Copper plating is most commonly achieved using a double cyanide solution, because the acid sulfate solution can not e utilize on steel or on zinc base articles.
Copper plating is wisdom used alone are alone as a protective or decorative plating since it readily mature. It strongly accelerates the corrosion of steel and most other basis metals, when they are exposed at pores or sites of mechanical damage. Electroplated copper coatings are, however, often used as the initial or undercoat on difficult basis irregular and highly recessed articles because of their excellent covering and throwing power.
In such cases copper deposits of one to two ten thousands of an inch of an inch are applied, and then the articles are thoroughly rinsed and transferred immediately to a nickel plating bath. The simple double cyanide bath is slow and is too alkaline for zinc base dies casting. For these purposes a solution containing Rochelle salt sodium potassium tartarate is used at a higher temperature and current density. It may be pointed out that the copper in copper cyanide is monovalent, i.e. only one electron is needed to deposit each atom, compared with two electrons per atom from the copper sulfate bath.
Thus at the same current density the rate of deposition is twice as great in the cyanide copper bath as in the copper sulfate bath. Copper cyanide baths give a very smooth but matt deposit; addition can be made to provide a lustrous deposit but this is less necessary since copper is usually only in undercoat.
Showing posts with label Copper Plating. Show all posts
Showing posts with label Copper Plating. Show all posts
Monday, May 18, 2009
Tuesday, August 5, 2008
Copper Plating Physical Properties
Data on the physical, mechanical, and electrical properties of electrodeposited copper were comprehensively reviewed. In the table is describe the ranges for high-strength, hard, lowly stressed, good leveling, or thermally stable electrodeposited copper. The high strength copper was deposited from copper sulfate baths containing triisopropanolamine or molasses and thiourea and in copper cyanide baths containing potassium thiocyanate solution with PR current and in the copper sulfate bath containing naphthalene disulfonic acid and thiourea or several other addition agents.
The deposits with a low electrical resistivity were obtained in copper flouroborate and sulfate baths at 30oC, which contained no addition agents. These deposits also were thermally stable to 400oC, changed very little in density, and exhibited low stress, less than 3.0 kg/cm2. The properties for the good-leveling copper were measured for specimens deposits in a copper sulfate bath containing a sulfonate compound and the operating conditions on the properties and structure of copper electrodeposits is described in reference.
The grain structure of copper deposits usually correspond to one of four types. Deposits from the sulfate baths containing no addition agents are columnar. Additions of gelatin, phenolsulfonic and many other agents cause the fibrous structure.
Properties of copper electrodeposited:
The deposits with a low electrical resistivity were obtained in copper flouroborate and sulfate baths at 30oC, which contained no addition agents. These deposits also were thermally stable to 400oC, changed very little in density, and exhibited low stress, less than 3.0 kg/cm2. The properties for the good-leveling copper were measured for specimens deposits in a copper sulfate bath containing a sulfonate compound and the operating conditions on the properties and structure of copper electrodeposits is described in reference.
The grain structure of copper deposits usually correspond to one of four types. Deposits from the sulfate baths containing no addition agents are columnar. Additions of gelatin, phenolsulfonic and many other agents cause the fibrous structure.
Properties of copper electrodeposited:
Sunday, July 27, 2008
Equipment for Copper Plating
Steel tanks lined with rubber or plastic are preferred for large acid copper baths, but glass fiber reinforced plastic tanks are used for small volumes of solution. Lining materials that are generally suitable for either the sulfate or the fluoborate bath are properly formulated natural hard rubber, neoprene rubber, polyethylene, or elasticized vinyl chloride polymers. Air lines can be made of hard rubber or polymerized vinylidine chloride. Special grades of carbon pipe and tubing make efficient heat exchangers or less expensive. Rubber or rubber lined filters are used for continuous filtration, but stainless steel is satisfactory for short periods. Graphite is recommended for use as heat exchanger for copper fluoborate solution.
Preparation of Basis Metals
Because loose, nonadherent displacement films of copper are formed on steel and zink when these bases metals are immersed in acid copper baths, a cyanide copper or nickel strike plate is required before plating in acid baths. If the bases metal is completely covered, the strike plate can be as thin as 1.3 μm, 2.5 μm is sometimes preferred for parts of complex shape. After plating in the cyanide bath, the work should be thoroughly rinsed, dipped in a dilute solution of hydrochloric or sulfuric acid to neutralize any undissolved alkaline material, and rinsed again before plating in the acid bath.
Nickel or nickel alloys, when appropriately surface activated by cathodic treatment, reverse current etching in sulfuric acid, or other method, can be plated directly in an acid copper bath. Contact should be made to the work before immersion. Stainless and chromium steels are plated in acid baths with adherent copper deposits by first striking in a solution concentrated in sulfuric acid but dilute in copper sulfate 240 g/l sulfuric acid 112 g/l CuSO4.5H2O.
Preparation of Basis Metals
Because loose, nonadherent displacement films of copper are formed on steel and zink when these bases metals are immersed in acid copper baths, a cyanide copper or nickel strike plate is required before plating in acid baths. If the bases metal is completely covered, the strike plate can be as thin as 1.3 μm, 2.5 μm is sometimes preferred for parts of complex shape. After plating in the cyanide bath, the work should be thoroughly rinsed, dipped in a dilute solution of hydrochloric or sulfuric acid to neutralize any undissolved alkaline material, and rinsed again before plating in the acid bath.
Nickel or nickel alloys, when appropriately surface activated by cathodic treatment, reverse current etching in sulfuric acid, or other method, can be plated directly in an acid copper bath. Contact should be made to the work before immersion. Stainless and chromium steels are plated in acid baths with adherent copper deposits by first striking in a solution concentrated in sulfuric acid but dilute in copper sulfate 240 g/l sulfuric acid 112 g/l CuSO4.5H2O.
Monday, July 14, 2008
Avoid Sandy Deposit
Between 2 and 35 mg/l chloride is added in the form of hydrochloric acid to electro refining solutions to precipitate silver and avoid and avoid "sandy" deposits. From 30 to 100 mg/l of chloride is recommended for bright copper plating with many modern brighteners.
Nitrates were reduced to ammonia at the cathode in copper sulfate baths. A reduction product of the sulfate ion, which is said to have a grain coarsening effect, can be removed by heating the bath and adding an oxidizing agent, but oxidizing agents such as hydrogen peroxide or potassium permanganate are said to reduce throwing power.
In the fluoborate bath, lead is the only metallic impurity known to interfere with the deposition of ductile plates; it can be precipitated by adding sulfuric acid. Besides lead, metals like silver, gold, arsenic, and antimony might be codeposited with copper, but the effect of such impurities are not known.
