TECHNICAL DATA SHEET CUPROBRITE Revolutionary & New generation Bright Acid Copper Plating Process

Transcription

1 TECHNICAL DATA SHEET CUPROBRITE 3006 Revolutionary & New generation Bright Acid Copper Plating Process Cuprobrite 3006 is a bright acid copper plating process which produces highly levelled, brilliant, smooth and ductile copper deposits. The process is designed to produce uniform brightness at both high and low current density levels. Cuprobrite 3006 is specially formulated for decorative plating on metal wherein faster brightness can be achieved at shorter plating time. The bright copper deposit from Cuprobrite 3006 bath provides an excellent undercoat for subsequent Nickel and Chromium plating on most metallic substrates. To insure good adhesion, steel parts should be completely covered with a cyanide copper or acid nickel strike prior to acid copper plating. Similarly, the Zinc die cast parts should be given a minimum thickness of microns in cyanide copper bath before plating with bright acid copper bath. Due to its outstanding levelling characteristics, the surface imperfections of the base metal are covered completely resulting in a brilliant final finish with less nickel thickness, thus reducing the overall plating cost. Cuprobrite 3006 process is ideally suitable for plating on artificial jewellery components where it prepares excellent undercoat for subsequent Nickel and/or other 'Nickel-free' processes. This process can also be adopted for plating on different plate substrate such as ABS, Aluminium & it Alloys etc. The salient features are given as under : 1. Process has a wide brightness range, especially at low current density area which is the essential requirement for plating on plastics. 2. Has a wide useful operating range, thereby the solution control is very easy. 3. The bath can be operated at wide bath temperature range ºC. 4. Excellent brightness and levelling at shorter plating time. 5. Good, bright & glowing finish. 1

2 SOLUTION COMPOSITION RANGE OPTIMUM Copper Sulphate (Pure grade g/l 225 g/l Sulphuric Acid (chemically pure grade) ml/l 35 ml/l Chloride Ion PPM 80 PPM Cuprobrite 3006 Make-up 8-10 ml/l 10 ml/l Cuprobrite 3006 Part A ml/l 0.5 ml/l Cuprobrite 3006 Part B ml/l 0.5 ml/l Cuprobrite Wetter ml/l (Optional) (Optional) OPERATING CONDITIONS RANGE OPTIMUM Temperature ºC. 25 ºC Cathode Current density A/dm A/dm 2 Anode Current density A/dm A/dm 2 Anodes Phosphorised copper Anode bags Polypropylene Agitation Vigorous and uniform, low pressure air. SOLUTION MAKE-UP 1. Fill the treatment tank two thirds full of water, preferably deionised water and heat to 60 ºC. Note : In case of normal supply of water is used, the chloride content should be analysed and then to be used. In case the water contains high chloride, the use of deionsed water is recommended. 2. Dissolve required amount of copper sulphate in hot water with continuous agitation. 3. To the solution, add 2.0 g/l activated carbon (approved quality and stir well and allow to settle for overnight). 4. Carefully filter the treated solution into the plating tank. 5. Add the measured quantity of Sulphuric acid, agitating to mix well and add more water to make up the final level. 6. Add the required amount of AR grade Hydrochloric acid and mix well. Normally 128 ml AR HCL (35-37%) is required for 1000 litre of copper solution prepared from deionised water to provide a chloride concentration of 40 PPM. If other than deionised water is used, the amount of chloride ion present in the water must be substracted from the 40 PPM. Value and addition of Hydrochloric acid is to be adjusted to obatin optimum value of chloride. 7. Cool the solution to operating temperature and add the required quantity of Cuprobrite 3006 Makeup and Cuprobrite 3006 Part A. Then mix the solution well by employing air agitation. 2

