Origin of Surface Defects in PCB Final Finishes by the Electroless Nickel Immersion Gold Process

Kim, Bae-Kyun; Lee, Seongjae; Kim, Jong-Yun; Ji, Kum-Young; Yoon, Young-Suk; Kim, Mi-Yang; Park, Song-Hae; Yoo, Jong-Soo

doi:10.1007/s11664-007-0360-9

Cited by 56 publications

(20 citation statements)

References 4 publications

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“…In order to realize interconnections for highly integrated circuits, the Electroless Nickel Immersion Gold (ENIG) technique is widely used in microelectronic before components assembly [8]. The goal of this process consists in obtaining a Nickel film on interconnections pads, with a high uniformity and excellent conductivity.…”

Section: Methodsmentioning

confidence: 99%

Statistical investigations of an ENIG Nickel film morphology by Atomic Force Microscopy

et al. 2016

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Abstract. The morphology of a Nickel layer grown by an Electroless Nickel Immersion Gold (ENIG) technique used for microelectronics interconnections is determined by Atomic Force Microscopy (AFM) investigations. The root mean square (rms) roughness, determined over a scanned area is a function of the AFM scanned area size. In this work, we propose to consider the dynamic scale theory and the power spectrum density (PSD) analysis in order to perform a comprehensive determination of the surface properties of the ENIG nickel layer. Results highlight the existence of a first regime with a roughness exponent of 0.95 and a fractal dimension (DF) of the nickel film about 2.05. This case study is presented in order to propose further investigations. In fact, same experimental procedure should be performed in a magnetic shielded zone where a very low noise level is available such as the Low-Noise Underground Laboratory (LSBB) of Rustrel (France).

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Section: Methodsmentioning

confidence: 99%

Statistical investigations of an ENIG Nickel film morphology by Atomic Force Microscopy

et al. 2016

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“…Before the studies, however, we examined the UBMs without soldering in order to preclude the involvement of pre-existing defects, such as nodular cracks or spike penetration, that could cause black pad failure of the solder joint. [26][27][28] Figure 7a shows the Ni-P pad surface after removing the thin Au layer by cyanide etching. The surface has a smooth nodule structure with a diameter of about 2.1 lm.…”

Section: Growth Of Imcs After Reflow Soldering and Agingmentioning

confidence: 99%

Inhomogeneous Consumption of the Electroless Ni-P Layer at the Solder Joint Formed with Sn-3.5Ag-0.7Cu

2009

Journal of Elec Materi

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This report investigates the phenomenon of interfacial serration at the joint between Sn-3.5Ag-0.7Cu solder (SAC) and electroless Ni-P underbump metallization (UBM) during aging. For comparison, the interface between SAC and electrolytic Ni UBM was also examined under similar aging conditions. The joint in the electrolytic Ni/SAC sample showed a smooth, flat interface between the Ni and intermetallic compounds, even after a long aging time. In contrast, electroless Ni-P/SAC exhibited an irregular interface, the irregularity of which became more severe with increased aging time. This observed roughness was initiated by large breaks across the P-rich layer. The breaks were filled with the overlying Ni-Sn-P phase material, which provided an easier interdiffusion path for Ni and Sn in the opposite direction. As a result, the local consumption of the Ni(-P) layer was accelerated, and the interface was serrated. The local maximum consumption rate of the Ni-P layer, as calculated from the minimum thickness of this layer in each sample with aging time, was similar to that of an electrolytic Ni layer.

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“…An appropriate Pd(P) layer prevents the Ni(P) layer from being attacked by the Au plating bath; thus, galvanic hypercorrosion of the Ni(P) layer (generally termed ''black pads'') can be significantly reduced. [6][7][8][9][10] The Au and Pd(P) finishes are customarily deposited within a range of 0.05 lm to 0.3 lm (thickness) in realistic applications of the Au/Pd(P)/ Ni(P) surface finish. 11 The influence of the Pd(P) thickness on the soldering reaction between the Sn-3Ag-0.5Cu alloy and the trilayer structure [i.e., Au/Pd(P)/Ni(P)] has recently been examined by Ho et al 12 The reaction refers to a liquid-solid reaction in which the Sn-3Ag-0.5Cu alloy is a liquid but the Au/Pd(P)/Ni(P) trilayer is solid.…”

Section: Introductionmentioning

confidence: 99%

Solid–Solid Reaction Between Sn-3Ag-0.5Cu Alloy and Au/Pd(P)/Ni(P) Metallization Pad with Various Pd(P) Thicknesses

Hsu

et al. 2011

Journal of Elec Materi

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The effect of Pd(P) thickness on the solid-solid reaction between Sn-3Ag-0.5Cu and Au/Pd(P)/Ni(P) at 180°C was investigated in this study. The reaction was conducted after reflow, thereby removing the Au/Pd finish before the solidstate reaction. The reaction products included (Cu,Ni) 6 Sn 5 , Ni 2 SnP, and Ni 3 P, and their growth strongly depended on the Pd(P) thickness, especially for the former phases [i.e., (Cu,Ni) 6 Sn 5 and Ni 2 SnP]. As the Pd(P) thickness increased from 0 lm, to 0.1 lm, to 0.22 lm, the (Cu,Ni) 6 Sn 5 exhibited a needle-like dense layer, chunk-like morphology, and discontinuous morphology, respectively. The alternative phase (Ni 2 SnP) behaved in a manner opposite to that of (Cu,Ni) 6 Sn 5 , growing with a discontinuous morphology to a dense layer with increasing Pd(P) thickness. However, this strong dependence disappeared when the solder joints were subsequently subjected to solid-state aging. The (Cu,Ni) 6 Sn 5 and Ni 2 SnP both became layered structures for all cases examined. A high-speed ball shear (HSBS) test was conducted to quantify the mechanical response of the interfacial microstructures. The HSBS test results showed that any initial difference in shear strength caused by the various Pd(P) thicknesses could be reduced after the solid-state aging, which is consistent with the microstructural evolution observed. The mechanical strength of the solder joints was decreased due to the presence of a bi-intermetallic structure of (Cu,Ni) 6 Sn 5 /Ni 2 SnP at the interface. Detailed analysis of the growth of (Cu,Ni) 6 Sn 5 and Ni 2 SnP is also provided.

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Origin of Surface Defects in PCB Final Finishes by the Electroless Nickel Immersion Gold Process

Cited by 56 publications

References 4 publications

Statistical investigations of an ENIG Nickel film morphology by Atomic Force Microscopy

Statistical investigations of an ENIG Nickel film morphology by Atomic Force Microscopy

Inhomogeneous Consumption of the Electroless Ni-P Layer at the Solder Joint Formed with Sn-3.5Ag-0.7Cu

Solid–Solid Reaction Between Sn-3Ag-0.5Cu Alloy and Au/Pd(P)/Ni(P) Metallization Pad with Various Pd(P) Thicknesses

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