Organic impurities originating from decomposition of addition agents or leaching of elastomeric tank linings sometimes embrittle deposits, but can be removed by treating the solution with an appropriate activated carbon, followed by filtration, alfa-Naphtylamine was identified as an injurious contaminant leached from certain rubber tank linings. As little as 10 mg/l alfa-naphtylamine caused as irregular tank linings. As little as 10 mg/l alpha-napthylamine caused an irregular pattern of uneven copper plate having ridges and valleys. Treatment with activated carbon is desirable when a new bath is being prepared, especially the flouborate bath, which may be contaminated with impurities leached from rubber shipping drums. An instance has been reported of embritlement traceable to impurities from wood tanks.
Tuesday, July 8, 2008
Effects of Impurities (Acid Copper)
Acid copper baths are more tolerant of ionic impurities than many other plating solutions. Many metallic ions introduced regularly by carryover with the work, by dissolution of impurities in the anode, or by dissolution of the basis metal (for example, iron, nickel, or zinc) can be expected to accumulate in the bath, because conditions are usually not satisfied for effecting co deposition of such metallic impurities (nickel, cobalt zinc, iron) with copper. For example, less than 2 ppm nickel was codeposited with copper in a sulfate bath containing 15 g/l nickel.
Nickel and iron reduce the conductivity of the sulfate bath to the same degree as an equivalent increase in copper. The deposition potentials of arsenic and antimony are apparently near that of copper in the sulfate bath, since codeposition was reported to occur. Arsenic and antimony in concentration of 10 to 80 g/l and 0.02 to 0.1 g/l, respectively, embrittled deposits and roughness surfaces. Additions of gelatin or tannin, however, effectively inhibited codeposition of these impurities and prevented roughness and embrittlement caused by them. Antimony readily codeposits with copper, but only small amounts of arsenic could be detected. Bismuth, like arsenic and antimony, caused granular deposits. Antimony and bismuth are believed to form insoluble complex compound with arsenate.
Small concentration of alkali metal and alkaline earth salts were found to smooth copper deposits. Tin salts were also reported to smooth deposits and were, at one time, purposely added to the sulfate, and silver partly. If silver is a contaminant, a small amount will be codeposited with copper. A high current density favors the codeposition of silver. Silver chloride caused pitting in semibright copper plate.
Nickel and iron reduce the conductivity of the sulfate bath to the same degree as an equivalent increase in copper. The deposition potentials of arsenic and antimony are apparently near that of copper in the sulfate bath, since codeposition was reported to occur. Arsenic and antimony in concentration of 10 to 80 g/l and 0.02 to 0.1 g/l, respectively, embrittled deposits and roughness surfaces. Additions of gelatin or tannin, however, effectively inhibited codeposition of these impurities and prevented roughness and embrittlement caused by them. Antimony readily codeposits with copper, but only small amounts of arsenic could be detected. Bismuth, like arsenic and antimony, caused granular deposits. Antimony and bismuth are believed to form insoluble complex compound with arsenate.
Small concentration of alkali metal and alkaline earth salts were found to smooth copper deposits. Tin salts were also reported to smooth deposits and were, at one time, purposely added to the sulfate, and silver partly. If silver is a contaminant, a small amount will be codeposited with copper. A high current density favors the codeposition of silver. Silver chloride caused pitting in semibright copper plate.
Friday, July 4, 2008
Maintenance and Control on Acid Copper Plating
The concentration of copper sulfate or copper fluoborate can be approximated by specific gravity measurements, but the contribution of sulfuric acid to the specific gravity of the sulfate bath must be taken into account. The acid concentration of fluoborate bath is controlled by measuring pH, using colorimetric pH papers.
Filtration requirements depend on the dirt load of the air, any dirt brought in by the work, and the amount of detached anode sludge particles. If the cathodes are steel and if they are incompletely protected with copper or nickel strike, particles that become detached from immersion deposits will also contribute to the filtration requirements. Although it is possible to maintain acceptably smooth deposits with only occasional batch filtration, continuous filtration is usually preferred. Cellulosic filter aids are satisfactory, but siliceous filter aids should be avoided when the flouborate solution is filtered papers are satisfactorily.
Sunday, June 29, 2008
Operating Condition (Acid Copper Plating)
Temperature may vary from 18 to 60 oC; however, a temperature between 32 and 43 oC is common, since it can be maintained economically with little or no heating or cooling. An increase in the temperature results in a higher conductivity and reduced anode and cathode polarization. Degreasing the temperature from 35 to 15 oC brought about a considerable grain refinement in plates deposited at 3 A/dm2. A temperature below 30oC is recommended for plating bright copper in acid baths to maintain good leveling power. These solutions are customarily agitated with air.
Current density and agitation must be balanced in order to obtain deposits having desired properties. For producing electrotypes, cathode current densities of 16 to 22 A/dm2 are generally employed when using the sulfate bath agitated with air. Fast moving endless wire can be plated at 50 A/dm2. Still higher current densities are used when sufficient agitation can be supplied. Impinging of jets of electrolyte on the surface of the cathode is said to permit a current density of 215 A/dm2. When movement of the work is impractical or when air agitation fails to provide good mixing at all significant surfaces, the density is usually kept at 3.7 to 5.4 A/dm2. It is claimed that higher current densities are practical with the fluoborate bath when agitation is the same as for the sulfate bath. Acceptable deposits 25 μm thick were obtained without agitation at 38 A/dm2.
In either the sulfate or the fluoborate bath, an increase in current density results in increased cathode polarization (but not to the extent noted for many other solutions). Cathode films become more depleted in copper(II) ion and more concentrated in sulfate ion when the current density is increased. Clear evident has been reported of grain refinement produced by increasing the current density.
Wednesday, June 25, 2008
Brightening Agents
Find Brightening Agents:
Thiourea additions brighten copper deposited from acid sulfate baths. A patent disclosed the use of 0.002 to 0.005 g/l. An appreciable grain-refining and brightening effects of thiourea are attributed to its adsorption in copper deposits and the resulting effect on crystal nucleation.
Sulfide ions created when thiourea decomposeds reduce the ductility of copper deposits. Combined with dextrin, molasses, lignosulfonats, mercaptobenzimdazoles, naphthalene sulfonic acid, or tribenzylamine and other organic agents, small concentrations of thiourea were once employed for brightening purposes, but have been largely superseded by better brighteners that have little or no harmful effect on ductility.
Sulfonated acetylthiourea or sulfanated aryl and alkyl substitution products of acetylthiourea were developed for bright copper plating from acid baths. Another process utilized the sulfonation products of sulfurized aromatic compounds presence of anhydrous aluminum chloride or thionyl chloride in the presence of anhydrous aluminum chloride and sulfuric acid. Acetyl cyanide was proposed as a brightener for either the sulfate or the floroborate bath. Several complex amines was patented as brightening agents in 1958. In 1958, a patent disclosed a combination of thiohydantion (a thiourea derivative) and a multiringed aromatic amine. A substituted amino benzene sulfonic acid was disclosed in another patent for brightening copper deposited from the copper sulfate bath.
