A friend who recently wanted to change his mobile phone has a discovery: In the mid- to low-end price mobile phones of 1000-2000, all the major brands have a lot of cool back cover mobile phones, or grating lines, or diamond texture, with a glass of Throughout the texture, if you don’t hold it in your hands, you definitely think that this is a mobile phone with a glass back cover, but in fact it is a plastic material. The process of this plastic phone back cover is the fancy glass cover process that we are discussing today.
Figure imitation glass plastic cover three processes
First, why imitation glass cover phone so hot?
1.5G and wireless charging environment + cost control, choose plastic material
In the mobile phone cover field, in order to cope with the arrival of 5G and meet the wireless charging function, the non-metallization of the back cover of mobile phones is the inevitable result. Among the three non-metallic materials, glass, ceramics and plastics, the plastic texture is the worst, but the cost is the lowest; while the ceramics have a low yield rate and are expensive, and only a few high-end models are used; the glass is of moderate price and has excellent texture. Brand flagship's preferred material.
In order to seize the low-end market in mobile phones and into emerging markets such as India, high quality and low price are key factors. The advantages of low-cost plastics are evident here.
Figure material phone back cover cost price
2. The increase in the value of plastic and the trend of imitating glass back cover brought by iPhone X
With the progress of process technology, the surface of the plastic cover plate can make a variety of effects to enhance its potential value, but now the mainstream process effect is still three kinds of imitation glass, imitation ceramics, imitation metal. With the glass back cover brought by the iPhone X, the plastic-imitation glass process is the hottest one.
Figure iPhone X physical map from the network
Finally, the plastic material, which has been recognized as a low-grade product for a long time, ushered in the second spring with the rise of imitation glass technology.
Second, the process of imitation glass plastic cover What?
There are three types of plastic glass cover plastic technology: PC/PMMA composite sheet, IMT injection molding, transparent PC injection back spray. The following small series gives you a brief introduction to these three processes.
1. PC/PMMA Composite Board Process
PC/PMMA composite sheet refers to a composite sheet obtained by co-extrusion of PMMA and PC, including a PMMA layer and a PC layer. The composite sheet combines the advantages of the above two sheets, the surface hardness of which can reach the surface hardness after being hardened by acrylic, and also has the toughness of the PC sheet and can withstand the impact of greater strength.
Figure PC/PMMA composite plate phone back cover processing process (3D)
The difference between the manufacturing process of the composite plate 2.5D cover plate and the 3D cover plate processing is that the 2.5D glass requires only hot pressing, the equipment cost is low, the price is naturally cheaper, and the price is more advantageous.
Figure 2.5D Composite Plate Cell Phones: OPPO A3 and Realme 1 (Indian Market)
However, the 2.5D composite sheet also has a fatal flaw: due to the molding process and other reasons, the edge of the sheet is prone to cracks, and the touch appearance is not sufficiently exquisite. 2.5D composite board has been used for many years, and because of the above defects, it is suitable for lower-end mobile phones with a price of about 1,000 yuan. In the mobile phone with a price of 1,500 yuan, the 3D composite board technology has more texture advantages.
Figure vivo Z1 picture comes from the network
2. IMT In-mold Injection Molding Process
IMT (IN Mold Transfer, also known as Insert Mold Three-dimensional) process can be understood as IMR process 3D molding IML injection molding and then tear off the carrier layer PET, leaving a 3D optical nano-decorative layer on the plastic surface, and Traditional IMR comparisons have increased 3D optical texture and PVD color film layers with greater curvature.
Figure IMT technology mobile phone: OPPO A7 ice flame blue and Huawei enjoy 8 blue version comes from the network
The IMT process flow is as follows:
Substrate (PET, PC, TPU) → UV transfer (Lines can be diversified) → Screen printing release agent (for substrate and plastic peeling) → Screen printing LOGO → Optical plating (Can be a variety of colors, such as Samsung S8 Gold Silver Blue Black Violet) → Screen printing background color (one or two black, or other colors) → Screen printing varnish (mainly to prevent red ink, one or more channels) → Printing adhesive (in order to combine with plastic) → Tablet Hot bending forming → sheet trimming trimming → peeling the film (some with two films) → sheet and plastic injection → uncovered part of the film vacuum coating (middle frame) → stripping the IMT part of the sheet, spray UV → CNC machining
The advantage of the IMT process is that it can do a lot of assembly structures through injection molding, reducing the processing complexity of the metal middle frame, but on the other hand, the disadvantages are also very prominent: the process flow is too long, each process has yield loss, and the through rate is not high. It is rumored that the overall yield of the IMT process is currently less than 50%. Low yield leads to higher costs, and more importantly, the overall delivery cycle of mobile phones will be much longer.
Figure IMT's IMT-like gradient plastic phone back cover, there is a buckle structure
3. Transparent PC injection back spray
Transparent PC mirror injection back spray is also a process that can achieve the effect of imitation glass, its essence is injection molding, in the case of a smaller wall thickness can also choose injection compression molding technology, do 3D back cover than 3D composite sheet technology The yield rate is high. In the case that 3D composite sheet or IMT process can not meet the mass production, transparent PC mirror injection back spray is a good alternative solution.
to sum up:
In the three kinds of glass back cover technology, IMT is a new process, although the yield is not enough, but the texture and other effects are better, can do the edge, can do with a complex assembly structure of the back cover, save the overall structure of the phone Cost of production. As the technology continues to mature, IMT injection molding process will inevitably be the first choice.
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