Effect of different soldering temperatures on the properties of COB light source

2021 ◽  
Vol ahead-of-print (ahead-of-print) ◽  
Author(s):  
Zhao Wang ◽  
Yuefeng Li ◽  
Jun Zou ◽  
Bobo Yang ◽  
Mingming Shi
Keyword(s):  
Light Source ◽  
Void Ratio ◽  
Light Attenuation ◽  
Luminous Flux ◽  
Luminous Efficiency ◽  
Junction Temperature ◽  
Light Sources ◽  
Content Type ◽  
Soldering Temperature ◽  
Practical Engineering

Purpose The purpose of this paper is to investigate the effect of different soldering temperatures on the performance of chip-on-board (COB) light sources during vacuum reflow soldering. Design/methodology/approach First, the influence of the void ratio of the COB light source on the steady-state voltage, luminous flux, luminous efficiency and junction temperature has been explored at soldering temperatures of 250°C, 260°C, 270°C, 280°C and 290°C. The COB chip has also been tested for practical application and aging. Findings The results show that when the soldering temperature is 270°C, the void ratio of the soldering layer is only 5.1%, the junction temperature of the chip is only 76.52°C, and the luminous flux and luminous efficiency are the highest, and it has been observed that the luminous efficiency and average junction temperature of the chip are 107 lm/W and 72.3°C, respectively, which meets the requirements of street lights. After aging for 1,080 h, the light attenuation is 84.64% of the initial value, which indicates that it has higher reliability and longer life. Originality/value It can provide reference data for readers and people in this field and can be directly applied to practical engineering.

scholarly journals Development of portable device for measurement of dynamic and static light-emission WOLED characteristics

2021 ◽  
Vol 1 (1(57)) ◽  
pp. 30-33
Author(s):  
Ihor Helzhynsky ◽  
Stepan Kutsiy ◽  
Andriy Veryha ◽  
Khrystyna Ivaniuk ◽  
Taras Dudok
Keyword(s):  
Light Source ◽  
Data Exchange ◽  
Light Emission ◽  
Spectral Characteristics ◽  
Light Flux ◽  
Luminous Flux ◽  
Visible Range ◽  
Light Sources ◽  
Measuring Device ◽  
Routine Work

The research object of this work is the parameters of organic light-emitting diodes, namely power and luminous flux. Determination of these parameters can be carried out using a photodiode and requires measuring the dark current of the sensor (photodiode), measuring the current of the photodiode when illuminated by the LED under investigation. And also take into account the relationship between the light flux received by the sensor and its output current, and take into account the spectral characteristics of the sensor. Calculate the investigated parameters of the LED based on the measurements. Carrying out these measurements requires laboratory instruments and workplace organization, and further calculations are routine work. It is possible to increase the measurement accuracy by improving the existing methods for measuring the required parameters, and it is possible to automate the process of measurements and calculations using a modern microprocessor radioelement base. Microcontrollers are widespread such radioelements. They have the necessary peripherals for independent operation and have sufficient computing power to implement the required measuring device. Its application makes it possible to automate the measurement process, carry out the necessary calculations, save correction constants, accumulate and process the obtained data, analyze these received data, exchange data with a computer, etc. So, the work is aimed at developing a methodology that will allow the simultaneous measurement of power and luminous flux of planar light sources. And also on the feasibility of this technique in the device and software with the ability to measure the power of the light source in an arbitrary band of the spectral visible range. Thus, it is possible to determine what power in watts a light source emits with the dynamics of supply currents in the optical bands, knowing the spectrum of this source without using glass filters. So, the result of applying the technique is to determine the power of light radiation (in watts) or the luminous flux (in lumens) of the emitter (light sources).

scholarly journals Influence of a Light Source Installed in a Luminaire of Opal Sphere Type on the Effect of Light Pollution