Polyacrylamides, the reaction product of aminothiazole, acrylaminates, thiocarboxylic acid amides, tetrahydropyranyl amides, homopolymers of 1-3-dioxolane, and a combination of phenol polyglycols and thiosemicarbozones are also included among the brightening agents patented since 1955.
Some of these brightening agents also induce leveling. For example, a surface finish of 0.46 μm with 12.5 μm of good leveling bright copper or to only 0.1 μm with 25 μm. Such processes deposit copper with a leveling power much higher than typical bright nickel deposits.
Thiourea additions brighten copper deposited from acid sulfate baths. A patent disclosed the use of 0.002 to 0.005 g/l. An appreciable grain-refining and brightening effects of thiourea are attributed to its adsorption in copper deposits and the resulting effect on crystal nucleation.
Sulfide ions created when thiourea decomposeds reduce the ductility of copper deposits. Combined with dextrin, molasses, lignosulfonats, mercaptobenzimdazoles, naphthalene sulfonic acid, or tribenzylamine and other organic agents, small concentrations of thiourea were once employed for brightening purposes, but have been largely superseded by better brighteners that have little or no harmful effect on ductility.
Sulfonated acetylthiourea or sulfanated aryl and alkyl substitution products of acetylthiourea were developed for bright copper plating from acid baths. Another process utilized the sulfonation products of sulfurized aromatic compounds presence of anhydrous aluminum chloride or thionyl chloride in the presence of anhydrous aluminum chloride and sulfuric acid. Acetyl cyanide was proposed as a brightener for either the sulfate or the floroborate bath. Several complex amines was patented as brightening agents in 1958. In 1958, a patent disclosed a combination of thiohydantion (a thiourea derivative) and a multiringed aromatic amine. A substituted amino benzene sulfonic acid was disclosed in another patent for brightening copper deposited from the copper sulfate bath.
Polyacrylamides, the reaction product of aminothiazole, acrylaminates, thiocarboxylic acid amides, tetrahydropyranyl amides, homopolymers of 1-3-dioxolane, and a combination of phenol polyglycols and thiosemicarbozones are also included among the brightening agents patented since 1955.
Some of these brightening agents also induce leveling. For example, a surface finish of 0.46 μm with 12.5 μm of good leveling bright copper or to only 0.1 μm with 25 μm. Such processes deposit copper with a leveling power much higher than typical bright nickel deposits.
Sunday, June 22, 2008
Addition Agents
Many kind of Additives:
Addition agents for brightening, hardening, grain refining, surface smoothing, increasing the limiting current density, and reducing trees are frequently added to the acid copper sulfate bath, but the use of a particular addition must be evaluated for each application, because undesirable characteristics can then be avoided. For example, many of the addition are generally higher when addition agent proposed result in embitterment of the plate. Deposition potentials greatly increased by adding gelatin (0.2 g/l) or glue. These additions result in grain refinement, but this is chiefly unidirectional, because the structure remains columnar and becomes more fibrous. Gelatin additions to the sulfate bath introduce porosity, organic inclusions both.
The effects of glycine, one of the amino acids formed by the hydrolysis of gelatin, are similar to the effects of gelatin. Cystine and methionine, like gelatine, are cathode-polarizing agents. On the other hand, dicarboxylic amino acids appeared more effective than monocarboxylic.
Phenolsulfonic acid is used in the electrotyping industry, but the results with it depend on the sulfonation and purification procedures. Deposits become harder and smoother after a bath has been electrolyzed or dummied for a short time following an addition of phenol or phenolsulfonic acid.
The smoothing and grain refining tendencies of addition agents are sometimes associated with the formation of complex ions with copper or of colloids at or near the cathode interface. Gelatin of glycine, for example, forms complex ions with copper and also exist in colloidal form. Particles of colloids arising form additions of selenious and arsenic oxides have been observed by ultramicroscopic examination to concentrate at the cathode.
With 0.14 to 0.42 mg/l selenious oxide and 0.0065 to 0.13 mg/l aresnious oxide, grain structure was refined, surfaces were smoothed, and density was improved. Nevertheless, the ability of a colloidal or ionic addition agent to improve the deposit cannot be conclusively predicted in advance on the basis of a general knowledge of its ionic or colloidal behavior in electrolytes. Thus, in a copper (II) nitrate bath colloidal addition agents were effective as cathode polarizers, but did not result in surface smoothing or grain refining.
Addition agents for brightening, hardening, grain refining, surface smoothing, increasing the limiting current density, and reducing trees are frequently added to the acid copper sulfate bath, but the use of a particular addition must be evaluated for each application, because undesirable characteristics can then be avoided. For example, many of the addition are generally higher when addition agent proposed result in embitterment of the plate. Deposition potentials greatly increased by adding gelatin (0.2 g/l) or glue. These additions result in grain refinement, but this is chiefly unidirectional, because the structure remains columnar and becomes more fibrous. Gelatin additions to the sulfate bath introduce porosity, organic inclusions both.
The effects of glycine, one of the amino acids formed by the hydrolysis of gelatin, are similar to the effects of gelatin. Cystine and methionine, like gelatine, are cathode-polarizing agents. On the other hand, dicarboxylic amino acids appeared more effective than monocarboxylic.
Phenolsulfonic acid is used in the electrotyping industry, but the results with it depend on the sulfonation and purification procedures. Deposits become harder and smoother after a bath has been electrolyzed or dummied for a short time following an addition of phenol or phenolsulfonic acid.
The smoothing and grain refining tendencies of addition agents are sometimes associated with the formation of complex ions with copper or of colloids at or near the cathode interface. Gelatin of glycine, for example, forms complex ions with copper and also exist in colloidal form. Particles of colloids arising form additions of selenious and arsenic oxides have been observed by ultramicroscopic examination to concentrate at the cathode.
With 0.14 to 0.42 mg/l selenious oxide and 0.0065 to 0.13 mg/l aresnious oxide, grain structure was refined, surfaces were smoothed, and density was improved. Nevertheless, the ability of a colloidal or ionic addition agent to improve the deposit cannot be conclusively predicted in advance on the basis of a general knowledge of its ionic or colloidal behavior in electrolytes. Thus, in a copper (II) nitrate bath colloidal addition agents were effective as cathode polarizers, but did not result in surface smoothing or grain refining.
Thursday, June 19, 2008
Primary Constituent on Bath Function
Copper flouborate is more soluble than copper sulfate. Metal ion concentration can be more than double in the flouborate bath in comparison with a copper sulfate solution containing 50 to 75 g/l of sulfate acid.
