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Applications of titanium in the electronic industry
CHAPTER 14
Applications of titanium in the electronic industry Shulong Yea,b, Yongyun Zhanga, Peng Yua a
Department of Materials Science and Engineering, Southern University of Science and Technology, Shenzhen, China b Institute of Applied Physics and Materials Engineering, University of Macau, Macau, China
Contents 1 Introduction 2 Representative applications 2.1 The computer industry 2.2 The mobile phone industry 2.3 Wearable devices 2.4 Other products 3 Concluding remarks Acknowledgments References
269 271 271 272 274 276 277 277 277
1 Introduction Titanium is the fourth most-abundant metal existing in the upper crust of the earth, next only to aluminum, iron, and magnesium. The utilization of titanium and its alloys has been widely explored in many industries because they offer a unique combination of high specific strength, outstanding corrosion resistance, and good biocompatibility [1, 2]. However, until now, titanium and its alloys were mainly used in aerospace, chemical processing, marine engineering, defense, and biomedical areas, where their unique properties override affordability [1–6]. However, the requirements for low-cost raw materials and processing methods in other industries, such as electronic devices, automotive parts, architecture, sporting goods, and other consumer products, have become a major stumbling block for wider applications of titanium products.The applications of titanium and its alloys will continue to expand if affordability is improved. With the rapid development of the electronics industry over the last decades, the demand for electronic products has rapidly grown. Consumers Titanium for Consumer Applications https://doi.org/10.1016/B978-0-12-815820-3.00019-8
© 2019 Elsevier Inc. All rights reserved.
269
270
Titanium for consumer applications
have enjoyed the convenience brought by electronic technology. Excellent properties such as high specific strength and superior corrosion resistance have laid the firm groundwork for the applications of titanium and its alloys in high-quality consumer electronics. Hence, there is a trend in recent years that titanium and its alloys have become increasingly attractive for electronic applications such as computers, mobile phones, and wearable devices. However, due to the fast updating speed of electronic products, it is necessary to evaluate the relationship between performance, cost, and processing methods of titanium and its alloys, as compared to other, more affordable materials used in current electronic industries. Traditionally, titanium parts are typically fabricated by subtractive manufacturing techniques, that is, primarily by machining forged blanks [7]. The insufficient formability and machinability of titanium and its alloys limit their applications and makes the products expensive. This problem becomes even more serious when titanium and its alloys are considered in electronic devices where many components have complex shapes in thin walls. New approaches that allow cost-effective production of high-performance intricate titanium products are expected to open new market opportunities for titanium and its alloys. Cui [3] compared the cost-saving potential of new technologies, such as powder metallurgy, hot isostatic press (HIP) casting, etc. Among them, powder metallurgy is considered most economically feasible to fabricate titanium and its alloys for electronic applications, and the demand for the technology is expected to increase. Apart from the fabrication cost, the design of alloys using less costly alloying elements has also been investigated to improve the performance-to-cost ratio and to penetrate cost-sensitive markets such as the electronics industry. For example, a titanium alloy of Ti-0.5Fe-0.1N was reported to have the potential to be used as a structural material for consumer electronic goods [8]. The alloy was strengthened by low-cost elements, including O, N, and Fe. With grains refined by the addition of Fe, the alloy can achieve balanced strength and ductility. Furthermore, the alloy has an additional advantage in that the microstructures can be tailored during brazing when used in some practical application cases such as glasses frames.This alloy is therefore suitable for electronic applications that require high mechanical properties. Apart from this, titanium alloys with high interstitial element contents have also been tried for electronic applications, where the requirement for material ductility is not strict. Both commercially pure titanium (CP Ti) and Ti-6Al-4V alloy can be made from high‑oxygen-content raw materials to reduce the material’s cost if the ductility can meet requirements.
Applications of titanium in the electronic industry
271
In the following sections, some electronic parts made from titanium will be introduced, which may help in understanding the recent development of titanium in the electronics industry.