Energies ◽  
2020 ◽  
Vol 13 (2) ◽  
pp. 306 ◽  
Author(s):  
Przemyslaw Tabaka ◽  
Pawel Rozga
Keyword(s):  
Light Source ◽  
Spectral Distribution ◽  
Spectral Characteristics ◽  
Measurement Data ◽  
Luminous Flux ◽  
Light Pollution ◽  
Light Sources ◽  
Pollution Effect ◽  
The Impact ◽  
Effect Of Light

The article presents the results of the studies concerning the influence of a light source installed in luminaire of opal sphere type on the light pollution effect of the night sky. It is known from literature reports that the effect of light pollution is influenced by the spectral distribution of light. Although the influence of the spectral distribution has been widely studied from different perspectives, there is still a need to study this phenomenon—for example, from the point of view of the spectral reflection properties of the ground, on which the lanterns are installed. Hence, the above-mentioned aspect was considered in the authors’ investigations. The luminaire considered has been equipped with 20 different light sources, including the latest generation of lamps (light-emitting diodes, LEDs) as well as the conventional ones. With respect to these light sources, the measurements of light distribution and spectral distribution of emitted radiation of the luminaire were performed. Having these measurement data, the simulations were carried out using the DIALux software, and the calculations were made using the specially prepared calculation tool. On the basis of the results obtained in this way this was stated that the type of light source installed in the luminaire has a significant effect on the sky glow. An important factor affecting light pollution is not only the value of the luminous flux emitted upward but also the spectral characteristics of the emitted radiation, the impact of which is most noticeable. The conclusions from the studies indicate the next steps in the analysis of the light pollution effect. These steps will be focused on extended analysis of LEDs as modern and developed light sources.

Impact of thermal interface material on luminous flux curve of InGaAlP low-power light-emitting diodes

2021 ◽  
Vol ahead-of-print (ahead-of-print) ◽  
Author(s):  
Muna E. Raypah ◽  
Mutharasu Devarajan ◽  
Shahrom Mahmud
Keyword(s):  
Low Power ◽  
Thermal Resistance ◽  
Thermal Management ◽  
Light Output ◽  
Luminous Flux ◽  
Thermal Interface Material ◽  
Junction Temperature ◽  
Thermal Interface ◽  
Content Type ◽  
Thermally Conductive

Purpose One major problem in the lighting industry is the thermal management of the devices. Handling of thermal resistance from solder point to the ambiance of the light-emitting diode (LED) package is linked to the external thermal management that includes a selection of the cooling mode, design of heatsink/substrate and thermal interface material (TIM). Among the significant factors that increase the light output of the of the LED system are efficient substrate and TIM. In this work, the influence of TIM on the luminous flux performance of commercial indium gallium aluminium phosphide (InGaAlP) low-power (LP) LEDs was investigated. Design/methodology/approach One batch of LEDs was mounted directly onto substrates which were glass-reinforced epoxy (FR4) and aluminium-based metal-core printed circuit boards (MCPCBs) with a dielectric layer of different thermal conductivities. Another batch of LEDs was prepared in a similar way, but a layer of TIM was embedded between the LED package and substrate. The TIMs were thermally conductive epoxy (TCE) and thermally conductive adhesive (TCA). The LED parameters were measured by using the integrated system of thermal transient tester (T3Ster) and thermal-radiometric characterization of LEDs at various input currents. Findings With the employment of TIM, the authors found that the LED’s maximum luminous flux was significantly higher than the value mentioned in the LED datasheet, and that a significant reduction in thermal resistance and junction temperature was revealed. The results showed that for a system with low thermal resistance, the maximum luminous flux appeared to occur at a higher power level. It was found that the maximum luminous flux was 24.10, 28.40 and 36.00 lm for the LEDs mounted on the FR4 and two MCPCBs, respectively. After TCA application on the LEDs, the maximum luminous flux values were 32.70, 36.60 and 37.60 lm for the FR4 and MCPCBs, respectively. Moreover, the findings demonstrated that the performance of the LED mounted on the FR4 substrate was more affected by the employment of the TIM than that of MCPCBs. Research limitations/implications One of the major problems in the lighting industry is the thermal management of the device. In many low-power LED applications, the air gap between the two solder pads is not filled up. Heat flow is restricted by the air gap leading to thermal build-up and higher thermal resistance resulting in lower maximum luminous flux. Among the significant factors that increase the light output of the LED system are efficient substrate and TIM. Practical implications The findings in this work can be used as a method to improve thermal management of LP LEDs by applying thermal interface materials that can offer more efficient and brighter LP LEDs. Using aluminium-based substrates can also offer similar benefits. Social implications Users of LP LEDs can benefit from the findings in this work. Brighter automotive lighting (signalling and backlighting) can be achieved, and better automotive lighting can offer better safety for the people on the street, especially during raining and foggy weather. User can also use a lower LED power rating to achieve similar brightness level with LED with higher power rating. Originality/value Better thermal management of commercial LP LEDs was achieved with the employment of thermal interface materials resulting in lower thermal resistance, lower junction temperature and brighter LEDs.

