Etchant Baths

Copper Etchant Baths. One of the most promising applications of coupled transport is the renovation of circuit board etchant solutions that contain copper.61 The printed circuit board industry produces more than ten million gal-lons/year of spent etchant solutions in which copper, other salts and etchant chemicals are concentrated. Coupled transport permits continuous on-site removal of copper from the etchant solutions and simultaneous regeneration of the etchant solution. This represents a considerable savings in the costs of manufacturing circuit boards. 

On the product side of the membrane, concentrated sulfuric acid (100 g/2) is employed. Thus, copper sulfate is formed. Copper could be recovered by precipitating the copper sulfate or by electrodepositing the copper. In the latter case, the overall oxidation-reduction reaction, 

Copper recovery from etchant baths is a particularly promising application of coupled transport because the high copper concentrations in the etchant solutions result in high fluxes. A relatively small unit is, therefore, able to process a large volume of solution. 

Etching Process Feed Solution Liquid Product Solution 

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Copper etchants do not directly influence the electroless plating process, but are used merely to remove unwanted copper, and should not affect the deposit properties. The costs of waste treatment and disposal have led to disuse of throw-away systems such as chromic—sulfuric acid, ferric chloride, and ammonium persulfate. Newer types of regenerable etchants include cupric chloride, stabilized peroxide, and proprietary ammoniacal etchant baths. 

The combination of a positive charge and reducibility of tetrazolium salts finds use as anticorrosion agents for metals.634,635 The y are components of an oxidant/etchant bath composition for silicon dioxide corrosion-resistant surfaces.636 They are also used as antistatic agents in polyamide... 

Preliminary Examination of PATE Imaging Characteristics. The data herein have shown that PATE resins are easily photolyzed in the deep UV region to form crosslinked films which are of sufficient integrity for photoresists. However, in addition to these film performance properties, a potential resist material must meet other equally important criteria. For example, the masked (unphotolyzed) portion of the resist film must be removed prior to etching, without damage to the cured film. Also, the cured films must withstand an etchant bath. Therefore, since PATE resins seem to meet the necessary requirements of solubility and solvent resistance, investigation of performance under crude simulated processing conditions was undertaken. 

Concentrated waste solutions are obtained from spent metal plating baths and etchants. However, the majority of metal wastes are soflds or sludges obtained from the hydrolysis of metal-bearing solutions and industrial process effluents. Most of these water-insoluble wastes are composed of hydroxides or basic salts of the contained metals. Eor processing by hydrometallurgical routes the materials must be brought into solution usually by acid or ammoniacal or alkaline digestion. 

The major source of hazardous metals from chromating and other chemical conversion processes, as well as from electro- and electroless plating, is generally the process baths themselves. Spent cleaners and etchants also can contain large quantities of metal removed from workpieces. 

Raw materials for PC board manufacture that contain metals include the following o Copper foil (encasing the board) o Etchants chromic acid, cupric chloride, ferric chloride o Catalysts stannous tin, palladium chloride o Electroless copper bath copper sulfate... 

The main constraints on ARO at this time are highly concentrated, oxidative solutions like chromic acid, nitric acid and peroxy-sulfuric etchant. Their process rinses can be recovered and metals separated but, reconcentrating to near (40-70% of) bath strength, achievable with other solutions, shortens membrane life. WTI is working to develop membranes and operating procedures to improve system economies. Right now a life of 4-6 months is typical in most applications. 

Use Fertilizers, chemicals, dyes and pigments, etchant, alkylation catalyst, electroplating baths, iron and steel, rayon and film, industrial explosives, lab reagent, nonferrous metallurgy. 

Fluorad. [3M] Fluorinaied alkyl mixtures surfactant wettit, spreading and leveling agent for use in electrolyte systems, coatings, alkaline cleaners, floor polisites, etchants, plating baths emul-... 

The rate of etching under diffusirMi-controlled kinetics is therefore increased by spraying the etchant onto the substrate as opposed to immersing it in a static bath of etchant. This is the reason that commercial PCM is carried out in a spray etching machine (Fig. 1) where etchant is sprayed from nozzles at typical pressures of 2-4 bar. Due to the size limitations of such machines, typically CHM applied to large parts is carried out in large tanks that can hold as much as 44,0001 of etchant (Dini 1984). 

Uses Mfg. of acetic anhydride, cellulose acetate, vinyl acetate monomer acetic esters prod, of plastics, pharmaceuticals, cosmetics, aroma chems., dyes, insecticides, photographic chemicals, food additives solvent reagent acidifier solvent for electronic materials etchant (semiconductor mfg.) aluminum brightener laundry sour boiler water additive coagulant for latex buffer in cosmetics buffer, acidifier in textile baths preservative, acidity regulator in foods flavor, solvent, vehicle in foods, pharmaceuticals color diluent sanitizing solutions for food contact... 

During the etching process, the mask layer and the substrate are both immersed in the etching media which can be a wet chemical etching bath or plasma. Although the etchant mainly reacts with the substrate, the mask layer is also attacked. The relationship between the etching of the substrate and the mask layer is the... 

Abrade the surface lightly with fine sandpaper or treat with chromic acid etchant (E-20 etchant, Marbon Co.). When etching, best results are obtained by immersing the areas to be bonded in an 80°C (176°F) bath for 50-60 seconds. 

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