Ammoniacal etching solutions

A pilot plant on recovery of copper from ammoniacal etching solutions was run with a good performance, as described in refs. [186,187]. LIX54 in kerosene was used as the membrane phase in SLM. Large pilot-plant HF contactors Liqui cel (diam. 25.4 cm, length 71.1 cm) with surface area of 130 m2 have also been used [186]. 

A similar approach, but for removal of copper, was presented by Yang and Kocherginsky [192]. One of the key steps in printed circuit board production is etching of a thin copper layer. Ammoniacal etching solutions are widely used for this purpose. Earher an SLM-based method was developed to treat wastewater containing ammonia and copper [187]. In this... 

Treatment of ammoniacal etching solutions by SLM-based technique... 

The chemical and mechanical properties of dry-film photoresists have been tailored to withstand various plating solutions and acid or ammoniacal-etching solutions. They can be grouped in terms of the processing chemistry used to develop the image ... 

Copper removal and recovery from ammoniacal etching solutions... 

Ammoniacal etching solutions are widely used in the electronic industry to etch a thin copper layer on printed circuit boards. During this process a spent etching solution with Cu(II) content up to 160 mg L is formed. Traditionally this solution is submitted to neutralization in order to achieve copper precipitation. After this treatment, the generated ammoniacal wastewater still contains several mg of copper and must be appropriately managed. In particular, copper concentration in this wastewater must be reduced to less than 5 mg L in order to be reused or safely discharged. The predominant form of copper (II) ions in this wastewater is [Cu(NH3)4] ". ... 

Copper removal from industrial ammoniacal wastewater (e.g., ammoniacal etching solutions) L1X54 5mgL copper level in the treated water High selectivity to copper Long term stability Yang and Kocherginsky (2007)... 

CEER process — (Capenhurst electrolytic etchant regeneration process) Electrochemical process for continuous copper removal from printed circuit board etching solutions employing either cupric chloride or ammoniacal etchant. In a cell divided by a cation exchange membrane the etching process is essentially reversed. In case of the cupric chloride etchant the etchant solution is pumped to the anode, the processes are at the... 

The HFSLM technology is also a promising effective way to concentrate and recover (i) Cu from industrial ammoniacal wastewater, e.g., ammoniacal spent etching solutions widely used in the electronic industry to etch a thin Cu layer on printed circuit boards, obtaining Cu(II) levels lower than regulation limits (ii) Ni from wastewater of stainless steel industry. 

Chemical reduction is used extensively nowadays for the deposition of nickel or copper as the first stage in the electroplating of plastics. The most widely used plastic as a basis for electroplating is acrylonitrile-butadiene-styrene co-polymer (ABS). Immersion of the plastic in a chromic acid-sulphuric acid mixture causes the butadiene particles to be attacked and oxidised, whilst making the material hydrophilic at the same time. The activation process which follows is necessary to enable the subsequent electroless nickel or copper to be deposited, since this will only take place in the presence of certain catalytic metals (especially silver and palladium), which are adsorbed on to the surface of the plastic. The adsorbed metallic film is produced by a prior immersion in a stannous chloride solution, which reduces the palladium or silver ions to the metallic state. The solutions mostly employed are acid palladium chloride or ammoniacal silver nitrate. The etched plastic can also be immersed first in acidified palladium chloride and then in an alkylamine borane, which likewise form metallic palladium catalytic nuclei. Colloidal copper catalysts are of some interest, as they are cheaper and are also claimed to promote better coverage of electroless copper. 

Cu " salts. Show an etching effect in ammoniacal solution preferentially on W(IOO) faces (Millner-Sass solution). 

Ferric chloride solutions are used as etchants for copper, copper alloys, Ni/Fe alloys, and steel in PC applications, electronics, photoengraving arts, and metal finishing. Current use of ferric chloride etchant in printed wiring fabrication is extremely limited in the United States because of costly disposal of the copper-containing etchant, and the much better commercial support for ammoniacal and cupric chloride etchants. There is still considerable use for alloy etching and photochemical machining applications. 

Modern ammoniacal etchants are mildly alkaline solutions containing ammonium carbonate, cupric and chlorite ions together with proprietary additives. Metallic etch resists including tin-lead are not usually attacked but the pH and solution composition must be maintained in order to preserve the etch rate and prevent sludge formation. A possible set of reactions is ... 

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