2 Representative applications 2.1 The computer industry With the living standards continuing to improve over the last decades, the demand for digital multimedia products has grown steadily. The laptop industry first catered to these trends. In 1999, Fujitsu Limited unveiled a new half-notebook-sized (A5) handheld PC, INTERTOP CX300, for the Japanese market (shown in Fig. 1A). It was the first reported commercial product in the computer industry that has used CP Ti (99.5% purity) for the top cover of the casing. The application demonstrates that titanium can be used as a computer casing material to achieve a thin-walled frame while offering sufficient strength at the same time. Compared with magnesium, which is a premier metal used for computer casings, the strength of titanium is much higher. Furthermore, the excellent corrosion resistance of titanium can benefit the subsequent coating treatment of the casing. Another typical product is the Powerbook G4 designed by Apple Inc. (shown in Fig. 1B), in which Grade 1 CP Ti foil was used to make the outer skin. The titanium foil was wrapped around a very stiff carbon fiber lightweight support frame for the necessary structural rigidity. Thus, the high strength-to-weight ratio of titanium paved the way for the application of
Fig. 1 (A) Fujitsu [9] and (B) Apple [10] laptops with titanium casing.
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Titanium for consumer applications
titanium on the Powerbook G4 and made this product one of the lightest laptops at that time. Titanium has also found applications in some computer peripheral products [11]. The outer shell of the mouse is constructed of Grade 1 CP Ti to improve the touch feeling of fingertips during use. The mouse is designed to be an expression of identity and elegance. It is a unique product that demonstrates the elegance of titanium. Apart from the previous examples, titanium is considered a promising candidate material for the substrate of hard disk drives [1]. As a nonmagnetic material, titanium can prevent detrimental interference with the data storage process. The most cost-effective choice among titanium alloys is Ti-3Al-2.5V (Grade 9), which is sometimes referred to as “half 6-4” and has high strength and ductility in the annealed condition [12]. The alloy can offer a mechanical strength that is 20%–50% higher than that of CP Ti at both room and elevated temperatures. More importantly, it has better cold formability than Ti-6Al-4V (Grade 5) and can be precisely cold-rolled into foil. Compared to 5086 aluminum alloy, which is commonly used for hard disk substrates, Ti-3Al-2.5V alloy provides significant advantages. In the annealed condition, the ultimate tensile strength-to-density ratio of Ti3Al-2.5V is 1.49 times higher, and the yield strength-to-density ratio is 2.83 times higher than those of 5086 aluminum alloy [12]. Thus, for the disk substrate of the same weight, its thickness can be reduced with the use of the titanium alloy. Moreover, the melting temperature of the titanium alloy is substantially higher than that of the aluminum alloy, implying a much better heat-distortion resistance. The higher temperature stability permits the disk to be coated at high temperatures and thus improves the disc production rates. On the other hand, the lower coefficient of thermal expansion of titanium alloys contributes to the reduction of dislocation between the read/write head and disk. The permission of closer read/write head tolerances can increase disc storage capacity when using a titanium alloy substrate. Fig. 2 shows a thin titanium foil disk substrate working with recording heads.
2.2 The mobile phone industry Mobile phones are representative items of communication products that have experienced the same trend as laptops. Some manufacturers tried to use titanium to produce upscale mobile phones for the demands of businessmen who require efficient and high-quality phones. For example, Nokia Inc. released a mobile phone named Nokia 8910 with a titanium casing,
Applications of titanium in the electronic industry
273
Fig. 2 Thin titanium foil disk substrate with recording heads [13].
which was welcomed by the business world (shown in Fig. 3). The use of titanium makes the mobile phone casing strong and significantly improves the feeling when held. The miniaturization trend on mobile phones makes the phones more fragile when they drop to the ground. As a result, mobile phone shells have been developed recently as a remedy to protect the phones. Due to the high specific strength of titanium alloys, they have been used for phone shell fabrication. A typical example is the iPhone shells designed by Gray Inc., as shown in Fig. 4. These cases are made of machined Ti-6Al-4V alloy,
Fig. 3 Nokia mobile phone with titanium casing [14].
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Titanium for consumer applications
Fig. 4 Titanium cases provide persistent protection of phones [15].
which can fit the frame well. The high precision process during machining produces a series of textured lines across its body, which is impossible to be replicated by hand and adds a complication to the multifaceted profile of the cases. The cases are available in a variety of colors and are sold at a relatively high price. The protective effect of these cases can prolong lifespans of these mobile phones. Compared with the phone cases made of silica gel, titanium alloys phone cases would not be stained from being oxidized.
