Is Mini/Micro LED good?
Good! With excellent performance in contrast, resolution, brightness, viewing angle, color performance, life span, etc., Mini/Micro LED has become a strong competitor for future display technology. High-end display products such as TVs, tablet computers, smart watches, and smart speakers based on Mini/Micro LED technology have sprung up. It is estimated that the output value of Mini/Micro LEDs is expected to reach US$5.1 billion by 2025. But it is not good-too expensive, ordinary consumers say it is really "not to be able to afford"! Mini/Micro LED has high requirements on materials and craftsmanship, which makes it difficult for consumers to experience this technology in the short term. Charm. From the perspective of the industrial chain, with the shrinking of the size of LED chips, the efficiency and yield of the packaging process have become key factors affecting the quality and cost of end products, and their role in the industrial chain has become increasingly significant. How can the efficiency and yield of packaging be improved? We know that a major challenge in the production of Mini/Micro LEDs lies in packaging the components on circuit substrates, such as printed circuit boards, glass substrates or flexible substrates. However, due to the small size of Mini/Micro LEDs, the pads must be smaller to achieve this process. This also means that a solution that can apply solder paste stably and effectively is of great benefit to the cost reduction and efficiency increase of Mini/Micro LEDs. As a material and matching material solution expert in the field of electronic packaging applications, the Welco solder paste we saw at the SEMICON China 2021 site is a good solution. At the exhibition site, LEDinside had the honor to interview Zhang Hanwen, the global product manager of Heraeus Electronics' advanced packaging and soldering materials, to have an in-depth communication on Heraeus Electronics' cutting-edge products and future plans in Mini/Micro LED.
Mini/Micro LED chip soldering high-quality solution: T7 solder paste
For the Mini/Micro LED field, Heraeus Electronics will mainly bring two new products at the SEMICON China 2021 site: Welco AP519 No. 6 powder solder paste and Welco LED100 No. 7 powder solder paste.
Welco AP519 No. 6 powder solder paste
"From the perspective of tin powder particle size, LED100 belongs to T7 (2-11μm) solder paste, and AP519 belongs to T6 (5-15μm). Zhang Hanwen introduced that LED100 is mainly for the soldering of Mini LED flip chip; AP519 is suitable for low temperature reflow applications of Mini LED and advanced semiconductor packaging.
LED100 has a lower solder powder particle size, smaller stencil openings, and stronger stability. It is the highest-level solution for Mini/Micro LED chip welding in Heraeus Electronics' current product series.
It is understood that, as a technologically advanced no-clean printed solder paste, Welco LED100 T7 has excellent demolding performance on 70μm stencil openings. It is specially designed by Heraeus Electronics for Mini LED chip bonding. It is suitable for Mini LED backlight and display screens of TV screens, monitors, tablets, video walls and other devices. In addition, Welco LED100 T7 also has excellent stability, which can help Mini LED companies improve yield and reduce production costs. Zhang Hanwen explained, “The size of Mini/Micro LED is very small, and the pads are also small. If the solder powder particle size of the solder paste product is too large, it will not be able to print normally through the ultra-small stencil openings, so the soldering must be improved. Yield rate and accuracy must be guaranteed even when the stencil opening is 70μm or less, the amount of tin drop is still stable. Heraeus Electronics' solder paste products use a printing method. In order to meet the needs of customers' production lines, We need to ensure that the performance of the solder paste remains stable even after continuous printing for more than 8-10 hours.” He said that after testing, T7 performed well in terms of void rate and stability, and there was little solder bead residue. Effectively help Mini LED companies improve product yield.
When it comes to product development, Zhang Hanwen is very emotional. It is reported that the smaller the particle size of tin powder, the easier it is to oxidize; once oxidized, the properties of the solder paste will be weakened, and more tin beads will be left during reflow, and the void ratio will also increase. Therefore, Zhang Hanwen believes that the biggest challenge in the development of LED100 is to find a suitable flux to ensure that the solder paste has excellent stability even with such a small tin powder particle size. "We also spent a lot of time and energy in the design of flux to overcome various challenges. We develop a mature product and market it to the market for at least 2 years." At present, Welco LED100 has successfully passed a company. Leading LED display supplier certification, and Welco AP519 has passed the advanced qualification certification of mainstream OSAT and LED display manufacturers.
Welco patented technology: the "secret" behind T7
Heraeus started as a small pharmacy in 1660, and has now grown into a family business with diversified products and businesses. Over the years, Heraeus has accumulated rich experience in the field of materials. In the LED field, Heraeus has more than 20 years of experience and technology accumulation, and can calmly face the challenges brought by different packaging paths of LED chips, providing Mini/Micro LED companies with one-stop system materials and solutions. Behind the brilliant achievements, Welco's patented technology is indispensable. Solder powder has a crucial influence on the performance of solder paste. Zhang Hanwen explained that the quality of solder powder is mainly reflected in: the stability of the amount of tin drop in the continuous and long-term printing operation; the splash, tin bead residue, void rate, bridging, tombstones, etc. during the reflow process Outstanding performance in terms of. The original Welco patented technology of Heraeus Electronics is different from the traditional solder powder production technology. It disperses the molten alloy in a special liquid medium and forms a very regular spherical shape based on the principle of surface tension of different media. The solder powder is directly adjusted through the process parameters. The size of the powder does not need to be screened, and the oxidation rate of the solder powder can be minimized in the production environment, so a purer, more concentrated powder can be obtained, and the particle size distribution is extremely narrow, and the surface is smooth.
The particle size distribution of Welco tin powder is very concentrated, which is better than the requirements of IPC technical standards, which helps customers to achieve smaller spacing. "The IPC technical standard requires more than 80%, and the products we make can basically achieve 85% or even more than 90%, and the surface of the solder powder is very smooth." Zhang Hanwen proudly said. In response to the industry's pursuit of fine pitch, Heraeus Electronics is also constantly developing next-generation products. "In the next year or two, solder paste products with smaller solder powder particle size will be released, such as No. 8 (2-8μm) and No. 9 powder (1-4μm)." Zhang Hanwen said. It is understood that currently, AP519 and LED100 are mainly developed and produced in factories in Singapore. As the Chinese Mini/Micro LED market matures and the demand for solder paste increases, they plan to produce these two products in China in the future in order to provide customers with better services.
