A metal mobile phone has to be "tempered" from production to listing, and the metal mobile phone used is the best among many products. It is precisely because manufacturers know this process very well that they will spend relatively more words or expenses on a mobile phone.
If the plastic shell is used, mass production can be realized only by opening the mold, and the yield can basically reach over 90%; The yield of shell with metal middle frame structure can reach 85-90%, but the yield of CNC products with large-area all-metal fuselage can reach 75%, which is already very high.
If the yield of 75% is still acceptable, then the secondary processing will make this data continue to decline. It is impossible to directly apply the metal shell to the metal process of mobile phones, and secondary processing must be carried out. The process of "secondary processing" includes surface treatment, such as polishing, wire drawing/sandblasting, anode and so on. By the time of secondary processing, the cost of all-metal CNC products is already high. If there are problems in these processes, such as a little scratch in wire drawing, it will take a lot of manpower and material resources to make up for it, and in many cases it can't be repaired, which has a great impact on the yield.
In addition, the reason why "secondary processing" will cause great yield loss is not only the problems in its own processing process, but also the influence of the previous CNC processing effect. All-metal NC products are made of a whole piece of metal through NC machining or forging and stamping, and the machining area is large, so it is easy to cause scratches during NC machining, and it is also difficult to avoid the appearance of impact lines, which lays the foundation for the subsequent secondary machining difficulties.