2.3 Wearable devices Wearable devices are products controlled by electronic components and software that can be incorporated into clothing or worn on the body like accessories. Nowadays, a variety of wearable devices, such as smart glasses and smartwatches, have been invented. The sales of these consumer electronics have been growing steadily. In the fabrication of wearable products, the utilization of titanium can increase the accessional values of these devices. Materials with superior corrosion resistance and good biocompatibility are considered suitable for wearable devices frequently in contact with human skin. Titanium products are resistant to corrosion by perspiration, which makes titanium an ideal material for wearable devices used in the sports. Moreover, the high specific strength of titanium makes the frame of the devices strong enough to protect the electronic components inside and significantly decreases the overall weight of the devices. Fig. 5 demonstrates a titanium glasses arm for augmented reality smart glasses fabricated by metal injection molding (MIM) [16]. MIM combines the merits of powder metallurgy and plastic injection molding, and offers design freedom in shape complexity and is suited for mass production [17, 18].
Applications of titanium in the electronic industry
275
Fig. 5 (A) Product design of smart glasses, (B) a photo of the Ti glasses arms after coloring, and (C) and (D) SEM micrographs showing delicate structures of the MIMed Ti glasses arm. (Courtesy of ElementPlus, Shenzhen, China.)
The glasses arm can be made of CP Ti or Ti-6Al-4V alloy. Fig. 5A shows the product design of the augmented reality smart glasses whereas Fig. 5B is a photo of the MIM-fabricated titanium glasses arms. The glasses arms are anodized to obtain different colors, during which titanium reacts with oxygen to form an oxide layer. The thickness of the oxide layer can be adjusted by heat or electrochemical treatment. When the thickness of oxide varies, the reflected light waves vary resulting in different colors of the part. It is worth mentioning that the titanium glasses arm is more than 170 mm long but weighs only 6.8 g, featuring an extremely complex curved surface and a thin wall structure with smallest wall thickness ~0.5 mm. Fig. 5C and D shows SEM micrographs revealing the complex details in the glasses arm. Therefore, it is both difficult and expensive by machining and other processing methods, such as forging or casting, to mass produce the component. In fact, it is challenging to the MIM process as well. These MIMfabricated glasses arms can achieve tolerances consistently controlled within ±0.5% of the nominal dimensions, as well as good densities and mechanical properties comparable to those of the cast counterparts.
276
Titanium for consumer applications
There are other examples of titanium wearable parts made by MIM. Sintered to a high density, the watch frame weighs ~6 g and has a curved surface and internal complex structures. All the complex structures are netshape-formed without machining. After being carefully designed to prevent dimensional distortion during sintering, tolerances controlled within ±0.5% of the nominal dimensions can be consistently achieved.
2.4 Other products Apart from the previously mentioned sectors, titanium parts have been used in other areas of the electronics industry. One typical product is the Digital Single Lens Reflex (DSLR) camera. Titanium has been used for the fabrication of the shell and lens of DSLRs. Fig. 6 shows a photo of a DSLR camera (Leica M-P 240), in which the top plate, base plate, and control elements are all precisely machined from dense titanium. The application of titanium in shells of DSLRs not only reduces the weight of DSLRs and makes them more portable but also restrains stains produced on the bayonet connected to the lens. Earphones can transform the electric signal received from the digital media receiver into sound waves. The market of earphones is expanding as the field of portable electronic products expands. Fig. 7 shows a photo of an earphone (ATH-CM2000Ti) in which titanium is used to produce its cavities. The use of titanium decreases the weight of the earphone. The machining process and carbon-like coating have ensured earphones are durable and portative. Moreover, titanium is nonmagnetic, which ensures that the electrical signal and sound quality are not affected by the material.
Fig. 6 Leica Digital Single Lens Reflex camera series “titanium” [19].
Applications of titanium in the electronic industry
277
Fig. 7 Titanium used on the cavities of earphones [20].
3 Concluding remarks In addition to their conventional markets in the aerospace, chemical processing, defense, and biomedical industries, titanium and its alloys nowadays are extending their applications into the electronics industry. Their exceptional attributes such as high specific strength, excellent corrosion resistance, significant biocompatibility, and nonmagnetic property make titanium and its alloys elegant materials for the fabrication of components in computers, mobile phones, digital cameras, and other wearable devices. Although most of the products are identified as upscale electronic devices, the market is expected to continue to grow. On the other hand, the rapid development of the electronics industry gives rise to increasing demand for cost-effective production methods and design of low-cost titanium alloys.
