The electroless gold plating process using potassium borohydride as the reducing agent has been investigated for impurity effects, material compatibility, bath agitation effects, and thickness uniformity and line resolution in selective plating of patterned substrates. Impurities may cause a decrease in plating rate [Ni(II) ], bath instability [Ni(II), Co(II), Fe(II) ], thickness nonuniformity (polyethylene, organics in deionized water), and nodule formation (some surfactants). Bath agitation is beneficial: it increases plating rate, minimizes porosity of thin deposits, and eliminates nodule formation. Edge build-up generally occurs in selective pattern plating but, with proper selection of bath compositions and agitation conditions, it can be maintained below 10% in the thickness range of 1-12 ~m. The rate of lateral growth of electroless gold deposits is about 60% of that of perpendicular growth under optimum plating conditions. Also considered in this paper are certain aspects of the scale-up and waste disposal problems associated with electroless gold plating.Electroless gold plating has been found to be useful in a variety of applications, especially for selective plating on patterned substrates for electronics applications. Such applications generally require pure soft gold with a thickness in the range of 1-15 ~m. A bath developed in this laboratory (1) has been found to be quite suitable for forming such deposits. Previous papers described the general bath characteristics (1), physical properties of deposits (2), bath operation with replenishment (3), reaction mechanism (4), and the nucleation and growth of deposits (5). The purpose of this paper is to describe several other aspects of the process which are important from the practical viewpoint and which have hitherto not been discussed. The topics covered include impurity effects, material compatibility, bath agitation effects, deposit thickness uniformity, and line resolution in selective plating of fine line patterned substrates. General recommendations are made as a guide for users of this process. Specific applications will be described in separate communications. Solution Preparation and Plating ProcedureCompositions of three electroless gold plating baths used are listed in Table I. Bath A was used often in our earlier studies (1-3) including those of impurity effects and porosity described in this paper. More recently, baths B and C have been used exclusively. These two baths contain less KCN and KBH4 and, therefore, are more preferable than bath A for practical reasons. Bath B gives the highest deposition rate (5-7 ~m/hr at 70~176 with vigorous agitation), but deposits with acceptable physical properties can be obtained only when plated with agitation. Bath C is slower plating (2 ~m/hr at 70~ with agitation) but gives better thickness uniformity on thin deposits in fine line plating. Details will be described in subsequent sections. It is convenient to prepare the baths by dilution of 5• concentrated stock solutions. These solutions can...
The photoelectrochemical oxidation of (i00), (I 11), and (i 11) n-InP and n-GaAs in several acidic solutions has been investigated. Specific interactions between the single crystal semiconductors and solvent selectively revea_l_crystal faces other than those originally exposed to the solvent. The relative stability of the n-lnP faces is (111) > ( 100) > ( 111). The first case of electron injection during the photoanodic dissolution of III-V compound semiconductors has been observed with (I 00) and ( 111) n-InP. Nucleophilic attack by Cl-or Br-produce intermediates whose potential and kinetics allow electron injection into the semiconductor conduction band reducing the number of photons required for the reaction from six to four. The conditions for selectively etching smooth surfaces on (100) n-lnP are discussed in detail along with the conditions for maintaining polished surfaces on n-lnP(lll) or A-face, which is difficult with conventional chemical polishes.
When cobalt-hardened electroplated gold is dissolved in either aqua regia or mercury, carbon-containing inclusions are extracted. The chemical identity of the extracts is established here by a variety of chemical and physical analyses. The indiscriminate use of the word "polymer" to refer to both the original inclusions and the extracts is inaccurate. The "polymer" separated upon dissolution of the gold in aqua regia is not an orgamc material but a known cobalt cyanide compound with the formula Cosn[Com(CN)~]2 9 xH20. On the other hand, the extract obtained after dissolution in mercury was shown to contain KsCoHI(CN)6. Based on the observation of the two different extracts and the chemistry of the plating solution, the form of the original inclusions is proposed to be either a Co(II)-or Co(III)-cyanide complex. Additional analyses on the bulk gold and on the aqua regia filtrate led to the following conclusions: (i) There is an additional source in the gold deposit for both cobalt and carbon apart from the cobalt cyanide complex. (ii) For cobalt, this additional source is the substitutional metallic form. (iii) For carbon, the additional source is an as yet unidentified compound probably derived from cyanide ions but containing a C:N ratio greater than one. This compound may be the source of the carbon found in the aqua regia filtrate, and it may account for the extraordinary amounts of hydrogen found in hard gold deposits. (iv) Some cautions are necessary in the aqua regia analyses for Co and C because of the limited solubility of "polymer."
Die stromlose Goldplattierung bei Verwendung von K‐hydridoborat als reduzierendesAgenz wird bezüglich der Arbeitsbedingungen untersucht.
The cyanoaurate (III) ion has been found to form and accumulate in acidic or neutral gold plating baths containing cyanoaurate(I) as the source of gold. This trivalent gold species brings about a decrease in plating current efficiency because its reduction to gold metal requires three faradays per mole, whereas only one faraday is consumed to reduce one mole of Au (I). The accumulation of Au (III) should therefore be minimized to produce gold deposits with a thickness unaffected by bath age. This paper describes various methods for achieving this objective, which include the use of the so‐called “dimensionally stable anode” and a techniqe of chemically reducing Au (III) to Au (I).
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.
hi@scite.ai
10624 S. Eastern Ave., Ste. A-614
Henderson, NV 89052, USA
Copyright © 2024 scite LLC. All rights reserved.
Made with 💙 for researchers
Part of the Research Solutions Family.