The reliability of small spacing display screen has always been the pain point of LED display technology. RGB devices have congenital defects based on their own structural dimensions. The metal electrochemical migration caused by the application of small spacing and high refresh rate of products is the main reason for the necrosis of lamp beads, and it is also the technical difficulty that the whole industry needs to overcome. For this reason, the display manufacturers try to coating the finished LED module and glue coated LED module (gob) to prevent the metal electrochemical migration caused by moisture in the small spacing LED display module. The protection treatment of the finished product end solves the protection problem, but at the same time, it also brings about such problems as the coating containing the peeling layer, the poor matte effect of the coating surface, which affects the display effect, the gob maintenance problem, the module consistency problem and so on, which affects the application of small spacing LED display screen.
Zhaochi optical element display product pioneers nano coating process to isolate moisture and improve the protection ability of LED lamp beads Jiangxi zhaochi Guangyuan Technology Co., Ltd. (formerly Shenzhen zhaochi Energy Saving Lighting Co., Ltd., hereinafter referred to as zhaochi Guangyuan) is a wholly-owned subsidiary of zhaochi group (Stock Code: 002429), mainly engaged in research and development, production and sales of lighting LED, backlight LED and display LED. LED display is a newly developed business segment of zhaochi Guangyuan. It decomposes the performance requirements of each product into comprehensive and refined indexes. Each performance difference is analyzed and demonstrated in detail on the basis of theory and practical verification. It is the quality concept firmly practiced by zhaochi Guangyuan display business department to achieve product leadership and quality leadership through the practice of single product performance optimization , we have made great efforts to solve the problem of electrochemical migration of small spacing metal. Next, we will introduce in detail how to deal with the problem of electrochemical migration of small spacing metal products.
Electrochemical migration mechanism of metals
Metal electrochemical migration is a physical migration phenomenon, which mainly occurs between the pad separator and chip electrode of the product with small spacing. Water vapor, electric field, metal ion and interface (GAP) are the four essential factors for metal electrochemical migration. Under the action of electricity and water vapor, the active metal ionizes to produce metal ions, and under the action of electric field force, the metal ions move directionally.
The water vapor comes from the application environment of small spacing LED display, and the electric field comes from the design of driving circuit of small spacing LED display. High refresh rate and back pressure will accelerate the metal electrochemical migration rate. The active metal ions that move in orientation come from the electrode material composition of LED chip and the metal composition of substrate metal pad, and the interface (GAP) of medium bonding is the interface of different materials of small spacing LED package.
Metal electrochemical migration on substrate
The silver on the LED substrate and the Cr in the LED chip electrode are all active metals. Under the premise of meeting the elements of electrochemical migration, the electrochemical migration is very easy to occur, resulting in the short circuit and leakage between the pads of the substrate and the chip electrode, resulting in the "Caterpillar" phenomenon. In serious cases, the CR at the bottom of the LED chip electrode is hollowed out, resulting in the die lamp of the chip electrode.
Metal electrochemical migration on chip
Therefore, the electrochemical migration of small spacing metal involves the raw material technology of LED lamp bead packaging, LED lamp bead packaging technology, small spacing LED display technology, and the application of small spacing LED display, which is the result of multiple factors and needs the joint efforts of the industry.
Nano coating technology of tera cell
Based on the mechanism of metal electrochemistry, zhaochi optical element and LED packaging raw material supplier jointly developed nano coating materials for LED display products. After the LED products completed the welding process, nano coating with waterproof, moisture-proof and excellent combination performance with LED substrate and colloid was applied to prevent water vapor from contacting the chip and substrate surface without affecting colloid and nano coating The combination of coating and substrate ensures the reliability of LED products. According to the metadata sharing of zhaochi light, the LED lamp beads with nano coating protection technology have no difference in photoelectric parameters and high and low temperature impact resistance from the conventional LED lamp beads, and the moisture-proof performance is significantly better than the mainstream small spacing products on the market.
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In addition to working hard on the electrochemical migration of metals at the R & D end, at the manufacturing end, since entering the field of small spacing device packaging at the beginning of 2019, the zhaochi optical element display team has been committed to establishing a control system suitable for display device packaging, and establishing independent display device control standards and specifications from incoming inspection, process technology, process quality control, etc. by the end of 2019, The manufacturing system for display devices has been established from six dimensions of human, machine, material, method, ring and measurement. Especially for the electrochemical migration of metals, MES information management system is adopted to carry out information and fine operation of production and manufacturing, to ensure the best combination of substrate, nano coating and packaging adhesive in the product packaging process, and to improve the air tightness of products.
As an enterprise that always practices quality first, zhaochi Guangyuan hopes to promote the healthy development of small spacing display field by strengthening its core competitiveness. Today, with the establishment of the display business division, zhaochi Guangyuan has accelerated the development of RGB products. According to Liu chuanbiao, general manager of zhaochi Guangyuan display business division, the 3000kk equipment invested in Nanchang automatic display factory built by zhaochi Guangyuan according to industry 4.0 has all entered the factory, and all the production processes have been completed. At present, it has been put into production in small batch. With the gradual release of production capacity, zhaochi optical elements will bring more and better product choices to the display field.
Source: Tera cell