Acknowledgments The authors thank the support from the Shenzhen Science and Technology Innovation Committee (grant number SGLH20161212155758670 and KQJSCX20180322152424539). In addition, the authors gratefully acknowledge the useful suggestions and critical read of this chapter by Professor Ma Qian of RMIT University, Melbourne, Australia.
References [1] C. Leyens, M. Peters, Titanium and Titanium Alloys Fundamentals and Applications, Wiley-VCH, Weinheim, 2003. [2] M. Qian, Titanium Powder Metallurgy: Science, Technology and Applications, Butterworth-Heinemann, Oxford, 2015.
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[3] C. Cui, B. Hu, L. Zhao, S. Liu,Titanium alloy production technology, market prospects and industry development, Mater. Des. 32 (3) (2011) 1684–1691. [4] S.R. Seagle, The state of the USA titanium industry in 1995, Mater. Sci. Eng. A 213 (1–2) (1996) 1–7. [5] H.J. Rack, J.I. Qazi, Titanium alloys for biomedical applications, Mater. Sci. Eng. C 26 (8) (2006) 1269–1277. [6] A.T. Sidambe, Biocompatibility of advanced manufactured titanium implants—a review, Materials (Basel) 7 (12) (2014) 8168–8188. [7] F.H. Froes, M. Qian,Titanium in Medical and Dental Applications,Woodhead Publishing, Duxford, 2018. [8] M. Yamada, An overview on the development of titanium alloys for non-aerospace application in Japan, Mater. Sci. Eng. A 213 (1–2) (1996) 8–15. [9] Handheld PC With Titanium Casing, Fujitsu Limited, Japan, 1999. http://pr.fujitsu. com/jp/news/1999/May/18-e.html. [10] Titanium PowerBook G4, Apple Inc., USA, 2001. https://en.wikipedia.org/wiki/ PowerBook_G4. [11] Computer Mouse With Titanium Shell, Intelligent Design B.V., The Netherlands, 2009. http://www.intelligent-design.nl/titanium_mouse.php. [12] C.W. Nelson, R.D. Weir, R.S. Weir, Titanium or titanium-alloy substrate for magnetic-recording media, US Patent 5,707,705, 1998. [13] J. White, The gas bearing Interface of opposed recording heads in a disk drive utilizing helium and thin titanium foil disks, J. Tribol. 136 (4) (2014). 041901-1-9. [14] Mobile Phone With Titanium Casing, Nokia Corporation, Finland, 2002. https:// en.wikipedia.org/wiki/Nokia_8910. [15] Titanium Protecting Case for Mobile Phone, Gray Brand, Singapore, 2015. https:// gray-international.com/. [16] S. Ye, W. Mo, Y. Lv, X. Li, C.T. Kwok, P. Yu, Metal injection molding of thin-walled titanium glasses arms: a case study, JOM 70 (5) (2018) 616–620. [17] R.M. German, Progress in titanium metal powder injection molding, Materials 6 (8) (2013) 3641–3662. [18] A. Dehghan-Manshadi, M.J. Bermingham, M.S. Dargusch, D.H. StJohn, M. Qian, Metal injection moulding of titanium and titanium alloys: challenges and recent development, Powder Technol. 319 (2017) 289–301. [19] Leica M-P ‘TITANIUM’ camera, Leica Camera AG, Germany, 2014. https://www. leicastore-uk.co.uk/products/leica-m-p-typ-240-titanium. [20] Earphone With Titanium Cavities, Audio-Technica Corporation, Japan, 2018. https:// www.audio-technica.co.jp/atj/show_model.php?modelId=3057.