3 FUNCTION OF SOLUTION CONSTITUENTS Copper Sulphate : Copper sulphate is the source of metal which is plated out on the work. It is important that the concentration of copper sulphate be maintained within the recommended limits. Low concentration will result in burning of the deposit at high current density areas, whereas high concentration will result in crystallisation of copper sulphate from the solution which will tend to plug air agitation coils and possibly coat the anodes resulting in anode polarisation. Sulphuric Acid : The principal function of Sulphuric acid is to increase the solution conductivity, which produces the desired current density with minimum voltage. Excessive sulphuric acid concentration will reduce the limiting current density and also reduce the levelling ability of the process. Chloride Ion : The careful control of the concentration of the chloride ions in bright acid copper plating solution is of paramount importance. Low chloride concentrations, (less than 20 PPM) will result in deposits with poor brightness, and the deposit becomes straited and the tendency towards treeing is slightly increased whereas high chloride concentrations will decrease levelling and reduce low current density brightness and increase the consumption of addition agents. Cuprobrite 3006 Make-up : Cuprobrite 3006 Make Up is used for initial make-up and this contains brightening agent, carrier brightner and grain refining agent. Normally Cuprobrite 3006 Make Up is not required to be added for maintenance. However, occassional additions are required in case of burning occurs at high current density areas and also to compensate the drag-out losses. Cuprobrite 3006 Make Up may be required to be added if the bath is given a batch carbon treatment. The quantity required to be added is to be determined by conducting Hull Cell trials. Specially, addition of ml/kah should suffice most of the plating requirements. Cuprobrite 3006 Part A : Cuprobrite 3006 Part A is used for initial make-up and for maintenance purpose. It is responsible for brightness & levelling of the system. To maintain consistent results Cuprobrite 3006 Part A & 3006 Part B is to be regularly added, preferably on 1000 ampere hour basis, as the performance of the system will be dependent on the respective proportion of Cuprobrite 3006 Part A and Cuprobrite 3006 Part B i.e. excess or deficiency of one additive will creat deficiency or excess of other respectively. Lower concentration of Cuprobrite 3006 Part A and or high conc. of Cuprobrite 3006 Part B will result in over all dullness and brightness especially at low current density areas. Excess addition of this Cuprobrite 3006 Part A or lower addition of Cuprobrite 3006 Part B may result in 'skip' plating at LCD and also poor adhesion towards top-coats. Cuprobrite 3006 Part B : Responsible for maintenance of brightness and grain refining when used in combination with Cuprobrite 3006 Part A. It must be present in the bath at a certain ratio. This ratio should be carefully established depending upon the process requirement and bath should be maintained by carrying out Hull Cell at regular intervals. Lower addition of Cuprobrite 3006 Part B or excess of Cuprobrite 3006 Part A will result in overall poor brightness, burning at HCD and also will result more job to job variation. Excess additon of Cuprobrite Part B or lower addition of Cuprobrite 3006 Part A will change the deposit colouration towards more redish and also induces lower current density dullness. 3

4 Cuprobrite Wetter : Cuprobrite Wetter is special blend of suitable orange wetting agent to be used to remove pitting defect, if applicable. Addition of ml./lt. should suffice the requirement. Regular addition may not be required, if fine pit marks are observed, especially for plating on ABS plastic this can even be added quite frequently. SOLUTION CONTROL AND MAINTENANCE It is essential that the bath constituent i.e. chloride, copper sulphate and sulphuric acid content should be checked and adjusted to optimum level on a weekly basis. Laboratory plating tests can be carried out in an air agitated Hull Cell. It is recommended that the panels be made of the same metal being plated and have the same surface finish. With experience, the brightners can be controlled by these tests. Copper sulphate should be added to the solution through anode bag or through a filter. Sulphuric acid may be added directly to the plating solution. Brightners should be added on the basis of ampere hours of operation. Small frequent additions are prefered. The temperature should be held reasonably close to 25 ºC. The low current density areas are brightened, but below 20 ºC, the tendency to burn is increased. At temperatures above 32 ºC the low current density areas have a tendency to become hazy. This may be overcomed partially by increasing the feeding rate of the Cuprobrite 3006 Part A. As a guidline, the following rate of individual product should be maintained. For quick and bright deposit : Cuprobrite 3006 Part A ml/kah Cuprobrite 3006 Part B ml/kah For ABS plating : Cuprobrite 3006 Part A ml/kah Cuprobrite 3006 Part B ml/kah Cuprobrite Wetter Occasional addition is helpful. However, regular addition of ml. per 1000 lit. of working solution per day would be advisable. Usually, best result can be achieved while using Cuprobtie 3006 Part A higher than Cuprobrite Part B ~ may be in 2:1 ratio. Purification Treatments : With normal use of Cuprobrite bright acid copper plating process, oxidation and/or batch carbon treatment becomes necessary in case of drag-in of impurities, the plating solution should be pumped into a treatment tank and treat the solution with activated carbon. 4

