How handheld devices cope with the rigors of modern life
By Mark Hazel, Segment Leader, Handheld Devices
In April 2013, the mobile phone celebrated its 40th birthday. It has evolved from a briefcase-sized battery and handset that stretched the definition of mobile, to a device no bigger than your hand that offers incredible computing power. This radical decrease in size and the ability to pack in so much power owes a lot to the performance offered by modern engineering plastics.
The mobile phone has gone from the domain of the very rich or very important to a device that is within reach of everyone; indeed, you will be hard-pressed to go a whole day without seeing someone using one for gaming, texting, surfing, photographing and even phoning!
Their design evolution has been remarkable, from briefcase-sized behemoths to tiny handheld devices smaller than a TV remote. However, for all this change in size, phones are arguably tougher than they used to be, thanks not only to their advanced design, but also to the materials used in their construction.
Mark Hazel, Segment Leader, Handheld Devices at DuPont, explains the design evolution, which has also been mirrored in the development of many other devices, including gaming hardware, tablets and laptops: "In the early days, when phones became much more widely available, many used to be comprised of a stiff plastic chassis with decorative and sometimes removable front and back covers. This chassis gave the phone its strength and provided the mounting frame for all of the internal electronics. However, as they evolved, with larger screens and more powerful electronics, this chassis concept became less attractive functionally, as users wanted the screen size but without the body bulk. Many OEMs therefore steadily reverted to a design where the screen and rear cover act as significant parts of the structure, freeing up much more internal space for the enhanced electronics."
This approach to design in handheld devices has meant that the plastics used for the structure also have to offer aesthetic appeal, as the components they form are no longer solely structural elements. "As well as strength and aesthetics we also have to consider a myriad of other design constraints," Hazel continues. "In handheld electronics applications, one of these is Radio Frequency Interference (RFI) compatibility. If the material picks up moisture, it changes its RFI characteristics and detunes itself. This means that the battery has to supply more power to the antenna, and the battery life suffers as a result. At DuPont we have developed enhanced materials, which are less prone to moisture absorption."
One material that is ticking all the boxes for handheld device manufacturers is DuPont™ Zytel® HTN high-performance polyamide resin. Zytel® HTN helps make mobile phone housings thinner, lighter and more durable, while making a range of gaming, laptop and tablet parts longer-lasting and easier to produce. It offers properties such as stiffness, lightweighting, strength, design freedom and the potential for lower production costs to a new generation of thin frames, spines and housings.
Zytel® HTN provides excellent flow and dimensional stability, promoting the development of thinner and lighter components for the latest generation of electronic and electrical devices. Zytel® HTN is also available in a halogen-free, flame-retardant grade in compliance with recycling programs for discarded electronic products. Specific grades can also withstand high-temperature circuit assembly methods, including those using lead-free solder.
"All the materials that we have developed are highly stiff and protect the parts from excessive deflection, if dropped," Hazel elaborates. "Screens and circuit boards cannot twist or deform too much, so stiffness is vital. We use 50 percent glass filler to achieve the best stiffness and toughness (only possible in nylons such as Zytel® HTN), but we also have to consider RFI compatibility, colorability and surface finish. It is a fine balancing act. We have also developed a repetitive-impact test, which, rather than testing impact test bars to discover the energy to shear, actually tests and measures the number of times a sample can be hit until it breaks. This test is much more representative of the use a handheld device will see and demonstrates that Zytel® HTN offers class-leading performance.”
Hazel concludes, "We have spent many years collaborating with manufacturers to fine-tune engineering polymers to their specific applications. DuPont is also working to get better surface finishes and, keeping one eye on the future, we are looking at alternative glass-filled plastics, which have the potential to offer even greater performance and compatibility with electrical and electronic applications."
Through material science-driven innovation, DuPont has expanded its Zytel® HTN portfolio with a Renewably Sourced (RS) grade. This grade allows manufacturers to address even more aggressive sustainability goals and provides an exceptional balance of properties, including impact resistance, stiffness and low warpage. Zytel® RS HTN also offers better RFI performance for electronic applications requiring radio wave transparency, such as mobile phones, GPS, digital assistants and cameras.