The Mobile Phone: Parts and Choice of Materials
The mobile phone is one of the greatest inventions of all time (Guthrie, 2008). It has revolutionized the way people communicate and perform their day to day activities. Cell phones allow remote communication with people in far-away places, including those in other continents. Initially, cell phones were only meant to people to call and send short messages in the form of SMSs. However, cell phones have now advanced and are being used for a wide variety of purposes including taking pictures and videos, listening to music, browsing the internet, playing games, organizing events amongst other uses. The functionalities that a phone can offer depends on its make and the manufacturer responsible for producing it. As such, phones are very different and the choice of material used varies from phone to phone. However, all phones have common parts and functionalities. The ultimate aim is to discuss these common elements and the factors that come into play in the choice of appropriate materials for each part.
Parts and Functions of a Mobile Phone
This is the outer covering of the phone that enclosed inner components and protects them from damage.
Like the computer’s keyboard, a phone’s keypad acts as an input device that the phone’s user utilizes to input text and commands. It contains alphanumeric keys that are used for both dialing and texting (Caelia, 2010).
3) A microphone
When one speaks to a phone, his or her sound energy is first converted into an electrical signal by the microphone. This signal can then be processed by the phone.
4) An antenna
After the conversion of a speaker’s sound energy into electrical impulses, the resultant signals must be converted to electromagnetic waves that can be transmitted over the air (Guthrie, 2009). This function is achieved by the phone’s antenna. In addition, electromagnetic waves originating from the remote individual are converted to electrical signals that the phone can process by the antenna. Therefore, the antenna’s main purpose is to convert electrical signals to electromagnetic waves and vice versa (Guthrie, 2009).
5) Speaker or Ear Piece
When speaking to a remote individual on a cell phone, electromagnetic waves from the remote individual are converted to electrical signals that are then converted to sound energy by the speaker (Guthrie, 2009).
Like a computer’s monitor, a cell phone’s display acts like an output device that enables a user to visualize the phone’s data and events taking place. It is through the display that one sees what he or she is typing and also sees videos and pictures if the phone has these capabilities.
7) A Circuit Board
The circuit board is the heart of the phone. It contains several electrical and electronic components such as a microprocessor (the phone’s brain), resistors, diodes and transistors (Fitzek & Reichert, 2007). The microprocessor performs electronic logic to enable the phone to achieve its functionalities. The circuit board also contains memory elements (ROM and Flash Memory), which is used to store the phone’s Operating System (OS) as well as user’s data such as phone numbers (Brain et al., n.d.).
Figure 1. Circuit Board. This figure shows both the front and back views of a cell phone’s circuit board.
Just like any other electrical gadget, the mobile phone needs power to switch on and function. The battery stores power in chemical form so that the phone can operate even when it is not plugged to an electrical socket.
9) Subscriber Identity Module (SIM) card
A phone’s SIM card is a removable device that helps to identify a specific subscriber on the mobile network (Guthrie, 2009). It is the one that holds the service-subscriber key (also known as IMSI) that helps the mobile network to recognize the individual using the phone and to route calls to and from him or her.
Choice of Material for Each Part
The choice of material for each part depends on several factors. The most important factor is the function that the part is intended to achieve. Other factors include weight, cost of the material, political considerations and manufacturer preferences.
The main role of the casing is to protect inner components of the phone. As such, the material used should not be brittle otherwise the mobile device will easily break. Further, the material should be solid and lightweight since a cell phone is meant to be carried from place to place. Plastic suffices as the most appropriate material as it meets the above conditions. Though metal is solid and is not brittle, it is too bulky and unsuitable. Further, most metals conduct electricity, yet the casing should be an insulator that not only protects inner components from mechanical damage but also insulates them from electrical damage.
Most of the factors discussed above apply to the keypad. It should also be solid and lightweight and plastic is the best material to use for this purpose. Additionally, beneath the plastic that forms the upper covering of the keypad, there is an elastic rubber. The rubber helps when pressing the keys to input data on the phone. When a key is pressed, it is required to depress and touch the circuit board to input data. When it is released, it is required to stop touching the circuit board and go back to its neutral position. To achieve this functionality, a material with elastic properties is needed. Silicone rubber is used as it is solid and highly elastic.
3) Microphone and Speaker
Microphones and speakers are very similar in nature and are made from the same materials. Therefore, discussing them as one entity is appropriate. A microphone or speaker usually consists of four main parts: a diaphragm, cone, voice coil and magnet (Harris, 2001). A lot of considerations go into the choice of the best material to use in making the diaphragm. The most common materials that are utilized to make a diaphragm are plastic, paper and thin metal (Harris, 2001). A perfect diaphragm material should be: (1) stiff, to avoid unrestrained cone movements (2) light to reduce the force required to start it and (3) achieve excellent damping ratios in order to minimize cases of vibrations progressing even after the electrical impulse has been discontinued. Usually, the three requirements cannot be satisfied at the same time utilizing available materials and engineers have to make trade-offs in their design endeavors. For example, though paper has very low mass and has great damping ratios, it is not rigid enough.