Applications of titanium in the electronic industry Shulong Yea,b, Yongyun Zhanga, Peng Yua a
Department of Materials Science and Engineering, Southern University of Science and Technology, Shenzhen, China b Institute of Applied Physics and Materials Engineering, University of Macau, Macau, China
Contents 1 Introduction 2 Representative applications 2.1 The computer industry 2.2 The mobile phone industry 2.3 Wearable devices 2.4 Other products 3 Concluding remarks Acknowledgments References
269 271 271 272 274 276 277 277 277
1 Introduction Titanium is the fourth most-abundant metal existing in the upper crust of the earth, next only to aluminum, iron, and magnesium. The utilization of titanium and its alloys has been widely explored in many industries because they offer a unique combination of high specific strength, outstanding corrosion resistance, and good biocompatibility [1, 2]. However, until now, titanium and its alloys were mainly used in aerospace, chemical processing, marine engineering, defense, and biomedical areas, where their unique properties override affordability [1–6]. However, the requirements for low-cost raw materials and processing methods in other industries, such as electronic devices, automotive parts, architecture, sporting goods, and other consumer products, have become a major stumbling block for wider applications of titanium products.The applications of titanium and its alloys will continue to expand if affordability is improved. With the rapid development of the electronics industry over the last decades, the demand for electronic products has rapidly grown. Consumers Titanium for Consumer Applications https://doi.org/10.1016/B978-0-12-815820-3.00019-8
© 2019 Elsevier Inc. All rights reserved.
269
270
Titanium for consumer applications
have enjoyed the convenience brought by electronic technology. Excellent properties such as high specific strength and superior corrosion resistance have laid the firm groundwork for the applications of titanium and its alloys in high-quality consumer electronics. Hence, there is a trend in recent years that titanium and its alloys have become increasingly attractive for electronic applications such as computers, mobile phones, and wearable devices. However, due to the fast updating speed of electronic products, it is necessary to evaluate the relationship between performance, cost, and processing methods of titanium and its alloys, as compared to other, more affordable materials used in current electronic industries. Traditionally, titanium parts are typically fabricated by subtractive manufacturing techniques, that is, primarily by machining forged blanks [7]. The insufficient formability and machinability of titanium and its alloys limit their applications and makes the products expensive. This problem becomes even more serious when titanium and its alloys are considered in electronic devices where many components have complex shapes in thin walls. New approaches that allow cost-effective production of high-performance intricate titanium products are expected to open new market opportunities for titanium and its alloys. Cui [3] compared the cost-saving potential of new technologies, such as powder metallurgy, hot isostatic press (HIP) casting, etc. Among them, powder metallurgy is considered most economically feasible to fabricate titanium and its alloys for electronic applications, and the demand for the technology is expected to increase. Apart from the fabrication cost, the design of alloys using less costly alloying elements has also been investigated to improve the performance-to-cost ratio and to penetrate cost-sensitive markets such as the electronics industry. For example, a titanium alloy of Ti-0.5Fe-0.1N was reported to have the potential to be used as a structural material for consumer electronic goods [8]. The alloy was strengthened by low-cost elements, including O, N, and Fe. With grains refined by the addition of Fe, the alloy can achieve balanced strength and ductility. Furthermore, the alloy has an additional advantage in that the microstructures can be tailored during brazing when used in some practical application cases such as glasses frames.This alloy is therefore suitable for electronic applications that require high mechanical properties. Apart from this, titanium alloys with high interstitial element contents have also been tried for electronic applications, where the requirement for material ductility is not strict. Both commercially pure titanium (CP Ti) and Ti-6Al-4V alloy can be made from high‑oxygen-content raw materials to reduce the material’s cost if the ductility can meet requirements.
Applications of titanium in the electronic industry
271
In the following sections, some electronic parts made from titanium will be introduced, which may help in understanding the recent development of titanium in the electronics industry.
2 Representative applications 2.1 The computer industry With the living standards continuing to improve over the last decades, the demand for digital multimedia products has grown steadily. The laptop industry first catered to these trends. In 1999, Fujitsu Limited unveiled a new half-notebook-sized (A5) handheld PC, INTERTOP CX300, for the Japanese market (shown in Fig. 1A). It was the first reported commercial product in the computer industry that has used CP Ti (99.5% purity) for the top cover of the casing. The application demonstrates that titanium can be used as a computer casing material to achieve a thin-walled frame while offering sufficient strength at the same time. Compared with magnesium, which is a premier metal used for computer casings, the strength of titanium is much higher. Furthermore, the excellent corrosion resistance of titanium can benefit the subsequent coating treatment of the casing. Another typical product is the Powerbook G4 designed by Apple Inc. (shown in Fig. 1B), in which Grade 1 CP Ti foil was used to make the outer skin. The titanium foil was wrapped around a very stiff carbon fiber lightweight support frame for the necessary structural rigidity. Thus, the high strength-to-weight ratio of titanium paved the way for the application of
Fig. 1 (A) Fujitsu [9] and (B) Apple [10] laptops with titanium casing.