Change in sulfuric acid concentration have more influence than changes in copper sulfate concentration on solution conductivity and anode and cathode polarization. For example, specific conductivity in nearly doubled when the concentration of sulfuric acid is raised from 50 to 100 g/l. An additional increase in free acid concentration to 200 g/l, which is level widely used in electro refining, reduces the resistivity from 4.2-4.3 to 1.6-1.9 ohm-cm. Cathode polarization decrease when a small amount of sulfuric acid is added to a solution of copper sulfate, reaches a minimum at about 0.4 M (38 g/l), and increase with a further increase in sulfuric acid effect on grain size, but some grain refinement was detected as a result of increasing the sulfuric acid concentration to 1.5 N (72 g/l).
If acid concentration in the flouborate bath is too low (pH mote than 1.7), deposits are dull, dark, and brittle. Boric acid is added to stabilize the bath and prevent decomposition of copper flouborate, this increases resistivity slightly. In bath with concentration of more than 15 g/l fluoboric acid or 220 g/l copper flouboric, an increase in the concentration of either the salt or the acid lowers the resistivity.
The next is Addition of Agents
Change in sulfuric acid concentration have more influence than changes in copper sulfate concentration on solution conductivity and anode and cathode polarization. For example, specific conductivity in nearly doubled when the concentration of sulfuric acid is raised from 50 to 100 g/l. An additional increase in free acid concentration to 200 g/l, which is level widely used in electro refining, reduces the resistivity from 4.2-4.3 to 1.6-1.9 ohm-cm. Cathode polarization decrease when a small amount of sulfuric acid is added to a solution of copper sulfate, reaches a minimum at about 0.4 M (38 g/l), and increase with a further increase in sulfuric acid effect on grain size, but some grain refinement was detected as a result of increasing the sulfuric acid concentration to 1.5 N (72 g/l).
If acid concentration in the flouborate bath is too low (pH mote than 1.7), deposits are dull, dark, and brittle. Boric acid is added to stabilize the bath and prevent decomposition of copper flouborate, this increases resistivity slightly. In bath with concentration of more than 15 g/l fluoboric acid or 220 g/l copper flouboric, an increase in the concentration of either the salt or the acid lowers the resistivity.
The next is Addition of Agents
Sunday, June 15, 2008
Bath Function on Acid Copper Electroplating
Bath Function of Acid Copper:
The concentration of copper sulfate is not particularly critical, although the resistivity of the solution is greater when the concentration is increased. Cathode polarization increases slightly at copper sulfate concentrations above 1 M (250 g/l). A concentration of less than 60 g/l copper sulfate results in a decreased cathode efficiency. When very high cathode current densities are used, a high concentration of copper sulfate, within the limits such on table is recommended. The solubility of copper sulfate is decreased when the sulfuric acid concentration is increased.
To improve the throwing power of some bright copper sulfate baths used for plating printed circuit boards, a low copper sulfate concentration such as 60 g/l of CuSO4 5H2O is combined with 80 g/l of sulfate acid, 30 mg/l of hydrochloric acid, and appropriate brighteners. Analogously, copper flouborate solutions containing 56 g/l of Cu(BF4)2, 160 g/l of fluoboric acid and brighteners are also regarded as thigh throw baths for through hole plating. Air agitation is used for both types of solutions.
Copper(II) sulfate (CuSO4.5 H2O) and sulfuric acid, or copper (II) flouborate (Cu(BF4)2) and fluoboric acid, are the primary constituents of the metal ions in solutions such as those can look on the table. Copper can be deposited at very low cathode current densities from the acid-free aqueous solutions of the salt, but at higher current densities the deposits from the sulfate bath are spongy and contain occluded salts. Plate characteristics are improved, solution conductivity is increased, and anode and cathode polarization are greatly reduced when free acid is added to either solution. The acid also prevents the preparation of basic salts.
Formulation of Commercial Acid Copper Baths | ||
Copper Sulfate Solution | Average Concentration | Concentration Limits |
Copper Sulfate, CuSO4. 5H2O, g/l | 188 | 150-250 |
Sulfuric Acid, H2SO4, g/l | 74 | 45-110 |
Specific gravity, at 25 oC | 1.165 | 1.115-1.21 |
Resistivity, at 21oC, ohm-cm | 4.2-4.3 | |
Saturday, June 14, 2008
Acid Copper Plating Principle
The Principle of Electroplating:
The copper (II) (Cu2+) salts in either the sulfate on the flouborate bath are highly ionized except for small amounts of less ionized complex salts formed with certain addition agents. The addition of sulfuric acid to the sulfate solution, or flouboric acid to be flouborate bath, is necessary for obtaining acceptable deposits. Because of the highly conductivity of commercial solutions, and because anode and cathode polarizations are small, voltages required for depositing copper are less for acid than for alkaline baths. Electrorefining plants employ the copper sulfate bath largely for this reason. Tank voltages for refining copper are frequently as low as 0.2 V for a cathode and anode current density of 1.6 to 2.2 A/dm2.
Anode and cathode polarizations are nearly negligible in purified solutions used at low current densities. Even at the high cathode current density of 21.5 A/dm2, 6 V current source is ample when the solution is efficiently agitated. Excessive polarization of the solution is efficiently agitated. Excessive polarization of the anodes in the sulfate bath may occur when the anode current density exceeds about 5 A/dm2 without encountering excessive anode polarization.
Because of the low cathode polarization, the acid baths do not have as good throwing power as alkaline solution. The plate distribution closely approximate; the primary current distributions, the deviation was found to be 10.8 % or less for the sulfate bath. This disadvantage is largely overcome in electroforming practice by appropriate current shields.
Anode and cathode efficiencies are nearly 100% at all practical current densities. The rate of deposition obtainable depends chiefly on the efficiency of agitation in preventing excessive polarization. Acceptable deposits were reported at a current density as high at 260 A/dm2, equivalent to 3.63 mm/hr, with violent agitation.
The character of copper deposits is influenced by the concentrations of copper salts and of free said, the temperature, the cathode current density, and the nature and degree of agitation. Dense deposits with good surface smoothness up to a thickness of 500 μm or more can be produced without addition agents.
The copper (II) (Cu2+) salts in either the sulfate on the flouborate bath are highly ionized except for small amounts of less ionized complex salts formed with certain addition agents. The addition of sulfuric acid to the sulfate solution, or flouboric acid to be flouborate bath, is necessary for obtaining acceptable deposits. Because of the highly conductivity of commercial solutions, and because anode and cathode polarizations are small, voltages required for depositing copper are less for acid than for alkaline baths. Electrorefining plants employ the copper sulfate bath largely for this reason. Tank voltages for refining copper are frequently as low as 0.2 V for a cathode and anode current density of 1.6 to 2.2 A/dm2.
Anode and cathode polarizations are nearly negligible in purified solutions used at low current densities. Even at the high cathode current density of 21.5 A/dm2, 6 V current source is ample when the solution is efficiently agitated. Excessive polarization of the solution is efficiently agitated. Excessive polarization of the anodes in the sulfate bath may occur when the anode current density exceeds about 5 A/dm2 without encountering excessive anode polarization.
