Investigation on effects of solder paste voids on thermal and optical performance of white high-power surface-mounted device LEDs

2019 ◽  
Vol 32 (2) ◽  
pp. 104-114
Author(s):  
Muna Raypah ◽  
Mutharasu Devarajan ◽  
Shahrom Mahmud
Keyword(s):  
Thermal Resistance ◽  
High Power ◽  
Heat Dissipation ◽  
Free Water ◽  
Heat Diffusion ◽  
Solder Paste ◽  
Optical Performance ◽  
Content Type ◽  
Color Shift ◽  
Filling State

Purpose The presence of voids in the solder layer has been considered as one of the main issues causing reliability problems in optoelectronic devices. Voids can be created due to trapped gas, clean-up agent residues (fluxes), poor wettability at interface or shortcoming of the reflow process. The voids hinder the heat conduction path and subsequently, the thermal resistance will increase. The purpose of this paper is to investigate the influence of lead-free water-washable Sn96.5Ag3.0Cu0.5 (SAC305) solder paste (SP) voids on the thermal and optical performance of white high-power (HP) surface-mounted device (SMD) light-emitting diode (LED). Design/methodology/approach Five LEDs are mounted on five SinkPAD substrates by using the SP. The SMT stencil printing is used to control the thickness of the SP and reflow oven for the soldering process. The fraction of voids in the SP layer is calculated using the X-ray machine software. The thermal parameters of the LEDs with different voids fraction and configuration are measured using a thermal transient tester (T3Ster) system. In addition, the optical characterizations of the LEDs are determined by the thermal and radiometric characterization of power LEDs (TeraLED) and the electroluminescence by using the spectrometer. Findings The results showed that the thermal performance and temperature distribution are improved for the LED with lower voids fraction and good filling state of soldering. In addition, luminous flux, efficacy and color shift of the LEDs with different fraction and configurations of voids on the SP layer are compared and discussed. It is found that the color shift of LED1 of low voids fraction and higher thickness are less than other LEDs. Originality/value The paper provides valuable information about the effect of water-washable SAC305 SP voids fraction and filling state of solder on the thermal and optical performance of ThinGaN HP SMD LED. A comprehensive overview of the outcomes is not available in the literature. It was shown experimentally that the voids fraction, height and configuration of the SP layer could strongly influence the heat dissipation efficiency and thermal resistance. This study can help in heat diffusion investigation and failure analysis of HP SMD LEDs.

Effects of solder paste on thermal and optical performance of high-power ThinGaN white LED

2018 ◽  
Vol 30 (3) ◽  
pp. 182-193 ◽  
Author(s):  
Muna E. Raypah ◽  
Mutharasu Devarajan ◽  
Fauziah Sulaiman
Keyword(s):  
Thermal Resistance ◽  
Thermal Management ◽  
High Power ◽  
Junction Temperature ◽  
Critical Parameters ◽  
White Led ◽  
Solder Paste ◽  
Optical Performance ◽  
Content Type ◽  
Color Shift

Purpose Thermal management of high-power (HP) light-emitting diodes (LEDs) is an essential issue. Junction temperature (TJ) and thermal resistance (Rth) are critical parameters in evaluating LEDs thermal management and reliability. The purpose of this paper is to study thermal and optical characteristics of ThinGaN (UX:3) white LED mounted on SinkPAD by three types of solder paste (SP): No-Clean SAC305 (SP1), Water-Washable SAC305 (SP2) and No-Clean Sn42/Bi57.6/Ag0.4 (SP3). Design/methodology/approach Thermal transient tester (T3Ster) machine is used to determine TJ and total thermal resistance (Rth–JA). In addition, the LED’s optical properties are measured via thermal and radiometric characterization of power LEDs (TeraLED) system. The LED is mounted on SinkPAD using SP1, SP2 and SP3 by stencil printing to control a thickness of SP and reflow soldering oven to minimize the number of voids. The LED with SP1, SP2 and SP3 is tested at various input currents and ambient temperatures. Findings The results indicate that at high input current, which equals to 1,200 mA, Rth–JA and TJ, respectively, are reduced by 30 and 17 per cent between SP1 and SP2. At same current value, Rth–JA and TJ are minimized by 42 and 25 per cent between SP1 and SP3, respectively. In addition, at an ambient temperature of 85°C, Rth–JA and TJ are decreased by 34 and 7 per cent between SP1 and SP2, respectively. Similarly, the reduction in Rth–JA and TJ between SP1 and SP3 is 44 and 10 per cent, respectively. Luminous flux, luminous efficacy and color shift of the LED with the three types of SPs are compared and discussed. It is found that the SP1 improves the chromatic properties of the LED by increasing the overall light efficiency and decreasing the color shift. Originality/value Thermal and optical performance of ThinGaN LEDs mounted on SinkPAD via three types of SPs is compared. This investigation can assist the research on thermal management of HP ThinGaN-based LEDs.

