Housing

    The first thing we see when we are looking at the device is phone housing, and that's what makes the first impression about the gadget. And to make it as more attractive as possible, manufacturers are driven not only by design solutions but by the use of different materials as well.
    HOUSING COMPONENTS
phone's housing components
Face Shell
Face shell is the basic structure of a cell phone. Phone's camera, handset, buttons and infrared sensor need to embed in the face shell for fixing. Polycarbonate is a typical material used widely in mobile phone shell.
Bottom Shell
Bottom shell is the basic structure of a cell phone as the mobile face shell. Bottom shell inlays face shell for fixing the outer components of mobile phone.
Battery Cover
Mobile phone manufactures in accordance with the requirements for appearance design take different materials to make the back cover. There are few common back covers--- 2.5D non-removable cover, metal non-removable cover, plastic removable cover, etc. nowadays, many mobile manufacture are beginning to set foot in back cover customized service for production differentiation.
    HOUSING MAETRIALS AND TECHNOLOGY
Material Types
Commonly, there are two most-used materials types for making the mobile phone housing: Plastic and Metal. However, as the development of mobile phone, there are more and more synthetic substances materials used in the phone casing, such as ceramic, wood and fabrics, etc.
Plastic Technology
Nowadays there are two synthetic substances in use of phone housings manufacturers: Acrylonitrile butadiene styrene (ABS) and Polycarbonate (PC). Compared to metal, plastic is lighter so your phone is less likely to weigh down in your pocket. As plastic is an insulator rather than a conductor, it also won't lead to an adverse impact on phone reception in the same way that a metal case would.
  • Acrylonitrile butadiene styrene
    ABS is rarely used in pure state as it has low resistance to ultraviolet and is sensitive to atmosphere influences. Such housing would become fragile and start to scatter in a short time. But there is one advantage - it is much cheaper than polycarbonate.
  • Polycarbonate
    More recently, several handset manufacturers have moved towards using a polycarbonate unibody case. Handsets with a polycarbonate unibody Compared to typical plastic casing, a polycarbonate unibody case is much tougher and has much better impact resistance and scratch resistance. Polycarbonate cases can also feel great in the hand with a premium build quality that can rival metallic cases.
  • ABS+PC
    In order to make the phone housing more durable and less expensive, manufacturers usually add in ABS a part of polycarbonate, for material to become more lasting and keep its advantages. Such kind of mixture is really good for accurate molding of all the little elements like air grids, legs and bases for electronic components fastening, diminutive snaps and screw holes, boards junctions etc. And finally, such phone housing is ready for assembling and doesn't need any additional processing.
Metallic Technology
Metal has long been associated with premium high-end design and style on a mobile phone. Feeling rigid and expensive, a metal case gives a phone that desired premium feel in your hand. To that extent, many smart phone manufacturers have chosen to use metal on their design-conscious phones.
  • Aluminum + Anodization
    Aluminum alloys have their advantages as well. With the stiff alloys used in smart phones, there is a significant structural advantage that helps to protect internal components and durable. Because of metal's higher stiffness, it's also harder to scratch the surface. However, with anodization treatment, scratches are more likely be visible if they expose the untreated surface. Another key advantage is the much higher thermal conductivity of aluminum, which allows for better performance in situations where a device is thermally limited.  The primary disadvantage of using a metal case is that it will weaken the phone signal. Just like a mirror reflects light waves, a metallic case reflects the radio waves that your mobile phone uses to communicate.
  • Oxidation
    The cell phones manufacturers in order to make phone housings more solid and comfortable in use are planning to change the structure of metal. The technology is called Micro Arc Oxidation, and it changes the structure of aluminum so it starts look like plastic. The special work piece called "unibody" is used as the basis, it is processed with high voltage of 10 000V. The material becomes five times stronger compared to aluminum and three times stronger than steel. Now the phone housing can be much thinner and would be still very solid. As HTC founders say, such housings will even start a trend not to use cover cases for the phones in future.
  • Die casting
    Die casting is a metal casting process that is characterized by forcing molten metal under high pressure into a mold cavity. The mold cavity is created using two hardened tool steel dies which have been machined into shape and work similarly to an injection mold during the process. Most die castings are made from non-ferrous metals, specifically zinc, copper, aluminium, magnesium, lead, pewter and tin based alloys. Depending on the type of metal being cast, a hot- or cold-chamber machine is used.
Material Comparison
Material Advantages Disadvantages Samples

PC(polycarbonate)

Lighter, don't attenuate radio signals,    low price

Poor conductor of heat, low flexibility in structure, cheap feeling, easily to collect fingerprints and smudges

Galaxy note, Galaxy S III, NOKIA N9, etc

ABS (acrylonitrile butadiene styrene)

Cheaper than PC, don't attenuate radio signals, light

Low anti-corrosion property,  fragile.

ABS is commonly used in mobile phone protection shell.

ABS+PC

Lighter, less expensive, durable, good for accurate molding,

Poor conductor of heat, cheap feeling

 

Metallic

Durable, premium feeling, better help to protect internal components, good conductor of heat

High cost, heavier, weaken reception signal and lower download speeds

HTC ONE M8,Iphone6.