Because of the low cathode polarization, the acid baths do not have as good throwing power as alkaline solution. The plate distribution closely approximate; the primary current distributions, the deviation was found to be 10.8 % or less for the sulfate bath. This disadvantage is largely overcome in electroforming practice by appropriate current shields.
Anode and cathode efficiencies are nearly 100% at all practical current densities. The rate of deposition obtainable depends chiefly on the efficiency of agitation in preventing excessive polarization. Acceptable deposits were reported at a current density as high at 260 A/dm2, equivalent to 3.63 mm/hr, with violent agitation.
The character of copper deposits is influenced by the concentrations of copper salts and of free said, the temperature, the cathode current density, and the nature and degree of agitation. Dense deposits with good surface smoothness up to a thickness of 500 μm or more can be produced without addition agents.
Saturday, June 7, 2008
Application of Acid Copper Electroplating
Electro deposition of copper from acid baths is extremely used for electroforming, electrorefining, manufacture of copper powder and electroplating. Refiner and electroformers; in particular, employ acid solutions because costs of chemicals and power are low and because the baths are simply and easy to control. Electroformed copper articles are produced in several important fields of industry, including electrotypes, phonograph records, band instruments, heat exchangers and reflectors. More than 2700 metric tons of copper anodes are consumed annually in making electrotypes valued at about $ 100,000,000.
Modern method of electrotype molding differ greatly from the procedures of the early forties. Developments have been announced concerning the electroforming of complex shapes with reentrant angles, which can not be made by other methods, for radar, aircraft and other industries. Many kilometers of steel wire are given a copper cyanide "strike" and plated with copper in acid solutions to produce a high strength electrical cable. Thick deposits of copper (200 µm) are apply to steel rolls and then engrave for use in printing and marking paper and textile.
Stainless steel cooking vessel are copper plated in acid bath to improve the diffusion characteristic of outer surface and avoid local hot spots. Copper plating for stopping of carburizing of selected areas is accomplished by striking in cyanide bath followed by plating in cyanide solutions. Acid copper plating sometimes used for building up worn or over machines parts, especially when copper surfaces are desired for protection against fretting corrosion.
Modern method of electrotype molding differ greatly from the procedures of the early forties. Developments have been announced concerning the electroforming of complex shapes with reentrant angles, which can not be made by other methods, for radar, aircraft and other industries. Many kilometers of steel wire are given a copper cyanide "strike" and plated with copper in acid solutions to produce a high strength electrical cable. Thick deposits of copper (200 µm) are apply to steel rolls and then engrave for use in printing and marking paper and textile.
Stainless steel cooking vessel are copper plated in acid bath to improve the diffusion characteristic of outer surface and avoid local hot spots. Copper plating for stopping of carburizing of selected areas is accomplished by striking in cyanide bath followed by plating in cyanide solutions. Acid copper plating sometimes used for building up worn or over machines parts, especially when copper surfaces are desired for protection against fretting corrosion.
Saturday, May 31, 2008
Composition of Printed Wire Board Plating
Excessive amount of organic additives or the decomposition products associated with the additives can result in brittle deposits. Possibly the biggest pitfalls in studying the causes of these deposits are the difficulties in analyzing the addition agents and identifying the culpable decomposition product. The researcher disclosed an analytical scheme for controlling solid or aqueous stock solutions of ore additive (2-mercaptobenzimidazole), while others claimed that the key was the use of only a minimum amount of proprietary leveler.
Optimum ductility has been obtained by using solutions free of organic additives. In some cases continuous carbon filtration is also used, in another, multistage and periodic reverse current. However, even with these precautions, brittle copper deposits could be obtained. Along this line, showed that multilayer boards containing excess ammonia and a low pyrophosphate to copper ratio failed much more quickly by cracking than did boards plated with ductile copper. To minimized cracking in the plated through holes by applying a thin deposit of copper pyrophosphate (5-7.5 µm) followed by 25 µm of ductile cyanide copper. Plated through hole copper cyanide deposits were less susceptible to cracking than pyrophosphate deposits.
Brittle copper deposit for the way solder peeled away from copper surfaces during adhesion test and solder joint divorced themselves from copper pads. The failure were eliminated when copper pyrophosphate plating was done with no organic additives in the bath, or by use of a nickel diffusion barrier from a pyrophosphate bath. It was postulated that brittle copper obtained with organic additives exhibits a diffusion rate different from that of pyrophosphate copper without organic additives. Skip printing is occasionally encountered when plating printed circuit boards. This problem manifests itself as depressions in the form of teardrops around the plated through holes. The depressions are probably caused by variable thickness of the cathode film during plating. Interfaces produced by cavitations in the solution due to high agitation around the holes are immediately filled with desorbed brighteners and are thereby locally insulated. The primary causes of the variable cathode film which lead to skip plating are excessive or decomposed brighteners, improper current density, agitation or both eliminated skip plating. Test method for printed circuit boards with plated through holes are given in various specifications. Item such as electrical continuity, temperature cycling, bend strength, and plating thickness are checked.
Optimum ductility has been obtained by using solutions free of organic additives. In some cases continuous carbon filtration is also used, in another, multistage and periodic reverse current. However, even with these precautions, brittle copper deposits could be obtained. Along this line, showed that multilayer boards containing excess ammonia and a low pyrophosphate to copper ratio failed much more quickly by cracking than did boards plated with ductile copper. To minimized cracking in the plated through holes by applying a thin deposit of copper pyrophosphate (5-7.5 µm) followed by 25 µm of ductile cyanide copper. Plated through hole copper cyanide deposits were less susceptible to cracking than pyrophosphate deposits.
Brittle copper deposit for the way solder peeled away from copper surfaces during adhesion test and solder joint divorced themselves from copper pads. The failure were eliminated when copper pyrophosphate plating was done with no organic additives in the bath, or by use of a nickel diffusion barrier from a pyrophosphate bath. It was postulated that brittle copper obtained with organic additives exhibits a diffusion rate different from that of pyrophosphate copper without organic additives. Skip printing is occasionally encountered when plating printed circuit boards. This problem manifests itself as depressions in the form of teardrops around the plated through holes. The depressions are probably caused by variable thickness of the cathode film during plating. Interfaces produced by cavitations in the solution due to high agitation around the holes are immediately filled with desorbed brighteners and are thereby locally insulated. The primary causes of the variable cathode film which lead to skip plating are excessive or decomposed brighteners, improper current density, agitation or both eliminated skip plating. Test method for printed circuit boards with plated through holes are given in various specifications. Item such as electrical continuity, temperature cycling, bend strength, and plating thickness are checked.
