Thermal and mechanical effects of voids within flip chip soldering in LED packages

Liu, Yang; Leung, Siu Fai; Zhao, Jia; Wong, Chi-Yin; Yuan, Chengye; Zhang, Guoqi; Sun, Fenglian; Luo, Lingling

doi:10.1016/j.microrel.2014.07.034

Cited by 42 publications

(22 citation statements)

References 11 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…where C and M are 1.31×10 -4 and 0.166, respectively [130]. This model shows that BLT of particle-filled TIM depends on the yield stress of the material τy and the applied pressure P. τy can be expressed as [179]   (8) where A and fm are the constant and maximum particle volume fraction, respectively.…”

Section: Thermal Resistance Of Thermal Interface Materials (Tim) and Imentioning

confidence: 96%

See 1 more Smart Citation

Heat and fluid flow in high-power LED packaging and applications

Luo

Qiu

Liu

et al. 2016

Progress in Energy and Combustion Science

403

121

View full text Add to dashboard Cite

Light-emitting diodes (LEDs) are widely used in our daily lives. Both light and heat are generated from LED chips and then transmitted or conducted through multiple packaging materials and interfaces. Part of the transmitted light converts into heat along the light propagation; in return, the accumulation of heat leads to the degradation of light output. The accumulated heat negatively influences the reliability and longevity of LEDs, and thus thermal management is critical for LED packaging and applications. On the other hand, in LED packaging processes, many fluid flow problems exist, such as phosphor coating, silicone injection, chip bonding, solder reflow, etc. Amongst them, phosphor coating is the most important process which is essential for LED performance. Phosphor gel is a kind of non-Newton fluid and its coating process is a typical fluid-flow problem. Overall, since LED packaging and applications present many heat and fluid flow problems, obtaining a full understanding of these problems enables advancements in the development of LED processes and designs. In this review, the emphasis is placed on heat generation in chips, heat flow in packages and application products, fluid flow in phosphor coating process, etc. This is a domain in which significant progress has been achieved in the last decade, and reporting on these advances will facilitate state-of-the-art LED packaging and application technologies.

show abstract

Section: Thermal Resistance Of Thermal Interface Materials (Tim) and Imentioning

confidence: 96%

“…(4) here. a) Rc models Past literature is replete with models of Rc at the solid-solid interface[113,114,[130][131][132][133]. These studies have all asserted that Rc is a function of surface roughness, slope of asperity, apparent area of contact, mechanical properties of solid bodies, and load between the surfaces.…”

mentioning

confidence: 99%

Heat and fluid flow in high-power LED packaging and applications

Luo

Qiu

Liu

et al. 2016

Progress in Energy and Combustion Science

403

121

View full text Add to dashboard Cite

show abstract

“…However, as previously discussed, sapphire substrates possess high thermal resistance, which is a critical bottleneck to efficient thermal management. Various chip designs, including flip-chip and vertical structure chip designs, have been developed to resolve the self-heating issues associated with the low thermal conductivity substrates [92][93][94]. The flip-chip design is an effective solution for enhancing heat dissipation as the total thermal resistance is reduced by attaching the LED active region directly to the package substrate through interconnect materials.…”

Section: Thermal Management Of Gan-based Light-emitting Diodes For Aumentioning

confidence: 99%

Thermal Management and Characterization of High-Power Wide-Bandgap Semiconductor Electronic and Photonic Devices in Automotive Applications

Lundh

Shervin

et al. 2019

Journal of Electronic Packaging

View full text Add to dashboard Cite

GaN-based high-power wide-bandgap semiconductor electronics and photonics have been considered as promising candidates to replace conventional devices for automotive applications due to high energy conversion efficiency, ruggedness, and superior transient performance. However, performance and reliability are detrimentally impacted by significant heat generation in the device active area. Therefore, thermal management plays a critical role in the development of GaN-based high-power electronic and photonic devices. This paper presents a comprehensive review of the thermal management strategies for GaN-based lateral power/RF transistors and light-emitting diodes (LEDs) reported by researchers in both industry and academia. The review is divided into three parts: (1) a survey of thermal metrology techniques, including infrared thermography, Raman thermometry, and thermoreflectance thermal imaging, that have been applied to study GaN electronics and photonics; (2) practical thermal management solutions for GaN power electronics; and (3) packaging techniques and cooling systems for GaN LEDs used in automotive lighting applications.

