LED packaging principle
LED package is mainly to provide a platform for LED chips, so that LED chips have better performance of light, electricity and heat. Good packaging can make LEDs have better luminous efficiency and good heat dissipation environment, and good heat dissipation environment can enhance LEDs. The service life.
LED packaging technology is mainly built on five main considerations, namely optical extraction efficiency, thermal resistance, power dissipation, reliability and cost performance (Lm/$).
Each of the above factors is a very important part of the package. For example, the light extraction efficiency is related to cost performance; the thermal resistance is related to reliability and product life; and the power dissipation is related to customer applications. On the whole, the best packaging technology is to take care of every point, but the most important thing is to think from the customer's standpoint, to meet and exceed customer needs, is a good package.
For the packaging material composition of LED, the LED package is mainly composed of substrate, chip, solid crystal glue, phosphor, encapsulant, etc. We first paste the chip on the substrate with solid crystal glue, and use the gold wire to make the chip and the substrate. Electrically connected, then mix the phosphor with the encapsulant, match the different phosphor ratios, and the appropriate chip wavelength to get different colors. Finally, the mixture of phosphor and encapsulant is poured into the substrate, and the baking is heated to make the glue. After the material is cured, the most basic LED package is completed.
There are many kinds of LED chip packages, and different styles of packages should be used according to the actual photoelectric characteristics. However, the common LED packages have the following five common patterns.
First, the LED chip soft package, this package style is generally used in the LED display of character display, digital display, and electric display. The soft package of the LED chip is to directly bond the LED chip on the PCB printing plate, and connect the desired characters and display effects through the welding wire. These chips and wire bonds are then protected with a transparent resin.
Second, the pin packing method. The main advantage of this kind of package is that it can flexibly control the angle of light emitted by the LED chip, and it can also easily realize the function of measuring light. The pin package method only needs to fix the chip on the lead frame and then encapsulate it with epoxy resin. Can be a single LED device.
Third, the patch packaging method. This method is to stick the LED chip on the small lead frame and solder the electrode lead.
Four, double in-line package method. This is what we often call the piranha packaging method. This packaging method has many advantages, not only the thermal resistance and low heat dissipation performance, but also the input power of the LED is relatively large, and can reach between 0.1w and 0.5w. But the production cost is also relatively high.
Fifth, the power type packaging method, this method is also commonly used in LED projection lamps and high-power LED panel lamps. The advantage of this LED chip packaging method is that the heat of the chip can be quickly dissipated into the outside air, and the temperature difference between the LED chip and the environment is kept at a very low value.