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...

Die stromlose Goldplattierung bei Verwendung von K‐hydridoborat als reduzierendesAgenz wird bezüglich der Arbeitsbedingungen untersucht.

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The rapidly increasing demand for high-quality electron devices in recent years has generated a corresponding interest in methods for detecting, measuring, controlling, and removing surface contaminants (1). Contamination, even at trace levels, may cause significant fabrication problems as in diffusion welding operations. It may also degrade electrical performance characteristics, shorten lifetime, and reduce the reliability of completed devices. In addition, cleanliness is essential in order to establish reproducible material conditions which, in turn, can simplify the problems of statistical quality control.

In the fabrication and processing of electronic components, it is often necessary to use neutral or reducing protective atmospheres for various heat treating operations. Such operations as encapsulation, cleaning, brazing, glazing, surface oxide reduction and degassing of components all require the use of protective atmospheres in which oxidizing impurities must either be minimized or precisely controlled for optimum results. The presence of water or oxygen or both in amounts as small as a few parts per million can often profoundly affect the results of these operations. A variety of techniques has been reported for analysis of either of these impurities. A simple technique whereby a single instrument may be used to analyze for both of these constituents is described here.