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Consumer Electronics: LCPs take up the challenge for speed

Also, download this story from the electronic issue here

Liquid crystal polymers (LCPs), which exhibit tough properties, suit a highly demanding technology and data-driven era, against the backdrop of the upcoming 5G and 3D-printing arena, says Angelica Buan in this report.

The human attention span has now shortened to eight seconds from 12 minutes, according to a study. While technology cannot be blamed for how the brain copes with the “fear of missing out” anxiety, one thing is clear: we are living in an era of speed, connectivity and mobility.

The emergence of next generation technologies such as the 5G

Electronic appliance and device manufacturers are now competing to deliver not only speed, but also innovations to produce thinner, smaller and more lightweight products.

LCPs in the running for electronics

Engineering plastics like liquid crystal polymers (LCPs) meet the requirement for smaller and thinner electrical components, especially for high performance electronic display technologies such as plasma, LCDs (liquid crystal displays), and LEDs (light-emitting diodes). They are also favoured as a substitute for other polymer compounds because of their dielectric nature and conductive properties.

LCPs are a family of polymers that produce thermoplastic parts with unique processing characteristics and extremely high performance, so they are commonly used to replace metals, ceramics, and other plastics due to high thermal resistance, excellent flowability, and opportunities for weight or wallstock reductions.

Most commercial LCPs are aromatic polyesters characterised by high thermal and mechanical performance, inherent flame retardancy, good weatherability, excellent electrical properties1, high resistance to stress cracking, and chemical inertness. This makes them ideal for use in electrical and electronic components (including fiberoptic cables, PCBs, chip carriers, connectors (conventional, radiofrequency (RF), and fibre-optic), and other surface-mount components), microelectromechanical systems (MEMS), automotive applications (including components for ignition and transmission systems, lamp sockets, pump components, coil forms, and sensors), printer/copier/fax components, cookware, high-barrier/retort-processed food containers, plus components for chemical processing (including pumps, meters, and valves).

Commonly processed via injection moulding, LCP parts can be joined via thermoplastic welding techniques, particularly ultrasonic and laser welding. Owing to the highly rigid structure of their molecular chains and their liquid crystalline nature, which tend to be nearly linear and to occupy a stacked orientation that maintains its order regardless of solid or liquid phase, LCPs are highly anisotropic.

Essentially, primary bonds within an LCP polymer chain are highly attractive and hard to break, while secondary bonds between molecular chains are weaker and much easier to break. Although most thermoplastics and especially fibre-reinforced thermoplastics exhibit some degree of anisotropy after processing, the moulded properties of LCPs can be significantly different in flow and cross-flow directions3, which requires some care when designing parts and tools for these polymers to take advantage of (and avoid the challenges of) this characteristic. The highly ordered and linear nature of these molecular chains provides LCPs with self-reinforcing properties in the flow direction and contribute to excellent mechanical properties. However, LCP’s high anisotropy also means that weldlines (where flow fronts with different molecular orientations converge) are weaker and thus prone to warpage and thermal-expansion differentials. Because of this, LCPs are typically reinforced with glass fibre and mineral fillers, to reduce anisotropy.

LCPs can also can be moulded into large, thickwalled parts. The thermal stability typical of LCPs enables processors to efficiently reuse regrind and recycle reject parts, which again reduces material losses and lowers effective part cost.

LCPs meet the requirements for electrical components

Demand for lightweight and miniaturised components in the electrical & electronics sector, the largest application segment that already accounted for over 55% of the global volume share in 2018, as well as in the transportation and automotive industries, is driving the global LCP market. It is poised to cross US$174 million by 2025, according to a report by Mordor Intelligence.

The emergence of next generation technologies such as the 5G (fifth generation network technology) that promises 100 times faster speed than its 4G predecessor; 3D printing, future electronic packaging and Internet of Things (IoT)-related products, to cite a few possible breakthroughs in the near future, is expected to further boost LCP demand.

Solutions for thinner, smaller devices

SumikaSuper LCPs are used to produce connectors

Rising interest in connected mobility, smart cities, and video-streaming services is redefining speed in accessing data. Without negating the fancy for miniaturisation, companies like Sumitomo Chemical Advanced Technologies are rolling out new grades of LCP to enable production of smaller components that can deliver higher speed data transfer.

The Japanese chemicals company says it has developed three new grades of LCPs to enable manufacturers to produce connectors and other components that can render high-quality as well as highspeed data transfer without signal loss/decay, distortion, and interference. But there is more to the developments of these new LCPs, which also aim to address other datarelated concerns like data bottlenecks and data integrity.

The new SumikaSuper LCP grades are specifically designed for high-speed connectors, including backplanes and automotive connectors for infotainment. SumikaSuper E6205L is a lower dielectric constant polymer that is ideal for connectors requiring higher data transfer speeds. SumikaSuper SR1205L is for connectors that require both a lower dielectric constant as well as a lower dissipation factor (lower loss tangent).

