Knowledge Base

Mobile Casing Materials: Metal VS Plastic

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Title Image.jpgIn our on-going series of articles about mobile phones and the clever technology behind them, we’ve been looking at various aspects of your mobile phone, how they’re produced and how they all work together to bring you today’s smart and seamless smartphone experience.


Our series of articles has so far taken us on a journey through different types of display technology and pixel arrangements, processor technology from ARM and Intel, geolocation technology such as GPS and network technology such as 3G and 4G. We’ve also had time to look at the software that runs on your smartphone: the mobile operating system and user interface design. Finally, we explored the multitude of different ways that we can interact with a smartphone: by using a hardware keyboard or software keyboard, a touchscreen display, voice recognition technologies or a stylus pen.


In our latest article, we turn our attention to something that determines how your smartphone looks and how it feels in your hand. It can also be an important determinant of the coverage quality you receive and the download speeds that you receive over 3G and wi-fi. We are, of course, talking about the materials that are used in the casing of your mobile phone. In this article, we compare metal and plastic phones and ask what the choice of material may mean for your new phone.


Metallic Casing: Premium Feel


Metal.jpgMetal 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 smartphone manufacturers have chosen to use metal on their design-conscious phones. For example, the HTC One S features a metal shell that is made from aircraft-grade aluminium which has undergone a microarc-oxidation process to make it even tougher. Other phones featuring metal include Samsung’s Wave 3 which uses aluminium and the Apple iPhone 4S which features a metallic rim that doubles-up as an antenna.


Whilst metallic phones are known for aesthetics and premium feel, there are disadvantages too. 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.


A metallic case essentially works as a Faraday cage. Examples of Faraday cages in daily life include microwave ovens which use a metallic shell to confine the high energy microwave radiation inside the oven. Alternatively, mobile phone manufacturers often use anechoic chambers when testing their phones: it keeps other radio signals outside so the test can occur under controlled conditions. As metallic phone cases act as a partial Faraday cage, they can weaken reception which sometimes means fewer bars of reception on your phone and lower download speeds. Battery life may also be degraded as more energy is required to maintain the connection with the mobile network.


A further disadvantage of metal is that it tends to be heavier than plastic. This means that it can be more difficult to build a lightweight phone using metal. Recent developments have helped to reduce the weight difference between metal and plastic by creating lighter alloys with the iPhone 5 being rumoured to use a super-light alloy dubbed Liquidmetal.

Plastic Casing: Lighter and Improved Reception


Galaxy Nexus.jpgAs an alternative to metal casing, many smartphones instead use plastic casing. 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.


The primary criticism of phones with plastic casing is that it can cause a phone to feel cheap in the hand. Plastic can also collect fingerprints and smudges quickly, particularly on handsets with a glossy finish. This “cheap” aesthetic and feeling has been a common criticism of devices such as Samsung’s Galaxy smartphones (including the Galaxy Note, Galaxy Nexus and Galaxy S III) and has prompted considerable research into making better plastic cases. A further disadvantage of plastic is that it can be harder to grip than metal: particularly after exercise, with sweat, the reduced friction offered by plastic can make it easier to lose hold of your phone.


Smartphone manufacturers have tried to counter the criticisms of plastic in several different ways. ‘Research In Motion’ developed the BlackBerry Bold 9000 with a plastic backing that is textured like leather. This helps to give it a premium feel without having to switch to a different material.


Meanwhile, Samsung has employed a textured plastic back cover (“HyperSkin”) on their recent handsets including the Galaxy S II, Galaxy Note and Galaxy Nexus. The aim of HyperSkin is to provide improved grip and increased friction whilst also reducing the number of fingerprints. Finally, the new Galaxy S III uses HyperGlaze technology with the ‘Pebble Blue’ edition being textured like metal. According to Samsung, this gives the handset a premium metallic-like feel. However, the faux-metal look has been criticised as unconvincing by some reviewers.


