The back shell may be the sexiest part of a mobile phone

In the era of full screens, it is increasingly difficult to tell which brand and model it is by looking at the front of a mobile phone. Especially in the screen state, everyone is a piece of black glass, and no one should laugh at the "popular face."

Gradually, when we judge the beauty and ugliness of a mobile phone, we will focus on the design of its camera module.

Looking back at 2020, the camera modules of two mobile phones are more in line with my aesthetics. One is the two-color cloud-level design pioneered by the vivo X50 series, and the other is the star ring design of the Mate40 series. The former gives me a sense of neatness and order visually, while the star ring shape of the latter makes me shine.

▲ The left is vivo X50 Pro+, the right is Huawei Mate40 Pro

If the camera is the biggest factor affecting the appearance of a mobile phone, then the material and craftsmanship of the back cover determines the texture of the mobile phone.

In fact, with the homogenization of the front face design of mobile phones today, the back of mobile phones has quietly become the "main battlefield" of manufacturers. The thoughts spent on the back, including design, material and craftsmanship, became the focus of the introduction at the new machine launch conference.

Just look at the new machine equipped with a 5nm chip, except for the Mate40 RS version that uses nano-microcrystalline ceramic material, Xiaomi 11 provides a plain leather version, and the back shells of other models are made of glass.

Why does the new flagship phone no longer use plastic or metal as the material of the back shell? Is glass necessarily the optimal solution? Looking back at the design changes on the back of mobile phones over the past decade, we may be able to peek into the answer.

Plastic is not cheap

At the beginning of the emergence of smart phones, plastic was favored by mobile phone manufacturers because the material was relatively low in manufacturing difficulty and cost, light and drop resistant, and would not affect the signal.

However, plastics should not be synonymous with "cheap". Good craftsmanship can still make users wonder. It is also very interesting to say that manufacturers have also racked their brains in order to make the polycarbonate material look different from plastic.

Regarding the use of plastic materials, Nokia's Lumia series can be said to be perfect. The mixed polycarbonate (PC/ABS) and the painting process on both sides have achieved the magical effect of radiance from the inside to the outside. The advanced matte look, soft skin-friendly feel, and young and colorful color schemes make the Lumia series a glimpse.

▲ Lumia 800

Its rival is the iPhone 5c. Apple improved the injection molding process by installing a metal frame in a hard-coated polycarbonate shell to improve the firmness of the back. And through electrostatic painting to form a uniform transparent coating, so that the back shell of the mobile phone is as smooth as a peeled egg.

Samsung, who has been complained about "Wannian Plastic", has a soft spot for this material. It has tried to make plastic into a leather texture, such as the Note3 series. If the back shell is not touchable, it is difficult to see that it is a piece of plastic. This process is also continued on subsequent S series models, Chromebooks and other products.

The craftsmanship of the LG G3's rear shell is also worth mentioning. It adds a brushed decorative film on the polycarbonate shell, and adds a scratch-resistant coating to make the plastic material into a metal texture.

Lenovo has made plastic into a fabric texture. The back shell of VIBE X (S960) has a finely etched bite-grained texture, and the specially configured spray paint makes the polycarbonate back cover look like a metal fabric.

At the launch of Meizu 15, its "Ru Kiln White" version became the highlight of the promotion. Meizu stated that "the combination of the metal body and the piano paint process has finally achieved a texture close to that of ceramics."

In the era of "glass is king", some manufacturers have also played new tricks with plastics. For example, the back shell of realme V5 uses "super-coated optical technology and second-generation AG effect, which can look like fake AG glass.

Another example is the OPPO Reno5 series. The "Aurora Blue" version is 3D printed to achieve the star diamond effect on the polycarbonate material. The "Moonnight Black" version uses a dip dyeing process to achieve a silver-black gradient visual effect.

Although the processing technology of plastics is constantly improving, it can be found that the direction of manufacturers is to try their best to get rid of the "plastic feel" and imitate it into the texture of metal, glass, ceramics, and leather.

That being the case, why not just use materials that are trying to imitate? It is not ruled out that some manufacturers have cultivated plastic materials to "show off their skills", but in recent years, we have indeed seen less and less plastic materials on flagship fuselages.