The cone is usually made of either polyester foam or rubber (Harris, 2001). The cone should be elastic, and both of these materials achieve this requirement. However, polyester foam is cheaper and lighter than rubber but has the additional disadvantage that it is easily degraded by environmental conditions such as the presence of water vapor, light and high temperatures, effectively reducing its lifespan. The voice coil is made of an iron core and wires (Harris, 2001). The wires are usually made of copper because of its high electrical conductivity and low mass (Guthrie, 2009). Silver and aluminum can also be used but are sparingly utilized; aluminum because it poses difficulties in establishing connections and silver because it is expensive. The magnet is almost always a small permanent magnet made from magnetic materials such as ferrites and Samarium cobalt (Guthrie, 2009). However, because a phone is meant to be as lightweight as possible, Samarium cobalt is used because it has lower mass than ferrites.
Phone antennas are usually made of ceramics, an example of which is coltan, which is an ore of niobium and tantalum elements (Piccirillo, 2011). Here, political issues also come into play during the selection of the best material to use. The main source of coltan is the Democratic Republic of Congo, a country ravaged by war and political turmoil for long (Piccirillo, 2011). The continued use of coltan has generated political debate as manufacturers of electronic devices are accused of fueling violence and gross human rights abuses in Congo because buying coltan directly or indirectly funds the bloody war. However, alternative sources of niobium and tantalum have been discovered in Brazil and Australia (Piccirillo, 2011).
The display is usually a Liquid Crystal Display (LCD) (Thomas, 2010). According to Thomas (2010) an LCD screens consists of “thin layers of glass with liquid crystals sandwiched between them.” These liquid crystals light up when electrically charged (Thomas, 2010). Other materials which could be used but are not used in phone displays are Light Emitting Diodes (LEDs) (Guthrie, 2009). LEDs have better quality displays than LCDs. However, in the battle between cost and quality, cost triumphs because quality is not as important in a phone display as cost.
6) Circuit Board
The circuit board is made up of several electrical components such as resistors, capacitors, diodes, transistors, a microprocessor and a printed circuit board among others (Guthrie, 2009). Each of these components is made of specially selected materials to suit its purpose. For instance, the material used to make a resistor must be able to adhere to Ohm’s law of resistance (Guthrie, 2009). Capacitors require a material that has an elevated permittivity. These materials include mica, plastic, paper and ceramic (Guthrie, 2009). Microprocessors consist of millions of transistors that utilize semiconductor material. The most heavily used semiconductors in the electronics industry are silicon and germanium (Guthrie, 2009). However, phones utilize silicon because it can be used at higher temperatures than germanium (Guthrie, 2009).
The considerations that have to be put in mind while choosing the material to be used in manufacturing a phone’s battery include the weight of the material (since the battery has to be small in size and mass) and its ability to keep power for longer periods. The two materials that fit this criterion are lithium ion and nickel-metal hydride (Piccirillo, 2011).
8) SIM Card
The SIM card is made of a plastic and semiconductor material. Thus, the considerations mentioned above for semiconductors also apply in the choice of SIM card material.
Summary and Conclusion
In conclusion, the 9 main parts of a phone are the casing, keypad, microphone, antenna, speaker, display, circuit board, battery and SIM card (Caelia, 2010). Each part is made from material that is carefully selected depending on the function of the part, cost of material, weight (all components have to be as lightweight as possible), political considerations and manufacturer preferences. Casings and keypads are usually made in plastic (Caelia, 2010). In addition, a keypad has a silicone rubber (Guthrie, 2009). Microphones and speakers have diaphragms, cones, voice coils and magnets that adhere to a certain selection criteria (Guthrie, 2009). Antennas are usually made of ceramics while the display is mostly an LCD employing thin glass layers and liquid crystals. The circuit board has several electrical components that also require careful selection. The battery usually uses nickel-metal hydride or lithium iron so that it can retain power for longer periods of time and still achieve significant miniaturization (Piccirillo, 2011). Finally, the SIM card is made of plastic and silicon semiconductor material (Guthrie, 2009).
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Guthrie A.G, 2009, Technological Revolution: Impacts of Cell Phones, McGraw-Hill Professional, New York City.
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Piccirillo, C., 2011, Materials in Mobile Phones – Their Importance and Their Choice. [online] Available at: < http://www.suite101.com/content/materials-in-mobile-phones--their-importance-and-their-choice-a345606> [Accessed 2 April 2011].
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