scholarly journals Performance and Thermal Analysis of Aluminium Oxide Filled Epoxy Composite as TIM for LEDs

2014 ◽  
Vol 11 (1) ◽  
pp. 35-41 ◽  
Author(s):  
Nur Jamaludin ◽  
P Anithambigai ◽  
S Shanmugan ◽  
D Mutharasu
Keyword(s):  
Thermal Conductivity ◽  
Thermal Resistance ◽  
Epoxy Resin ◽  
Milling Process ◽  
Thermal Interface Material ◽  
Junction Temperature ◽  
System Level ◽  
Al2o3 Powder ◽  
Effective System ◽  
Transient Measurement

Al2O3powder with various particle sizes was prepared by milling process and mixed together with epoxy resin in order to increase the thermal conductivity of resin and decrease the junction temperature of the LEDs. Al2O3 powder filled epoxy resin was applied as thermal interface material (TIM) for an effective system level analysis of thermal transient measurement. The result depicted that the milled Al2O3 powder for 3 hour powder showed the highest thermal conductivity and hence lower in thermal resistance of LED. Moreover, the driving currents also influence the thermal resistance and achieved low thermal resistance when measured at 350mA. The thermal properties of the sample were tested using t3ster. The surface morphology of the samples was tested using FESEM.

Development of a Compliant Nanothermal Interface Material

2011 ◽  
Author(s):  
David Shaddock ◽  
Stanton Weaver ◽  
Ioannis Chasiotis ◽  
Binoy Shah ◽  
Dalong Zhong
Keyword(s):  
Thermal Conductivity ◽  
Thermal Resistance ◽  
Thermal Stresses ◽  
Performance Testing ◽  
High Thermal Conductivity ◽  
Thermal Interface Material ◽  
Thermal Interface Materials ◽  
Thermal Interface ◽  
Bondline Thickness ◽  
Interface Materials

The power density requirements continue to increase and the ability of thermal interface materials has not kept pace. Increasing effective thermal conductivity and reducing bondline thickness reduce thermal resistance. High thermal conductivity materials, such as solders, have been used as thermal interface materials. However, there is a limit to minimum bondline thickness in reducing resistance due to increased fatigue stress. A compliant thermal interface material is proposed that allows for thin solder bondlines using a compliant structure within the bondline to achieve thermal resistance <0.01 cm2C/W. The structure uses an array of nanosprings sandwiched between two plates of materials to match thermal expansion of their respective interface materials (ex. silicon and copper). Thin solder bondlines between these mating surfaces and high thermal conductivity of the nanospring layer results in thermal resistance of 0.01 cm2C/W. The compliance of the nanospring layer is two orders of magnitude more compliant than the solder layers so thermal stresses are carried by the nanosprings rather than the solder layers. The fabrication process and performance testing performed on the material is presented.

Integration of Silver Heat Spreaders in LTCC utilizing Thick Silver Tape in the Co-fire Process

2015 ◽  
Vol 2015 (CICMT) ◽  
pp. 000062-000066 ◽  
Author(s):  
T. Welker ◽  
S. Günschmann ◽  
N. Gutzeit ◽  
J. Müller
Keyword(s):  
Thermal Conductivity ◽  
Thermal Resistance ◽  
Heat Sink ◽  
Junction Temperature ◽  
Large Area ◽  
Heat Spreader ◽  
Integration Density ◽  
Heat Spreaders ◽  
Cte Mismatch ◽  
Pattern Resolution