Thermal Resistance Analysis of Sn-Bi Solder Paste Used as Thermal Interface Material for Power Electronics Applications

2014 ◽  
Vol 136 (1) ◽  
Author(s):  
Rui Zhang ◽  
Jian Cai ◽  
Qian Wang ◽  
Jingwei Li ◽  
Yang Hu ◽  
...  
Keyword(s):  
Thermal Resistance ◽  
Power Electronics ◽  
Heat Dissipation ◽  
Laser Flash ◽  
Acoustic Microscopy ◽  
Thermal Interface Material ◽  
Solder Paste ◽  
Good Reliability ◽  
Thermal Interface ◽  
Power Modules

To promote heat dissipation in power electronics, we investigated the thermal conduction performance of Sn-Bi solder paste between two Cu plates. We measured the thermal resistance of Sn-Bi solder paste used as thermal interface material (TIM) by laser flash technique, and a thermal resistance less than 5 mm2 K/W was achieved for the Sn-Bi TIM. The Sn-Bi solder also showed a good reliability in terms of thermal resistance after thermal cycling, indicating that it can be a promising candidate for the TIM used for power electronics applications. In addition, we estimated the contact thermal resistance at the interface between the Sn-Bi solder and the Cu plate with the assistance of scanning acoustic microscopy. The experimental data showed that Sn-Bi solder paste could be a promising adhesive material used to attach power modules especially with a large size on the heat sink.

MEMS Based Metal Plated Silicon Package for High Power LED

2006 ◽  
Vol 326-328 ◽  
pp. 309-312 ◽  
Author(s):  
Sung Jun Lee ◽  
Ji Hyun Park ◽  
Chang Hyun Lim ◽  
Won Kyu Jeong ◽  
Seog Moon Choi ◽  
...  
Keyword(s):  
Thermal Resistance ◽  
High Power ◽  
Power Dissipation ◽  
Heat Dissipation ◽  
High Efficiency ◽  
Low Cost ◽  
Wafer Level ◽  
High Power Led ◽  
Key Factor ◽  
Mems Technology

By the development of high power LED for solid states lighting, the requirement for driving current has increased critically, thereby increasing power dissipation. Heat flux corresponds to power dissipation is mainly generated in p-n junction of LED, so the effective removal of heat is the key factor for long lifetime of LED chip. In this study, we newly proposed the silicon package for high power LED using MEMS technology and estimated its heat dissipation characteristic. Our silicon package structure is composed of base and reflector cup. The role of base is that settle LED chip at desired position and supply electrical interconnection for LED operation, and finally transfer the heat from junction region to outside. For improved heat transfer, we introduced the heat conductive metal plated trench structure at the opposite side of LED attached side. The depth and the diameter of trench were 150 and 100um, respectively. Copper with high thermal conductivity than silicon was filled in trench by electroplating and the thickness of copper was about 100um. Reflector cup was formed by anisotropic wet etching and then, silicon package platform could be fabricated by eutectic bonding between base and reflector cup. The thermal resistance of silicon package was about 6 to 7K/W from junction to case, and also, thermal resistance reduction of 0.64K/W was done by metal plated trench. This result could be comparable to that of other high power LED package. Our silicon package platform is easy to be expanded into array and wafer level package. So, it is suitable for future high efficiency and low cost package.