Metal, looks beautiful

Metal also had a glorious time before glass dominated the back shell of high-end phones.

The HTC One, released in 2013, is the world's first all-metal smartphone. Its one-piece aluminum body made a deep impression, and it won the "iF Design Gold Award" the following year.

The arrival of iPhone 5 has set off a "metal frenzy." Its back glass spliced ​​aluminum alloy design made iPhone 5 one of the most attractive mobile phones at the time.

In the subsequent iPhone 7 era, Apple took the metal manufacturing process to a new level. At the beginning of its release, its jet black version was hard to find.

▲ Picture from: businessinsider

According to Apple's introduction, the manufacturing process of the bright black version of the rear case is very complicated. It can be roughly summarized into 7 steps. One is to cut and form a whole piece of aluminum alloy; the other is to drill and cut the lens compartment directly on the fuselage; the third is to polish the fuselage with different cutters of a milling machine; the fourth is to polish the fuselage with special compounds; The oxidation process coats the surface of the fuselage, six is ​​dyeing by capillary effect, and the seventh is magnetized iron powder infiltration for finer polishing.

After such complicated steps, the bright black version of iPhone 7 gives people a peculiar texture of round and jade. However, the disadvantages are also obvious: easy to scratch and paint off.

At this stage, metal materials have become commonplace on flagship phones. For example, Huawei P8, P9, Meizu MX6, OPPO R9, etc., are all aluminum alloy back shells.

▲ Huawei P8

Although the cost of metal materials is low, the material strength is high, and the heat dissipation is good, you will find that the color and texture of the mobile phone case using metal materials are similar. This is because the metal is poorly dyed and the paint is easy to scratch and peel off. Compared with plastic, it is less plastic.

In addition, the impact of metal on mobile phone signals is very significant. In the past, the back shells of mobile phones made of aluminum alloy can basically see the clear antennas exposed outside, in a three-stage arrangement, which destroys the beauty of the integrated back.

The popularity of wireless charging has also made metal materials seem outdated. The metal back shell will generate surrounding current during wireless charging, which will consume part of the interactive magnetic field, commonly known as "eddy current." The energy "hijacked" by the metal is converted into heat, causing the temperature of the phone to rise.

▲ Illustration of wireless charging with metal and glass materials. Picture from: Corning

For wireless charging, the lower the conductivity of the back shell of the mobile phone, the better. The conductivity of aluminum is 25 times higher than that of stainless steel, and the conductivity of glass is almost zero. Therefore, it is reasonable for glass to become the mainstream material for flagship phones.

Glass, the best solution for current function and beauty

After using metal materials for 5 years, Apple finally replaced it with glass in the iPhone 8 era, and added the wireless charging function this year. It can be seen that the advancement of functions is also forcing design changes to a certain extent.

But when it comes to the design of the front and rear glass, iPhone 4/4S must have a name. The double-sided tempered glass and the metal middle frame make it stand out from the crowd of plastic machines. But the problem is also coming. The glass is too delicate and accidentally dropped to the ground, which may surprise you (scare).

However, with the advancement of glass technology, toughness and scratch resistance have been improved, and glass has begun to show its talents on high-end machines with its high-end and crystal texture.

For example, the back shell of the hammer T1 is a piece of carefully polished 3D curved glass. Anyone who sees it can't help but be surprised. It also became the only domestic mobile phone that won the "iF Design Gold Award" in 2015.

However, the use of glossy tempered glass as the backplane seems a bit monotonous and mediocre. So in recent years, around the glass material, manufacturers have begun to explore new processing technology.

One of the weather vanes is the "AG effect". AG glass (Anti-GlareGlass) is treated by a special chemical process, so that the reflective surface of the original glass becomes a matte diffuse reflective surface, which looks like a frosted effect, and also has a certain scratch resistance and anti-stick fingerprint effect. Promote.

On this track, the iPhone 11 Pro series is not the first, OnePlus is. The OnePlus 6T "Electric Violet" color released in 2018, through the AG etching process to create a full of gradual look and feel.

