Fig 1 - uploaded by Sehoon Yoo
Content may be subject to copyright.
Source publication
The effect of bath life of Ni(P) on the brittle-fracture behavior of Sn-3.0 wt.% Ag-0.5 wt.% Cu (SAC)/electroless nickel immersion gold (ENIG) was evaluated in this study. The bath lives of Ni(P) for the ENIG surface finish in this study were varied from 0 to 3 metal turnover (MTO), which were indirectly indicative of Ni(P) bath life, with "0 MTO''...
Contexts in source publication
Context 1
... test printed circuit board (PCB) in this study, a solder mask-defined (SMD) type FR-4 board, is shown in Fig. 1. The diameter and thickness of the Cu pad on the test PCB were 400 lm and 10 lm, respectively. The thickness of the photoimageable solder mask (PSR) of the test PCB was 15 lm. The Cu pad was finished with ENIG. The bath life of Ni(P) of the ENIG was either 0 and 3 MTO. The concentrations of P in the Ni(P) were 6.98 wt.% and 7.74 wt.% ...
Context 2
... have reported that brittle frac- ture at the interface resulted from the weak adhe- sion of the P-rich layer and/or nano-voids formed in the Ni-Sn-P layer. 5,9 To observe the nano-voids formed in the Ni-Sn-P layers of the 0 and 3 MTO samples, the interfaces of the 0 and 3 MTO samples were observed by cross-sectional TEM; the results are shown in Fig. 10. The sizes of the nano-voids in the 3 MTO sample were higher than those in the 0 MTO sample. In the 0 MTO sample, the sizes of nano-voids were approximately 5-10 nm. The sizes of the nano-voids in the 3 MTO sample were 20- 40 nm. There are two mechanisms of nano-void formation. One is the Kirkendall void mechanism which results from ...
Similar publications
In this study, the joint effect of rice husk ash (RHA) reinforcement as an alternative silica source and electroless nickel immersion silver (ENIAg) surface finish on the intermetallic compound (IMC) formation and shear strength of the Sn–0.7Cu solder system was investigated. A series of plain and composite lead-free solder systems (Sn–0.7Cu−xRHA;...
The effects of the thickness of the Ni layer in thin electroless-nickel electroless-palladium immersion gold (thin-ENEPIG) surface-finished printed circuit boards (PCB) with Sn-3.0Ag–0.5Cu (SAC305) solder joints during aging treatment were investigated. We evaluated the interfacial reactions and mechanical properties of 0.3–1.0 µm thick Ni layers i...
Aim: Little is known about the reparability of glass ionomer cements (GICs) after storage in acid environments. The aim of this study was to evaluate the solubility and repairability of GICs immersed in acid solutions and subjected to brushing. Methods: Thirty discs of each GIC (Vitremer, VitroFil LC, VitroFil, and Maxxion R) were divided into thre...
To understand the stability of strongly weathered muddy slate slopes under water immersion effects, we obtained shear strength parameters of the weakly layered structures within this slate through direct shear tests. Point load tests were performed on in-site slate samples with varying water immersion durations to assess the water immersion’s softe...
The shear performance and fracture behavior of microscale ball grid array structure Sn–3.0Ag–0.5Cu solder joints with different substrate surface finishes (Cu with organic solderability preservatives and electroless Ni/immersion Au) combinations under electro-thermo-mechanical (ETM) coupled loads with increasing current density (from 1.0 × 10³ to 6...
Citations
... In general, a very thin Ni-Sn-P layer was formed in between the (Cu,Ni) 6 Sn 5 and Ni 3 P layers [3,11,20]. Many studies indicated that organic nanoparticles were formed in this Ni-Sn-P layer and increased the brittleness of the solder joints [21][22][23]. ...