The influence of soldering process parameters on the optical and thermal properties of power LEDs

2020 ◽  
Vol 32 (4) ◽  
pp. 191-199
Author(s):  
Przemysław Ptak ◽  
Krzysztof Górecki ◽  
Agata Skwarek ◽  
Krzysztof Witek ◽  
Jacek Tarasiuk
Keyword(s):  
Thermal Resistance ◽  
Process Parameters ◽  
Printed Circuit Board ◽  
Luminous Flux ◽  
Circuit Board ◽  
Optical Parameters ◽  
Light Sources ◽  
Content Type ◽  
Soldering Process ◽  
Design Engineers

Purpose This paper aims to present the results of investigations that show the influence of soldering process parameters on the optical and thermal parameters of power LEDs. Design/methodology/approach The power LEDs were soldered onto metal core printed circuit board (MCPCB) substrates in different soldering ovens: batch and tunnel types, characterized by different thermal profiles. Three types of solder pastes based on Sn99Ag0.3Cu0.7 with the addition of TiO2 were used. The thermal and optical parameters of the diodes were measured using classical indirect electrical methods. The results of measurements obtained were compared and discussed. Findings It was shown that the type of oven and soldering thermal profile considerably influence the effectiveness of the removal of heat generated in the LEDs tested. This influence is characterized by thermal resistance changes. The differences between the values of this parameter can exceed 20%. This value also depends on the composition of the soldering paste. The differences between the diodes tested can exceed 15%. It was also shown that the luminous flux emitted by the diode depends on the soldering process used. Practical implications The results obtained could be useful for process design engineers for assembling power LEDs for MCPCBs and for designers of solid-state light sources. Originality/value This paper presents the results of investigations into the influence of the soldering profiles and soldering pastes used on the effectiveness of the removal of heat generated in power LEDs. It shows and discusses how the factors mentioned above influence the thermal resistance of the LEDs and optical parameters that characterize the light emitted.

MODELLING OF VERTICAL SURFACES RADIATION IN CONNECTION WITH THE EVALUATION OF THE OBTRUSIVE LIGHT

2021 ◽  
Author(s):  
P. Becak ◽  
T. Novak
Keyword(s):  
Light Source ◽  
Distribution Curve ◽  
Field Measurements ◽  
Active Surface ◽  
Vertical Surface ◽  
Luminous Flux ◽  
Real Field ◽  
Light Sources ◽  
The Real ◽  
The Creation

The issue of the luminous flux radiation to the upper hemisphere is very broad and complex. The paper deals with the modelling of the vertical surface radiators. It presents an approach to unify the behaviour of these types of light sources. These will be understood as cosine radiators. If this cosine distribution curve is taken into account, then only the luminance and the light-active surface can be known to supplement the information about the radiation of such the light source. The luminance and radiated surface can be obtained relatively easily from real field measurements. The article presents the implementation of this data into lighting calculations and the creation of the distribution curves which are necessary for the radiation calculations of these surfaces. It also analyses the influence of the luminance and active areas on the radiated luminous flux and assign these values to the real radiators.

