Key features of packaging technology around LED light source components

With the increasing demand for component output in LED lighting applications, traditional LED packaging not only limits component specification, but also disadvantageous heat dissipation. Novel unpackaged LEDs have better heat dissipation conditions, while integrating epitaxial, die and package processes. Conveniently paired with secondary optics to design lighting fixtures...

LED light source applications will gradually shift to LED general lighting applications after the peak demand for LCD backlight applications. However, unlike the LCD backlight module design, the LCD backlight module does not need to consider the optical and lighting application conditions, and the luminous efficiency requirements of the unit module are the main requirements; however, in addition to the brightness requirements, the LED lighting application must additionally consider the optical type. , heat dissipation, whether it is conducive to secondary optical design, and the requirements of the design and configuration of the luminaire , in fact, the requirements for LED light source components are higher.

Early packaging technology limits multiple heat dissipation issues affecting high-brightness design development

Early LED light source components, packaging materials mainly used in the shell-type package, in the early use of high luminous efficiency blue LED is quite common, and in the smart phone, mobile phone products thin design needs, the use of surface adhesion (surface-mountdevices; SMD The demand for LED light sources is increasing, and the LED light source components designed with surface adhesion technology can accelerate the production processing efficiency by using tape and tape loading materials, increase processing efficiency through automated production, and bring LED packaging. The new application market of technology, coupled with the subsequent advancement of epitaxial structure and packaging technology, is mutually reinforcing, and the luminous efficiency of LED light source materials can gradually surpass the performance of traditional lamps.

In view of lighting application requirements, lighting fixtures have higher and higher requirements for luminous performance, and LED light sources are currently the key to the optical output performance. The luminous efficiency is mainly represented by epitaxial, die and packaging technology solutions. At present, the unit luminous efficiency of epitaxial has been approaching the limit, and the space for luminous efficiency to jump and grow is relatively limited. Continuously increasing the grain area and improving the packaging technology is a feasible solution that can greatly increase the luminous efficiency of a unit component. However, if the cost performance of components can be improved, the increase in die area will be less cost-optimized, but the choice of packaging technology will directly affect the cost of the terminal material components. That is to say, packaging technology will become the cost of LED lighting. .

Wafer-level package introduction LEDs are small in size and highly reliable

Chip Scale Package (CSP) is the most popular packaging technology solution in the LED industry in 2013. In fact, CSP is not a new technology in the semiconductor industry, but it is still a novel advanced technology in the application of LED light source components. The purpose of the traditional semiconductor wafer level packaging application is to reduce the final volume of the packaged components, while improving heat dissipation and improving the application reliability and stability of the wafer itself. The wafer level package of the LED light-emitting component is mainly defined as the package body is close to the LED chip or the package volume is not more than 20% of the wafer, and the wafer-level packaged LED itself must also be a functionally complete package component.

Wafer-level packaging is mainly to improve the continuous increase of logic chip pins, component heat dissipation performance and wafer miniaturization. Through the integration benefits of wafer-level packaging, the parasitic phenomenon of the components of the wafer can be reduced, and the component integration of the Level 2 package can be increased. The application level of the wafer level package in the LED light source device can also achieve a significant degree of benefit.

A typical wafer-level package does not require an additional secondary substrate, lead frame, etc., but the wafer can be directly attached to the carrier. The wafer-level package is used to fabricate the P/N electrode of the LED diode at the bottom of the wafer. The surface mount automation method can be used for component assembly. If it is necessary to wire the component manufacturing process, the wafer level package can relatively improve the assembly and test process, and achieve the dual purpose of reducing processing complexity and cost.

The LED chip-level packaging solution enables components to achieve better heat dissipation performance, high lumen output, high package density, more flexibility, and simplified substrate. At the same time, the wire bonding process is reduced and the reliability of the terminal components can be improved.