272
Titanium for consumer applications
titanium on the Powerbook G4 and made this product one of the lightest laptops at that time. Titanium has also found applications in some computer peripheral products [11]. The outer shell of the mouse is constructed of Grade 1 CP Ti to improve the touch feeling of fingertips during use. The mouse is designed to be an expression of identity and elegance. It is a unique product that demonstrates the elegance of titanium. Apart from the previous examples, titanium is considered a promising candidate material for the substrate of hard disk drives [1]. As a nonmagnetic material, titanium can prevent detrimental interference with the data storage process. The most cost-effective choice among titanium alloys is Ti-3Al-2.5V (Grade 9), which is sometimes referred to as “half 6-4” and has high strength and ductility in the annealed condition [12]. The alloy can offer a mechanical strength that is 20%–50% higher than that of CP Ti at both room and elevated temperatures. More importantly, it has better cold formability than Ti-6Al-4V (Grade 5) and can be precisely cold-rolled into foil. Compared to 5086 aluminum alloy, which is commonly used for hard disk substrates, Ti-3Al-2.5V alloy provides significant advantages. In the annealed condition, the ultimate tensile strength-to-density ratio of Ti3Al-2.5V is 1.49 times higher, and the yield strength-to-density ratio is 2.83 times higher than those of 5086 aluminum alloy [12]. Thus, for the disk substrate of the same weight, its thickness can be reduced with the use of the titanium alloy. Moreover, the melting temperature of the titanium alloy is substantially higher than that of the aluminum alloy, implying a much better heat-distortion resistance. The higher temperature stability permits the disk to be coated at high temperatures and thus improves the disc production rates. On the other hand, the lower coefficient of thermal expansion of titanium alloys contributes to the reduction of dislocation between the read/write head and disk. The permission of closer read/write head tolerances can increase disc storage capacity when using a titanium alloy substrate. Fig. 2 shows a thin titanium foil disk substrate working with recording heads.
2.2 The mobile phone industry Mobile phones are representative items of communication products that have experienced the same trend as laptops. Some manufacturers tried to use titanium to produce upscale mobile phones for the demands of businessmen who require efficient and high-quality phones. For example, Nokia Inc. released a mobile phone named Nokia 8910 with a titanium casing,
Applications of titanium in the electronic industry
273
Fig. 2 Thin titanium foil disk substrate with recording heads [13].
which was welcomed by the business world (shown in Fig. 3). The use of titanium makes the mobile phone casing strong and significantly improves the feeling when held. The miniaturization trend on mobile phones makes the phones more fragile when they drop to the ground. As a result, mobile phone shells have been developed recently as a remedy to protect the phones. Due to the high specific strength of titanium alloys, they have been used for phone shell fabrication. A typical example is the iPhone shells designed by Gray Inc., as shown in Fig. 4. These cases are made of machined Ti-6Al-4V alloy,
Fig. 3 Nokia mobile phone with titanium casing [14].
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Titanium for consumer applications
Fig. 4 Titanium cases provide persistent protection of phones [15].
which can fit the frame well. The high precision process during machining produces a series of textured lines across its body, which is impossible to be replicated by hand and adds a complication to the multifaceted profile of the cases. The cases are available in a variety of colors and are sold at a relatively high price. The protective effect of these cases can prolong lifespans of these mobile phones. Compared with the phone cases made of silica gel, titanium alloys phone cases would not be stained from being oxidized.
2.3 Wearable devices Wearable devices are products controlled by electronic components and software that can be incorporated into clothing or worn on the body like accessories. Nowadays, a variety of wearable devices, such as smart glasses and smartwatches, have been invented. The sales of these consumer electronics have been growing steadily. In the fabrication of wearable products, the utilization of titanium can increase the accessional values of these devices. Materials with superior corrosion resistance and good biocompatibility are considered suitable for wearable devices frequently in contact with human skin. Titanium products are resistant to corrosion by perspiration, which makes titanium an ideal material for wearable devices used in the sports. Moreover, the high specific strength of titanium makes the frame of the devices strong enough to protect the electronic components inside and significantly decreases the overall weight of the devices. Fig. 5 demonstrates a titanium glasses arm for augmented reality smart glasses fabricated by metal injection molding (MIM) [16]. MIM combines the merits of powder metallurgy and plastic injection molding, and offers design freedom in shape complexity and is suited for mass production [17, 18].
