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The authors have studied water-repellency technology using a roughness structure fabricated by electroplating. This paper examined the relationship between surface morphology and water-repellency o...

Chromium plating has excellent corrosion resistance and is widely used in industry. However, it also has a high environmental load. As an alternative, electric Ni-W plating is attracting attention. However, it is not widely used because the stress is high and the film is prone to cracks. Furthermore, although it is necessary to thicken the film to improve the corrosion resistance, there are also problems that the current efficiency is low and the plating time is long. Therefore, we investigate a film with high corrosion resistance by using the jet-flow plating method that enables plating at a high current density. Our results show that the jet-flow plating enables plating of 50 µm, and high corrosion resistance is obtained by randomly generating fine cracks in the film at 20 A·dm−2. We also found that the stress changed depending on the current density and shape of the crack also changed.

Traditionally, a highly concentrated mixed solution of chromic acid and sulphuric acid has been used as an etchant for electroplating on ABS plastics. However, this etchant is hazardous and the sub...

An economic and low toxicity gold plating process for bio-compatible device fabrication was investigated. A tiopronin-gold complex altered by mercaptothiodiazole or mercaptotriazole derivatives gave a form of the complex that could be reduced autocatalytically to enable electroless gold plating. Catalytic ca. 5 nm gold particles were selectively grafted into cycloolefin polymer and polyethylenenaphthalate film surfaces by adsorption of tiopronin-gold complex from solution into 20‐30 nm deep ultra-violet light modified surface layers followed by reduction with sodium borohydride. Exposure of the catalyst adsorbed surfaces to baths composed of tiopronin-gold complex, mercaptothiodiazole and ascorbic acid resulted in selective electroless plating on the modified surfaces. Observation of the interface cross-section by transmission electron microscopy revealed that the gold deposits were physically anchored to the substrate by nanometer scale octopus trap like structures.

Plating stress in nickel plating increases with high current density. A remedy for this has been demonstrated by using a step control method through combining plating at 20 A dm−2 (low current density) and 40 A dm−2 (high current density). Internal stress could be reduced in comparison to plating at a fixed current density by the initial formation of crystals at a 20 A dm−2 low current density, such that a state of low stress was maintained by epitaxial growth.

In order to induce adhesion of electroless CuNiP deposition to polyimide (PI) film substrate, surface modification of PI film with an aqueous dispersion of ozone micro–nano bubbles was investigated. The treatment resulted in maximum adhesion strength of 1·14 kN m−1 for a treatment time of 5 min. Structure of the modified PI surface, the PI/plating interface, mechanism for adhesion and laminate properties were analysed. Despite increased adhesion, surface roughness of PI was not notably changed by the ozone induced surface modification. Contact of PI surface with high ozone concentration micro–nano bubbles with sufficient frequency was found to modify the surface with a low total ozone concentration of the aqueous dispersion. Cross-sectional observation of the interface suggested that formation of a thin nanoporous anchor layer on the PI surface was responsible for plating adhesion. This method provides an environment friendly and improved process for plating on PI using low concentration ozone treatment.

It becomes important to measure mechanical properties of local area of materials because of downsizing of industrial materials, and the fracture of materials often starts at the nanoscale defects. Therefore, the measurement of hardness of the local area of materials is one of key technologies to develop new materials. Nanoindentation is the depth sensing indentation method and can measure the mechanical properties of nanoscale area of materials. The hardness of materials under the controlled environment like high temperature is a big issue in energy or environment industries. Therefore, it becomes important to measure high temperature mechanical properties of nanoscale area of materials by nanoindentation. However, the shape of indenter may change when an indenter contacts to the material surface at high temperatures, and the nanoindentation at high temperatures may lead to inaccuracy of measurements. Nanoindentation does not measure indented are directly but converts the indentation depth to the indented area by area function. In order to correctly convert the indentation depth to the indented area, it is necessary to derive the area function of indented area at high temperatures. In this report, the area function is proposed that considers the change of indenter shape during repeating contact at heated materials. By using this proposed area function, nanoindentation hardness and the reduced modulus of sapphire were obtained at 303K, 473K, 673K, 873K and 1073K successfully. The nanoindentation can be used at high temperatures, if this proposed area function is used.