Unpackaged LED solution popular high illumination angle, luminous efficiency

It is also aimed at the high-brightness performance of components, low-cost requirements and more convenient production conditions, and has promoted the use of novel unpackaged LEDs (EmbeddedLEDChip). Comparing the characteristics of unpackaged LEDs with wafer-level packaged LED components, unpackaged LEDs perform better for component heat dissipation, without packaged LED fabrication technology, integrated epitaxial, die and package processes, and components can also be used with secondary optics. The design integration can also make the finished product have higher brightness, larger illuminating angle and smaller volume characteristics, and at the same time can achieve the purpose of compression production cost. The illuminating element can provide a diversified and more flexible design space for the lighting industry.

In the conventional package architecture, an internal cavity is formed by the reflective cup, and the driving power connection is processed by the wafer wire-bonding process. Although the process is simple, the heat dissipation capability of the terminal component is also limited. In the novel LCD backlight and lighting design requirements, the LED light source component must increase the driving wattage of the unit component while reducing the lighting area requirement. The key to heat dissipation becomes the technical bottleneck of such application requirements.

Unpackaged LEDs can reduce component thermal resistance by about 10 times compared to conventional packages, while unpackaged LEDs do not require a reflective cup cavity, which saves the cost of reflective cups and optimizes the cost performance of the overall component. The advantages of packaged LED technology , the non-packaged LED is matched with a special fluorescent film, and the LED's illumination angle can be further improved to 160 degrees. The luminous efficiency, mechanism characteristics and heat dissipation advantages of the components can be effectively improved.

The unpackaged LED technology has a very small light-emitting area and a large illumination angle. Compared with the performance of the light source components of the conventional packaging scheme, the optical performance of the unpackaged LED technology is closer to the point light source, and this material property makes the packageless LED technology more It is suitable for secondary optical processing design, and the smaller light-emitting area also means that the volume of the component is relatively smaller. It can also be fabricated into a LED light source module with a thinner optical lens, especially for lamps with limited space in some mechanisms. Product use requirements, such as LCD direct-lit backlights or flat panel products.

If compared with the wafer-level package, the unpackaged LED technology introduces the bonding process of the fluorescent film in the process, which makes it easier to control the illuminating performance characteristics in the LED light source lighting application, so that the luminaire needs to match the illuminating color in the production process. Detection and matching procedures greatly simplify production.

Improve heat conduction architecture without package LED thermal resistance

In the traditional LED package, the wafer must be heat-transferred through the sapphire substrate and the insulating paste, and in the unpackaged LED technology, the concept of the Flip-chip wafer structure and the metal substrate eutectic fabrication is used. In the package of the unpackaged LED component, the thermal resistance of the component itself can be lower because of the design structure of the flip chip and the metal substrate eutectic, and therefore the packaged LED technology is at the same driving wattage, the illuminating core of the chip The temperature can be effectively reduced, and at the same time, the wafer temperature can be reduced and the high temperature may cause component failure or shortened life.

However, unpackaged LEDs are not perfect process technology. Because of the purpose of designing unpackaged LEDs, it is necessary to integrate the surface adhesion technology of epitaxial, die, packaging process and component finished products. The technical difficulty of integration is quite high, especially in In the key flip-chip structure design, it is very difficult to maintain the high reliability of the unpackaged LED. It is mainly to seek high reflectivity, high thermal conductivity and good adhesion of the diode material, and these materials must have high stability. The traits must also withstand the high temperature, high pressure, and high current environmental conditions during component operation.

In addition, the unpackaged LED itself has no outer package for protection. If the lighting device needs to be installed in a high temperature, high humidity and harsh environment, the protective layer design must be applied to the component to increase the service life of the light source device.

In addition, in the unpackaged LED process, the fluorescent film is used to replace the traditional packaging material in the package process, and the fluorescent film is also internally filled with phosphor powder to match the LED light source and the phosphor powder to produce white light. The choice of phosphor powder will affect the reliability, luminous efficiency and high temperature performance of the unpackaged LED components in lighting applications.

After all, the fluorescent film is different from the traditional packaging materials. In the process, it is necessary to deal with the problem of bonding and testing. It is not only the difference of production equipment, but also the related process equipment needs to be optimized and improved, which will increase the complexity of initial production of unpackaged LED components. .