show abstract

“…As the uncertainties in both voids measurement and shear force measurement are large, the relationship between the void ratio increase and shear force decrease is not clearly matched. According to some previous studies [29][30][31], the intermetallic compounds (IMCs) at the interfaces between the solder joint with electrode pad and substrate can determine the shear strength of the solder joint. A complicated competition between voids and IMC is assumed to occur during the thermal shock ageing test, in which the voids generation will limit the growth of the IMC layer [31], and the growth of the IMC layer can change the composition of the solder joint, resulting in cracks and more voids [29].…”

Section: Thermal Shock Testmentioning

confidence: 99%

Random Voids Generation and Effect of Thermal Shock Load on Mechanical Reliability of Light-Emitting Diode Flip Chip Solder Joints

Fan

Wu²,

Jiang

et al. 2019

Materials

View full text Add to dashboard Cite

To make the light-emitting diode (LED) more compact and effective, the flip chip solder joint is recommended in LED chip-scale packaging (CSP) with critical functions in mechanical support, heat dissipation, and electrical conductivity. However, the generation of voids always challenges the mechanical strength, thermal stability, and reliability of solder joints. This paper models the 3D random voids generation in the LED flip chip Sn96.5-Ag3.0-Cu0.5 (SAC305) solder joint, and investigates the effect of thermal shock load on its mechanical reliability with both simulations and experiments referring to the JEDEC thermal shock test standard (JESD22-A106B). The results reveal the following: (1) the void rate of the solder joint increases after thermal shock ageing, and its shear strength exponentially degrades; (2) the first principal stress of the solder joint is not obviously increased, however, if the through-hole voids emerged in the corner of solder joints, it will dramatically increase; (3) modelling of the fatigue failure of solder joint with randomly distributed voids utilizes the approximate model to estimate the lifetime, and the experimental results confirm that the absolute prediction error can be controlled around 2.84%.Materials 2020, 13, 94 2 of 16 power, heat generation, and packaging density are becoming higher and the operation condition is severer, the demand on the highly reliable LED CSP is dramatically increasing [9,10]. For the package to be effective, the solder joint plays critical roles in electric conduction, heat conduction, and mechanical connection. Actually, because the LED CSP always inevitably suffers the thermal cycling and even shocks from outside environments, the mismatches of thermal expansion among all packaging components under these conditions always generate periodic stress and strain in the package level [11,12]. The increase of loads on a LED CSP has put forward more requirements on the reliability of a solder joint, because the fatigue failure of the solder joint under the thermal cycling condition will lead to the failure of whole package. Therefore, the thermal shock load on the mechanical reliability of the LED flip chip solder joints has always been one of the critical bottlenecks in the development of LED CSP technology [13][14][15].Among all solder alloys, the lead-free Sn96.5-Ag3.0-Cu0.5 (SAC305) is considered as one of the most popular chip-attach candidates owing to its cost effectiveness, good solderability, and favorable mechanical strength [16,17]. It has widely been used in the flip chip soldering, but such solder connections are prone to failure over time under the thermal cycling [18] or mechanical bending test [19]. D. Kong et al. [20] used the Anand model to simulate the stress-strain response of the SnAgCu-based solder joint under the condition of thermal cycle loading and predicted its lifetime with the Manson-Coffin model. They found that the addition of a certain amount of Ce and Fe in the SnAgCu solder joint could significantly increase its fatigue ...

show abstract

Thermal and mechanical effects of voids within flip chip soldering in LED packages

Cited by 42 publications

References 11 publications

Heat and fluid flow in high-power LED packaging and applications

Heat and fluid flow in high-power LED packaging and applications

Thermal Management and Characterization of High-Power Wide-Bandgap Semiconductor Electronic and Photonic Devices in Automotive Applications

Random Voids Generation and Effect of Thermal Shock Load on Mechanical Reliability of Light-Emitting Diode Flip Chip Solder Joints

Contact Info

Product

Resources

About