Saturday, May 24, 2008
Plating of Printed Wiring Board
When printed conductors are used on both sides of a printed wiring board, electrical connection between the two sides of the board are most reliable made via plated through holes in the board. Because copper is widely used as the base conductor metal in a printed circuit, it is widely used as the base conductor metal in a printed circuit; it is natural that copper also be used for plating the through holes. Copper pyrophosphate solution finds their primary application in this process because the product has consistently met engineering requirements and rigid quality demands. Board-thickness-to-hole-diameter ratios of 8:1 can be satisfactorily plated. This capability of pyrophosphate solutions has helped greatly in furthering the art of multilayer board fabrication.
The success of copper pyrophosphate solutions is attributed to the good throwing power attainable with these solutions. Relationship between throwing power as determined with a Haring cell and plating thickness on printed wiring boards. The effects of changes in bath composition and operating conditions on throwing power are summarized by Dini at al. a discussion of the electrochemical principles which make it possible to achieve good plate distribution in holes was presented.
Because of rigid quality and engineering requirements placed on printed wiring boards, some of the operating conditions are refined to provide optimum results. For example, many installations move the boards mechanically during plating in addition to agitation over the entire rack area. An informative through somewhat oversimplified explanation of the theoretical and practical reasons behind solution agitation for through hole plating. Preplating treatment of the board is also more critical; when pattern plating is used, a neutral or acid immersion cleaner should be used to avoid the resist breakdown resulting from use of an electrolytic cleaner.
The problems associated with the process include brittle deposits and occasionally, skip plating. The first is the biggest problem. Brittle deposits fail prematurely by cracking because the thermal expansion of the epoxy glass laminate in the z axis (thickness direction) is considerably higher than for copper. Actually, the corfficient of expansion for copper is 1.7 x 10-5 cm/(cm. oC) and for epoxy glass boards 6 x 10-5 cm/(cm.oC) up to 105 oC and above this temperature, it is approximately 40 x 10-5 cm/(cm.oC). For this reason, a ductile copper which will elongate plastically and accommodate this increase in thickness without fracturing is desired. An extensive analysis of cracking in plated through was published.
The success of copper pyrophosphate solutions is attributed to the good throwing power attainable with these solutions. Relationship between throwing power as determined with a Haring cell and plating thickness on printed wiring boards. The effects of changes in bath composition and operating conditions on throwing power are summarized by Dini at al. a discussion of the electrochemical principles which make it possible to achieve good plate distribution in holes was presented.
Because of rigid quality and engineering requirements placed on printed wiring boards, some of the operating conditions are refined to provide optimum results. For example, many installations move the boards mechanically during plating in addition to agitation over the entire rack area. An informative through somewhat oversimplified explanation of the theoretical and practical reasons behind solution agitation for through hole plating. Preplating treatment of the board is also more critical; when pattern plating is used, a neutral or acid immersion cleaner should be used to avoid the resist breakdown resulting from use of an electrolytic cleaner.
The problems associated with the process include brittle deposits and occasionally, skip plating. The first is the biggest problem. Brittle deposits fail prematurely by cracking because the thermal expansion of the epoxy glass laminate in the z axis (thickness direction) is considerably higher than for copper. Actually, the corfficient of expansion for copper is 1.7 x 10-5 cm/(cm. oC) and for epoxy glass boards 6 x 10-5 cm/(cm.oC) up to 105 oC and above this temperature, it is approximately 40 x 10-5 cm/(cm.oC). For this reason, a ductile copper which will elongate plastically and accommodate this increase in thickness without fracturing is desired. An extensive analysis of cracking in plated through was published.
Wednesday, May 21, 2008
Structure and Properties
The report that based on physical property data, x-ray evidence, and behavior on annealing, pyrophosphate deposits produced without organic addition agents have a large grain size. For deposits produced in baths containing organic additives. With increasing concentrations of brighteners, a superimposed lamellar structure is obtained. Extremely fine grained brittle copper (200-1000 A grain size, elongation 0.5 % or less, and hardness greater than 190 KHN50) which may result from improper bath operation can be identified metallographically by etching the plated sample in an ammonium hydroxide solution.
Copper pyrophosphate deposits show tensile strength variations from 27 to 70 kg/mm2, yield strengths from 14 to 36 kg/mm2, hardness from 83 to 250 kg/mm2, and elongations from 1 to 39 %. Several investigators have related these variables to solutions content and operating conditions. Some property data are included on effects of proprietary additives. Strength and ductility became less with amounts of one proprietary additive, while strength and ductility increased with use of another proprietary. Concentration of up to 1 g/l of 2.5 dimercapto-1,3,4 thiadiazole in fresh solutions lowered strength and hardness and increased elongation. Concentrations greater than 1 g/l restored values to those shown for the original solution.
Copper pyrophosphate deposits show tensile strength variations from 27 to 70 kg/mm2, yield strengths from 14 to 36 kg/mm2, hardness from 83 to 250 kg/mm2, and elongations from 1 to 39 %. Several investigators have related these variables to solutions content and operating conditions. Some property data are included on effects of proprietary additives. Strength and ductility became less with amounts of one proprietary additive, while strength and ductility increased with use of another proprietary. Concentration of up to 1 g/l of 2.5 dimercapto-1,3,4 thiadiazole in fresh solutions lowered strength and hardness and increased elongation. Concentrations greater than 1 g/l restored values to those shown for the original solution.
Tuesday, May 20, 2008
Maintenance and Control (Pyrophosphate Copper)
Equipment
The equipment, a tank, heater, and filter, is similar to that used for bright nickel plating. A steel tank coated with rubber, Koroseal, PVC, or a plastisol is suitable, although rubber linings should be leached before use with dilute solution of potassium hydroxide to remove all alkali soluble matter which might contaminate the plating solution. For heating the solution, either steam heating coils or electric immersion heaters made of stainless steel or Duriron may be used.
Continuous filtration will help prevent rough deposits. The filter should be constructed of stainless steel, rubber, or PVC-lined steel or cast iron. OFHC anodes are best; however, electrolytic sheet and rolled electrolytic copper anodes are also satisfactory. Cast anode of good purity can also be used but they should be free of impurities such as lead, nickel, silver, and tin because these tend to promote deposit roughness. Anode bags are not usually used; they are not needed, and can restrict circulation of the plating solution around the anode and cause polarization. Anodes can be left in the bath when it is not being used since they do not dissolve in the absence of applied current.
Purification
Cyanide, oil, lead, zinc, decomposition products of the organic additives, and excess orthophosphate are the impurities most often encountered in a copper pyrophosphate plating bath.
Cyanide, oil and lead cause streaked, dull deposits and also lower the effective current density range. Precautionary method will prevent these materials from entering the bath. Thorough rinsing when copper cyanide striking is used will prevent cyanide contamination; a clean air line of lead coils, lining, fittings, or filters will prevent lead contamination.