Meanwhile, for high-speed digital and wireless devices where electromagnetic interference (EMI) is a concern, owing to its deterioration of signal quality, SumikaSuper SZ6911EM has been specifically designed to provide EMI shielding. This grade incorporates ferromagnetic particles that convert incident EM waves into heat energy, which subsequently can be bled off by thermal management systems.

Trends in device miniaturisation (and connector miniaturisation and sub-miniaturisation with requirements for comparable or higher mechanical performance in thinner wallstock), plus use of higher density interconnects have reduced space and increased complexity on printed circuit boards (PCBs), Sumitomo said.

Putting so many high-speed, high-frequency interconnects in such close proximity increases transmission loads and along with it crosstalk, which increases the need for connector materials with lower dielectric constants and dissipation factors. “Crosstalk between mobile phones is annoying; crosstalk between autonomous vehicles could prove deadly,” Sumitomo explained.

Additionally, it said that high-profile website hacks are a constant reminder of the need to protect data integrity without impacting signal speed.

Manufacturers are now continually upgrading connector performance to assure more reliable data transmission with greater clarity and at a faster speed, for which, LCP is suited for, it said.

Eco-friendliness: a standard for market growth

High-performance, durable materials like LCPs with eco-friendly properties are the hallmark of technological innovations.

Celanese’s Vectra LCPs are halogen-free polymers

US materials company Celanese, which manufactures a range of standard and specialty LCP grades, offers Vectra and Zenite LCPs. Both grades are halogen-free polymers that provide high-temperature performance in eco-friendly thin-wall applications with precise and stable dimensions, it says. These highly crystalline, thermotropic (melt-orienting) thermoplastics consist of rigid, rod-like macromolecules that are ordered in the melt phase to form liquid crystal structures.

Celenese adds that its Vectra LCP Fit50 LCP, with 50% regrind material, has recently received UL approval for flame class V-0 at 0.20-mm thickness. This LCP contains 30% mineral reinforced material and shows flow capability and outstanding warpage performance, according to Celanese.

Its flame-retardant performance is ideal for ultrathin wall and complex connector applications such as SIM (subscriber identity module) cards and board-to-board connectors in smart phones, tablets, ultra-books and other mobile communication devices.

Other advantages of electronic connectors manufactured using Vectra LCP FIT50 include the maintenance of good dimensional stability, and improved overall processing, especially in filling performance, according to Celanese.

New fields to conquer

Incorporating LCPs into aircraft windshields

With technologies rapidly evolving, the commercial application for LCPs is expected to likewise expand and to cover more industries.

For aerospace applications, LCPs are being considered in the new design for aircraft windshields. The LCPs can diffuse any wavelength of laser light, according to a team of researchers that presented their findings at an American Chemicals Society’s meeting recently.

This is an important breakthrough in aviation safety. Laser strikes are a growing problem, according to the US Federal Aviation Administration.

The agency reported receiving 6,754 reports of laser strikes on aircraft in 2017 or a 250% increase since it started tracking laser strikes in 2010. Either a prank or a deliberate act, pointing laser beams affects the pilot’s night vision, incapacitating the pilot and thus could cause a fatal accident on flight. As yet, experts have not come up with a single solution to impede all wave lengths of laser light. Notwithstanding that existence of laws that penalise this act may not be enough.

Incorporating LCPs into aircraft windshields could provide a vital layer of protection against any colour of bright, focused light. This method, doing away with reengineering the aircraft’s windshield, adds a layer of LCP to the glass that harnesses the existing power system for windshield defrosting.

The team, led by researchers from the Lewis University in Illinois, placed a solution of liquid crystals called N-(4-methoxybenzylidene)-4-butylaniline (MBBA) between two 1-sq in. panes of glass. MBBA has a transparent liquid phase and an opaque crystalline phase that scatters light. By applying a voltage to the apparatus, the researchers caused the crystals to align with the electrical field and undergo a phase change to the more solid crystalline state.

The researchers found that the aligned crystals blocked up to 95% of red, blue and green beams, through a combination of light scattering, absorption of the laser’s energy and cross-polarisation. The liquid crystals could block lasers of different powers, simulating various distances of illumination, as well as light shone at different angles onto the glass.

The next step is to scale up from 1-sq in. to the size of an entire aircraft windshield. The team is also testing different types of liquid crystals to find even more efficient and versatile ones that return to the transparent state more quickly once the laser is removed.

With all the technology for it, LCPs’ potential to corner more growth areas may be hampered by the fact that it is more expensive than standard thermoplastics. For now, cost limits its application to niche areas.

Nevertheless, that could change soon with new discoveries of methods to produce more cost effective LCPs.

(IMA)


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