Thermal transient characteristics of die attach in high power LED PKG

Heat removal in packaged high-power light-emitting diode (LED) chips is critical to device performance and reliability. Thermal performance of LEDs is important in that lowered junction temperatures extend the LED's lifetime at a given photometric flux (brightness). Optionally, lower thermal resistance can enable increased brightness operation without exceeding the maximum allowable Tj for a given lifetime. A significant portion of the junction-to-case thermal resistance comes from the joint between chip and substrate, or the die-attach layer. In this study, we evaluated three different types of leading die-attach materials; silver epoxy, lead-free solder, and an emerging nanosilver paste. Each of the three was processed via their respective physical and chemical mechanisms: epoxy curing by cross-linking of polymer molecules; intermetalic soldering by reflow and solidification; and nanosilver sintering by solid-state atomic diffusion. High-power LED chips with a chip area of 3.9 mm2 were attached by the three types of materials onto metalized aluminum nitride substrates, wire-bonded, and then tested in an electro-optical setup. The junction-to-heatsink thermal resistance of each LED assembly was determined by the wavelength shift methodology, described in detail in this paper. We found that the average thermal resistance in the chips attached by the nanosilver paste was the lowest, and it is the highest from the chips attached by the silver epoxy: the difference between the two was about 0.7°C/W, while the difference between the sintered and soldered was about 0.3°C/W. The lower thermal resistance in the sintered joints is expected to significantly improve the photometric flux from the device. Simple calculations, excluding high current efficiency droop, predict that the brightness improvement could be as high as 50% for the 3.9 mm2 chip. The samples will be functionally tested at high current, in both steady-state and pulsed operation, to determine brightness improvements, including the impact of droop. Nanosilver die-attach on a range of chip sizes up to 12 mm2 are also considered and discussed.

Download Full-text

High Temperature Reliability of High-power LED Module Using Die Attach Material of Nano-silver Paste

Chinese Journal of Luminescence ◽

10.3788/fgxb20163709.1159 ◽

2016 ◽

Vol 37 (9) ◽

pp. 1159-1165

Author(s):

陈佳 CHEN Jia ◽

李欣 LI Xin ◽

孔亚飞 KONG Ya-fei ◽

梅云辉 MEI Yun-hui ◽

陆国权 LU Guo-quan

Keyword(s):

High Temperature ◽

High Power ◽

Silver Paste ◽

Nano Silver ◽

Die Attach ◽

High Power Led

Download Full-text

Improved Heat Dissipation and Optical Performance of High-Power LED Packaging with Sintered Nanosilver Die-Attach Material

Journal of Microelectronics and Electronic Packaging ◽

10.4071/imaps.264 ◽

2010 ◽

Vol 7 (3) ◽

pp. 164-168 ◽

Cited By ~ 2

Author(s):

Paul Panaccione ◽

Tao Wang ◽

Xu Chen ◽

Susan Luo ◽

Guo-Quan Lu

Keyword(s):

Thermal Resistance ◽

High Power ◽

Heat Removal ◽

High Current ◽

Die Attach ◽

High Power Led ◽

Silver Epoxy ◽

The Difference ◽

Nanosilver Paste ◽

The Impact

Heat removal in packaged high-power light-emitting diode (LED) chips is critical to device performance and reliability. Thermal performance of LEDs is important in that lowered junction temperatures extend the LED's lifetime at a given pho-tometric flux (brightness). Optionally, lower thermal resistance can enable increased brightness operation without exceeding the maximum allowable Tj for a given lifetime. A significant portion of the junction-to-case thermal resistance comes from the joint between chip and substrate, or the die-attach layer. In this study, we evaluated three different types of leading die-attach materials; silver epoxy, lead-free solder, and an emerging nanosilver paste. Each of the three was processed via their respective physical and chemical mechanisms: epoxy curing by cross-linking of polymer molecules; intermetalic soldering by reflow and solidification; and nanosilver sintering by solid-state atomic diffusion. High-power LED chips with a range of chip areas from 3.9 mm2 to 9.0 mm2 were attached by the three types of materials onto metalized aluminum nitride substrates, wire-bonded, and then tested in an electro-optical setup. The junction-to-heatsink thermal resistance of each LED assembly was determined by the wavelength shift methodology. We found that the average thermal resistance in the chips attached by the nanosilver paste was the lowest, and it was highest from the chips attached by the silver epoxy. For the 3.9 mm2 die, the difference was about 0.6°C/W, while the difference between the sintered and soldered was about 0.3°C/W. The lower thermal resistance in the sintered joints is expected to significantly improve the photometric flux from the device. Simple calculations, excluding high current efficiency droop, predict that the brightness improvement could be as high as 50% for the 3.9 mm2 chip. The samples will be functionally tested at high current, in both steady-state and pulsed operation, to determine brightness improvements, including the impact of droop. Nanosilver die-attach on a range of chip sizes up to 12 mm2 are also considered and discussed.