The interfacial microstructure and brittle fracture reliability of solder joints on direct electroless gold (DEG) and electroless palladium immersion gold (EPIG), which are novel surface finishes for high-frequency package substrates, were evaluated in this study. A Cu6Sn5 intermetallic compound (IMC) was formed at the interface of Sn-3.0Ag-0.5Cu (SAC305)/DEG or SAC305/EPIG, while (Cu,Ni)6Sn5 and Ni3P were formed at the interface of SAC305/ENEPIG. After 1000 h of thermal aging, the IMC thickness of the SAC305/DEG and SAC305/EPIG samples increased by 217% and by 181%, respectively, while that of SAC305/ENEPIG increased by only 51%. Although ENEPIG had the lowest IMC thickness, its brittleness was higher than that of DEG and EPIG because of the different fracture paths. Fractures occurred between Cu6Sn5/Cu pad and Cu6Sn5/Cu3Sn interface for SAC305/DEG and SAC305/EPIG, while fractures mainly occurred in the Ni3P layer of SAC305/ENEPIG.
A growth of intermetallic compounds (IMCs) at the interface between electroless Ni/immersion Au (ENIG) and Sn-3.0Ag-0.5Cu (SAC305) solder and related brittle fracture behavior of solder joint with microstructure changes of electroless Ni-P was investigated. An amorphous columnar Ni-P and an amorphous structureless Ni-P surface finishes were used for the comparison. The (Cu,Ni)6Sn5 IMC layers with a similar thickness were formed between solder and ENIG interface at the as-reflowed stage for both Ni-P surface finishes. During thermal aging, the interfacial IMC thicknesses for columnar Ni-P and structureless Ni-P increased up to 400 and 800 h, respectively, and then decreased with thermal aging time. This decrease of IMC thickness with thermal aging was due to spalling. The spalling rate of the columnar Ni-P sample was higher than that of the structureless sample. The shear strength decrease with aging time was lower for the columnar Ni-P sample than the structureless Ni-P sample. Brittle fracture for the columnar Ni-P sample was lower than for the structureless Ni-P sample.
The electroless nickel immersion gold process often produces defects, such as pinholes and black pads that can cause brittle fractures at the interface between the solder and metal pad. Contamination in electroless Ni plating solutions with increasing metal turn over (MTO) is believed to be one of the causes of the formation of surface defects. MTO means indirectly Ni bath life, with ‘‘0 MTO’’ indicating a freshly plating bath and ‘‘2 MTO’’ an aged plating bath, which is supplemented twice with the initial amount of metallic salts and the reducing agent. In this study, surface defects on the Ni-plated layer were investigated to understand the correlation between the MTO solutions and defect factors by solder resist (SR) dissolution. The characteristics of the contaminated MTO solutions were analyzed by total organic carbon and liquid chromatography mass spectrometry (LC-MS). LC-MS detected the component (melamine) of the hardener of the SR at 2.14 ppm in the 2 MTO, and 2.52 ppm in the 2.5 MTO solutions. Electroless nickel plating was conducted in a 0 MTO solution with hardener addition. Pinholes were observed in solutions containing more than 2 ppm of a hardener. In particular, the content of phosphorus in the defective area was higher than that in the non-defective area. Consequently, as the MTO solution increased, the hardener was dissolved in the Ni solution, which caused defects in the nickel surface layer, such as pinholes and black pads.
The growth of interfacial intermetallic compound and the brittle fracture behavior of Sn-3.0Ag-0.5-Cu solder (SAC305) joints on electroless nickel immersion gold (ENIG) surface finish have been investigated using Ni-P plating solution at temperatures from 75°C to 85°C and fixed pH of 4.5. SAC305 solder balls with diameter of 450 μm were mounted on the prepared ENIG-finished Cu pads and reflowed with peak temperature of 250°C. The interfacial intermetallic compound (IMC) thickness after reflow decreased with increasing Ni-P plating temperature. After 800 h of thermal aging, the IMC thickness of the sample prepared at 85°C was higher than for that prepared at 75°C. Scanning electron microscopy of the Ni-P surface after removal of the Au layer revealed a nodular structure on the Ni-P surface. The nodule size of the Ni-P decreased with increasing Ni-P plating temperature. The Cu content near the IMC layer increased to 0.6 wt.%, higher than the original Cu content of 0.5 wt.%, indicating that Cu diffused from the Cu pad to the solder ball through the Ni-P layer at a rate depending on the nodule size. The sample prepared at 75°C with thicker interfacial IMC showed greater high-speed shear strength than the sample prepared at 85°C. Brittle fracture increased with decreasing Ni-P plating temperature.
