The rapid rise of LED lighting applications is expected to expand the demand for high-power LED products. To ensure that high-power LEDs meet market requirements, packagers are trying to achieve cost-effective and extended use by improving packaging materials and die layout. The purpose of life.
The high-power light-emitting diode (LED) light source that is often published in the industry is mostly tens of watts or even hundreds of watts of LED packaging technology. From the perspective of the application side of the optical system, it does not make much sense, but how can it be dozens of The elimination of heat up to hundreds of watts is the key. To achieve this goal, it is necessary to effectively reduce the thermal resistance (Rjc) of a single LED package.
The power driven by the LED package is limited by the thermal resistance of the package and the associated thermal module (Rca), which determine the maximum power value that the LED's system thermal resistance and steady state can tolerate. In order to reduce the thermal resistance of the package, the operator tries to increase the distribution distance of the LED crystal in the package. However, the LED die area is not too large. The excessive light-emitting area makes the subsequent optics difficult to handle and limits the application of the product. It is not necessary to package more LED chips in a single body in order to achieve high power packaging, because there are still many factors to be considered, especially for the application surface.
Multi-die package materials continue to evolve
As the LED package power increases, the multi-chip package becomes a trend. The traditional high-power LED package adopts the plastic pre-mold lead frame (Fig. 1a), and the package carrier ( Carrier), also known as Die Pad, is a continuous metal block that cannot meet the electrical requirements of multi-die serial connection. The electrical series-parallel method directly affects the LED die electrical measurement bin (Bin). Precision, reliability life, and drive circuit design required for the package to be applied. Therefore, many LED package types have been proposed one after another. Figure 2 shows typical examples of several representative high-power LED packages.
Figure 1 shows the structure of common high-power LED package
Figure 2 Typical representative high power LED package
The high-power LED package structure widely used in the industry, the main difference can be roughly distinguished from the material selection of the package carrier, the implementation is nothing more than the use of high thermal conductivity ceramic substrate or directly on the metal substrate for the crystal substrate package (Figure 1b) ), becoming a package form of chip on board (COB). However, because of the high price of high thermal conductivity ceramic substrates, there is also an economical choice for the use of low thermal conductivity ceramics with thermal vias (Figure 1c), adding sintered metal to the thermal vias. (such as silver) as a heat conduction path; in addition, there is an advanced method to use the semiconductor process silicon as the carrier (Figure 1d) to achieve thermoelectric separation, while having high power density and low thermal resistance (<0.5 °C / W) Features, is expected to introduce high-power LED packaging into another revolution. As LED power and power density are upgraded, LEDs will accelerate the replacement of traditional light sources in various applications.
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