Another approach to bridging the gap between metal and plastic can be found on the original iPhone where Apple used a part-metal, part-plastic back cover. Whilst most of the device used metal casing, the bottom part of the phone used plastic casing instead. This is the part of the phone that houses the radio antennas. The part-metal, part-plastic design allows for the phone to use premium metal materials whilst affording the improved signal quality that is offered by plastic casing.


iPhone Original.jpg
The original iPhone used a back cover which was part metal, part plastic. The antenna is housed in the plastic region.


Polycarbonate Unibody: Plastic with a premium feel


Lumia.jpgMore recently, several handset manufacturers have moved towards using a polycarbonate unibody case. Handsets with a polycarbonate unibody include the Nokia Lumia 800 and the HTC One X. 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.


The downside of a polycarbonate unibody case is that it is not possible to remove or change the battery in the device. This can be a huge issue for users that require a replaceable battery – power users for instance. It can also more difficult to insert your SIM card into a polycarbonate unibody phone: the phone will often have a push-in SIM card slot. In a plastic handset with removable battery cover, it is possible to instead insert the SIM card directly into the holder.


Your thoughts…


In this article, we’ve explored mobile phone casing materials and discussed how the choice of casing material is a trade-off between reception quality and aesthetics. Whilst metallic cases are typically tougher, more durable and premium-feeling, they can be heavy and have an adverse effect on coverage. The alternative, plastic casing is lighter and provides better coverage but can sometimes feel cheap and gather fingerprints. More recently, some manufacturers have been moving towards a polycarbonate unibody which can give your phone more of a premium feel whilst maintaining many of the benefits of plastic.


Are you more concerned about design and the way that your phone looks or is the quality of reception on your phone more important? Do you normally buy an additional external case for your phone or do you prefer to use it without an extra case? If you could design your perfect smartphone, would you build it from metal, plastic or a polycarbonate unibody? We’d love to hear your thoughts… please drop us a comment below and let us know what you think!


Ken Lo writes about mobile technology and the mobile industry at Ken's Tech Tips.


Hi groovemaneuver, I assume you've not regretted a single purchase in you life. I may have paid a pretty penny, but it still doesn't mean I get a perfect phone. Though, if I'm lucky, I get told I'm some sort of marketing tool? Surely, whenever you are buying a new phone, you are influenced by marketing or you wouldn't need a new phone? Though, thank you for your insight...
I like the strength of a metal phone, not worried by the extra weight. My HTC Desire S is a slippery son of a ...... though, so I have got a rubber case for it. That makes it grippy, and it bounces a bit too if dropped!. A nice alternative would be carbon though. Don't think it would reduce the signal as much as metal, would be ubber light, ubber swank and ubber strong.

Plastic with a premium feel must be the way to go haha... But I do love metal. Polycarbonate does look nice. Shiny plastic does not though.


The first thing you do when you get a new phone is to buy a new case to stick it in. I don't think I have ever seen the manufacturers design for more than a couple of minutes.

Ken, you seem to be confusing how a Faraday cage actually works...

iceqntrider, I make few purchases that I regret these days. Due to being skint, I have to do the research before parting with any money. It doesn't hurt for anyone else, either, though! I just get sick of Apple having too much money (by their own admission!) and making it through to some considerable extent, their pushing marketing in everyone's face.

Paying a lot and not getting perfection or even close enough to perfection to be reasonable value - see anything wrong with that picture? Also, marketing doesn't as you suggest (joking?) make me "need" a new phone, the ability to support functions that I NEED and my old phone doesn't have makes me look for a new phone. Or if I lose my old one. Or if my old one fails and I can't replace a component. Rarely happens in any case. Define 'need', you know? I recently bought my first ever new laptop, and when I bought it I felt guilty as it was more than I strictly needed in specification, or I could have repaired an old one on the cheap and I'd only decided on a new one due to forum recommendations and a lot of reading later I started to feel marketed-to. However, it's a massive leap in spec. so I don't regret it at all now, based on evidence, as it's genuinely a big help to what I need to get done, especially as a student and IT techie. I see a lot of keeping-up-with-the-Joneses action in people (network contracts don't help) and it's a bit ridiculous when viewed objectively. I hope the rest of your phone works nicely apart from the feel of the materials, at least. Apple haven't got it all wrong, make no mistake...


very good i think brilliant