In subsequent product lines, OnePlus has been upgrading the AG glass process. In the era of OnePlus 8, OnePlus used the fifth generation of AG technology, and its haze was upgraded from 20%-30% of the first generation to 64%-82%. Liu Zuohu said that this kind of feel is as addictive as a cat.

There are many mobile phones using AG technology. For example, the recently released X60 series, the shimmer and colorful version of the back cover, using "satin AG technology", feels as smooth as silk, with a wonderful look of water flowing under different angles of light.

In addition to AG, various coating processes are often mentioned by manufacturers. For example, Samsung Galaxy Note 10 has a special color scheme called "Monet Color", which is made by multi-layer nano-coating and adding a layer of prism PET material, and then processed by a similar semiconductor microcrystalline process to create a mirror effect The colorful colors.

▲ Picture from: biometricupdate

In the introduction of Meizu 17's official website, it uses "awe-inspiring next-generation machine-engraved electroplating process, which combines 23 layers of colors, fine texture, and high-quality texture, to create a miracle on 0.6mm glass. The feel is not metaphysics, but science."

The star diamond technology used in the OPPO Reno5 Pro series gives the glass back cover a "bling~bling~" look and feel. It feels a bit like sandpaper, and it looks like a galaxy is flowing.

However, in the high-end machine camp, glass seems to have been unable to meet the needs of flagships. Materials such as ceramics and plain leather have begun to show their ground.

Minor materials, unconventional choice

Huawei can be said to love ceramic materials. Starting from the P7 ceramic version, to the P40 super cup and Mate40 RS version released in 2020, the ceramic back shell has repeatedly appeared and has become a symbol of its flagship product.

In August 2018, the release of Mi MIX2S emerald color ushered in the era of colored ceramics for smartphones. The ceramic back case is no longer "black or white". Then the Mi MIX3 was released with a new sapphire blue color scheme. Xiaomi's efforts in ceramic processing technology should be among the best.

▲ Xiaomi MIX3

On Zhihu, someone once commented on the ceramic back case like this: "If there is no gravity, ceramics feel better than glass." Even though the ceramic has a bright and strong texture and good heat dissipation capacity, it is still slightly thicker than glass. In addition, the current processing difficulty of ceramics is still higher than that of glass, and the yield rate is low. Therefore, it is difficult to popularize in the high-end machine camp in a short period of time. It can only be used as a configuration for some flagship machines to show their personality.

Another trend in the past two years is "sugar skin". For example, Huawei Mate30, Mate40 series, OPPO Find X2, iQOO 5 and other products are all available in plain leather version.

▲ OPPO Find X2 plain leather version

The plain leather version is actually a kind of artificial leather, covering various coatings on the fabric base to achieve a waterproof effect. Compared with the glass material, the plain leather is less affected by the ambient temperature, and it won't feel cold in winter, and it won't be stained with fingerprints. But its shortcomings are also very obvious, such as low thermal conductivity, poor heat dissipation of the fuselage, easy to wear and so on. The overall quality is not as good as glass.

In addition to ceramics and plain leather, some manufacturers use more niche materials to create the back shell. For example, the German company Carbon Mobile tried to build a mobile phone with mixed carbon fiber composite materials, priced at 799 Euros.

▲Picture from: Android authority

Motorola has launched the Moto X bamboo wood version, and Xiaomi and OnePlus have also used this material, but the market response has been mediocre. NuAns NEO, a niche Japanese manufacturer, is obsessed with pure natural materials and has launched a large number of mobile phones made of special materials.

▲ Moto X Style

On the whole, glass is still the mainstream choice for high-end phones in the future. However, the craftsmanship surrounding the glass will continue to be updated. For example, OPPO's electrochromic technology used on the Reno5 Pro+ Artist Limited Edition allows the color of the glass back shell to be switched freely, which is full of futuristic sense.

"No matter how the back of the phone changes, you can't see it with the protective cover." Seeing this, some friends might think so. But in fact, if you occasionally remove the protective cover, you can get a moment of pleasing from the back of the phone, which is the charm of the material and design.

Tell simple and easy-to-read stories. Work email: wanghelong@ifanr.com.

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