Thermal resistance of high power LED influenced by ZnO thickness and surface roughness parameter

2016 ◽  
Vol 33 (1) ◽  
pp. 15-22 ◽  
Author(s):  
Shanmugan Subramani ◽  
Mutharasu Devarajan
Keyword(s):  
Thin Film ◽  
Surface Roughness ◽  
Thermal Resistance ◽  
Heat Sink ◽  
Heat Dissipation ◽  
Roughness Parameter ◽  
Junction Temperature ◽  
Zno Thin Film ◽  
Content Type ◽  
Cu Substrates

Purpose – The purpose of this research is to study the effect of thickness and surface properties of ZnO solid thin film for heat dissipation application in LED. Heat dissipation in electronic packaging can be improved by applying a thermally conductive interface material (TIM) and hence the junction temperature will be maintained. ZnO is one of the oxide materials and used as a filler to increase the thermal conductivity of thermal paste. The thickness of these paste-type material cannot be controlled which restricts the heat flow from the LED junction to ambient. The controlled thickness is only possible by using a solid thin-film interface material. Design/methodology/approach – Radio Frequency (RF)-sputtered ZnO thin film on Cu substrates were used as a heat sink for high-power LED and the thermal performance of various ZnO thin film thickness on changing total thermal resistance (R th-tot) and rise in junction temperature were tested. Thermal transient analysis was used to study the performance of the given LED. The influence of surface roughness profile was also tested on the LED performance. Findings – The junction temperature was high (6.35°C) for 200 nm thickness of ZnO thin film boundary condition when compared with bare Cu substrates. Consecutively, low R th-tot values were noticed with the same boundary condition. The 600 nm thickness of ZnO thin film exhibited high R th-tot and interface resistance than the other thicknesses. Bond Line Thickness of the interface material was influenced on the interface thermal resistance which was decreased with increased BLT. Surface roughness parameter showed an immense effect on thermal transport, and hence, low R th (47.6 K/W) value was noticed with low film roughness (7 nm) as compared with bare Cu substrate (50.8 K/W) where the surface roughness was 20.5 nm. Originality/value – Instead of using thermal paste, solid thin film ZnO is used as TIM and coated Cu substrates were used as a heat sink. The thickness can be controlled, and it is a new approach for reducing the BLT between the metal core printed circuit board and heat sink.

Qualitative analysis of coupling effect of fluid velocity distribution in microchannels on the performance of the LED water cooling system

2019 ◽  
Vol 29 (10) ◽  
pp. 3893-3907
Author(s):  
Yuanlong Chen ◽  
Tingbo Hou ◽  
Xiaochao Zhou
Keyword(s):  
Velocity Distribution ◽  
High Power ◽  
Heat Dissipation ◽  
Cooling System ◽  
Fluid Velocity ◽  
Water Cooling ◽  
Content Type ◽  
Aspect Ratios ◽  
High Power Led ◽  
Water Cooling System

Purpose The purpose of this paper is to ensure adequate thermal management to remove and dissipate the heat produced by a light-emitting diode (LED) and to guarantee reliable and safe operation. Design/methodology/approach A three-dimensional (3-D) computational fluid dynamics (CFD) model was used to analyze the distribution of fluid velocities among microchannels at four different aspect ratios. Findings The results showed that at the same inlet flow rate, the larger the aspect ratio of the microchannels, the better the uniformity of the internal fluid velocity and thus better the heat dissipation performance on the surface of the high-power LED chip. In addition, the thermal performance of a high-power LED water cooling system with four different aspect ratios’ microchannel structures is further studied experimentally. Specifically, the coupling effect between the fluid velocity distribution in the microchannels and the heat dissipation performance of a high-power LED water cooling system is qualitatively analyzed and compared with the simulation results of the fluid velocity distribution. The results fully demonstrated that a larger aspect ratio of the microchannels results in better heat dissipation performance on the surface of the high-power LED chip. Originality/value Optimizing the structural parameters to facilitate a relatively uniform velocity distribution to improve the water cooling system performance may be a key factor to be considered.

