The effect of different LED packaging technologies on the light efficiency of LED modules

LED package and component specifications

EMC (Epoxy Molding Compound) is a package design made by Epoxy material and etching technology. The components belong to a highly integrated frame form. Due to material and structural characteristics, EMC has high heat resistance, UV resistance, high integration and high energy. The advantages of current drive and small size are the packaging technologies developed under the premise of high integration of LED lighting applications, increased photoelectric conversion efficiency and high reliability. In terms of EMC packaging, EMC uses epoxy resin as epoxy resin. The epoxy resin has the advantages of high UV resistance, high temperature stability, and low expansion coefficient of the package, thus attracting this package application into backlight applications. Market, environmental lighting applications.

To improve the LED lighting performance, it is the easiest way to use multiple components to make the module light source, but multiple components will cause heat treatment problems and circuit complexity problems. The picture shows a 200W light source module.

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EMC packaging material properties have a relatively small thermal expansion coefficient

In the implementation of EMC packaging, due to the use of epoxy film molding materials, the performance of the components with mechanical, bonding and corrosion resistance of the components is good, and the curing shrinkage and thermal expansion coefficient of the packaging materials are relatively small when performing packaging treatment. The stability of the components is good, and the manufacturing process and comprehensive characteristics have their packaging technology highlights. Therefore, the LED packaged LED light-emitting components are widely used in electronic applications, and even not only for lighting applications, but also for LCD TV backlight applications. There are also LED light sources that introduce related packaging solutions. As for the relevant industry, the current focus is on the improvement of the luminous efficiency of the EMC packaging process and the thin design of the components, while continuously improving the cost and competitive advantage of the EMC package through cost optimization.

Especially compared with PPA or ceramic substrate, EMC packaging scheme is mainly made of epoxy resin material, which makes it easier to realize large-scale large-scale production demand. The expansion of throughput further compresses manufacturing cost, and the application of epoxy resin material is more For flexibility, not only can the size be easily redesigned, but also the material is smaller and easier to cut. The design of the end product components is more flexible and flexible, and the finished terminal light source component can drive high wattage in a small volume. Especially in the light source products of 0.2W~2W, it is very competitive.

COB packaging solution multi-chip integration advantages

The COB (chip on board) packaging scheme is to adhere the LED bare wafer to the interconnect substrate by using conductive or non-conductive glue, and then perform wire bonding to complete the electrical connection fabrication, but in fact, if the bare die is to be used Without any treatment exposed to the air, the wafer itself can easily be damaged by contamination or human touch, or even cause damage to some functions or damage the function of the wafer! In order to improve the protection of the bare wafer, the material in the form of a glue can be used to completely seal the electrical connection between the wafer and the bond wire.

LED COB technology is commonly found in MCOB packages and COB packages. Looking at the LED COB package first, most COB packages (including Japan's packaged COB application technology) are mostly processed on a substrate-based package basis, that is, multiple wafers are integrated on a substrate and then packaged. A copper foil is disposed under the substrate of the substrate, and the copper foil can provide excellent electrical conductivity treatment, but it does not contribute much to optical processing. Unlike traditional COB, MCOB (Muilti Chips On Board) technology is used to place the wafer in an optically designed cup-like structure. The effect of the component can be optimized according to the pre-designed optical characteristics. Multiple sets of cup-shaped optical structures are integrated for integration, thereby providing better light output effects of LED single components, effectively utilizing physical optical optimization structures to improve overall component luminous efficiency, and MCOB can also respond to low power and high power packaging requirements. .

MCOB optical design advantage components with higher light output performance

COB has many unique material advantages, such as COB light source's low production cost and remarkable heat dissipation effect, which makes it have high packing density and high output optical density. Compared with most traditional LED packaging technology, COB packaging technology is made of COB packaging technology. The panel light source is softer in actual lighting use than in lighting, and has considerable development potential in the LED light source market for lighting. In general, COB light source technology is leading by Japanese manufacturers, and most manufacturers have begun to invest in the COB market. The COB packaging mode has also been greatly improved in key substrate materials, from early copper substrate design solutions to aluminum substrate applications, and even parts. The industry has begun to introduce ceramic substrates for the production of COB packaging products, and continuously optimize the life, reliability and key luminous efficiency of COB light sources.

It has also been mentioned that the MCOB technology can also be called a multi-cup integrated COB packaging technology. The actual production method is to integrate the LED cluster into a multi-cup type, and use multiple optical cup structures to make the light emitted by the LED chip. The optimization of the cup-shaped optical body enables the light-emitting direction to be concentrated directly above, improving the light output parameter performance of the components of the LED light source component and improving the luminous flux. The advantage of the MCOB package is that it can improve the glare and zebra pattern while improving the luminous flux. At the same time, it can improve the luminous efficiency of the LED driven per watt. If compared with traditional LED SMD chip package or other high-power packaging methods, COB can package multiple sets of chips on a metal substrate to reduce the heat dissipation design and obtain good light efficiency, while MCOB directly dissipates heat through the substrate. The cost of the bracket is reduced, and the overall component also has the advantage of small thermal resistance, and the heat generated when the LED emits light can also quickly dissipate.

COB/MCOB still has related technical problems to be broken

In the actual design of the product, such as barrel lights and recessed lamps, the MCOB components can be directly used as metal heat sinks to reduce the additional cost of the heat sink. In addition, for a 10W luminaire, if it is a traditional LED light source, it must be packaged into 10 LED components using 10 1W LEDs. If integrated with COB or MCOB packaging technology, 10 1W LED packages can be used in a single COB or MCOB package. In fact, the secondary optical design is used to improve the output light shape, which not only simplifies the manufacturing and assembly costs, but also simplifies the PCB design. The heat dissipation and mechanism processing of the LED itself is more concise, and even the secondary optical design will have more LED design. The solution costs are lower and the effect is better.

Although COB and MCOB have many advantages, there are actually market restrictions. For example, the thermal resistance of COB using aluminum substrate is large and the reliability is low. It is easy to cause light failure early in the lamp and even malfunction. The latter improvement method is to use ceramic substrate for integration, but in fact, although the ceramic substrate is a good substrate option, the cost is not very affinitive, and the cost problem in low power application will lead to the lack of user interest. COB and MCOB's large-scale wafer packaging still has problems such as thermal resistance improvement and light efficiency optimization. In addition, the lighting field does not necessarily pay for the COB and MCOB packaging standard parts, and the component standards are inconsistent, and it is difficult to enter into large quantities. Lighting application market.

In addition, CSP technology has become the focus of hot discussion in the market. The technology of CSP is defined as the package volume and the LED chip are the same, or the package volume should be no more than 20% of the LED chip, and the LED can still have a full-featured package component, and the CSP technology pursues the miniaturization of the component volume. Decrease, but still have to maintain the same light efficiency as the same wafer, and the most direct features of the key components can be reduced to the low-cost, small light-emitting area, longer component life design, plus small The volume component also means that the secondary optics have higher optical flexibility, lower processing cost, and the finished lamp product can practice the highest brightness and maximum illumination angle in extremely small optical structures, especially in LED bulbs and LED tubes. With excellent design flexibility, it is hopeful to become the mainstream of packaging technology.