• Proceedings of the Korean Institute of Surface Engineering Conference
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• 2018.06a
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• pp.33.1-33.1
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• 2018

pH is expressed mathematically as $pH=-{\log}[H^+]$, is a measure of the hydrogen ion concentration, [$H^+$] to specify the acidity or basicity of an aqueous solution. The pH scale usually ranges from 0 to 14. Every aqueous solution can be measured to determine its pH value. The pH values below 7.0 express the acidity, above 7.0 are alkalinity and pH 7.0 is a neutral solution. The solution pH can be determined by indicator or by measurement using pH sensor, which measuring the voltage generated between a glass electrode and a reference electrode according to the Nernst Equation. The pH value of solutions depends on the temperature and the activity of contained ions. In nickel electroless plating process, the controlled pH value in some limited ranges are extremely important to achieve optimal deposition rate, phosphorus content as well as solution stability. Basically, nickel electroless plating solution contains of $Ni^{2+}ions$, reducing agent, buffer and complexing agents. The plating processes are normally carried out at $82-92^{\circ}C$. However, the change of its pH values with temperatures does not follow any rule. Thus, the purpose of study is to understand the relationship between pH and temperature of some based solutions and electroless nickel plating solutions. The change of pH with changing temperatures is explained by view of the thermal dynamic and the practical measurements.

• Journal of the Korean institute of surface engineering
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• v.48 no.5
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• pp.199-204
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• 2015

Recently, fuel cell is a good alternative for energy source. Separator is a important component for fuel cell. In this study, The surface of separator was modified for corrosion resistance and electric conductivity. Reduced graphene oxide (rGO) was made by Staudenmaier's method. Nickel, phosphorus and rGO were coated on 6061 aluminum alloy as a separator of proton exchange membrane fuel cell by composite electroless plating. Scanning electron microscope, energy-dispersive X-ray spectroscopy and X-ray photoelectron spectroscopy were used to examine the morphology of Ni-P-rGO. Surface images were shown that the rGO was dispersed on the surface of Ni-P electroless plating, and nickel was combined with the un-reduced oxygen functional group of rGO.

• Journal of the Microelectronics and Packaging Society
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• v.17 no.1
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• pp.75-80
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• 2010

Electroless nickel plating on porous carbon substrate was investigated. The pore sizes of carbon substrates were 16-20 ${\mu}m$ and over 20 ${\mu}m$. The carbon surface was changed from hydrophobic to hydrophilic after immersing the substrate in an ammonia solution for 40 min at $60^{\circ}C$. The contact angle of water was decreased from $85^{\circ}$ to less than $20^{\circ}$ after ammonia pretreatment. The content of phosphorous in nickel deposit was decreased with increasing pH and then deposits became crystallized. The thickness of nickel deposit was increased with increasing pH. The minimum concentration of $PdCl_2$ for the electroless nickel plating was 5 ppm and the thickness of nickel was not significantly affected by the concentration of $PdCl_2$.

• Journal of the Microelectronics and Packaging Society
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• v.17 no.1
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• pp.55-61
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• 2010

An impact bending test method was used to evaluate the reliability for the solder joint of lead-free solder ball. In order to standardize the test method, the four point impact bending test was applied under the conditions of various frequencies and amounts of +/-amplitude respectively. Effects on the results were analysed. The optimum condition for impact bending test achieved in this study was the frequency of 10 Hz, and the amplitude of (+12/-1)~(+15/-1). 3 kinds of surface finishes Cu-OSP (Organic Solderability Preservative), ENIG (Electroless Nickel Immersion Gold), and ENEPIG (Electroless Nickel, Electroless Palladium, Immersion Gold) were used. Fracture surface showed that cracks were initiated and fractured along the intermetallic layer in the case of surface finishes of Cu-OSP and ENIG, while in the case of ENEPIG the cracks were initiated and propagated in the solder region.

• Corrosion Science and Technology
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• v.7 no.1
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• pp.61-67
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• 2008

In this paper, electrochemical and microstructural characteristics of nickel-plated Alloy 600 were investigated in order to identify the performance of electroless Ni-plating on Alloy 600 in high-temperature aqueous condition with the comparison of electrolytic nickel-plating. For high temperature corrosion test of nickel-plated Alloy 600, specimens were exposed for 770 hours to typical PWR primary water condition. During the test, open circuit potentials (OCP's) of all specimens were measured using a reference electrode. Also, resistance to flow accelerated corrosion (FAC) test was examined in order to check the durability of plated layers in high-velocity flow environment at high temperature. After exposures to high flow rate aqueous condition, the integrity of surfaces was confirmed by using both scanning electron microscopy (SEM) and energy dispersive spectroscopy (EDS). For the field application, a remote process for electroless nickel-plating was demonstrated using a plate specimen with narrow gap on a laboratory scale. Finally, a practical seal design was suggested for more convenient application.

