addition to having excellent electrical properties, plastics also have desirable mechanical, chemical and physical properties that enhance their capabilities for electrical and electronic applications. Some plastics can be easily molded to form rigid protective packages for delicate microcircuits, while other extremely flexible plastics are useful as wire and cable coatings.

Dr. Donald V. "Don" Rosato serves as president of PlastiSource, Inc. a prototype manufacturing, technology development and marketing advisory firm located in Concord, Mass., and is the author of the Vol 1 & 2 "Plastics Technology Handbook".