For a long time, aluminum alloy has always been the protagonist of the middle frame material of mobile phones because of its advantages of light weight, low price, and easy processing.
With the development of mobile phones in the direction of full-screen and ultra-thin, to maintain the strength of the body and support the large screen, a higher-strength metal middle frame is required. High-strength aluminum alloy, stainless steel and liquid metal are all good candidates. .
The reason for the diversification of middle frame materials is that the materials themselves have their own advantages but all have shortcomings that are difficult to break through.
Compared with the three material characteristics of aluminum alloy middle frame, stainless steel middle frame and liquid metal middle frame, which side do you stand on?
| Aluminum 7075-T6 | Stainless Steel sus304 | Liquid Metal EON1 | |
| Bending strength/MPa | 570 | 590 | 2200 |
| Yield strength/MPa | 500 | 240 | / |
| Vickers Hardness/HV | 150 | 200 | 500 |
| Density g/cm3 | 2.82 | 7.85 | 6.72 |
| Processing difficulty | Easy | Disaster | Easy |
| Process maturity | Mature | immature | / |
| Yield | 80% | 30-40% | Approaching "Net Shape" |
| Appearance | Varied | less | Diverse in theory |
| Pprice/RMB | 100-200 | 200-300 | 120-150 |
| Application Model Representative | iPhone5, iPhone6, OPPO R15 | iPhone4，iPhoneX， Xiaomi 6, Hammer M1L | Turing phone |
NO.1 Physical properties of materials
Aluminum alloy
The aluminum alloy material is very light, and its specific gravity is only one-third of that of stainless steel;
Low strength, it is easy to cause the mobile phone to be bent or bent;
Since the "bending door" incident of the iPhone 6, the iPhone 6S has adopted a 7-series aviation aluminum alloy with a strength of 700 MPa, but this series of alloys has poor corrosion resistance and is prone to stress corrosion.
Moreover, the hardness of the aluminum alloy is only about 150. The relatively soft performance will cause bump marks on the aluminum alloy middle frame, which will affect the appearance.
Stainless steel
The most common 304 stainless steel has a strength of 520 MPa. The strength of common stainless steel is between 1300 and 1400 MPa. The Vickers hardness of stainless steel is about 200. The relatively high strength and hardness can meet the support of large-screen double-sided glass. iPhoneX The middle frame design also returns to stainless steel.
However, the heat dissipation performance of stainless steel is poor, and its thermal conductivity is only 14 /W·(m·k) (14 /W·(m·k) for stainless steel VS 204/W·(m·k) for aluminum alloy). It will lead to accelerated aging of electronic components; and the larger specific gravity will increase the weight of the whole machine.
Liquid metal
The strength of liquid metal is 2 to 3 times that of traditional high-strength steel and 10 times that of magnesium-aluminum alloy. In addition, it has high hardness, high wear resistance, corrosion resistance, good heat dissipation, and is light and thin. box, Liquidmetal has significant advantages.
NO.2 Processing technology
Aluminum alloy
Due to the characteristics of the material itself, aluminum alloy can be combined with forging + a small amount of CNC, stamping + a small amount of CNC, etc., which can greatly reduce material costs and CNC processing time;
Aluminum alloy materials have strong dyeability and mature anodizing process, making it easier to process high-grade, beautiful and diverse appearance effects.
Stainless steel
Stainless steel has high hardness and poor CNC machining performance. Compared with aluminum alloy, the processing time and tool wear are doubled.
From a whole piece of stainless steel to the one-piece stainless steel middle frame, nearly 30 kinds of knives and hundreds of steps that require extremely high craftsmanship have to be experienced during this period. Complicated processes lead to low yield and low production efficiency.
In addition, the stainless steel middle frame is generally colored by PVD process. The mainstream design is to polish and then make a highlight effect through PVD. Compared with aluminum alloy, its color types are relatively simple.
Liquid metal
Liquid metal can be shaped like plastic through injection molding, die-casting and other processes. It is light, thin and compact, and can be molded at one time. It is close to "net shape" in technology and saves a lot of post-processing.
Liquid metal can theoretically make a variety of colors, but there are still few attempts. At present, the main coloring method is PVD coloring, and the color is relatively single. Anodizing is also possible in theory, but there is no actual mass production case.
NO.3 Cost and Manufacturability
Aluminum alloy
The aluminum alloy middle frame is still the most widely used metal middle frame at present. It has the characteristics of light weight, low production cost, mature technology, gorgeous color and good texture, and has already achieved mass production.
Stainless steel
Due to the high hardness of stainless steel, CNC processing is difficult, resulting in high cost, long time-consuming, and relatively low processing yield. Currently, it has not been popularized by mainstream manufacturers.
In addition to Apple, among the mainstream manufacturers, Xiaomi used stainless steel in MI4 and MI6, but gave up stainless steel in MI8 and switched to 7-series aluminum alloy. In order to achieve mass production of stainless steel middle frames, it is urgent to solve the problems of production technology and cost.
Liquid metal
Although liquid metal has many advantages, and the cost is lower than that of stainless steel, at present, no second manufacturer has really adopted it except for the Turing mobile phone;
Because the technical barriers of liquid metal are very high, the requirements for the equipment used are also high, and there are relatively few production companies, the production capacity is too low, and a complete industrial chain has not yet been formed. Therefore, there is still a long way to go before mass production of liquid metal way to go.
Comprehensive summary
To sum up, with the advancement of technology and changes in market demand, the mobile phone industry will continue to explore new materials and processing technologies to meet consumers' expectations for higher-quality and more stylish mobile phones. Therefore, stainless steel and liquid metals have emerged as potential candidate materials.
Stainless steel has high strength and hardness, which can meet the needs of large-screen double-sided glass design, but its heat dissipation performance, weight and processing cost become considerations.
Liquid metal has super strength, hardness, wear resistance and heat dissipation, and has the advantages of being light, thin, and one-time molding, but technical barriers and imperfect industrial chains limit its mass production and application.
In the selection of mobile phone middle frame materials, aluminum alloy is still the most widely used material at present. It is light in weight, low in cost, and mature in processing technology, and has achieved large-scale mass production.
As an enterprise focusing on the aluminum industry, CHALCO is mainly engaged in the production of aluminum strips, providing a rich selection of aluminum alloy materials for the mobile phone industry. Through continuous innovation and improvement of processing technology, the mobile phone industry can further improve the strength and aesthetics of the aluminum alloy middle frame. As an important aluminum supplier for 3C digital products, CHALCO will continue to give full play to its advantages in the field of aluminum sheets, provide diversified aluminum alloy materials for the mobile phone industry, and help the development and innovation of the mobile phone industry.