Nowadays, industrial products are downsized, and the structure of materials is controlled with the nanometer precision, and it becomes very important to measure the mechanical properties of local area of bulk material. Especially the hardness and the elastic modulus are important mechanical properties. The orientation dependence of hardness and reduced modulus of single crystal sapphire surface was investigated by nanoindentation. The conventional technique to measure the hardness of materials using an optical micrometer cannot evaluate mechanical properties of a local region of several µm or less. However, nanoindentation can measure mechanical properties of very small surface area of materials, and is expected to detect the micro structure dependence of mechanical properties. Nanoindentation uses very small indenter made of diamond, and measures the indentation depth. The measured depth is converted to the indented area size using the area function. The area function of the indenter can be obtained using a standard material (fused quartz) in advance. Therefore nanoindentation can measure the indented area size without using an optical micrometer. In this report, it was shown that the nanoindentation could detect the structure dependence of mechanical properties of materials. The specimen was a single crystal sapphire with c - axis surface, and the indenter was Berkovich type diamond tip. It was confirmed that the nanoindentation hardness was the lowest, and the reduced modulus was the largest, when the ridge line of indenter was oriented to the m - axis of single crystal. The nanoindentation could detect the structure dependence of a local area of mechanical properties materials.

The surfaces of the connector terminals used for electrical connection of components are electroplated with Sn, Au, or Ag in order to improve reliability. For electronic devices that require particularly high reliability, hard gold is used. The characteristics of gold deposits of various surface morphologies were examined. Gold films with increased surface roughness exhibited superior friction and wear properties without a large increase in contact electrical resistance after friction testing. Increasing the surface roughness also resulted in higher solder adhesion strength and improved corrosion resistance to sulfur dioxide gas.

Watt’s nickel bath and nickel sulfamate bath are commonly applied for plating of micro-fabrication parts. In particular, the nickel sulfamate bath produces nickel plating with low residual stress and high tensile strength. Nickel sulfamate baths are therefore used extensively for electroforming and Micro Electro Mechanical Systems (MEMS). Boric acid is usually used as a pH buffering agent in the plating bath. However, boron-containing effluents are increasingly regulated because of environmental concerns. To solve these problems, organic acids such as acetic acid and citric acid were investigated as alternatives to boric acid. The pH buffering action of the organic acid baths was higher than that of the boric acid bath. Furthermore, the mechanical properties of nickel films obtained from a low-concentration nickel plating bath using an organic acid buffer were superior to those obtained from a bath buffered with boric acid. Nickel films with good mechanical properties were obtained from high-concentration nickel baths, which showed good pH stability even without a buffering agent in the formulation. Subsequent SEM and XRD analyses of these plating films revealed a defect free cantilever structure prepared with MEMS.

Deposition of a heavier coating requires more careful attention to process control to prevent nodules and pitting. Electroless nickel plating is sensitive to deficiencies such as pit, pinhole and nodules. These defects are generally caused by the bath ingredients and operating conditions. This study specifically examined that the defects free electroless Ni-P deposits for heavy coating. Results of our investigation show that selection of complexing agent, elimination of insoluble particles from the plating solution using fine filtration, selection of pH adjustor and operating conditions are critical factors to avoid these defects.

近年の電子機器の高機能化に伴い, 実装部品の内部接続の高密度化が求められている。それゆえ, 無電解ニッケルめっきおよび置換金めっきは高い信頼性を有するプリント配線板を作製するための重要な工程となっている。信頼性を低下させる要因の1つは, パラジウム触媒が銅配線間の樹脂上に吸着して発生するニッケルの異常析出である。そのため, パラジゥム触媒フリーでの銅配線上への無電解ニッケルめっき法の開発が望まれている。そこで, 本研究ではパラジウム触媒フリーで銅配線上に無電解ニッケルめっきを施す手法を検討し, 銅上で触媒活性を有するヒドラジンを次亜リン酸を含む無電解ニッケルめっき浴に混合する手法を考案した。本法の適用により, パラジウム触媒フリーで銅上に無電解ニッケルめっきが可能となり, 異常析出の発生も抑制された。

Boric acid is generally added to buffer the pH and improve the life expectancy of a nickel plating bath. The plating industry has requested alternatives to boric acid because its use will be restricted in the future. In this study, the hull cell, pH buffer correlation and cathode current efficiency tests were conducted using 21 different substitute buffering agents. From these 21 agents, acetic acid, propionic acid, nickel acetate and citric acid showed the same appearance and buffering ability as boric acid. Physical properties, such as Vickers hardness, tensile strength and internal stress test were measured on nickel samples made using these four buffering agents, as well as boric acid. When using these four organic compounds, the internal stress somewhat higher compared with a standard boric acid bath, but the other physical properties were almost all the same, except in the case of citric acid. It was found that citric acid produced samples with higher Vickers hardness. For all the buffers, as current density increased, Vickers hardness decreased and tensile strength increased. The physical properties of samples made with these buffers show the same trends vs. current density as those made with boric acid bath.

