LED flip-chip assembly with electroplated AuSn alloy (original) (raw)
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Microelectronics Reliability, 2010
The thermal performance of flip-chip (FC) light-emitting diodes (LEDs) with different numbers of Au stub bumps has been investigated by using thermosonic bonder. The LEDs were mounted on the aluminium nitride (AlN) sub-mounts which have superior thermal conductivity (230 W/mK), and the high power Chip-on-Plate (COP) package was proposed to be used for our measurement. In order to understand the thermal performance of the high power FC-LEDs, the experimental measurement and finiteelement model (FRM) numerical simulation have been used. It is found that the thermal performance of our 1 Â 1 mm 2 FC-LEDs can only be improved when using at least 6 Au stub bumps as interconnected metals. Moreover, the surface temperature of FC-LEDs is significantly reduced while using 20 Au stub bumps.
Journal of Electronic Materials, 2018
In this study, a low-cost aluminum nitride (AlN) sintering process to produce thick AlN film substrate with a high thermal conductivity is developed. The thermal conductivity of the present produced thick AlN film substrate is about 163.8 W/mK, which is very close to the reported thermal conductivity of the AlN material. Also, a Sn-Bi die-bonding system is developed to die-bond light emitting diodes (LEDs) on the present sintered AlN substrate with a relatively low die-bonding temperature (below 160°C). In this work, to enhance a better wetting at the die-bonding interface, three external forces (10 N, 15 N, and 20 N) were applied on LED chips during the die-bonding process. We found that the 15-N applied force can achieve a better die-bonding interface among three external forces (10 N, 15 N, and 20 N). The LED die-attached on the AlN substrates by 15 N normal force has the best shear strength (41.5 MPa), compared to the shear strength of 36.9 MPa and 31.5 MPa of the LED dieattached on AlN substrates by 20 N and 10 N normal force, respectively. The LED chips die-attached on the AlN substrate by 15-N normal force shows the best thermal resistance (7.3°C/W). The agreement between the thermal resistance tests and the shear strength tests implies that the better diebonding interface produced a higher shear strength and a lower thermal resistance of the LED chips die-bonded on the AlN substrates.
Joint structure in high brightness light emitting diode (HB LED) packages
Materials Science and Engineering A-structural Materials Properties Microstructure and Processing, 2006
We present the transmission electron microscopy (TEM) analysis of 1.5μm-thick Au–20Sn solder joint between a high brightness light emitting diode (HB LED) and a Si heat sink. Due to intermetallic compound formation, global Sn depletion occurred in the thin solder, which raised the melting point of the solder and caused local incompleteness of bonding.
physica status solidi (a), 1999
Heat generated by ohmic losses is a critical parameter for performance and lifetime of light-emitting diodes (LEDs). The temperature of InGaN MQW LEDs during operation has been investigated depending on the forward current using three independent methods. First, the temperature of the active region was derived from the electroluminescence spectra of the devices. Second, temperature dependent micro-Raman scattering by phonons was used to determine the local temperature. Finally, a finite element simulation was performed to get a full temperature profile of the device. While the first method yields the temperature of the active region, the latter two can map the thermal distribution. All three independent methods reveal maximum operation temperatures about 120 to 130 C at a forward current of 30 mA, corresponding to a power density of 705 W cm ± ±2 .
AlN thin Film Coated Cu Substrates as Heat Sink for High Power LED Applications.
International Journal of Engineering Sciences & Research Technology, 2013
Heat generates from power electronics must be dissipated to maintain operating temperatures within specification. Thermal management is an important design consideration in which thermal interface material (TIM) plays important role on reducing the thermal resistance between hot and cold points. AlN thin film and AlN/Al stack were used as TIM and Cu substrates was used as heat sink. The observed total thermal resistance (R th-tot ) was low for AlN thin film coated Cu substrate. Noticeable decrease in junction temperature (T J ) rise (∆T J = 6 °C) was recorded for the LED using AlN thin film as TIM. AlN and AlN/Al thin film stack were not supported to enhance the luminosity of the given 3W LED but driving current influenced on optical properties noticeably.
Bump and Underfill Effects on Thermal Behaviors of Flip-Chip LED Packages: Measurement and Modeling
IEEE Transactions on Device and Materials Reliability, 2014
The goal of this study is to experimentally and numerically study the thermal behaviors of flip-chip (FC) light emitting diode (LED) packages with and without underfill and further to compare it with conventional wire-bonding (WB) LED packages, in order to understand its thermal dissipation mechanism. In experimental analyses, the junction temperature (T j) and surface temperatures are measured by a junction temperature tester, thermal couples and an infrared thermal imager, while the numerical analysis is carried out by an ANSYS simulation. After the validation of the simulation model with experimental results, the effects of flip-chip bump number and underfill thermal conductivity on both T j and thermal resistance (R th) of the packages are investigated by this validated model. Furthermore, a simple model of effective thermal conductivity for a composite material of bumps and underfills is proposed for thermal analysis of the FCLED packages. Thermal results for the packages are presented and discussed in terms of volume fraction and thermal conductivity for bumps and underfills in this paper. Index Terms-light emitting diode, flip chip, junction temperature, thermal resistance I. INTRODUCTION n order to reduce the electricity energy consumption for alleviating the global warming problem, the high-power light emitting diode (LED), which features low power consumption, long lifetime and short response time, has the great potential to replace the conventional general lighting, such as incandescent and fluorescent lamps [1]-[2]. However, the LED issues with high cost, high junction temperature, low luminous efficiency, Manuscript received April, 2012.
Fabrication and Characterization of Flip-Chip Power Light Emitting Diode with Backside Reflector
2013
The electrical, optical, and thermal characteristics of flip-chip (FC) GaN-based light-emitting diodes (LEDs) with and without backside aluminum (Al) reflector have been investigated. The LEDs were mounted on the silicon (Si) sub-mounts which have superior thermal conductivity (150 W/m•K), and the Au stub bumps were used as the interconnecting metal to achieve the FC bonding process. Compared with the conventional FC-free LED, the light extraction and thermal conduction of FC LED have been improved and no significant degradation of forward and reverse I-V characteristics are observed. Moreover, adding a backside Al reflector can further enhance upward light emission. The optimum numbers of Au stub bumps are 24, that is, the optimum total area of Au stub bumps is about 22.8×10 4 μm 2 for a 1 mm×1 mm LED chips.