• Journal of the Microelectronics and Packaging Society
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• v.29 no.3
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• pp.63-71
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• 2022

In this study, the interfacial reaction and drop impact reliability of Sn-Ag-Cu (SAC) solder and electroless nickel autocatalytic gold (ENAG) were studied. In addition, the solder joint properties with the ENAG surface finish was compared with electroless nickel immersion gold (ENIG) and electroless nickel electroless palladium immersion gold (ENEPIG). The IMC thickness of SAC/ENAG and SAC/ENEPIG were 1.15 and 1.12 ㎛, respectively, which were similar each other. The IMC thickness of the SAC/ENIG was 2.99 ㎛, which was about two times higher than that of SAC/ENAG. Moreover, it was found that the IMC thickness of the solder joint was affected by the metal turnover (MTO) condition of the electroless Ni(P) plating solution, and it was found that the IMC thickness increased when the MTO increased from 0 to 3. The shear strength of SAC/ENEPIG was the highest, followed by SAC/ENAG and SAC/ENIG. It was found that when the MTO increased, the shear strength was lowered. In terms of brittle fracture, SAC/ENEPIG was the lowest among the three joints, followed by SAC/ENAG and SAC/ENIG. Likewise, it was found that as MTO increased, brittle fracture increased. In the drop impact test, it was confirmed that the 0 MTO condition had a higher average number of failures than the 3 MTO condition, and the average number of failures was also higher in the order of SAC/ENEIG, SAC/ENAG, and SAC/ENIG. As a result of observing the fracture surface after the drop impact, it was found that the fracture was between the IMC and the Ni(P) layer.

• Journal of the Korean institute of surface engineering
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• v.55 no.2
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• pp.102-119
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• 2022

Gold plating is used as a coating of connecter in printed circuit boards, ceramic integrated circuit packages, semiconductor devices and so on, because the film has excellent electric conductivity, solderability and chemical properties such as durability to acid and other chemicals. As increasing the demand for miniaturization of printed circuit boards and downsizing of electronic devices, several types of electroless gold plating solutions have been developed. Most of these conventional gold plating solutions contain cyanide compounds as a complexing agent. The gold film obtained from such baths usually satisfies the requirements for electronic parts mentioned above. However, cyanide bath is highly toxic and it always has some possibility to cause serious problems in working environment or other administrative aspects. The object of this investigation was to develop a cyanide-free electroless gold plating process that assures the high stability of the solution and gives the excellent solderability of the deposited film. The investigation reported herein is intended to establish plating bath composition and plating conditions for electroless gold plating, with thiomalic acid as a complexing agent. At the same time, we have investigated the solution stability against nickel ion and pull strength of solder ball. Furthermore, by examining the characteristics of the plated Au plating film, the problems of the newly developed electroless Au plating solution were improved and the applicability to various industrial fields was examined. New type electroless gold-plating bath which containing thiomalic acid as a complexing agent showing so good solution stability and film properties as cyanide bath. And this bath shows the excellent stability even if the dissolved nickel ion was added from under coated nickel film, which can be used at the neutral pH range.

• Journal of the Microelectronics and Packaging Society
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• v.27 no.3
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• pp.29-34
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• 2020

The behavior of brittle fracture of electroless nickel immersion gold (ENIG) /Sn-3.0wt.%Ag-0.5wt.%Cu (SAC305) solder joints was evaluated. The pH of the electroless nickel plating solution for ENIG surface treatment was changed from 4.0 to 5.5. As the pH of the Ni plating solution increased, pin hole in the Ni-P layer increased. The thickness of the interfacial intermetallic compound (IMC) of the solder joint increased with pH of Ni plating solution. The high speed shear strength of the SAC305 solder joint on ENIG surface finish decreased with the pH of the Ni plating solution. In addition, the brittle fracture rate of the solder joint was the highest when the pH of the Ni plating solution was 5.

• Journal of the Korean institute of surface engineering
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• v.15 no.2
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• pp.57-67
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• 1982

Electroless Ni-plating is often utilized in industries due to its physical and mechanical characteristics in contrast to conventional electroplatings. Thus, electroless Ni-plating will be broadly applicated in many fields. However, The physial and mechanical properties of this depositss depend largely on the structure and P content of film and heat treatment. And here discused about the important results of those past research.

• Journal of the Korean Ceramic Society
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• v.26 no.1
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• pp.73-80
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• 1989

Preparation and characteristics of electroless Ni-P and Ni-B systems for semiconducting ceramics have been investigated as a function of deposit rate, reducing agent and pH variation. The effect of DMAB as ruducing agent is greater than that of sodium hypophosphite. The nickel electrode prepared from the nickel-phosphorus system with sodium hypophosphite shows low contact resistance of 0.99ohm compared with the resistance of 10chm in the electrode prepared from the nickel-boron system with DMAB. The contact resistance increases with increasing pH valuein the nickel-phosphorus system with sodium hypophosphite. The ratio of Ni to P is about 76.0/24.0 for the contact resistance of 0.99ohm in the above system.