Cyanide (which can be detected by a copper benzidine test) can be removed by treatment with either 1.25 ml/l of 30% H2O2 or with 0.1 to 0.2 g/l potassium permanganate followed by treatment with activated carbon. The tendency toward streaked, nonuniform pyrophosphate deposits due to residual traces of cyanide left on the surface after copper cyanide striking can be minimize by brief cathodic treatment in a solution of potassium pyrophosphate before it is placed in the plating bath. Oil can be removed by treating the bath with 2.5 to 6 g of activated carbon per liter of bath at 55oC for 4 to 8 hrs. Low current density electrolysis will remove lead.
It has been recommended however, a high P2O7/Cu ratio (preferably 7.5:1) be maintained under this circumstance so as to allow some excess pyrophosphate for complexing with the contaminant. Excessive additive decomposition products can caused stressed, brittle deposits. Control of addition agents plus occasional bath purification will minimize buildup of these products. An activated carbon alone is not sufficient purification. To ensure removal of the decomposition products, it is best to treat the solution.
The equipment, a tank, heater, and filter, is similar to that used for bright nickel plating. A steel tank coated with rubber, Koroseal, PVC, or a plastisol is suitable, although rubber linings should be leached before use with dilute solution of potassium hydroxide to remove all alkali soluble matter which might contaminate the plating solution. For heating the solution, either steam heating coils or electric immersion heaters made of stainless steel or Duriron may be used.
Continuous filtration will help prevent rough deposits. The filter should be constructed of stainless steel, rubber, or PVC-lined steel or cast iron. OFHC anodes are best; however, electrolytic sheet and rolled electrolytic copper anodes are also satisfactory. Cast anode of good purity can also be used but they should be free of impurities such as lead, nickel, silver, and tin because these tend to promote deposit roughness. Anode bags are not usually used; they are not needed, and can restrict circulation of the plating solution around the anode and cause polarization. Anodes can be left in the bath when it is not being used since they do not dissolve in the absence of applied current.
Purification
Cyanide, oil, lead, zinc, decomposition products of the organic additives, and excess orthophosphate are the impurities most often encountered in a copper pyrophosphate plating bath.
Cyanide, oil and lead cause streaked, dull deposits and also lower the effective current density range. Precautionary method will prevent these materials from entering the bath. Thorough rinsing when copper cyanide striking is used will prevent cyanide contamination; a clean air line of lead coils, lining, fittings, or filters will prevent lead contamination.
Cyanide (which can be detected by a copper benzidine test) can be removed by treatment with either 1.25 ml/l of 30% H2O2 or with 0.1 to 0.2 g/l potassium permanganate followed by treatment with activated carbon. The tendency toward streaked, nonuniform pyrophosphate deposits due to residual traces of cyanide left on the surface after copper cyanide striking can be minimize by brief cathodic treatment in a solution of potassium pyrophosphate before it is placed in the plating bath. Oil can be removed by treating the bath with 2.5 to 6 g of activated carbon per liter of bath at 55oC for 4 to 8 hrs. Low current density electrolysis will remove lead.
It has been recommended however, a high P2O7/Cu ratio (preferably 7.5:1) be maintained under this circumstance so as to allow some excess pyrophosphate for complexing with the contaminant. Excessive additive decomposition products can caused stressed, brittle deposits. Control of addition agents plus occasional bath purification will minimize buildup of these products. An activated carbon alone is not sufficient purification. To ensure removal of the decomposition products, it is best to treat the solution.
Thursday, May 15, 2008
Operating Condition Copper Pyrophosphate
The bath is usually operated between 50 and 60oC. Temperatures greater than 60oC can lead to the rapid formation of orthophospate. Current Density Cathode current density is a function of the temperature and agitation of the plating bath. However, under standard operating conditions a current density of 1 to 9 A/dm2 is appropriate.
The anode current density is fairly critical and should be kept between 2 and 4 A/dm2. At too high and anode current density, an insoluble oxide tends to form. If the anode current density is too low, the anode efficiency exceeds 100%. The operating current density range may be increased by ultrasonic, current interruption on reversal, and by increased metal concentration. Agitation Copper pyrophosphate solutions are among those which must be most vigorously agitated. Without sufficient agitation, a brownish deposit is obtained and the operating current density range is drastically lowered.
A solution can be continuously agitated by either one or a combination of three methods; air, mechanical movement of the cathode, or ultrasonic. When air agitation is used, the air should be supplied by a low pressure blower because compressed air can contain oil. Ultrasonic agitation can reduce anode and cathode polarization and permits a 4 to 4.5 times increase in the deposition rate over that obtained with intensive mechanical agitation. The combination of ultrasonic and periodic reverse current increased current efficiency and allowable anode current density. Many process plated over zinc die castings showed that ultrasonic agitation of copper pyrophosphate solutions displaced air or hydrogen gas from blind pockets and resulted in more uniform deposits than could be obtained with copper cyanide strikes. Treatment before Plating Conventional cleaning is used for parts to be plated in pyrophosphate solutions. For ferrous metals, a cyanide or copper pyrophosphate strike before plating is needed to ensure good adhesion. Zinc die castings are normally given a cyanide strike before copper pyrophosphate plating.
The anode current density is fairly critical and should be kept between 2 and 4 A/dm2. At too high and anode current density, an insoluble oxide tends to form. If the anode current density is too low, the anode efficiency exceeds 100%. The operating current density range may be increased by ultrasonic, current interruption on reversal, and by increased metal concentration. Agitation Copper pyrophosphate solutions are among those which must be most vigorously agitated. Without sufficient agitation, a brownish deposit is obtained and the operating current density range is drastically lowered.
A solution can be continuously agitated by either one or a combination of three methods; air, mechanical movement of the cathode, or ultrasonic. When air agitation is used, the air should be supplied by a low pressure blower because compressed air can contain oil. Ultrasonic agitation can reduce anode and cathode polarization and permits a 4 to 4.5 times increase in the deposition rate over that obtained with intensive mechanical agitation. The combination of ultrasonic and periodic reverse current increased current efficiency and allowable anode current density. Many process plated over zinc die castings showed that ultrasonic agitation of copper pyrophosphate solutions displaced air or hydrogen gas from blind pockets and resulted in more uniform deposits than could be obtained with copper cyanide strikes. Treatment before Plating Conventional cleaning is used for parts to be plated in pyrophosphate solutions. For ferrous metals, a cyanide or copper pyrophosphate strike before plating is needed to ensure good adhesion. Zinc die castings are normally given a cyanide strike before copper pyrophosphate plating.