ABS樹脂は, 家電部品や自動車などに応用され, プラスチックへのめっき材料として広汎に使用されている。一般的に, ABS樹脂は, 素材および析出金属問の密着性を得るために, H2SO4およびCrO3から成る強力な酸化剤によってエッチングする。近年, 環境汚染の規制は, WEEEやRoHS指令の文書に見られるように, 世界的に重要な関心事となっている。したがって, 有害物質を使用しない環境調和型エッチング技術が必要である。そこで, われわれは, クロム酸代替として光触媒である酸化チタンの使用に着目し, TiO2存在下で, UV照射を行うことにより, 有効な表面改質が可能であることを見いだした。本報ではABS樹脂中のブタジェン含有率を変化することにより, 密着強度の改善を検討した。その結果, ブタジェン含有率15～30%の範囲のABS樹脂で, 1.0kNm-1の密着強度が得られることがわかった。われわれはSEMおよびFE-TEM観察より, その密着性は粗れた樹脂表面なしで, ナノレベルのアンカー効果により得られることを確認した。

ABS resin has been widely applied as a plating substrate for plastics in applications such as the parts of vehicles and electrical devices. Hexavalent chromium has been applied as an etchant of plating on ABS resin. However, it is required to eliminate hexavalent chromium from the pretreatment process, since the prohibition of these treatments was determined by the EU directive on the End of Life Vehicles (ELV) from July, 2007. Therefore, alternative etching without hexavalent chromium has been investigated by using ultra violet irradiation (UV) and titanium oxide (TiO2) as a photocatalyst. We already achieved adhesion with the strength of about 1.0kNm−1 between ABS resin and deposited metal without hexavalent chromic acid etching. In this study, the mechanism of adhesion strength improvement with photocatalysts has been investigated using ABS specimens and rubber related ABS resin. As the results, the 1,2-polybutadiene distributed in the AS matrix was preferentially reformed and induced hydrophilicity on the reformed surface with the remaining network structure by cross-linking. In addition, we found that the reformed layer was composed a few μm thick and the catalyst penetrated into 30-40nm from the surface. It was concluded that the good adhesion strength between the deposited metal and resin was derived from the nano-anchor effect by the deposition of metal from the inside of 30-40nm of reformed resin.

ABS樹脂は, 最も身近な素材であり, 自動車や家電部品に幅広く使われている。一般的に, ABS樹脂および析出金属間の密着強度を改善するために, H2SO4およびCrO3を含有するエッチング溶液を使用する。また, その手法は工業的に40年以上行われている。近年, 環境汚染の問題はWEEE/RoHS指令に代表されるように, 世界的に重要なテーマとなっている。特に, 自動車における防錆表面処理技術は, EUのELV指令の環: 境負荷物質削減の大きな課題となっている。これらの規制により関係する部品は, 2007年7月以降, EU域内に6価クロムの使用が禁止となる。したがって, 有害物質を使用しない代替技術に変更が迫られている。われわれは, 光触媒である酸化チタンを利用したクロム酸を含まないエッチング代替処理に着目した。TiO2共存下において紫外線照射を行うことで, ABS樹脂表面が改質されることを見出した。この表面改質により, 無電解NiPめっき膜とABS樹脂との密着性が改善されることを確認した。さらに, 最適な条件下で, 約1kgf/cmの密着強度が得られた。

Electroless copper plating has been widely applied in the electronics field because the deposited films consist of a rock-like structure which is superior in ductility and conductivity. However, when electroless copper is deposited on a single orientation substrate like rolled copper foil, the deposited films are influenced by the performance of the following electro plating. Accordingly, our study aims at the preparation of electroless copper plating films consisting of blade and protrusion-like structures with many orientations. Deposited films consisting of blade and protrusion-like structures were obtained from a bath comprising 0.03 mol/dm3 of CuSO4·5H2O or CuC12, 0.3 mol/dm3 of formaldehyde and 0.24 mol/dm3 of EDTA and operated at pH 12.5 and 60°C. It was especially desirable to use EDTA of R=8 for the blade-like structure and R=16 for the protrusion-like structure. In our study, we are using “R” as the mole ratio obtained by dividing the value of the complexing agent concentration by that of the metallic salt concentration.

近年の電子機器の小型化・多機能化に伴い, 搭載されている基板の内部配線やパッケージには, 高密度化・高集積化が要求されている。一般に, 電子機器に内蔵されるプリント配線板 (PCB) やパッケージ部品には, 絶縁物質として有機材料が多く使用されている。この絶縁体表面に優れた密着性を有する導体層を形成することは, 超微細配線を実現するために必要不可欠な重要な技術である。また, 次世代のより微細な配線形成においては, 平滑な導体層形成が要求される。これらの理由から, 従来のような酸化剤による樹脂表面の粗化を伴うことのない, 平滑な樹脂への導体形成法について検討した。その結果, TiO2共存下において紫外線照射を行うことで, 樹脂表面にカルボニル基が形成されることを見出した。この表面改質により, 銅めっき膜と樹脂との密着性が改善されることを確認した。このようにして粗化していない平滑な樹脂においても, めっき銅皮膜との間で, 1.17kgf/cmの密着強度が得られた。

