The effect of Au plating thickness of BGA substrates on ball shear strength under reliability tests

Hung, S.C.; Zheng, P.J.; Lee, S.C.; Lee, J.J.

doi:10.1109/iemt.1999.804790

Cited by 23 publications

(10 citation statements)

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“…There are also suggestions that the brittle fracture is related to the redeposition of AuSn 4 at the interface after high-temperature annealing [ 6 , 10 , 42 , 43 , 44 , 45 , 46 ]. However, this can only happen if the amount of Au (i.e., the thickness of the Au coating) exceeds its solubility in β-Sn at the annealing temperature [ 24 ].…”

Section: Interfacial Reaction Issues With Ni(p) Metallizationmentioning

confidence: 99%

“…Figure 6 shows higher magnification bright-field TEM micrograph from the layer between (Cu,Ni) 6 Sn 5 and Ni 3 P. The composition of this phase is estimated to be 55 at-% Ni, 35 at-% Sn and 10 at-% P and it has a nanocrystalline structure, based on the selected area diffraction (SAD) results. It is unlikely that this phase is Ni 2 SnP [ 50 ] or Ni 3 SnP [ 40 , 44 ] reported earlier. The ternary NiSnP layer contains numerous small defects that have a pore-like appearance as can be seen from Figure 5 and Figure 6 .…”

Section: Interfacial Reaction Issues With Ni(p) Metallizationmentioning

confidence: 99%

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Combined Thermodynamic-Kinetic Analysis of the Interfacial Reactions between Ni Metallization and Various Lead-Free Solders

Laurila¹,

Vuorinen²

2009

Materials

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In this paper we will demonstrate how a thermodynamic-kinetic method can be utilized to rationalize a wide range of interfacial phenomena between Sn-based lead-free solders and Ni metallizations. First, the effect of P on the interfacial reactions, and thus on the reliability, between Sn-based solders and electroless Ni/immersion Au (ENIG) metallizations, will be discussed. Next, the effect of small amounts of Cu in Sn-based solders on the intermetallic compound (IMC), which forms first on top of Ni metallization, will be covered. With the help of thermodynamic arguments a so called critical Cu concentration for the formation of (Cu,Ni)6Sn5 can be determined as a function of temperature. Then the important phenomenon of redeposition of (Au,Ni)Sn4 layer on top of Ni3Sn4 IMC will be discussed in detail. The reasons leading to this behaviour will be rationalized with the help of thermodynamic information and an explanation of why this phenomenon does not occur when an appropriate amount of Cu is present in the soldering system will be given. Finally, interfacial reaction issues related to low temperature Sn-Zn and Sn-Bi based solders and Ni metallization will be discussed.

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Section: Interfacial Reaction Issues With Ni(p) Metallizationmentioning

confidence: 99%

Section: Interfacial Reaction Issues With Ni(p) Metallizationmentioning

confidence: 99%

Combined Thermodynamic-Kinetic Analysis of the Interfacial Reactions between Ni Metallization and Various Lead-Free Solders

Laurila¹,

Vuorinen²

2009

Materials

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“…During the aging, it was well known that Au atoms were diffused back to the interface between solder and Ni 3 Sn 4 intermetallic and resulted in the decreasing of bonding strength. 11,14) But Au was not found remaining at the interface of BGA pad and solder ball due to the limited spatial resolution of the SEM. Although there is no Au-Sn intermetallics was found in this case, Au-Sn intermetallics must have formed at the interface between Ni 3 Sn 4 intermetallics and solder.…”

Section: Resultsmentioning

confidence: 99%

“…Gold is plated on Ni surface of the ball pads not only to improve the wettability, but also to increase resistance to corrosion. 10,11) An increasing number of higher density BGA substrates require electroless surface finishes for feature size and routability. 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.…”

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 formation of AuSn after annealing has been reported not only between electroless Ni(P) and solder but also between electrolytic Ni coating and solder [2], [5], [6]. The weak interface between AuSn and Ni Sn is blamed for the failure [4], [5], [7].…”

mentioning

confidence: 99%

Interfacial reactions between lead-free SnAgCu solder and Ni(P) surface finish on printed circuit boards

Zeng

Vuorinen

Kivilahti

2002

IEEE Trans. Electron. Packag. Manufact.

113

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Transmission electron microscopy and scanning electron microscopy were employed to analyze the interfacial microstructure between Sn-Ag-Cu solder alloys and Ni(P)/Au metallizations. The intermetallic compound Cu 6 Sn 5 , containing a small amount of dissolved Ni, was found to form preferentially on the Ni coating. This compound layer served as a barrier for direct reaction of Sn with the Ni(P) coating. On the Ni(P) side, a nickel phosphide was identified. Thermodynamic evaluation of the Cu-Ni-Sn system was carried out to rationalize the enrichment of Cu at the solder/finish interface. Effects of the interfacial reactions on joint reliability are discussed.

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The effect of Au plating thickness of BGA substrates on ball shear strength under reliability tests

Cited by 23 publications

References 0 publications

Combined Thermodynamic-Kinetic Analysis of the Interfacial Reactions between Ni Metallization and Various Lead-Free Solders

Combined Thermodynamic-Kinetic Analysis of the Interfacial Reactions between Ni Metallization and Various Lead-Free Solders

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

Interfacial reactions between lead-free SnAgCu solder and Ni(P) surface finish on printed circuit boards

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