The influence of nickel/gold surface finish on the assembly quality and long term reliability of thermally enhanced BGA packages

Coyle, Richard; Holliday, A.; Mescher, P.; Solan, P.P.; Gahr, S.; Cyker, H.A.; Dorey, K.; Ejim, T.I.

doi:10.1109/iemt.1999.804792

Cited by 18 publications

(7 citation statements)

References 11 publications

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“…[4][5][6][7] However, there has been some concern about the reliability of these joints, given the weak interface between the eutectic Pb-Sn solder and the electroless Ni/Au metallization. [8][9][10][11] This concern has motivated recent investigations of interfacial reactions [6,7] and failure mechanisms [12,13] in joints that contain electroless Ni layers.…”

Section: Introductionmentioning

confidence: 99%

The microstructure of eutectic Au-Sn solder bumps on Cu/electroless Ni/Au

Song

Ahn

Morris

2001

J. Electron. Mater.

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In this work we studied the initial microstructure and microstructural evolution of eutectic Au-Sn solder bumps on Cu/electroless Ni/Au. The solder bumps were 150-160 µm in diameter and 45-50 µm tall, reflowed on Cu/electroless Ni/Au, and then aged at 200 o C for up to 365 days. In addition, Au-Ni-Sn-alloys were made and analyzed to help identify the phases that appear at the interface during aging.The detailed interfacial microstructure was observed using TEM. The results show that the introduction of Au from the substrate produces large islands of ζ-phase in the bulk microstructure during reflow. Two Au-Ni-Sn compounds are formed at the solder/substrate interface and grow slowly during aging. The maximum solubility of Ni in the ζ-phase was measured to be about 1 at.% at 200°C, while Ni in the δ-phase is more than 20 at.%. The electroless Ni layer is made of several sublayers with slightly different compositions and microstructures. There is, in addition, an amorphous interaction layer at the solder/electroless Ni interface.

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Section: Introductionmentioning

confidence: 99%

The microstructure of eutectic Au-Sn solder bumps on Cu/electroless Ni/Au

Song

Ahn

Morris

2001

J. Electron. Mater.

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“…However, there is insufficient space to allow bussing for the more common electrolytic Au/Ni plating. 7,8) The contact pads for the solder balls on the BGAs usually have an Au/Ni surface finish. Each layer of metal plated on BGA substrates has its own specific functions.…”

Section: Introductionmentioning

confidence: 99%

Effect of Isothermal Aging on Ball Shear Strength in BGA Joints with Sn-3.5Ag-0.75Cu Solder

et al. 2002

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The ball shear strength of BGA solder joints during isothermal aging was studied with Sn-3.5Ag-0.75Cu solder on three different pads (Cu, electroless Ni-P/Cu, immersion Au/Ni-P/Cu) at temperature between 70 and 170 • C for times ranging from 1 to 100 days. The reliability of solder ball attachment was characterized by mechanical ball shear tests. As a whole, the shear strength of BGA joints decreased with increasing temperature and time. The shear strength for both the immersion Au/Ni-P/Cu and electroless Ni-P/Cu pads was consistently higher than that of the Cu pad for all isothermal aging conditions. The fracture surface showed various characteristics depending on aging temperature, time, and the types of BGA pad. The P-rich Ni layer formed at the interface between (Cu, Ni) 6 Sn 5 and Ni-P deposits layer after aging, but fracture at this interface was not the dominant site for immersion Au/Ni-P/Cu and electroless Ni-P/Cu pad.

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“…The use of immersion Au/electroless Ni as an alternative surface finish for area array packages and printed circuit board (PCB) is increasing to meet the requirements of the increased density and electrical performance. 12,13) This trend is continuing despite the evidence that immersion Au/electroless Ni causes or contributes to catastrophic, brittle, and interfacial solder joint fractures. [14][15][16] The electroless plating defect is manifested as brittle fracture at the interface between the Ni deposits and the intermetallic compound.…”

Section: Introductionmentioning

confidence: 99%

Effect of Surface Finishes on Ball Shear Strength in BGA Joints with Sn-3.5 mass%Ag Solder

Lee

Jung

et al. 2002

Mater. Trans.

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The present study is aimed at the assessment on the reliability of solder ball attachment to the bond pads of BGA substrate with various plating schemes. The reliability of solder ball attachment is characterized by mechanical ball shear tests. In addition to the ball shear tests, SEM is performed to inspect the cross-section and the fracture surface of the tested specimens for failure analysis. The aging was conducted in convection ovens in air at 343, 393, 423 and 443 K respectively for times ranging 8.64 × 10 4 to 864 × 10 4 s. Without regard to the deposited layer, the shear strength of BGA joints decreased with the increasing temperature and time. After isothermal aging, the fracture surface shows various characteristics depending on aging temperature and time, and the types of BGA pad.

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The influence of nickel/gold surface finish on the assembly quality and long term reliability of thermally enhanced BGA packages

Cited by 18 publications

References 11 publications

The microstructure of eutectic Au-Sn solder bumps on Cu/electroless Ni/Au

The microstructure of eutectic Au-Sn solder bumps on Cu/electroless Ni/Au

Effect of Isothermal Aging on Ball Shear Strength in BGA Joints with Sn-3.5Ag-0.75Cu Solder

Effect of Surface Finishes on Ball Shear Strength in BGA Joints with Sn-3.5 mass%Ag Solder

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