Lead free interfacial structures and their relationship to Au plating including accelerated thermal cycle testing of non-leaden BGA spheres

Toshihiko, Taguchi; Kato, Ryuichi; Akita, S.; Okuno, Akihiro; Suzuki, Hisashi; Okuno, Tetsuya

doi:10.1109/ectc.2001.927805

Cited by 11 publications

(7 citation statements)

References 3 publications

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“…It is interesting to note that once the Ni 3 Sn 4 layer is consumed totally by forming a (Au, Cu, Ni) 6 Sn 5 layer, there is a chemical change as well as a physical change of the Au-containing compound that occurs simultaneously. Always, it is noticed that the Pb-phase envelops the (Au, Ni)Sn 4 layer, which is also confirmed by many other investigators [14] and [15]. While (Au, Ni)Sn 4 exists in a layertype morphology with the Pb phase on one side and with the Ni 3 Sn 4 layer on the other side, here, it has been found that AuSn 4 cannot exist in a layer morphology with the newly formed (Au, Cu, Ni) 6 Sn 5 layer.…”

Section: Reaction Mechanismssupporting

confidence: 81%

“…Due to the slight solubility (< 0.3 wt.%) and the fast diffusion of Au in the eutectic Sn-Pb at 150 • C, the AuSn 4 intermetallics in the bulk solder reconfigure to form the (Au, Ni)Sn 4 compound at the interface where Ni is available. It was reported elsewhere that within 48 h, a continuous layer of (Au, Ni)Sn 4 forms on the Ni 3 Sn 4 IMC layer [14] and [15]. This study has also found that shear strength decreases within 50 h of aging for the sample having a thicker Ni layer when the Au thickness is more than 0.6 µm (see Fig.…”

Section: Reaction Mechanismssupporting

confidence: 58%

“…It is surprising to see that the interfacial shear strength decreases rapidly within the first 50 h of aging. Other investigators have also reported a lower strength with brittle fracture after 48 h of aging [11], [13]- [15]. However, the new thing here is that for the thinner Ni layer, no significant change in shear strength has been found up to about an 0.9-µm-thick Au layer.…”

Section: Methodsmentioning

confidence: 61%

“…Cu 3 Sn was also detected underneath the (Cu, Ni) 6 Sn 5 for the solder joint with a thin Ni layer. Many other investigators have reported the same interfacial structures [11], [13]- [15]. As aging progresses, both (Au, Ni)Sn 4 and Ni 3 Sn 4 grow thicker by taking Sn atoms from the solder neighboring the interface.…”

Section: B Fracture Surface Morphology and Microchemistrymentioning

confidence: 82%

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Reliability of BGA Solder Joints on the Au/Ni/Cu Bond Pad-Effect of Thicknesses of Au and Ni Layer

Alam

Chan

et al. 2006

IEEE Trans. Device Mater. Relib.

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A systematic experimental work has been carried out to investigate the effect of thicknesses of the Au and Ni layers in the bond pad metallization on the reliability of ball grid array (BGA) solder joints as well as to understand the mechanism of Au diffusion to the solder interface. BGA solder balls of Sn-37 wt.% Pb have been bonded on BGA solder bond pads of Au/electrolytic Ni/Cu by reflowing at 225 • C for 0.5 min. The thickness of the Ni layer was varied from 0.35 to 2.8 µm, while the thickness of Au layer was varied from 0.1 to 1.3 µm. Solid state aging at 150 • C up to 1000 h has been carried out to simulate the ultimate interfacial reactions during the operational life of electronic devices. Cross-sectional studies of the solder-to-bond pad interfaces have been conducted by scanning electron microscopy equipped with an energy-dispersive X-ray analyzer to investigate the interfacial reaction phenomena. Ball shear tests have been carried out to obtain the mechanical strength of the solder joints and to correlate shear behavior with the interfacial reaction products. After the shear tests, fracture surfaces have also been investigated to understand the fracture modes. It has been found that Au embrittlement in the BGA Sn-Pb solder joints on Au/Ni/Cu BGA bond pads can be reduced by using either a thin Au layer or a thin Ni layer in the trilayer metallization of Au/Ni/Cu. It is easy to understand why Au embrittlement is reduced when a thin Au layer in the BGA bond pad is used; however, contrary to the usual expectation, it has been realized in this paper that a very thin Ni metallization is an effective means to maintain the mechanical integrity of the BGA SnPb solder joint. It is revealed that the out-diffusion of the Cu atoms during the aging period changes the chemistry and morphology of the intermetallic compounds (IMCs) at the solder interface, contributing to a significant reduction in brittleness. During aging at 150 • C, the thin Ni layer facilitates Cu diffusion from the bond pad toward IMCs. As a result, the brittle continuous layers of (Au, Ni)Sn 4 and Ni 3 Sn 4 are transformed into a nodular-shaped discontinuous layer of AuSn 4 and a layer of (Au, Cu, Ni) 6 Sn 5 , respectively. New interfacial reaction products with the modified morphology change the typical scenario of Au embrittlement at the BGA solder interface and thus improve the interfacial joint strength significantly.

