Thermoplastic Materials for Electronic Devices

 Consumer preference is driving the fast-growing global market of handheld electronic devices. Key product attributes that contribute to the look and feel of the device are continually sought by consumers when choosing among today’s wide range of consumer electronics. To meet these consumer requirements, OEMs and designers are seeking high-performance materials for electronic devices that provide strength, scratch resistance, aesthetics/soft touch, and light weight. While meeting consumer needs, manufacturers also must consider functional demands such as radio frequency interference (RFI), flame retardancy, and environmental impact.

Engineering thermoplastics play an increasingly vital role in this high-growth consumer market. Specifically, semi-crystalline resins from DuPont deliver performance, aesthetics, design freedom, and in some cases, more sustainable material solutions. These advanced polymer options are being increasingly specified in applications ranging from soft-touch parts to structural components.

Flexible Solutions Offer Versatility

For flexible applications, DuPont™ Hytrel® polyester thermoplastic elastomer delivers outstanding flex fatigue and consistent properties over a wide temperature range and does not stiffen at low temperatures. It boasts a hardness range from 30 to 85 Shore D, along with excellent tear resistance and flex fatigue for use in memory card slot doors. Due to its particularly good adhesion to PC or PC/ABS, Hytrel® can also be used in overmolded grips and protective edges. The material has also attracted interest in cables. A renewably sourced polymers (contains a minimum of twenty percent renewably sourced materials) option is Hytrel® RS which allows OEMs to maintain performance while helping to reduce their environmental footprint.

For covers and mechanisms, acetal is often regarded within the thermoplastic industry as one of the stiffest unreinforced engineering polymers.  DuPont™ Delrin® acetal offers  strong chemical resistance, excellent spring properties, and has inherently low friction. For hinges, slide rails, rotating mechanisms, and snap fits, Delrin® provides the desired low friction and spring properties.

Meanwhile, a renewably sourced option for covers and mechanisms is DuPont™ Sorona® poly trimethylene terephthalate. It delivers good chemical resistance, and excellent surface finish and scratch resistance with no painting required. It exhibits better scratch resistance than ABS and PC/ABS and higher pencil hardness after air oven aging and moisture aging.

For structural applications, the DuPont™ Zytel® HTN family of semi-aromatic polyamides offers a stiff and strong option for use in handheld electronic devices. With a glass reinforcement level of 50%-55%, these materials can help stop excessive deflection of screens or circuit boards. They offer excellent flow for the production of thin parts (0.8 mm to 1.2 mm), are lighter and less costly than metal alloy, and easily colorable. A renewably sourced grade, Zytel® RS, is derived from castor plants, helping manufacturers to address even more aggressive sustainability goals.

From a processing perspective, DuPont™ Zytel® HTN grades can also contribute to energy, cost, and time savings thanks to its excellent flow and dimensional stability. A halogen-free, flame-retardant grade is available for addressing recycling programs for discarded electronic products. Specific grades can withstand high-temperature circuit assembly methods, including those using lead-free solder. Meanwhile, a low-moisture DuPont™ Zytel® HTN grade has been developed to provide excellent property retention along with improved radio frequency interference (RFI) performance. In devices such as cell phones, the ability of radio frequencies to pass through the material is a key to getting good connections and battery life. Stable RFI properties over time will deliver a better signal as the antenna remains well tuned.

Technical support complements material experience

DuPont has concentrated on the development of materials for electronic devices and as a result nearly all of its resins sold into consumer electronics have been developed to respond to  the expressed needs of the industry. To support the customer, the company complements its extensive product experience with technical support. DuPont Performance Polymers has the capabilities to provide Computer Aided Engineering (CAE) during the design phase, on-site technical support, tool and customized gate design, and mold-flow simulation.

DuPont collaborates with part designers to help them optimize performance and moldability. Parts must be capable of being fully packed for optimum strength and to reduce sink marks. Among the general rules for good plastic design are no sharp corners and even thin walls for optimum cycle time. This is supported by gate locations that will not freeze off prematurely.

DuPont also has made available guidelines that can help minimize material warpage. A goal for processors is to keep flow fronts as straight as possible across the width of a part, avoid flow front from changing direction sharply in a corner, and avoid flow hesitation and cutouts on the sides of parts that give a flexible bending axis. Other considerations include avoiding race tracking in thicker curved edges, minimizing shrinkage in directions most prone to bending, and ensuring proper ejection to avoid sticking parts.