Solderability of BGA Joints between Cu Core Solder Balls with Sn/Ag Multi Plating and Ni/Au Coated Pads

Sakatani, Shigeaki; Saeki, Toshio; Kohara, Yasuhiro; Uenishi, Koji; Kobayashi, Kojiro F.; Yamamoto, Masahiro

doi:10.5104/jiep.6.509

Cited by 10 publications

(3 citation statements)

References 3 publications

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“…Little precipitation of Bi was observed, and alballs melted like Sn-Ag-Cu-Bi balls. 15) There was a rather linear relationship between the heating rate and onset temperature for all of the solders. Since the onset melting temperature is dependent on the heating rate, the solidus temperature is generally determined as the value at the heating rate of 0 K/s by extrapolating this relation.…”

Section: Melting Behavior Of Solder Ballsmentioning

confidence: 99%

Melting and Joining Behavior of Sn/Ag and Sn-Ag/Sn-Bi Plating on Cu Core Ball

et al. 2002

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We fabricated Cu core Sn-Ag solder balls by plating pure Sn and Ag on Cu balls and clarified that Sn/Ag plating began to melt at a rather low temperature, the eutectic temperature of Sn-Ag-Cu. This early melting at the eutectic temperature was ascribed to the diffusion of Cu and Ag into the Sn plating during the heating process. We investigated the solderability of the BGA joint with the Ni/Au coated Cu pad to compare it with that of the commercial Sn-Ag and Sn-Ag-Cu balls. After reflow soldering, we observed a eutectic microstructure composed of β-Sn, Ag 3 Sn, and Cu 6 Sn 5 phases in the solder, and a η -(Au, Cu, Ni) 6 Sn 5 reaction layer was formed at the interface between the solder and the Cu pad. The BGA joint using Cu core solder balls could prevent the degradation of joint strength during aging at 423 K because of the slower growth rate of the η -(Au, Cu, Ni) 6 Sn 5 reaction layer formed at the solder-pad interface. Furthermore, we were able to fabricate Cu-cored, multicomponent Sn-Ag-Bi balls by sequentially coating binary Sn-Ag and Sn-Bi solders onto Cu balls. The coated balls also exhibited almost the same melting and soldering behaviors as those of the previously alloyed Sn-2Ag-0.75Cu-3Bi solders.

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Section: Melting Behavior Of Solder Ballsmentioning

confidence: 99%

Melting and Joining Behavior of Sn/Ag and Sn-Ag/Sn-Bi Plating on Cu Core Ball

et al. 2002

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“…[1][2][3][4][5][6] Weak joints are a result of the formation of a P-rich layer due to excessive diffusion of Ni into the solder at the joint interface. This problem becomes more serious in small products due to their microscopic soldered joints.…”

Section: Introductionmentioning

confidence: 99%

Joints Soldered on Electroless Ni–Au Surfaces Using Cu-Containing Flux: Strength, Microstructure and Mechanism of Improvement

et al. 2005

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The critical issue for soldering on electroless Ni-Au surface finishes is fragile solder joints. Previous studies have indicated that these weak joints are a result of the formation of a P-rich layer at the joint interface. In this study, the new flux, which contains a Cu compound, demonstrates improved solder joint strength for solder ball attachment on electroless Ni-Au surface finishes. Cross-sectional analysis revealed that this new flux gives a thinner P-rich layer at the joint interface than that seen with a conventional flux. Moreover, the formation of a uniformly thin Cu-Sn intermetallic layer on the Ni-P plated surface is observed after reflow soldering. We conclude that this Cu-Sn layer formation during reflow impedes extra diffusion of Ni into solder from the plating surface so that the growth of a P-rich layer can be effectively inhibited and, thus, the joint strength is improved.

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“…However, it is also reported that soldering on an ENIG surface finish often results in fragile joints. [1][2][3][4][5][6][7][8][9] One of the plausible reasons for this joint degradation is related to the formation of a P-rich layer at the interface, which is induced by Ni diffusion into the molten solder during heating. Therefore, when soldering on an ENIG, the suppression of Ni dissolution or diffusion is believed to be effective in improving joint strength.…”

Section: Introductionmentioning

confidence: 99%

Effects of Zn-Bearing Flux on Joint Reliability and Microstructure of Sn-3.5Ag Soldering on Electroless Ni-Au Surface Finish

et al. 2010

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Joint reliability and microstructure for Sn-3.5Ag soldering on an electroless Ni-P/Au surface finish were investigated, using the flux bearing Zn(II) stearate. The content of the zinc compound in the flux varied from 0 mass% to 50 mass%. The results of both shock and pull strength tests for as-reflowed solder joints showed that Zn-bearing fluxes gave higher joint strength than did flux without Zn compound. Additionally, the use of flux containing 50 mass% of Zn(II) stearate provided the smallest reduction rate in pull strength in regard to aging treatment at 150 C for 1000 h. According to the microstructure of the aged joints, both an interfacial intermetallic layer and a P-rich layer of the joint obtained by the use of the flux without Zn(II) stearate became thick with prolonged aging. On the other hand, a slow growth of the interfacial reaction layer was observed for the joint with Zn(II) stearate in flux during annealing. It is presumed that the formation of the interfacial intermetallic compound with Zn at reflow works effectively in suppressing the diffusion of Ni into the solder matrix during subsequent aging, and this can maintain a relatively high joint strength for those joints with Zn(II) stearate in flux. After damp heat treatment with 85 C/85% RH up to 500 h, no sign of corrosion was observed in either joint. Moreover, there was no significant change of the microstructure, nor of the pull strength, with or without Zn(II) stearate in flux.

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Solderability of BGA Joints between Cu Core Solder Balls with Sn/Ag Multi Plating and Ni/Au Coated Pads

Cited by 10 publications

References 3 publications

Melting and Joining Behavior of Sn/Ag and Sn-Ag/Sn-Bi Plating on Cu Core Ball

Melting and Joining Behavior of Sn/Ag and Sn-Ag/Sn-Bi Plating on Cu Core Ball

Joints Soldered on Electroless Ni–Au Surfaces Using Cu-Containing Flux: Strength, Microstructure and Mechanism of Improvement

Effects of Zn-Bearing Flux on Joint Reliability and Microstructure of Sn-3.5Ag Soldering on Electroless Ni-Au Surface Finish

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Solderability of BGA Joints between Cu Core Solder Balls with Sn/Ag Multi Plating and Ni/Au Coated Pads

Cited by 10 publications

References 3 publications

Melting and Joining Behavior of Sn/Ag and Sn-Ag/Sn-Bi Plating on Cu Core Ball

Melting and Joining Behavior of Sn/Ag and Sn-Ag/Sn-Bi Plating on Cu Core Ball

Joints Soldered on Electroless Ni&ndash;Au Surfaces Using Cu-Containing Flux: Strength, Microstructure and Mechanism of Improvement

Effects of Zn-Bearing Flux on Joint Reliability and Microstructure of Sn-3.5Ag Soldering on Electroless Ni-Au Surface Finish

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Joints Soldered on Electroless Ni–Au Surfaces Using Cu-Containing Flux: Strength, Microstructure and Mechanism of Improvement