Layer Structure and Thickness Effects on Electroplated AuSn Solder Bump Composition

Bonafede, S.; Huffman, Alan; Palmer, William D.

doi:10.1109/tcapt.2006.880506

Cited by 8 publications

(8 citation statements)

References 12 publications

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“…The phenomenon of the dark region containing both Au 5 Sn and AuSn phases has been also observed in Ref. 7.…”

Section: Resultssupporting

confidence: 62%

“…The reaction kinetics of producing the 80Au-20Sn alloy by reflowing the electroplated Au/Sn/Au structure had been investigated. 7 The microstructure of Au-Sn eutectic solder bumps fabricated by plating and reflow processes had been studied. 8 In this research, we focused on producing high-quality Au-Sn eutectic joints between large Si chips and ceramic packages using electroplated Au/Sn/Au layers.…”

Section: Introductionmentioning

confidence: 99%

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Fluxless Bonding of Large Silicon Chips to Ceramic Packages Using Electroplated Eutectic Au/Sn/Au Structures

Wang

Kim

Lee

2009

Journal of Elec Materi

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A fluxless process of bonding large silicon chips to ceramic packages has been developed using a Au-Sn eutectic solder. The solder was initially electroplated in the form of a Au/Sn/Au multilayer structure on a ceramic package and reflowed at 430°C for 10 min to achieve a uniform eutectic 80Au-20Sn composition. A 9 mm 9 9 mm silicon chip deposited with Cr/Au dual layers was then bonded to the ceramic package at 320°C for 3 min. The reflow and bonding processes were performed in a 50-mTorr vacuum to suppress oxidation. Therefore, no flux was used. Even without any flux, high-quality joints were produced. Microstructure and composition of the joints were studied using scanning electron microscopy with energy-dispersive x-ray spectroscopy. Scanning acoustic microscopy was used to verify the joint quality over the entire bonding area. To employ the x-ray diffraction method, samples were made by reflowing the Au/Sn/Au structure plated on a package. This was followed by a bonding process, without a Si chip, so that x-rays could scan the solder surface. Joints exhibited a typical eutectic structure and consisted of (Au,Ni)Sn and (Au,Ni) 5 Sn phases. This novel fluxless bonding method can be applied to packaging of a variety of devices on ceramic packages. Its fluxless nature is particularly valuable for packaging devices that cannot be exposed to flux such as sensors, optical devices, medical devices, and laser diodes.

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“…The phenomenon of the dark region containing both Au 5 Sn and AuSn phases has been also observed in Ref. 7.…”

Section: Resultssupporting

confidence: 62%

Section: Introductionmentioning

confidence: 99%

Fluxless Bonding of Large Silicon Chips to Ceramic Packages Using Electroplated Eutectic Au/Sn/Au Structures

Wang

Kim

Lee

2009

Journal of Elec Materi

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“…Once the layers are deposited, the stack is annealed to create the Au 0.8 Sn 0.2 eutectic material. This deposition approach has been demonstrated for both the IC interconnect [41,51,52] and hermetic MEMS packaging [31,32,33,37,38]. Figure 4 depicts an implementation of this approach in the fabrication of a WLVP for an RF resonator device with vertical feedthroughs [35].…”

Section: Bonding Approachesmentioning

confidence: 99%

Wafer-Level Vacuum Packaging of Smart Sensors

Hilton

Temple

2016

Sensors

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The reach and impact of the Internet of Things will depend on the availability of low-cost, smart sensors—“low cost” for ubiquitous presence, and “smart” for connectivity and autonomy. By using wafer-level processes not only for the smart sensor fabrication and integration, but also for packaging, we can further greatly reduce the cost of sensor components and systems as well as further decrease their size and weight. This paper reviews the state-of-the-art in the wafer-level vacuum packaging technology of smart sensors. We describe the processes needed to create the wafer-scale vacuum microchambers, focusing on approaches that involve metal seals and that are compatible with the thermal budget of complementary metal-oxide semiconductor (CMOS) integrated circuits. We review choices of seal materials and structures that are available to a device designer, and present techniques used for the fabrication of metal seals on device and window wafers. We also analyze the deposition and activation of thin film getters needed to maintain vacuum in the ultra-small chambers, and the wafer-to-wafer bonding processes that form the hermetic seal. We discuss inherent trade-offs and challenges of each seal material set and the corresponding bonding processes. Finally, we identify areas for further research that could help broaden implementations of the wafer-level vacuum packaging technology.

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“…The sequential electrodeposition technique has been used for the deposition of Sn-Au solder alloys [14,15] as the redox potential of Au is far too noble compared to that of Sn (Sn 2 +/Sn: -0.317 V; Au +/ Au: + 1.83 V). Ishii et al [14] successfully fabricated Sn-5wt.% Au bumps by electroplating 20 alternating layers of Sn and Au.…”

Section: Introductionmentioning

confidence: 99%

“…The micro-bumps with sizes in the range of 38.1 f.!m to 38.5 f.!m formed completely at 220°C. Bonafede et al [15] reported that increasing the number of layers does not increase the likelihood to obtain homogeneous Sn-Au eutectic alloy. Ezawa et al [16] successfully electroplated Ag-Sn metal stacks on photoresist masked wafers.…”

Section: Introductionmentioning

confidence: 99%

Effects of stacking sequence of electrodeposited Sn and Bi layers on reflowed Sn-Bi solder alloys

Lee

Goh

Haseeb

2012

2012 35th IEEE/CPMT International Electronics Manufacturing Technology Conference (IEMT)

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Eutectic Sn-Bi alloy is gaining considerable attention in the electronic packaging applications. This alloy exhibits favorable properties such as low melting temperature, good wettability, high yield strength and fracture strength at room temperature. Miniaturization of electronic devices limited the choices of deposition technique where electrodeposition is identified as one of the most suitable ones. This work focuses on the formation of eutectic Sn-Bi solder alloys by reflowing a metal stack containing sequentially electrodeposited Sn and Bi layers. Three layer sequential deposition of Sn-Bi alloys is a new attempt in the electroplating field. The effects of layer sequence on the composition and microstructure of the resulting alloy is investigated. Irrespective of the layering sequence, a homogeneous microstructure is achieved after reflow. Near eutectic alloy of composition Sn-54.6 wt.% Bi is obtained from this sequential plating method.

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Layer Structure and Thickness Effects on Electroplated AuSn Solder Bump Composition

Cited by 8 publications

References 12 publications

Fluxless Bonding of Large Silicon Chips to Ceramic Packages Using Electroplated Eutectic Au/Sn/Au Structures

Fluxless Bonding of Large Silicon Chips to Ceramic Packages Using Electroplated Eutectic Au/Sn/Au Structures

Wafer-Level Vacuum Packaging of Smart Sensors

Effects of stacking sequence of electrodeposited Sn and Bi layers on reflowed Sn-Bi solder alloys

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