Download Full-text

Thermal Characteristics Analysis of Die Attach Layer Based on Time-Constant Spectrum for High-Power LED

IEEE Transactions on Electron Devices ◽

10.1109/ted.2015.2474395 ◽

2015 ◽

Vol 62 (11) ◽

pp. 3715-3721 ◽

Cited By ~ 14

Author(s):

Wei Lai ◽

Xianming Liu ◽

Weimin Chen ◽

Xiaohua Lei ◽

Xueying Cao

Keyword(s):

Time Constant ◽

High Power ◽

Thermal Characteristics ◽

Die Attach ◽

High Power Led ◽

Characteristics Analysis

Download Full-text

Effects of Die-Attach Quality on the Mechanical and Thermal Properties of High-Power Light-Emitting Diodes Packaging

Advances in Materials Science and Engineering ◽

10.1155/2017/8658164 ◽

2017 ◽

Vol 2017 ◽

pp. 1-8 ◽

Cited By ~ 1

Author(s):

Piaopiao He ◽

Jinlong Zhang ◽

Jianhua Zhang ◽

Luqiao Yin

Keyword(s):

Thermal Stress ◽

Thermal Resistance ◽

Void Fraction ◽

High Power ◽

Thermal Strain ◽

Mechanical And Thermal Properties ◽

Total Thermal Resistance ◽

Light Emitting ◽

Die Attach ◽

High Power Led

The reliability of high-power light-emitting-diode (LED) devices strongly depends on the die-attach quality because voids may increase junction temperature and total thermal resistance of LED devices. Die-attach material has a key role in the thermal management of high-power LED package by providing low-contact thermal resistance. Thermal and mechanical analyses were carried out by experiments and thermal simulation. The quantitative analysis results show that thermal resistance of die-attach layer (thermal resistance caused by die-attach material and voids in die-attach layer) plays an important role in total thermal resistance of high-power LED packaging according to the differential structure function of thermal transient characteristics. The increase of void fraction in die-attach layer causes the increases of thermal resistance of die-attach layer; the thermal resistance increased by 1.95 K/W when the void fraction increased to 62.45%. The voids also make an obvious influence on thermal stress and thermal strain of chip; the biggest thermal stress of chip was as high as 847.1 MPa compared to the 565.2 MPa when the void fraction increases from being void-free to 30% in the die-attach layer.

Download Full-text

Evaluation of thermal transient characterization methodologies for high-power LED applications

Microelectronics Journal ◽

10.1016/j.mejo.2013.08.014 ◽

2013 ◽

Vol 44 (11) ◽

pp. 1005-1010 ◽

Cited By ~ 4

Author(s):

Stefan Müller ◽

Thomas Zahner ◽

Frank Singer ◽

Gabriele Schrag ◽

Gerhard Wachutka

Keyword(s):

High Power ◽

High Power Led ◽

Thermal Transient

Download Full-text

Characterization of High-Power COB LED Module Attached by Low-Temperature Sintered Nanosilver

Applied Mechanics and Materials ◽

10.4028/www.scientific.net/amm.853.389 ◽

2016 ◽

Vol 853 ◽

pp. 389-393 ◽

Cited By ~ 1

Author(s):

Jia Chen ◽

Xin Li ◽

Ya Fei Kong

Keyword(s):

High Power ◽

Junction Temperature ◽

Power Module ◽

High Brightness ◽

Ambient Temperatures ◽

Die Attach ◽

High Power Led ◽

Increasing Demand ◽

Nanosilver Paste

Along with the increasing demand of high power LED (>1W), multi-chip modules have made great progress to an inevitable trend. Thus, large packaging area is needed to dissipate heat efficiently. In other words, only when we find appropriate packaging materials to control the junction temperature well, can we achieve high-power LED devices in smaller packaging area. Obviously, a die-attach layer as the first-level packaging has a most significant impact on the thermal performance of a power module. So we introduce a novel die-attach material, nanosilver paste, which can be used for connecting multi-chips on the substrate because of its higher melting temperature and better thermal/electrical conductivity than conventional solders and adhesive films. What is more important, because of their ability to emit high brightness, LED packages are being exploited for other systems or fields, and in most cases are exposed to harsher environments. Therefore, the performance and stability of LED packages will be the key to assuring the reliable function of systems. So, in this paper, the optical and electrical properties of the LED device operating under various ambient temperatures from 27 to 120°C were determined. The test results showed that nanosilver paste was a very promising die-attach material in high power multi-chip modules packaging.

Download Full-text