The integration density in semiconductor devices is significantly increased in the last years. This trend is already described by Moore's law what forecasts a doubling of the integration density every two years. This evolution makes greater demands on the substrate technology which is used for the first level interconnect between the semiconductor and the device package. Higher pattern resolution is required to connect more functions on a smaller chip. Also the thermal performance of the substrate is a crucial issue. The increased integration density leads to an increased power density, what means that more heat has to dissipate on a smaller area. Thus, substrates with a high thermal conductivity (e. g. direct bonded copper (DBC)) are utilized which spread the heat over a large area. However, the reduced pattern resolution caused by thick metal layers is disadvantageous for this substrate technology. Alternatively, low temperature co-fired ceramic (LTCC) can be used. This multilayer technology provides a high pattern resolution in combination with a high integration grade. The poor thermal conductivity of LTCC (3 … 5 W*m−1*K−1) requires thermal vias made of silver paste which are placed between the power chip and the heat sink and reduce the thermal resistance of the substrate. The via-pitch and diameter is limited by the LTCC technology, what allows a maximum filling grade of approx. 20 to 25 %. Alternatively, an opening in the ceramic is created, to bond the chip directly to the heat sink. This leads to technological challenges like the CTE mismatch between the chip and the heat sink material. Expensive materials like copper molybdenum composites with matched CTE have to be used. In the presented investigation, a thick silver tape is used to form a thick silver heat spreader through the LTCC substrate. An opening is structured by laser cutting in the LTCC tape and filled with a laser cut silver tape. After lamination, the substrate is fired using a constraint sintering process. The bond strength of the silver to LTCC interface is approx. 5.6 MPa. The thermal resistance of the silver structure is measured by a thermal test chip (Delphi PST1, 2.5 mm × 2.5 mm) glued with a high thermal conducting epoxy to the silver structure. The chip contains a resistor and diodes to generate heat and to determine the junction temperature respectively. The backside of the test structure is temperature stabilized by a temperature controlled heat sink. The resulting thermal resistance is in the range of 1.1 K/W to 1.5 K/W depending on the length of silver structure (5 mm to 7 mm). Advantages of the presented heat spreader are the low thermal resistance and the good embedding capability in the co-fire LTCC process.

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.

Investigation on Carbon Nanotubes as Thermal Interface Material Bonded With Liquid Metal Alloy

2015 ◽  
Vol 137 (9) ◽  
Author(s):  
Yulong Ji ◽  
Gen Li ◽  
Chao Chang ◽  
Yuqing Sun ◽  
Hongbin Ma
Keyword(s):  
Thermal Conductivity ◽  
Thermal Diffusivity ◽  
Liquid Metal ◽  
Thermal Resistance ◽  
Plasma Treatment ◽  
Contact Surface ◽  
Thermal Interface Material ◽  
Thermal Interface ◽  
Bonding Material ◽  
Liquid Metal Alloy

Vertically aligned carbon nanotube (VACNT) films with high thermal conductance and mechanical compliance offer an attractive combination of properties for thermal interface applications. In current work, VACNT films synthesized by the chemical vapor deposition method were used as thermal interface material (TIM) and investigated experimentally. The liquid metal alloy (LMA) with melting point of 59 °C was used as bonding material to attach VACNT films onto copper plates. In order to enhance the contact area of LMA with the contact surface, the wettability of the contact surface was modified by plasma treatment. The thermal diffusivity, thermal conductivity, and thermal resistance of the synthesized samples were measured and calculated by the laser flash analysis (LFA) method. Results showed that: (1) VACNT films can be used as TIM to enhance the heat transfer performance of the contact surface; (2) the LMA can be used as bonding material, and its performance is dependent on the LMA wettability on the contact surface. (3) When applying VACNT film as the TIM, LMA is used as the bonding material. After plasma treatment, comparison of VACNT films with the dry contact between copper and silicon showed that thermal diffusivity can be increased by about 160%, the thermal conductivity can be increased by about 100%, and the thermal resistance can be decreased by about 31%. This study shows the advantages of using VACNT films as TIMs in microelectronic packaging.

Transient Thermo-Reflectance Method for Characterization of Thermal Interface Material Based on Carbon Nanotube Array

2009 ◽  
Author(s):  
Yang Zhao ◽  
Rong-Shiuan Chu ◽  
Arun Majumdar
Keyword(s):  
Thermal Conductivity ◽  
Carbon Nanotube ◽  
Thermal Resistance ◽  
Thermal Interface Material ◽  
Measuring System ◽  
Bonding Layer ◽  
Thermal Interface ◽  
Interface Resistance ◽  
Interface Thermal Resistance ◽  
Cnt Arrays

