Microstructure evolution of gold-tin eutectic solder on Cu and Ni substrates

Tsai, Jang-Zern; Chang, C. W.; Ho, Cheng–En; Lin, Yen‐Ting; Kao, C. R.

doi:10.1007/s11664-006-0185-y

Cited by 38 publications

(14 citation statements)

References 7 publications

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“…This observation is consistent with the microstructure results of reflowing a Ni/Au/Sn structure at 290°C. 15,16 While the eutectic microstructure and evolution of the plated Au/Sn on Ni after reflow were already investigated in Refs. 15 and 16, our research focus was to bond large Si chips to commercial ceramic packages without using any flux.…”

Section: Resultsmentioning

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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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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Section: Resultsmentioning

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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“…Au is frequently used in electronic products [79][80][81][82][83]. Au bump is used in flexible electronics, and Au finish is important for oxidation prevention.…”

Section: Limited Sn Supply (Au/sn/cu)mentioning

confidence: 99%

Phase Diagrams and Their Applications in Pb‐Free Soldering

Chen

Gierlotka

et al. 2012

Lead‐Free Solders: Materials Reliability for Electronics

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Pb-free soldering is one of the most important technologies in the electronics industry. A phase diagram is a comprehensive representation of thermodynamic properties of a multicomponent material system. Basic knowledge and information of phase diagrams of Pb-free solder systems are reviewed. In this chapter, several examples of applications of phase diagrams in Pb-free soldering are presented, including general applications of melting, solidification and intermetallic compounds (IMC) formation caused by interfacial reactions. With the aid of phase diagrams, interpretations of some abnormal phenomena in Pb-free soldering such as effective undercooling reduction by Co doping, unexpected IMC growth rate in Sn-Bi/Fe couples, unexpected solder melting in Sn-Sb/Ag joints, special up-hill diffusion in the Cu/Sn-Cu/Ni sandwich structure, and the influence of limited Sn supply upon the interfacial reactions in the Au/Sn/Cu sandwich specimens, and so on, will be given.

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“…Eutectic Au-20Sn (in wt.%) solder has been widely used for bonding applications in microelectronic and optoelectronic packages because it can provide relatively low melting point, high strength, low elastic modulus and high thermal conductivity [1][2][3][4][5][6][7][8][9][10][11]. The Au-Sn binary system has a complicated equilibrium phase diagram, as shown in Fig.…”

Section: Introductionmentioning

confidence: 99%

“…The Au-Sn/substrate systems have been extensively studied [8][9][10]16,[18][19][20][21][22][23]. Song et al [16] studied the microstructure of eutectic Au-Sn solder joints on Cu and reported that the microstructure is strongly affected by the addition of Cu from the substrate during reflow.…”

Section: Introductionmentioning

confidence: 99%