Wireless Charging
Wireless charging still has some issues, such as extremely slow charging speeds, pricey accessories, and the convenient charging not being worthy of the name. It should not only carry "giant" wireless charging accessories but also needs to find a plug. Despite the issues present, wireless charging is still in many ways a manifestation of progressive living conditions. For instance, the lack of various interfaces on mobile phones makes full-screen, waterproof, and dustproof designs more feasible; contact charging lessens device interface damage caused by connections; and there is no desktop clutter brought on by various long and short wires.
Due to high manufacturing costs, there are only a small number of wireless charging mobile phone models available. The zirconia back plate is not only attractive, but also scratch-resistant, wear-resistant, and corrosion-resistant, allowing it to meet the requirements of wireless charging.
Common Preparation Process of Zirconia Ceramic Mobile Phone Back Plate
Currently, the electromagnetic induction principle is typically used in wireless charging. The mobile phone is placed on the wireless charger for the purpose of charging by adhering a pre-made conductive coil to the back plate. But this process has the following flaws:
(1) Take up mobile phone space. Existing conductive coils use conductive metal wires, such as copper or aluminum wires, that are adhered to the battery back plate, which takes up space inside the phone.
(2) The heat dissipation effect is poor, and it is simple to emit heat. The back plate of the mobile phone has a conductive coil attached to it, which lowers overall thermal conductivity, affects the heat dissipation ability and performance stability of the mobile phones.
A New Preparation Process of Zirconia Ceramic Mobile Phone Back Plate
As depicted in the figure below, this process can be used to manufacture an integrated product consisting of a wireless charging coil and a zirconia ceramic back plate. Dry pressing or tape casting are two methods for preparing the zirconia body.
The following is the process flow block diagram:
(a picture)
Taking tape casting as an example, the following is the specific production process:
(1)Prepare the Ceramic Body;
Use zirconium balls as the grinding medium, methyl ethyl ketone as the solvent, and 10 kg of zirconia powder and 2-3 kg of glass powder (the glass powder can be made up of SiO2, Al2O3, B2O3, Na2CO3, and CaCO3). Among them, the mass percentage ratio of material, ball, and solvent is 1: (1.5-2): (0.5-0.8); the mixture is ball milled for 20-22 hours. Polyvinyl butyral (PVB) is added as binder; dimethyl phthalate as plasticizer, glyceryl oleic acid as dispersant. They are ball milled for 2-3 hours. Following vacuum defoaming and filtration, it is tape-cast to form a diaphragm with a thickness of 0.5-0.6mm, that is, a ceramic green body.
(2)Prepare Conductive Paste;
Take 8–15g of gold powder, 40–60g of nickel powder, 20–30g of tungsten powder, and 8–15g of borosilicate glass powder, add organic solvents such as terpineol and methyl cellulose, which account for 15-30% of the weight of the solid powder, and sand grind for 20-22 hours in a nano sand mill. To create conductive paste, the aforementioned raw materials should be combined uniformly.
(3)Screen Printing;
The conductive paste is screen printed with a thickness of 15-20 um onto the ceramic green body. After printing, it is put in a drying oven to dry for 20–30 minutes at a temperature of 100–120°C.
(4)Lamination and Isostatic Pressing;
After the drying is finished, the same ceramic body as in step (1) is punched with the wiring position reserved, aligned with the conductive coil's contact point, then covered on the surface of the ceramic body with the conductive paste. The two will be compressed by isostatic pressing, and in addition to taking on a flat shape, it can also take on a three-dimensional structure.
(5)Sintering;
A high-temperature reducing atmosphere furnace, such as a nitrogen or hydrogen sintering furnace, is used to sinter ceramics that have successfully completed the aforementioned steps. In order for the conductive paste to adhere to the zirconia ceramics and for the two ceramic green bodies to combine after sintering, the sintering temperature is between 1200°C and 1300°C.
(6)Post-Processing and Testing
To create a ceramic mobile phone back plate with wireless charging function, the sintered ceramic body is processed, ground, and polished. The finished wireless charging ceramic mobile phone back plate is then tested and examined for its charging efficiency on the test apparatus.
Conclusion
This process creates a wireless charging coil that is sandwiched between two ceramic sheets that have been laminated, and it also creates holes in the ceramic sheets for wiring. This structure conceals the charging ring within the ceramic, preventing the coil from being oxidized due to its contact with air and ensuring that the charging efficiency does not degrade, thereby maintaining the high charging efficiency of electronic products. In addition, the integrated design can save internal space, which helps the product's thinner and lighter design. The integration of the coil and back plate has no impact on the heat conduction design on the back of the mobile phone.