Vertically aligned carbon nanotube (CNT) arrays have been explored as advanced thermal interface materials because of their compliance and high cross-plane thermal conductivity. Our previous work showed that a CNT array directly bridging two surfaces by dry contact had a surface-surface interface resistance of order of 10 m2-K/MW. With an indium bonding layer, the interface thermal resistance was reduced by a factor of ten. Therefore, a more sensitive measuring system is needed to accurately determine the thermal resistance. In this paper, we achieved a higher sensitivity measurement by applying the phase sensitive transient thermo-reflectance technique to a front side heating and detecting system. A detailed analysis is presented. We used this technique to characterize a 71-μm long CNT array with packing density of 9.4 ± 1.4%. The CNT array was sequentially wetted with chromium/gold films and was bonded to a glass surface with an indium bonding layer. We found that the CNT array-surface interface resistance is 0.35 ± 0.11 m2-K/MW and the cross-plane thermal conductivity of CNT array is 94 ± 40 W/m-K.

scholarly journals D-GQDs Modified Epoxy Resin Enhances the Thermal Conductivity of AlN/Epoxy Resin Thermally Conductive Composites

Polymers ◽  
2021 ◽  
Vol 13 (23) ◽  
pp. 4074
Author(s):  
Duanwei Zhang ◽  
Fusheng Liu ◽  
Sheng Wang ◽  
Mengxi Yan ◽  
Xin Hu ◽  
...  
Keyword(s):  
Thermal Conductivity ◽  
Thermal Resistance ◽  
Epoxy Resin ◽  
Graphene Quantum Dots ◽  
Interfacial Thermal Resistance ◽  
Resin Matrix ◽  
Conductive Composites ◽  
Thermally Conductive ◽  
Branched Chains ◽  
Modified Epoxy

This article proposes a method of increasing thermal conductivity (λ) by improving the λ value of a matrix and reducing the interfacial thermal resistance between such matrix and its thermally conductive fillers. D-GQDs (graphene quantum dots modified by polyetheramine D400) with a π–π-conjugated system in the center of their molecules, and polyether branched chains that are rich in amino groups at their edges, are designed and synthesized. AlN/DG-ER (AlN/D-GQDs-Epoxy resin) thermally conductive composites are obtained using AlN as a thermally conductive and insulating filler, using D-GQDs-modified epoxy resin as a matrix. All of the thermal conductivity, electrically insulating and physical–mechanical properties of AlN/DG-ER are investigated in detail. The results show that D-GQDs linked to an epoxy resin by chemical bonds can increase the value of λ of the epoxy–resin matrix and reduce the interfacial thermal resistance between AlN and DG-ER (D-GQDs–epoxy resin). The prepared AlN/DG-ER is shown to be a good thermally conductive and insulating packaging material.

Performance of Cu-Al2O3 thin film as thermal interface material in LED package: thermal transient and optical output analysis

2018 ◽  
Vol 35 (1) ◽  
pp. 33-44 ◽  
Author(s):  
Wei Qiang Lim ◽  
Mutharasu Devarajan ◽  
Shanmugan Subramani
Keyword(s):  
Thermal Resistance ◽  
Light Emitting Diode ◽  
Annealing Effect ◽  
Thermal Interface Material ◽  
System Level ◽  
Output Analysis ◽  
Thermal Interface ◽  
Content Type ◽  
Cu Substrate ◽  
Layer Stacking

Purpose This paper aims to study the influence of the Cu-Al2O3 film-coated Cu substrate as a thermal interface material (TIM) on the thermal and optical behaviour of the light-emitting diode (LED) package and the annealing effect on the thermal and optical properties of the films. Design/methodology/approach A layer-stacking technique has been used to deposit the Cu-Al2O3 films by means of magnetron sputtering, and the annealing process was conducted on the synthesized films. Findings In this paper, it was found that the un-annealed Cu-Al2O3–coated Cu substrate exhibited low value of thermal resistance compared to the bare Cu substrate and to the results of previous works. Also the annealing effect does not have a significant impact on the changes of properties of the films. Research limitations/implications It is deduced that the increase of the Cu layer thickness can further improve the thermal properties of the deposited film, which can reduce the thermal resistance of the package in system-level analysis. Practical implications The paper suggested that the Cu-Al2O3–coated Cu substrate can be used as alternative TIM for the thermal management of the application of LEDs. Originality value In this paper, the Cu substrate has been used as the substrate for the Cu-Al2O3 films, as the Cu substrate has higher thermal conductivity compared to the Al substrate as shown in previous work.

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