scholarly journals Copper coin-embedded printed circuit board for heat dissipation: manufacture, thermal simulation and reliability

Circuit World ◽  
2015 ◽  
Vol 41 (2) ◽  
pp. 55-60 ◽  
Author(s):  
Yuanming Chen ◽  
Shouxu Wang ◽  
Xuemei He ◽  
Wei He ◽  
Vadim V. Silberschmidt ◽  
...  
Keyword(s):  
High Power ◽  
Heat Dissipation ◽  
Printed Circuit Board ◽  
Thermal Simulation ◽  
Circuit Board ◽  
Reflow Soldering ◽  
Content Type ◽  
Printed Circuit ◽  
Flatness Control ◽  
Copper Coin

Purpose – The purpose of this paper is to form copper coin-embedded printed circuit board (PCB) for high heat dissipation. Design/methodology/approach – Manufacturing optimization of copper coin-embedded PCB involved in the design and treatment of copper coin, resin flush removal and flatness control. Thermal simulation was used to investigate the effect of copper coin on heat dissipation of PCB products. Lead-free reflow soldering and thrust tests were used to characterize the reliable performance of copper coin-embedded PCB. Findings – The copper coin-embedded PCB had good agreement with resin flush removal and flatness control. Thermal simulation results indicated that copper coin could significantly enhance the heat-dissipation rate by means of a direct contact with the high-power integrated circuit chip. The copper coin-embedded PCB exhibited a reliable structure capable of withstanding high-temperature reflow soldering and high thrust testing. Originality/value – The use of a copper coin-embedded PCB could lead to higher heat dissipation for the stable performance of high-power electronic components. The copper coin-embedded method could have important potential for improving the design for heat dissipation in the PCB industry.

Optimizing and Analysis for the Microchannel Heat Sink of High-Power LED Array

2013 ◽  
Vol 684 ◽  
pp. 261-264
Author(s):  
Ru Chun Li ◽  
Xin Zhang ◽  
Qi Zheng
Keyword(s):  
Theoretical Analysis ◽  
Thermal Resistance ◽  
High Power ◽  
Heat Sink ◽  
Heat Dissipation ◽  
Water Flow Rate ◽  
Microchannel Heat Sink ◽  
Total Size ◽  
Cooling Water Flow Rate ◽  
Led Array

The high power light emitting diode (LED) array integrated with the microchannel heat sink is designed. Detailed theoretical analysis of the thermal resistance for the microchannel heat sink is obtained. The thermal resistance minimum is achieved by the heat sink structure optimization, the result of theoretical analysis is simulated by MATLAB software. The result shows that: the system acquired the best heat dissipation effect, when the total size of the radiator is fixed, the width of the cooling channel is 0.1mm, and the cooling water flow rate is 1 m/s, the minimum of thermal resistance is 0.019w/°C.

Experimental Investigation on the Heat Dissipation Performance of Bismuth-Based Alloy Thermal Conductive Sheet

2021 ◽  
Vol 1035 ◽  
pp. 655-662
Author(s):  
Qian Yu Wang ◽  
Chang Li Cai ◽  
Zhong Shan Deng
Keyword(s):  
Thermal Resistance ◽  
Power Density ◽  
High Power ◽  
Heat Dissipation ◽  
Electronic Devices ◽  
Thermal Interface Materials ◽  
High Power Density ◽  
Interface Thermal Resistance ◽  
Thermal Grease ◽  
Interface Materials

At present, the existing thermal interface materials (TIMs) cannot meet the heat dissipation requirements of some high-power density electronic devices. In this study, Bi-based low melting point alloy was made into a thermal conductive sheet to reduce the interface thermal resistance. The thermal conductivity of a thermal conductive sheet was found to be 37.83 W/(m·K), 10 times higher than Dow Corning 5021 thermal grease. In addition, the surface morphology of the Bi-based alloy thermal conductive sheet was changed in this experiment, which was divided into textured and planer type, and the measured interface thermal resistance values lower than Dow Corning 5021 thermal grease by approximately 30% and 27%, respectively. The results prove this Bi-based alloy thermal conductive sheets have the ideal heat dissipation performance and their wide application prospects in high-power density electronic devices.