Tuesday, May 13, 2008
Operating Conditions 1
A copper pyrophosphate plating bath may be operated over a relatively wide range of operating conditions. The optimum range, similar to that given by Counch and Stareck that is shown in table below:
Optimum Operating Conditions
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P2O7/Cu ratio 7.0:1 - 8.0:1
pH 8.0 - 8.8
Temperature,oC 50 - 60
Cathode current density, A/dm2 1 - 8
Anode and cathode efficiency, % 100
Anode/cathode ratio 1:1 - 2:1
Agitation (m3/min (m-2) of surface) 1 - 1.5
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The copper pyrophosphate bath is analyzed for both copper and pyrophosphate and it is therefore convenient to describe the bath in terms of the ratio between these constituents. For optimum plating, the weight ratio of pyrophosphate to copper should be kept in the range 7.1 to 8.1. Ratios of 8.5 : 1 or higher promote formation of orthophosphate and thereby decrease the bright plating range. Operation with ratio of less than 7:1 tends to produce a rough-surface and renders the bath unstable.
PH
Optimum solution pH, determined using either pH meter or pH papers, is in the range of 8 to 9. As discussed earlier, pH outside this range results in hydrolysis of pyrophosphate to ortho-phosphate or the formation of precipitates. Also if the pH is too high, both anode corrosion and operating current density range decrease.
Pyrophosphate bath will operate acceptably even at pH value as high as 9.3 provided the copper concentration exceeds 26 g/l. When a bath is operated with this high pH, the tendency to be roughness can be eliminated by increasing the P2O7/Cu ratio.
In practice, a pH of 7 to 9 is easily maintained because at this pH both anode and cathode efficiencies are virtually 100 %, there is no chemical breakdown of the constituents, and the solution is highly buffered. When adjustments must be made, pyrophosporic acid is used for lowering pH and potassium hydroxide for raising it.
Optimum Operating Conditions
-------------------------------------------------------------------
P2O7/Cu ratio 7.0:1 - 8.0:1
pH 8.0 - 8.8
Temperature,oC 50 - 60
Cathode current density, A/dm2 1 - 8
Anode and cathode efficiency, % 100
Anode/cathode ratio 1:1 - 2:1
Agitation (m3/min (m-2) of surface) 1 - 1.5
-------------------------------------------------------------------
The copper pyrophosphate bath is analyzed for both copper and pyrophosphate and it is therefore convenient to describe the bath in terms of the ratio between these constituents. For optimum plating, the weight ratio of pyrophosphate to copper should be kept in the range 7.1 to 8.1. Ratios of 8.5 : 1 or higher promote formation of orthophosphate and thereby decrease the bright plating range. Operation with ratio of less than 7:1 tends to produce a rough-surface and renders the bath unstable.
PH
Optimum solution pH, determined using either pH meter or pH papers, is in the range of 8 to 9. As discussed earlier, pH outside this range results in hydrolysis of pyrophosphate to ortho-phosphate or the formation of precipitates. Also if the pH is too high, both anode corrosion and operating current density range decrease.
Pyrophosphate bath will operate acceptably even at pH value as high as 9.3 provided the copper concentration exceeds 26 g/l. When a bath is operated with this high pH, the tendency to be roughness can be eliminated by increasing the P2O7/Cu ratio.
In practice, a pH of 7 to 9 is easily maintained because at this pH both anode and cathode efficiencies are virtually 100 %, there is no chemical breakdown of the constituents, and the solution is highly buffered. When adjustments must be made, pyrophosporic acid is used for lowering pH and potassium hydroxide for raising it.
Sunday, May 11, 2008
Ammonia Function on Pyrophosphate Plating
A small amount of ammonia is used to produce more uniform and lustrous deposits and to improve anode corrosion. Excess ammonia can cause suprous oxide, 140 g of ammonium hydroxide per square meter of exposed surface per day, or as determinate by chemical analysis of the bath. In some installations, gaseous ammonia is used. Ammonia consumption will increase with increasing temperature, pH, agitation and ammonia content in the bath.
Current had little effect on consumption. OrthophosphateOrthophosphate formed by hydrolysis of pyrophosphate is beneficial in that it promotes anode corrosion and acts as a buffer. It has no harmful effects on the plating characteristics of a bath until its concentration reaches about 100 g./l. Above this concentration, conductivity and bright plating range are decreased and banded deposits are obtained.Low pH (less than 7), high P2O7/Cu ratio, high temperature (greater than 60oC) in the plating bath or heat exchanger, or local overheating will cause orthophosphate to build up. Orthophosphate can't be removed only by either discharging the bath altogether or by diluting and rebuilding it.
Additives
When use at controlled, limited concentrations, organic additives refine the grain structure, impart leveling characteristics to the plating bath, and act as brighteners. However, decomposition products from an excessive additive concentration can cause brittle copper deposits. Thus for optimum quality deposits, no more additive should be added to a bath than is necessary to replace losses by consumption.Organic additives covered in the patent literature as brighteners include mercaptothiadiazoles, mercaptothiazoles, mercaptobenzimidiazole and pyrimidines.
Numerous other materials such as glyserol, triethanolamine, trioxyglutaric acid, diphenylamine sulfonic acid, napthalene disulfonic acid, gelatine, bakers yeast, casein, glycocoll, sodium selenite, sodium sulfite, Rochelle salt, sodium thiosulphate, potassium bromide, and the chlorides of As, Bi, Fe, Cr, Sn, Zn, Cd, Pb and alkali metals have been used as brighteners. Addition of small amounts of lead as lead carbonate are reported to improve plating properties. Organic acids such as oxalic, lactic, tartaric, malic, and citric or their ammonium or alkali salts also produce some brightening.
Current had little effect on consumption. OrthophosphateOrthophosphate formed by hydrolysis of pyrophosphate is beneficial in that it promotes anode corrosion and acts as a buffer. It has no harmful effects on the plating characteristics of a bath until its concentration reaches about 100 g./l. Above this concentration, conductivity and bright plating range are decreased and banded deposits are obtained.Low pH (less than 7), high P2O7/Cu ratio, high temperature (greater than 60oC) in the plating bath or heat exchanger, or local overheating will cause orthophosphate to build up. Orthophosphate can't be removed only by either discharging the bath altogether or by diluting and rebuilding it.
Additives
When use at controlled, limited concentrations, organic additives refine the grain structure, impart leveling characteristics to the plating bath, and act as brighteners. However, decomposition products from an excessive additive concentration can cause brittle copper deposits. Thus for optimum quality deposits, no more additive should be added to a bath than is necessary to replace losses by consumption.Organic additives covered in the patent literature as brighteners include mercaptothiadiazoles, mercaptothiazoles, mercaptobenzimidiazole and pyrimidines.
Numerous other materials such as glyserol, triethanolamine, trioxyglutaric acid, diphenylamine sulfonic acid, napthalene disulfonic acid, gelatine, bakers yeast, casein, glycocoll, sodium selenite, sodium sulfite, Rochelle salt, sodium thiosulphate, potassium bromide, and the chlorides of As, Bi, Fe, Cr, Sn, Zn, Cd, Pb and alkali metals have been used as brighteners. Addition of small amounts of lead as lead carbonate are reported to improve plating properties. Organic acids such as oxalic, lactic, tartaric, malic, and citric or their ammonium or alkali salts also produce some brightening.
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