The development of LED is attributed to the fact that in 1993 Japan Nichia Corporation realized the mass production of Blu-ray chips. The emergence of blue LEDs has opened up new areas of human lighting. With the development of LED technology, LED plant lights used in agricultural planting applications are also Initiated the era of innovation, the quality of LED plant lights and LED lamp beads have a close relationship, then how to choose a good LED lamp beads has become a top priority, the following articles will be analyzed in various aspects to help everyone clearer and deeper Understand the LED, and choose the LED plant lamp lamp beads suitable for the company’s products.
In the previous article, we introduced the LED production process. However, in the production process, the same batch of raw materials will have different quality in the production process due to various reasons. The appearance and process cannot be fully discriminated. Technical support, for the application of plant lights, you need to purchase according to the spectral parameters of plant lights.
The plant lamp is a parameterized product of the spectral technology. The lamp bead for the plant lamp and the lamp bead for the lighting are very different in the parameter expression. The lamp bead parameters provided by the current LED packaging enterprise cannot be adapted to the design parameter requirements of the plant lamp. The problem arises from the particularity of the plant lamp spectral testing technique and the spectral parameters of the plant lamp.
In the purchase of lamp beads, plant lamp manufacturers need to convert the lighting parameters of the lamp bead to the spectral parameters of the lamp lamp bead. This parameter conversion process is called the spectral parameterization of the plant lamp bead. The design of the plant lamp product must be Use parameterized lamp bead parameters, otherwise the design specifications are not based on implementation.
The parameterization of the lamp bead is very intuitive, such as:
Many of the technical products are parametric products, such as graphics cards for computers, and their representation parameters represent the performance and price of the graphics card.
The following is the spectral parameterization of the LED source.
The radiant power of the LED lamp bead is the main indicator determining the performance of the plant lamp product. The higher the radiation power, the higher the PPF value of the lamp bead, and the better the radiation performance of the plant lamp made.
The radiation power of the lamp bead is related to the chip area. The chip area is multiplied by the length and width of the chip. The larger the chip area, the higher the radiation power.
The radiant power of the LED lamp bead is determined by the radiant power level and price of the chip. The higher the radiant power of the chip, the more expensive the price.
Take the chip of Xiamen Sanan as an example, S-23BBMUP-C*******, the chip size is 23X10mil, this core has 4 radiation power levels (@20mA).
The radiant power of D24 and D27 is 8mW, that is to say, the same size of the chip, the PPF value of the lamp bead is different, and the radiant power level of the chip needs to be known when purchasing.
2. power consumption
The LED lamp bead is divided into power levels according to the current specification. The larger the current specification, the higher the power the chip bears, but the higher the heat generated by the chip.
Chips with different current specifications are packaged into different sizes, such as 2835, 5730, 3030, etc. The selection of different package specifications is based on the design requirements of the plant lamp structure. Generally, the low-power chip has high efficiency and low heat generation.
3. Radiation efficiency
Radiation efficiency of the lamp bead = radiant power / power consumption * 100%, radiation efficiency value is less than 100%.
Radiation efficiency expresses the proportion of radiant power generated per watt of electricity consumed, and the greater the radiation efficiency, the better.
Radiation efficiency is limited by the production technology of semiconductor materials, and is also limited by packaging technology and heat dissipation technology. The main reasons affecting radiation efficiency are:
The impact of a chip manufacturing quality
Different production equipment and chip technology affect the radiation efficiency of the chip, and it is an effective method to select the brand chip manufacturer.
Two bracket material
At present, there are aluminum brackets, brass brackets, copper brackets, etc. The aluminum brackets are the cheapest, and the copper brackets are the most expensive. Even the copper brackets have high quality of silver plating; the packaging materials also include various fixed and filled glues. quality.
The quality of the lamp of white light and rare earth process is also affected by the quality of the phosphor. The high-quality phosphor has low light decay; the white phosphor is mainly divided into aluminate and silicate, and the aluminate performance is better than silicate, aluminum. The acid salt is most representative of YAG. YAG has stable performance and low light decay. The chemical stability of silicate itself is poor, but the brightness is higher than YAG.
Three wire material
In addition to flip-chip and CSP packages, most lamp bead packages use a gold wire bonding process to connect the chip to the electrodes of the holder. Currently there are two kinds of alloy wires and pure gold wires on the market. The best gold wire is gold. The line is divided into 0.7, 0.9, 1.0, 1.2, etc. according to the thickness. The thicker the gold wire, the lower the heat group and the longer the lamp life.
4. PPF value
The PPF of the lamp bead needs special software to calculate. The power of the plant lamp is determined according to the PPF value of the LED lamp bead. If the packaging company cannot provide the PPF value of the lamp bead, it cannot become a qualified supplier of plant lamp bead. .
5. MPF value
Photon flux measurement in the range of 380nm-800nm, unit umol/s, for monochromatic lamp beads, MPF=PPF, for lamps packaged with phosphor, MPF value is greater than PPF value, phosphor packaged lamp Bead parameter expression needs to label both MPF and PPF parameters.
The QE value is the PPF value per watt. It is the derivation parameter of the spectral parameters of the plant lamp bead. The unit is umol/J. This parameter is the comprehensive index of the plant lamp bead and the most important performance comparison index. The QE value is the lamp. The parameters that must be marked after the bead spectrum is parameterized, the accuracy of the QE value relates to the spectral test technology level of the lamp bead, and the measurement error will cause the QE value to be distorted
7. radiation ratio
The relationship between the various radiation quantities within the defined band range is expressed in two ways.
Radiation content: The percentage of a band that accounts for the total amount of radiation. The amount of radiation is the weight of the radiation in a band that accounts for the total amount of radiation.
Radiation ratio: The ratio between the two bands. The radiation ratio is the unit weight between each other, usually R:B and R:FR.
The radiation ratio is only effective for the white and rare earth lamp beads, and the monochromatic light has no radiation ratio.
8. partial pressure specification
It is the voltage division of the chip, such as 3.0V-3.15V. For the light source connected in series and parallel mode, the voltage binning is controlled within 0.15V, so that the current distribution of each string source is uniform, which is beneficial to improve the life of the light source.
9. color temperature bin
For the color separation using white light beads, the packaging factory needs to provide the BIN code of color temperature. The white light of the plant lamp is relatively less strict, and the color BIN can be used to relax.
Evaluation rules for lamp spectral parameters
The radiation efficiency of the lamp bead is the basis of the spectral parameters. The comparison of PPF, MPF and QE is meaningful under the same radiation efficiency.
QE tends to be distorted as the amount of green light radiation increases. For monochromatic light beads, the larger the QE, the better.
At present, the QE of the LED lamp bead has not exceeded 2.2umol/J. The QE parameter of any test analysis is close to this upper limit, and the error between the test method and the measurement data needs to be evaluated.
In the future, when the LED lamp bead QE spans 2.2umol/J, the LED plant lamp will enter the full application environment, and other light sources will gradually withdraw from the application. The plant lamp spectrum technology will achieve QE of 3.0umol/J as the research goal in the next few years.