Thermal analysis of chip-on-flexible LED packages with Cu heat sinks by SnBi soldering

2016 ◽  
Vol 33 (1) ◽  
pp. 42-46 ◽  
Author(s):  
Yang Liu ◽  
Fenglian Sun ◽  
Cadmus A. Yuan ◽  
Guoqi Zhang
Keyword(s):  
Thermal Performance ◽  
Heat Dissipation ◽  
Light Emitting Diode ◽  
Experimental Tests ◽  
Heat Sinks ◽  
Solder Paste ◽  
Large Area ◽  
Content Type ◽  
Soldering Process ◽  
Solder Layer

Purpose – The purpose of this paper is to discuss the possibility of using soldering process for the bonding of chip-on-flexible (COF) light-emitting diode (LED) packages to heat sinks. The common bonding materials are thermal conductive adhesives. For thermal performance and reliability concerns, Tin-Bismuth (SnBi) lead-free solder paste was used for the connection of the COF packages and the Cu heat sinks by a soldering process in this study. Meanwhile, the geometrical effect of the SnBi solder layer on the thermal performance was also investigated. Design/methodology/approach – The effects of the bonding materials and the area of the solder layers on the thermal performance of the LED modules were investigated by finite element simulation and experimental tests. Findings – The SnBi soldered modules show much lower thermal resistance at the bonding layers than the adhesive-bonded LED module. Vertical heat transfer from the LED chips to the heat sinks is the primary heat dissipation mode for the SnBi soldered modules. Thus, the LED module with local solder layer shows similar LED thermal performance with the full-area soldered module. Meanwhile, the local soldering process decreases the possibility to form randomly distributed defects such as the large area voids and residue flux in the solder layers. Research limitations/implications – The research is still in progress. Further studies mainly focus on the reliability of the samples with different bonding materials. Practical implications – COF package is a new structure for LED packages. This study provides a comparison between SnBi solder and adhesive material on the thermal performance of the LED. Meanwhile, the authors optimized the geometrical design for the solder layer. The study provides a feasible bonding process for COF packages onto heat sinks. Originality/value – This study provides a soldering process for the COF LED packages. The thermal performance of the LED light source was improved significantly by the new process.

Thermal Transient Measurements on High Power LEDs with Different MCPCB Substrate

2012 ◽  
Vol 488-489 ◽  
pp. 1363-1368 ◽  
Author(s):  
P. Anithambigai ◽  
D. Mutharasu
Keyword(s):  
Thermal Resistance ◽  
High Power ◽  
Printed Circuit Boards ◽  
Heat Dissipation ◽  
Dielectric Material ◽  
Function Evaluation ◽  
Substrate Thickness ◽  
Circuit Boards ◽  
Thermal Transient ◽  
Transient Measurement

This study elucidates the significance of thermal transient measurement based on structure function evaluation particularly on high power LEDs. The metal core printed circuit boards (MCPCBs) were redesigned with reference to the product datasheet. Aluminium nitride was employed as the dielectric material of the MCPCBs and thermal performance of copper and aluminium substrate with different substrate thickness has been reported in this paper. It was observed that the aluminium based MCPCBs performed better heat dissipation compared to the copper based MCPCBs. In addition, when two different thicknesses of the MCPCB substrates were compared, it was observed that the thicker substrate performed a lower thermal resistance compared to the thinner substrate MCPCB. The junction to board thermal resistance was determined using the standard transient dual interface method.

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