Electroless nickel initial deposition and subsequent steady state deposition process on a nonconductor and conductor were investigated.It is indicated that phosphorus contents in the deposited films during the initial nickel deposition reaction were higher than the subsequent steady state deposited films. The plating baths containing acetic acid, propionic acid, succinic acid, malic acid, citric acid, glycine and aspartic acid as a complexing agent showed higher phosphorus in the deposited films.On the conductor, lactic acid and glycolic acid added bath showed the shortest induction time and deposited films readily changed to continuous films at the initial deposition steps. Also, it is confirmed that a bath exhibiting a higher deposition rate compared with a basic bath leads to extraneous particles during the initial deposition period.On the nonconductor, the morphology of initially deposited nickel was not a layer-by-layer structure on nonconductor, it is confirmed that deposited films are composed of fine particles. Also, particle sizes of nickel-phosphorus deposits ranged from 10 to 40nm.

Initial deposition rate and appearance of deposited nickel on glass are measured to realize the role of a complexing agent in the electroless plating bath.We evaluated carboxylic acids, hydro carboxylic acids and amino acids as complexing agent.Among these complexing agents, carboxylic acids and hydro carboxylic acids indicated an acceleration effect and amino acids showed a retardation effect on the plating rate.Deposited nickel particles are agglomerated ranging from 10 to 30nm in the early deposition stages.Glycine among the complexing agents showed the smallest particle sizes in the initial deposition stages and nickel was uniformly deposited and distributed on glass.Therefore, this may lead the improvement of the adhesion strength of deposited nickel on glass.

Electroless nickel plating is not initiated on the copper substrate since there is little catalytic action with respect to the oxidation reaction of sodium hypophosphite on the copper. Therefore, a palladium catalyst treatment is generally applied. However, the extraneous deposition of nickel on the resist or resin is often observed as a result of treatment with the palladium catalyst along with the shrinking of patterns.This research involved improving the selective deposition through the use of Dimethyl Amine Borane (DMAB) instead of the palladium catalyst. Selective deposition has improved with the addition of DMAB to the electroless nickel plating bath as a second reducing agent.The mechanism of the selective deposition on the copper through the use of DMAB in electroless nickel plating has been explained in this study.

An electro-graph test using zinc instead of cadmium was evaluated as a alternative porosity measurement method. This technique was effective in the porosity evaluation of electroless nickel plating on copper substrate.Pinholes of electroless nickel deposits produced on copper substrate by the conventional palladium catalyst process have been compared to direct electroless nickel plating on copper using DMAB as a second reducing agent.Results confirmed that fewer pinholes are produced on electroless nickel films when not using the palladium catalyst process than with films treated using the conventional palladium catalyst process. The direct electroless nickel plating films displayed excellent corrosion resistance.

An electroless nickel plating bath with a hydrazine reducing agent has been investigated. An electroless nickel plating bath with a deposition rate of about 3μm/hr and superior bath stability as compared to previously reported bath has been developed. The new bath is a simple system consisting of glycine and boric acid in addition to nickel and hydrazine. The optimum plating conditions for the bath are in the range of 85-90°C at a pH of 12. The deposits obtained from the developed bath are black with a surface morphology that has a dendrite structure. Characteristics of deposits such as specific resistance and solderability were superior to those of conventional nickel-phosphorus deposits. Results confirmed that nickel was directly deposited on a copper substrate from an electroless nickel plating bath with a hydrazine reducing agent without an activation step in pretreatment.

A double zincate pretreatment of Al for plating was investigated in a LiOH-based zincate solution. The zinc deposition rate from the LiOH-based zincate solution was lower than that from NaOH or KOH-based solutions, resulting in decreased deposition of Zn and dissolution of the Al substrate. This phenomenon was interpreted as a large coordination number for water molecules to bond with Li+ ions compared to Na+ and K+ in the zincate solutions. For a LiOH-based zincate solution at a concentration near the solubility limit of water, the concentration of free water molecules decreases due to a strong restriction around Li+ ions. This situation results in a decrease of the activity coefficient of OH- which leads to dissolution of the Al substrate, and decreases the coordination number for water molecules to in relation to Zn(OH)42- ions to accelerate the electron transfer from and Zn deposition on the Al substrate. Addition of Fe(III) ions to the LiOH-based zincate solution increased the rate of Zn deposition, suggesting that the co-deposition of Fe obstruct the growth of Zn deposition and results in imperfect insulation of the Al substrate by Zn deposition.