Realization of a Laboratory Tuneable Colour Light Source

2020 ◽  
pp. 90-98
Author(s):  
Nina Carli ◽  
Armin Sperling ◽  
Grega Bizjak
Keyword(s):  
Electric Current ◽  
Light Source ◽  
Closed Loop ◽  
Luminous Flux ◽  
Integrating Sphere ◽  
Practical Implementation ◽  
Light Sources ◽  
Output Spectrum ◽  
Calibration Source ◽  
Computer Controlled

A spectrally tuneable colour light source (TCLS) has been designed and constructed at Physikalisch-Technische Bundesanstalt (PTB), Germany. It consists of an integrating sphere with 24 LEDs which are driven by a computer-controlled power supply. It is intended for producing any visible spectral distribution and to mimic various light sources for use in laboratories as a calibration source. With the help of an integrated spectrometer, a closed loop operation was introduced to improve the performance of the TCLS and to spectrally stabilize its output spectrum. Before practical realization of the TCLS a series of simulations have been made to predict its performance and capability with a number of different target spectrums. During the practical implementation we have encountered difficulties, namely optimization of the output spectrum, dependency of LED spectra on the electric current through the LED and temperature of the LED, non-linearity of LED’s luminous flux with respect to electric current through the LED and some difficulties with small synthesis coefficient values, which were all successfully solved.

scholarly journals ENERGY-AWARE STAGE ILLUMINATION

2008 ◽  
Vol 18 (01n02) ◽  
pp. 107-129 ◽  
Author(s):  
FRIEDRICH EISENBRAND ◽  
STEFAN FUNKE ◽  
ANDREAS KARRENBAUER ◽  
DOMAGOJ MATIJEVIC
Keyword(s):  
Linear Programming ◽  
Approximation Algorithm ◽  
Light Source ◽  
Optimization Problem ◽  
Light Attenuation ◽  
Simple Problem ◽  
Light Sources ◽  
Energy Aware ◽  
Illumination Problem ◽  
Set Of Points

Consider the following illumination problem: given a stage represented by a line segment L and a set of light sources represented by a set of points S in the plane, assign powers to the light sources such that every point on the stage receives a sufficient amount – e.g. one unit – of light while minimizing the overall power consumption. Under the assumption that the amount of light arriving from a fixed light source decreases rapidly with the distance from the light source, this becomes an interesting optimization problem. We propose to reconsider the classical illumination problems as known from computational geometry literature under this light attenuation model. This paper examines the simple problem introduced above and presents different solutions, based on convex optimization, discretization and linear programming, as well as a purely combinatorial approximation algorithm. Some experimental results are also provided.

scholarly journals Modeling of Selected Lighting Parameters of LED Panel

Energies ◽  
2020 ◽  
Vol 13 (14) ◽  
pp. 3583 ◽  
Author(s):  
Krzysztof Baran ◽  
Antoni Różowicz ◽  
Henryk Wachta ◽  
Sebastian Różowicz
Keyword(s):  
Cooling System ◽  
Luminous Flux ◽  
Junction Temperature ◽  
Color Temperature ◽  
Light Sources ◽  
Factors Influencing ◽  
Forward Current ◽  
Color Rendering Index ◽  
Simulation Results ◽  
Color Rendering