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Section: Reaction Mechanismssupporting

confidence: 81%

Section: Reaction Mechanismssupporting

confidence: 58%

Section: Methodsmentioning

confidence: 61%

Section: B Fracture Surface Morphology and Microchemistrymentioning

confidence: 82%

See 2 more Smart Citations

Reliability of BGA Solder Joints on the Au/Ni/Cu Bond Pad-Effect of Thicknesses of Au and Ni Layer

Alam

Chan

et al. 2006

IEEE Trans. Device Mater. Relib.

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“…Characteristics of solder such as melting temperature, adhesion ability and thermal conductivity have attracted a lot of attention in microelectronics (Otiaba et al , 2011; Chung, 2001; Zhang et al , 2014b). Currently, lead-free solder alloys such as AuSn, SnAg, SnBiAg, SnAgCu, SnZn, SnBi, SnCuIn, SnZnBiSb/Cu, SnAgCuBiSbNi and SnAgBiCuGe have been proposed (Wu et al , 2001; Taguchi et al , 2001; Hwang et al , 2001; Nurmi et al , 2004; Collins et al , 2016; Ren and Collins, 2019; Dalton et al , 2018). Adding Cu into SnAg alloys will increase the eutectic alloy of Ag structure (Suganuma, 2001).…”

Section: Introductionmentioning

confidence: 99%

Investigation on effects of solder paste voids on thermal and optical performance of white high-power surface-mounted device LEDs

Raypah

Devarajan²,

Mahmud

2019

SSMT

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Purpose The presence of voids in the solder layer has been considered as one of the main issues causing reliability problems in optoelectronic devices. Voids can be created due to trapped gas, clean-up agent residues (fluxes), poor wettability at interface or shortcoming of the reflow process. The voids hinder the heat conduction path and subsequently, the thermal resistance will increase. The purpose of this paper is to investigate the influence of lead-free water-washable Sn96.5Ag3.0Cu0.5 (SAC305) solder paste (SP) voids on the thermal and optical performance of white high-power (HP) surface-mounted device (SMD) light-emitting diode (LED). Design/methodology/approach Five LEDs are mounted on five SinkPAD substrates by using the SP. The SMT stencil printing is used to control the thickness of the SP and reflow oven for the soldering process. The fraction of voids in the SP layer is calculated using the X-ray machine software. The thermal parameters of the LEDs with different voids fraction and configuration are measured using a thermal transient tester (T3Ster) system. In addition, the optical characterizations of the LEDs are determined by the thermal and radiometric characterization of power LEDs (TeraLED) and the electroluminescence by using the spectrometer. Findings The results showed that the thermal performance and temperature distribution are improved for the LED with lower voids fraction and good filling state of soldering. In addition, luminous flux, efficacy and color shift of the LEDs with different fraction and configurations of voids on the SP layer are compared and discussed. It is found that the color shift of LED1 of low voids fraction and higher thickness are less than other LEDs. Originality/value The paper provides valuable information about the effect of water-washable SAC305 SP voids fraction and filling state of solder on the thermal and optical performance of ThinGaN HP SMD LED. A comprehensive overview of the outcomes is not available in the literature. It was shown experimentally that the voids fraction, height and configuration of the SP layer could strongly influence the heat dissipation efficiency and thermal resistance. This study can help in heat diffusion investigation and failure analysis of HP SMD LEDs.

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The effect of solder paste composition on the reliability of SnAgCu joints

Nurmi

Sundelin

Ristolainen

et al. 2004

Microelectronics Reliability

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Lead free interfacial structures and their relationship to Au plating including accelerated thermal cycle testing of non-leaden BGA spheres

Cited by 11 publications

References 3 publications

Reliability of BGA Solder Joints on the Au/Ni/Cu Bond Pad-Effect of Thicknesses of Au and Ni Layer

Reliability of BGA Solder Joints on the Au/Ni/Cu Bond Pad-Effect of Thicknesses of Au and Ni Layer

Investigation on effects of solder paste voids on thermal and optical performance of white high-power surface-mounted device LEDs

The effect of solder paste composition on the reliability of SnAgCu joints

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