Applications of titanium in the electronic industry
275
Fig. 5 (A) Product design of smart glasses, (B) a photo of the Ti glasses arms after coloring, and (C) and (D) SEM micrographs showing delicate structures of the MIMed Ti glasses arm. (Courtesy of ElementPlus, Shenzhen, China.)
The glasses arm can be made of CP Ti or Ti-6Al-4V alloy. Fig. 5A shows the product design of the augmented reality smart glasses whereas Fig. 5B is a photo of the MIM-fabricated titanium glasses arms. The glasses arms are anodized to obtain different colors, during which titanium reacts with oxygen to form an oxide layer. The thickness of the oxide layer can be adjusted by heat or electrochemical treatment. When the thickness of oxide varies, the reflected light waves vary resulting in different colors of the part. It is worth mentioning that the titanium glasses arm is more than 170 mm long but weighs only 6.8 g, featuring an extremely complex curved surface and a thin wall structure with smallest wall thickness ~0.5 mm. Fig. 5C and D shows SEM micrographs revealing the complex details in the glasses arm. Therefore, it is both difficult and expensive by machining and other processing methods, such as forging or casting, to mass produce the component. In fact, it is challenging to the MIM process as well. These MIMfabricated glasses arms can achieve tolerances consistently controlled within ±0.5% of the nominal dimensions, as well as good densities and mechanical properties comparable to those of the cast counterparts.
276
Titanium for consumer applications
There are other examples of titanium wearable parts made by MIM. Sintered to a high density, the watch frame weighs ~6 g and has a curved surface and internal complex structures. All the complex structures are netshape-formed without machining. After being carefully designed to prevent dimensional distortion during sintering, tolerances controlled within ±0.5% of the nominal dimensions can be consistently achieved.
2.4 Other products Apart from the previously mentioned sectors, titanium parts have been used in other areas of the electronics industry. One typical product is the Digital Single Lens Reflex (DSLR) camera. Titanium has been used for the fabrication of the shell and lens of DSLRs. Fig. 6 shows a photo of a DSLR camera (Leica M-P 240), in which the top plate, base plate, and control elements are all precisely machined from dense titanium. The application of titanium in shells of DSLRs not only reduces the weight of DSLRs and makes them more portable but also restrains stains produced on the bayonet connected to the lens. Earphones can transform the electric signal received from the digital media receiver into sound waves. The market of earphones is expanding as the field of portable electronic products expands. Fig. 7 shows a photo of an earphone (ATH-CM2000Ti) in which titanium is used to produce its cavities. The use of titanium decreases the weight of the earphone. The machining process and carbon-like coating have ensured earphones are durable and portative. Moreover, titanium is nonmagnetic, which ensures that the electrical signal and sound quality are not affected by the material.
Fig. 6 Leica Digital Single Lens Reflex camera series “titanium” [19].
Applications of titanium in the electronic industry
277
Fig. 7 Titanium used on the cavities of earphones [20].
3 Concluding remarks In addition to their conventional markets in the aerospace, chemical processing, defense, and biomedical industries, titanium and its alloys nowadays are extending their applications into the electronics industry. Their exceptional attributes such as high specific strength, excellent corrosion resistance, significant biocompatibility, and nonmagnetic property make titanium and its alloys elegant materials for the fabrication of components in computers, mobile phones, digital cameras, and other wearable devices. Although most of the products are identified as upscale electronic devices, the market is expected to continue to grow. On the other hand, the rapid development of the electronics industry gives rise to increasing demand for cost-effective production methods and design of low-cost titanium alloys.
Acknowledgments The authors thank the support from the Shenzhen Science and Technology Innovation Committee (grant number SGLH20161212155758670 and KQJSCX20180322152424539). In addition, the authors gratefully acknowledge the useful suggestions and critical read of this chapter by Professor Ma Qian of RMIT University, Melbourne, Australia.
References [1] C. Leyens, M. Peters, Titanium and Titanium Alloys Fundamentals and Applications, Wiley-VCH, Weinheim, 2003. [2] M. Qian, Titanium Powder Metallurgy: Science, Technology and Applications, Butterworth-Heinemann, Oxford, 2015.
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