Small size, high sterilization efficiency, strong effect, green and environmental protection...Under the catalysis of epidemic prevention needs, UVC LED seems to have gained fame overnight. In fact, UVC LED has been in development for many years, but because of its immature technology and high cost, its market reputation has not been high. However, this year’s epidemic prevention business opportunities will undoubtedly drive the development of UVC LEDs at a faster-than-expected speed, which also means that it is time for UVC LEDs to display their talents. But if UVC LED is about to become popular, it is too early to say.
From the perspective of the packaging process, the selection of packaging materials and the improvement of processes are still difficult problems that restrict the large-scale commercialization of UVC LEDs, which specifically involve the anti-ultraviolet ability of the material, the photoelectric conversion efficiency of the product, the heat dissipation performance, and the air tightness. , And the purpose of solving these technical problems is to improve the light efficiency and service life of the product, thereby reducing costs.
As Hongli Bingyi R&D manager Ren Rongbin said: "The purpose of packaging is to emit more light and less heat. Semiconductor materials and chip packaging technology determine that the current luminous efficiency of UVC LED chips is less than 10%, and the packaging of UVC LED chips The structure basically determines the packaging process of UVC LED devices.” Ren Rongbin gave a professional speech on UVC LED packaging form, structure, process and water treatment applications at TrendForce's 2020 UVC LED Industry Seminar.
UVC LED packaging methods are diverse, all inorganic packaging technology stands out
Common UVC packaging forms include Lamp, Molding, TO, glass adhesive plane, glass adhesive ball head, glass ceramic metal CMH all-inorganic, COB, etc., which can be generally classified as organic packaging and semi-inorganic packaging (also called " Near-inorganic packaging") and all-inorganic packaging.
Taking the semi-inorganic package form of TO package as an example, in the choice of glass material, whether it is K9 glass or quartz glass, adhesive or solder, it is difficult to balance the relationship between light transmittance and UV aging resistance.
From a process point of view, it is difficult to ensure anti-aging performance and air tightness by using adhesive methods. Hongli Bingyi is considering and trying to simplify the package structure through redesign of the tube socket to achieve better results.
In fact, this type of semi-inorganic packaging form is currently the mainstream in the domestic market, with high cost performance and relatively mature technology, suitable for low-to-medium power products, such as 2mW and 4mW. For high-power products, the use of semi-inorganic packaging technology has problems such as lens drop and secondary reflow abnormality (solder paste) risks.
The all-inorganic package (SMD) form avoids the use of organic materials throughout the process. The product advantages include: good air tightness, high reliability, no need to worry about lens loss, aging of organic materials, etc.; in addition, the all-inorganic package has low thermal resistance and high bearing capacity Current density.
Hongli Bingyi independently researches and develops an all-inorganic UVC LED packaging process (CMH packaging technology) based on laser welding technology. It uses ceramic substrates, quartz glass, flux, glass cover and other materials to achieve the lens and substrate through laser welding technology. In combination, it greatly reduces the light decay problem caused by organic materials and the failure problem caused by damp and heat stress, and effectively improves the air tightness and reliability of UVC LED devices.
Three major difficulties in water purification applications, die-bonding technology and all-inorganic packaging technology, one by one
UVC LED photoelectric conversion efficiency is low, most of which is converted into heat, which directly affects the life of the chip. Currently, most products on the market use flip-chip structure and high thermal conductivity aluminum nitride ceramic substrates. The flip-chip structure puts forward high requirements on the die bonding process, and the die bonding process is closely related to thermal management, which has a great impact on the reliability of the entire product.
Taking water purification applications as an example, Ren Rongbin pointed out that UVC LEDs mainly face three technical difficulties in water purification applications: light extraction, heat extraction and LED protection.
The derivation of light is mainly to improve the heat dissipation performance, and to consider the issue of increasing the light transmittance in the selection of optical path materials.
The export of heat is related to the structural design, especially in the application of dynamic water sterilization modules. At present, the dynamic water sterilization module mostly uses high-power COB, and the choice of heat dissipation mode plays an important role in the export of heat.
The protection of LED is mainly to prevent water vapor intrusion. In this regard, Hongli Bingyi is exploring the possibility of direct contact with water.
Focusing on the various difficulties in water treatment applications, Hongli Bingyi considers various aspects such as die bonding process and material selection to provide corresponding solutions.
For example, Hongli Bingyi continuously improves the eutectic technology of UVC LED chips, and does a good job in the placement of UVC LED lamp beads, and controls the welding void rate during the welding process to within 5%. The lower the welding void rate, it means The better the heat dissipation effect, the longer the product life. It is said that the welding void rate of some large-size products on the market reaches 30%-40%.
Ren Rongbin introduced that Hongli Bingyi also made a lot of efforts in increasing the light output and protecting the LED. First, you can coat the surface of the quartz glass with an anti-reflection coating to increase its light transmittance; second, in terms of waterproofing, try to coat the surface of the bare chip, device or COB with a waterproof coating. Current studies have shown that when a waterproof film is coated on quartz glass, the light transmittance of the quartz glass before and after coating is basically unchanged, that is, the transmittance to the UVC band is basically maintained at the level of 90%-92%.
In terms of products, in the first half of this year, Hongli Bingyi launched 2525, 3535 and 6868 all-inorganic packaging products ranging from low power to high power. In 2021, Hongli Bingyi plans to add TO and COB modules, increase the power of a single lamp bead, and increase different light output angles.
With 7 years of professional experience, Hongli Bingyi UV LED packaging is going deeper and deeper
Founded in 2013, Honglibing developed the country's first all-inorganic packaged UV LED as early as 2014. On the road of UV LED packaging, Hongli Bingyi goes deeper and deeper. At present, in the field of all-inorganic packaging, the company has complete intellectual property rights from substrates, glass cover plates, laser sealing and welding processes, and laser sealing and welding equipment.
According to Ren Rongbin, Hongli Bingyi has applied for more than ten invention patents (9 authorized) for related core UV LED component packaging and application products. Among them, material-related patents accounted for 10%, packaging methods accounted for 35%, applications accounted for 25%, and equipment accounted for 30%.
For many years, Hongli Bingyi has actively participated in government projects related to UV LEDs. For example, together with the head office Hongli Zhihui, it participated in the 2015 Guangdong Province applied technology research and development special fund project-"All-inorganic high-reliability UV LED light source packaging technology and industrialization".
In terms of industry standards, Hongli Bingyi participated in the drafting of a number of industry standards on UV LED packaging and its application fields, including the Guangdong local standard-"Technical Requirements and Test Methods for UV Emitting Diodes", and the industry group standard-"GUV "Technical Specification for LED Sterilization and Disinfection Device"
It is worth noting that the industry group standard of "GUV LED Sterilization and Disinfection Device Technical Specifications" was released on September 24 and officially implemented on October 1.
With 7 years of professional packaging experience, Hongli Bingyi’s UV LED and VCSEL products are now widely used in the printing industry (exposure machine, offset printing machine, inkjet printer, etc.), coating industry, semiconductor equipment (lithography machine, exposure machine, etc.) ), recognition systems (face recognition, long-distance infrared monitoring and intelligent driving), air purification and other places. Among them, air purification uses all-inorganic UV LED packaging devices.
Nowadays, the development of UVC LED is at the right time. Hongli Bingyi will continue to base itself in the packaging field and deepen its layout on the road of exploring UVC LED packaging technology, continue to innovate, and contribute to the popularization of UVC LEDs.