What is LED flip chip? In recent years, flip chip technology is emerging in the chip field, especially in the high-power, outdoor lighting application market. However, due to the late development, many people do not know what is called LED flip chip, what are the advantages of LED flip chip? Today, HC LED screen editor will give you a simple explanation. First of all, from the LED dressing chip to explain the LED flip chip, and the advantages and popularization of LED flip chip.
To understand the LED flip chip, first understand what is the LED dressing chip
LED positive-loading chips are the earliest chip structures and are commonly used in low-power chips. In this structure, the electrodes are on top, and the materials from top to bottom are: P-GaN, light-emitting layer, N-GaN, substrate. Therefore, it is a formal dress compared to flip-chip.
LED flip chip and symptom chip diagram
In order to avoid the LEDs occupying the light-emitting area in the chip, which affects the luminous efficiency, the chip developer designed the flip-chip structure, that is, inverting the chip, so that the light excited by the light-emitting layer is directly emitted from the other side of the electrode (the substrate is finally stripped). The chip material is transparent. At the same time, the structure of the LED package factory wire bond is designed for the flip chip. Therefore, the whole chip is called a flip chip, and the structure is widely used in high power chips.
Three major genres of formal, flip-chip, vertical LED chip structure
Flip-chip technology is not a new technology, but it existed long ago. Flip-chip technology is not only used in the LED industry, but also in other semiconductor industries. At present, LED chip packaging technology has formed several genres, and different technologies have different unique applications.
At present, there are three main types of LED chip structures, the most common ones are formal structures, vertical structures and flip-chip structures. The positive-fit structure is prone to current crowding due to the p and n electrodes on the same side of the LED, and the thermal resistance is high, while the vertical structure can solve these two problems well, and can achieve high current density and uniformity. In addition to the material cost, the reduction of the cost of the future lamps is particularly important in reducing the number of LEDs. The vertical structure can well meet such requirements. This also results in vertical structures typically used in high power LED applications, while formal technology is typically used in small and medium power LEDs. Flip-chip technology can also be subdivided into two categories, one is flip-chip based on sapphire chip, the sapphire substrate is reserved for heat dissipation, but the current density is not obvious; the other is flip-chip structure and stripped lining. The bottom material can greatly increase the current density.
LED flip chip advantages
First, there is no heat dissipation through sapphire, which can be used with large current; second, the size can be made smaller, the optical is easier to match; third, the heat dissipation function is improved, the life of the chip is improved; and the fourth is the improvement of antistatic capability; The fifth is to lay the foundation for the subsequent development of packaging technology.
What is LED flip chip
It is understood that flip chip is called "flip-chip" compared to the traditional wire bonding method (Wire Bonding) and post-balling process. Conventionally, the electronic surface of the wafer connected to the substrate by metal wire bonding faces upward, and the electrical surface of the flip chip is turned downward, which is equivalent to turning the former over, so it is called "flip chip".
The LED chip is flip-chip mounted, and a GaN-based LED structure layer is grown on the sapphire substrate by MOCVD technology, and light emitted from the P/N junction light-emitting region is emitted through the upper P-type region. Due to the poor conductivity of P-type GaN, in order to obtain good current expansion, a metal electrode layer composed of Ni-A is formed on the surface of the P region by evaporation. The lead of the P region is taken up through the metal film of the layer. To achieve good current spreading, the Ni-Au metal electrode layer should not be too thin. For this reason, the luminous efficiency of the device is greatly affected, and it is usually necessary to take into account both the current expansion and the light extraction efficiency. However, in any case, the presence of the metal film always deteriorates the light transmission performance. In addition, the presence of wire bond pads also affects the light extraction efficiency of the device. The structure using GaN LED flip chip can fundamentally eliminate the above problem.
Based on the technology of flip chip, some manufacturers have developed LED flip chip gold-free chip scale packaging.
What is LED flip-chip gold-free chip scale package
Flip-chip gold-free chip-level package, based on flip-chip soldering technology, on the basis of traditional LED chip packaging, reduce the gold wire packaging process, save the lead frame, wire, leaving only the chip with phosphor and package adhesive . As a new packaging technology product, the flip-chip gold-free chip-level light source has no problems such as non-brightness, flicker, and high light decay caused by gold wire soldering or poor contact. Compared with the traditional packaging process, the package density of the chip-scale light source has increased by 16 times, the package size has been reduced by 80%, and the luminaire design space is larger. The flip-chip gold-free chip is favored by more and more LED lighting companies and terminal product application companies with more stable performance, better heat dissipation, more uniform light color distribution and smaller volume.
Difficulties in the popularity of LED flip chip:
1. Flip-chip LED technology currently has greater advantages in high-power products and integrated packaging. In small and medium-power applications, cost competitiveness is not very strong.
2, flip-chip LED subverts the traditional LED process, from chip to package, this will require higher equipment, take the package to say, the cost of the front-end equipment that can do flip-chip will certainly increase a lot, this is set The threshold is that some companies simply cannot access this technology.
LED flip chip manufacturers recommend:
As the only leading manufacturer of high-power LED integrated chips for Flip-chip technology in China, Jingke Electronics has launched a "chip-level LED lighting overall solution" this year, which can be used in LED chip manufacturing process. In the new wafer-level process, a part of the traditional packaging process is completed or the traditional packaging process is saved, so that the final package size of the LED is reduced and the performance is more stable. Its "Easy Series" and ceramic-based COB products are all based on the APT patented technology-Flip-chip soldering technology, which realizes the gold-free and solid-free plastic package of single-chip and multi-chip modules, with high brightness and high light efficiency. High reliability, low thermal resistance, good color consistency and many other advantages.
Dehao Runda "Aurora Borealis" 1A LED lighting high drive current flip chip, the chip can achieve 310 lumens under 1A current drive, 255 lumens LED chip driven by 700ma current, in addition to single point of high luminous flux, Suitable for light distribution design, interpretation of lighting art; comfortable light color quality, professional design for high quality lighting environment; also customer satisfaction with light efficiency and cost performance; industry leading thermal performance; reflow soldering process (IPC/JEDEC J- STD-020C); moisture sensitivity level 1; antistatic voltage 8000V (human body mode). Flip chip can be widely used in liquid crystal backlights, high-power LED lighting products, such as street lights, car lights and so on.
As one of the domestic LED chip manufacturers, Huacan Optoelectronics has accumulated considerable experience in the research and development of white LEDs and formed independent intellectual property rights. It has conducted in-depth and meticulous research on the process of flip-chip LEDs. Continuously improve the epitaxial and chip process technology, the current flip chip 45mil product test brightness is @1A, 100lm / W, reaching the domestic leading level. The professional R&D team of Huacan Optoelectronics is committed to the research and development of flip-chip LED chips. It has been successfully developed and will eventually realize the industrialization of flip-chip LED chip products.
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