study on the optical properties of cob led fluorescent replacement lights
In recent years, in the Led fluorescent replacement lights device family in the COB (chip on board) series of high speed growth. Led fluorescent replacement lights COB (chip on board) package refers to the Led fluorescent replacement lights chip is directly fixed in the printed circuit board (PCB), the chip and the circuit board through the wire bonding between the electrical connection of the Led fluorescent replacement lights packaging technology.In recent years, in the Led fluorescent replacement lights device family in the COB (chip on board) series application of high speed growth. Led fluorescent replacement lights COB (chip on board) package refers to the Led fluorescent replacement lights chip is directly fixed in the printed circuit board (PCB), the chip and the circuit board through the wire bonding between the electrical connection of the Led fluorescent replacement lights packaging technology. Which can be packaged in a small area of dozens or even hundreds of chips, and finally the formation of surface light source.
Compared with the point light source, the COB surface light source packaging technology has the advantages of low cost (only about 1 3 of the chip), saving space, easy heat dissipation, improving luminous efficiency and mature packaging technology. Due to high luminous efficiency and low manufacturing cost, COB Led fluorescent replacement lights light source package by a lot of packaging companies favorable.For a good or bad product, the most important is its color temperature, luminous flux and luminous efficiency. For high power COB package, its package structure, the size of the current, and thermal performance will affect the optical properties of Led fluorescent replacement lights.There are some people on the COB packaging technology and materials to do different research, but not on the current and lighting time to do in depth study. In this paper, the COB package of 3 and 10 strings is studied, the data under different current and at different time are tested, and the factors that affect the optical performance are analyzed through the data.1, the experiment1.1 Preparation of the productLed fluorescent replacement lights will be extended through the crystal, silver point, solid crystal, drying, binding the sample shown in Figure 1. And then through the requirements of color temperature to the right amount of fluorescent powder. Detection Through the software ZWL3907 to test the color temperature, after baking curing, as shown in Figure 2.1.2 Test methodsUsed for the powder machine (0.5m large integral sphere) as shown in Figure 3. The light color test was carried out on the samples with different current and different lighting time. 500mA, 600mA, 700mA, 800mA, 900mA, respectively, for different time, by using the constant current source to light up 1min, 5min, 10min respectively, in the light of the need to use the radiator (Figure 4) for cooling, otherwise it will burn.2, analysis and discussion600mA, 700mA, 800mA, 900mA, the measured color temperature, luminous flux and luminous efficiency, the results shown in Table 1. Table 1 shows the color temperature of the sample,Figure 5 is the luminous flux with the current changes in the law. Respectively, from 1777.232 to 2995.216, 1599.196 increased to 2952.519, increased 68.532%, 84.625%, can be found, the upward trend is sharp, indicating that the current change on the luminous flux has a significant change.Figure 6 is the light with the current changes in the law. It is not difficult to find that the luminous efficiency drops sharply from 114.37 to 98.89, from 107.51 to 96.79, and decreases by 13.535% and 9.971% respectively. As the current increases, the product heat increases, the heat can not be effectively derived, resulting in reduced light efficiency. But the current in the limited current conditions under the conditions of increase in luminous flux will be significantly increased. From the two sets of data to prove that the size of the current directly affect the Led fluorescent replacement lights optical performance.Figure 7 is the color temperature with the current changes in the law. When the current increased from 500mA to 900mA, the color temperature of the two samples increased from 2967 to 3017, from 2970 to 3048, increased 1.685%, 2.626%, the rising trend is slow, but the change of the current color temperature or direct influences.Set the constant current source to V = 35V, I = 600mA, and light samples, were lit 1min, 5min, 10min into a large sphere after the measurement, test the color temperature, luminous flux and luminous efficiency, the results in Table 2.Figure 8 is the luminous flux with the law of change. And the luminous flux decreased by 1.474%, 4.855%, 7.493%, 2.073%, 3.859% and 7.793%, respectively, and the decrease was larger with the longer lighting time.
Figure 9 is the luminous efficiency with the current changes. From the figure, it can be seen that the luminous efficiency is decreased by 2.527%, 4.617%, 6.671%, 2.171%, 4.903% and 7.579%, respectively. The longer the light is applied, Gradually increased. As the use of longer, the current remains unchanged, Led fluorescent replacement lights chips produce a lot of heat, heat accumulation in the chip, resulting in a chip to reduce the efficiency of light. When the thermal resistance is large, due to the PN junction temperature rise in the forward current at a value, the luminous flux will tend to saturation, and then gradually decreased. The results show that the time of lighting directly affects the Led fluorescent replacement lights optical performance.The current is at 600mA and the voltage is at 35V, and the lighting time is from 0 to 1min, 0 to 5min and 0 to 10min respectively. From Fig.10, we can observe the change of color temperature with the current. The color temperature of the two samples increases by 0.537 0.399%, 1.104%, 2.943%, the trend is slower, the longer the lighting time, the greater the color temperature change.3, the conclusionUsing COB package Led fluorescent replacement lights, through its luminous flux, color temperature, light efficiency and spectral energy distribution analysis, control current will gradually lead to a gradual increase in color temperature, luminous flux with the current increases, but the opposite light effect But gradually reduced.Control current, through the lighting time will lead to a gradual increase in color temperature, while the luminous flux decreased, the luminous efficiency is relatively lower.If you want to mass production of COB package of Led fluorescent replacement lights products, must solve its heat problem, due to the fixed number of crystals on the substrate, and the distance is very close, if the current exceeds the parameters or use of time will lead to Led fluorescent replacement lights chips produce a lot of heat, In the chip aggregation, thermal resistance, PN junction temperature rise, the luminous flux will gradually reduce the luminous efficiency will be relatively lower. So change the material, change the chip position, change the overall structure to increase the cooling capacity will make Led fluorescent replacement lights have a longer life, better light efficiency.