5 PLANT ACCESSORIES Equipment : Acid copper solutions are highly corrosive and precautions should be taken to protect outside tank walls and bottoms, plumbing, floors and any other equipment that may come in contact with the solution. Several coats of acid resistant paint will provide the necessary protection. Tanks : Plating tanks should be of rubber lined steel, polyethylene lined fibre glass or polypropylene. New tank linings should be leached with 3-5% sulphuric acid at ºC. Tanks should have sufficient free board height (6 inches) to contain any spray mist generated by air agitation. Exhaust ventilation is recommended to remove the spray mist. Agitation : Solutions for Cuprobrite should be air agitated. Polypropylene or PVC are recommended for the air lines. The agitation pipes should be accurately located midway between the cathode and anode bars and fixed in a suitable manner so that no drifting occurs. Air holes should be directed at a 45 ºC angle towards the bottom of the tank. Air holes should be 2 cm apart and 3 mm in diameter. This ensures even distribution of air and allow the agitation pipes to drain when the plating solution is employed. A clearance of 15 cm. should be maintained between the bottom of the rack and the top of the air agitation pipes. Low pressure air, not compressed air, should be used and the air should pass through a filter before entering the solution. Filtration : Continuous filtration is strongly recommended. However continuous filtration through activated carbon is not recommended as this will remove brightners. The pump and filter should have sufficient capcity to turn over the solution at least twice every hour. Because of the highly corrosive nature of the solution, all surfaces of the filter pump connections and filters that come in contact with the solution must be acid resistant. Plastic and hard rubber are recommended for pumps. PVC, rubber, Lucite or Polypropylene is recommended for filter chambers and polypropylene is recommended for filter discs. Racks: Plating racks must be coated with materials that will not contaminate the plating solution. Usually the type of rack coating used for bright nickel solution is satisfactory. Anodes : Phosphorised copper anodes with a minimum of 0.03 percent phosphorus should be used in Cuprobrite solution. Other anodes may cause excessive brightener consumption poor levelling and roughness. The anode area should be twice the cathode area. Anode bags should be used and they should be of polypropylene or Terylene. It is recommended that anode bags be rinsed thoroughly and leached in a 5% by volume sulphuric acid solution before using. The bags should then be thoroughly rinsed in a clear water before introducing to the plating tank. If anode baskets are used, they should be made of titanium. Cooling : It is recommended that the solution be operated at ºC. Loss of brightness and levelling occurs at temperatures above 32 ºC. Teflon, titanium or lead cooling coils or exchangers are recommended to cool the solution, if necessary. 5

6 ANALYTICAL CONTROL The copper sulphate, sulphuric acid and hydrochloric acid content of the bath should be checked regularly using the analytical procedures outlined below to ensure that the concentrations of these constituents are maintained within the recommended range. ANALYSIS FOR COPPER SULPHATE : Apparatus needed : 1 ml pipette : 50 ml burette : 500 ml Erlenmeyer flask Reagents required : Murexide Indicator : Liquid Ammonia : 0.1 M EDTA Procedure : Pipette 1 ml plating solution in a conical flask. Add few drops of liquor ammonia and few grains of murexide indicator. Add small quantity of DM water and titrate against 0.1M EDTA till brown to purple end point. Calculation : Copper Metal ml of 0.1M EDTA titrated x = gm/lt Copper Metal 0.1 Copper Sulphate : gm/lt Cu. Metal x 3.93 = gm/lt Copper Sulphate ANALYSIS FOR SULPHURIC ACID : Apparatus Needed : 1 ml. pipette : 50 ml. burette : 250 ml. Erlenmeyer flask. Reagents Needed : Methyl orange indicator solution : 0.1 N Sodium hydroxide solution. Procedure : Pipette 1 ml of plating solution in a conical flask. Add few drops of methyl orange indicator and small quantity of DM water to it. Titrate against 0.1 NaOH till pink to yellow end point. Calculation : ml of 0.1 N NaOH x 4.9 = gm/lt Sulphuric acid gm/lt Sulphuric acid = ml/ lt Sulphuric acid

7 ANALYSIS FOR CHLORIDE CONTENT : Apparatus Needed : Magnetic Stirrer : 50 ml Burette : 200 ml Beaker (Tall form) : 50 ml Pipette Reagents Needed : 1. 50% Nitric Acid Solution (HNO 3 ) Carefully add with stirring 20 ml. of concentrated nitric acid to 20 ml. of distilled water N Silver Nitrate Solution (AgNO 3 ) : Dissolve 17 gms of silver nitrate in distilled water and dilute to 1 ltr. in a volumetric flask and stir in an amber coloured bottle N Mercuric Nitrate Solution Hg(NO 3 : Dissolve gms of mercuric Oxide (HgO) in 5 ml of 50% Nitric acid solution. Dilute to one ltr. with distilled water. Standardize by titrating 25 ml of N Standard Chloride solution. ( gms/ltr NaCl) with the 0.01N Mercuric Nitrate solution using following formula : 0.002N x 25ml Sample Normality of Hg (NO 3 solution = ml Hg (NO 3 Titrated Procedure : 1. Pipette 50 ml of Cuprobrite operating solution into a 200 ml Beaker (Tall Form). 2. Add 40 ml of distilled water and 10 ml of 50% Nitric Acid solution. 3. Add sufficient 0.1 N Silver Nitrate solution to produce turbidity (usually 4-5 drops). 4. Immediately titrate with 0.1N Mercuric Nitrate Solution by dropwise additions with stirring until turbidity clears. Calculation : ml Hg(NO 3 titrated x Normality of Hg(NO 3 x 709 = mgm/ltr (PPM chloride) Conversion : Many dull and bright acid copper solutions can be converted to Cuprobrite 3006 acid copper solution. G&W Laboratory will be pleased to make recommendations for carrying out this conversion after performing the necessary analysis and small scale plating tests. Two litres sample should be submitted for trial purpose to G & W Laboratory. Issued on : Supersedes all earlier 7