Semiconductor light sources are currently the fastest growing and most energy efficient group of light sources used in lighting technology. Their lighting parameters, such as luminous flux, correlated color temperature and color rendering index depend on the value of the forward current, as well as the temperature of the junction. LED source manufacturers usually specify, in data sheets, the effect of junction temperature and forward current on the luminous flux for individual light sources. The difficulty, however, is the correct determination of temperature and then lighting parameters, by simulation methods for multi-source lighting systems. Determining the junction temperature which affects lighting parameters is particulary important in the case of LED panels and luminaires, where thermally coupled LED sources shaping the output lighting parameters are in close proximity to each other. Additionally, other factors influencing the temperature distribution of sources, such as the design and geometry of the cooling system, the design of the printed circuit and thermal interface material used, should be considered. The article is a continuation of the publication in this journal where the influence of factors influencing the temperature distribution of the LED panel is presented. The purpose of the research in this article was to confirm the possibility of using CFD (Computational Fluid Dynamics) software, as well as to determine the accuracy of the results obtained in the temperature analysis of the multi-source LED panel, and in determining the output lighting parameters of the LED panel based on it. In this article, based on previously published research, a LED panel model with a cooling system was made, and then the CFD software determined the junction temperature of all light sources. The determined temperature of the LED sources constituted the basis for determining the output lighting parameters of the panel: luminous flux, color temperature and color rendering index. The simulation results were verified by real measurements on the constructed LED panel prototype. The LED panel temperature difference between the simulation results and the real results on the prototype did not exceed 5%. Moreover, the error of lighting parameters between the simulation results obtained and the results on the LED panel prototype in the worst case was 4.36%, which proves the validity and accuracy of simulation studies.

scholarly journals INVERSE ANALYSIS APPLIED TO AN ILLUMINATION DESIGN

2007 ◽  
Vol 6 (1) ◽  
pp. 26
Author(s):  
P. S. Schneider ◽  
F. H. R. França
Keyword(s):  
Light Source ◽  
Inverse Analysis ◽  
Linear Equations ◽  
Three Dimensional ◽  
Visible Region ◽  
Radiation Energy ◽  
Luminous Flux ◽  
Bottom Surface ◽  
Light Sources ◽  
Illumination Design

This work investigates the application of the  inverse analysis to an illumination design of a three-dimensional rectangular enclosure. The problem consists of finding the luminous fluxes on the light source elements, located on the top of the enclosure, that satisfies a prescribed uniform luminous flux on the design surface, located on the bottom surface. The solution assumes that all the surfaces emit and reflect diffusely, and that the hemispheric spectral emissivities are wavelength independent in the visible region of the spectrum. The inverse analysis is described by a system of linear equations that is expected to be ill-conditioned since it involves the solution of a Fredholm integral equation of the first kind. To tackle the ill-conditioned system of equations, the TSVD (Truncated Singular Value Decomposition) regularization method is applied. In addition to presenting a methodology to solve for the luminous exchanges in a enclosure, starting from a thermal radiation energy balance, this work considers two design cases: one in which the light source elements cover the entire top surface; and one in which a reduced number of light sources are considered, a more practical solution. In both cases, the proposed inverse design is capable of providing a solution that satisfies the prescribed luminous flux on the design surface within average and maximum errors less than 1.0 % and 5.0 %, respectively.

Iterative Model for Simulating Light Intensity Variation of LED

2007 ◽  
Vol 364-366 ◽  
pp. 789-794 ◽  
Author(s):  
Hong Liu ◽  
Yan Nan Shen ◽  
Qiong Chen
Keyword(s):  
Light Intensity ◽  
Light Source ◽  
Engineering Application ◽  
Intensity Variation ◽  
Luminous Flux ◽  
Calculation Error ◽  
Light Sources ◽  
Luminous Efficacy ◽  
Led Light ◽  
Iterative Model

As a new kind of light source, LED light source has found wide application in many fields, especially in automotive lamp light source with the rise of luminous efficacy. The paper puts forward an iterative model, which approximates the light intensity variation of LED by adding up a series of the luminous flux of sub light sources with uniform light intensity, and accurately reflects the attenuation feature of LED light intensity. As long as the tracing ray is sufficient, the calculation error will be very small, and the result ideal, thus making it suitable for engineering application.

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