CHAPTER 3 DEVELOPMENT OF ELECTROPLATING SETUP FOR PLATING ABS AND POLYAMIDES

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1 82 CHAPTER 3 DEVELOPMENT OF ELECTROPLATING SETUP FOR PLATING ABS AND POLYAMIDES 3.1 BACKGROUND OF ELECTROPLATING DETAILS OF THE DEVELOPMENT OF ELECTROPLATING SETUP Polypropylene Tank for Electroplating Heating Elements Electroplating Anode Bags Copper and Nickel Anodes Transformer Demineralized Water Chemicals for Preparation of Electrolytic Solution 92

2 83 CHAPTER 3 DEVELOPMENT OF ELECTROPLATING SETUP FOR PLATING ABS AND POLYAMIDES 3.1 BACKGROUND OF ELECTROPLATING Electroplating involves using electrical current to form a coherent metal coating on an electrode. Electrolyte used in the electroplating process acts as a conducting medium for the passage of electricity between the anode and the cathode [82]. The sample to be coated is the cathode, which is connected to the negative terminal. The anode (positive) is the metal that dissolves and gets deposited on the cathode. When the electric current passes through the electrolyte, the negatively charged ions start to move towards the anode and the positively charged ions move towards the cathode. The exodus of ions through the electrolyte constitutes the flow of electric current in the circuit. The metallic ions with a positive charge in the electrolyte are drawn by the cathode. Due to this process the substrate gets plated [83]. Fig. 3.1 illustrates a typical line diagram of the plating unit for plating with Copper (Cu) and Nickel (Ni). Part description has been shown in the Table DETAILS OF THE DEVELOPMENT OF ELECTROPLATING SETUP The entire electroplating setup (fig. 3.2) is established at Alpha College of Engineering, Bengaluru, India. The details of the developments have been discussed in the ensuing paragraphs.

84 1 2 3 4 9 5 6 7 8 Fig. 3.1: Line diagram of the plating unit Table 3.

3 Fig. 3.1: Line diagram of the plating unit Table 3.1: Part description Table Part Part Description No No Description 1 Anode (+) 6 Temperature display 2 Cathode (-) 7 Transformer 0-12 Volts, 0-30 Amps 3 AC supply to heater (0-230V) 8 AC supply to transformer (0-230V) 4 Heater with glass cover 9 Air pipe from compressor 5 Electrolyte temperature sensor Fig. 3.2: Electroplating setup at Alpha College of Engineering, Bengaluru

85 3.2.1 Polypropylene Tank for Electroplating The polypropylene (pp) tank (fig. 3.3) is fabricated at Keyan reinforced plastics, Bengaluru, India.

4 Polypropylene Tank for Electroplating The polypropylene (pp) tank (fig. 3.3) is fabricated at Keyan reinforced plastics, Bengaluru, India. Two tanks, one each for Cu and Ni electroplating of dimensions 20 cm x 20 cm x 30 cm are fabricated. A 10 mm thick PVC coat is provided on the inner side of the tank to protect it from the chemicals / acids attack. Fig. 3.3: Polypropylene Tank used in the Study Heating Elements The heat sensing thermocouple, indicator and controller and heater [figs. 3.4 (a-d)] are procured from Thermo measure, (manufactures of thermocouples, RTD sensors and instruments), Bangalore. The universal temperature controller of type AOB508-A21 is used for display and control of temperature. The size of the instrument is 96 mm x 96 mm x 90 mm. A21 actually

5 86 represents one relay contact switched output and one alarm output channel. The instrument is capable of handling 0-20 ma of current and a power supply of 220V. The instrument is capable of measuring o C of temperature. K type thermocouple is used to sense the temperature. This thermocouple gives a very broad range of temperature detection. Type K covers the widest range from 200 C to 1,260 C. These thermocouples are usually made of Ni with excellent resistance towards corrosion. In order to measure uniform temperature within the electroplating bath the thermocouple is inserted in a glass tube filled with water. Infrared quartz heating element is used for heating of the electrolyte in the electroplating bath. The detailed specification of the heating element is summarized in Table 3.2. The advantages of using this type of heating elements are, Most of the energy is passed on as Infrared heat, With high precision the output can be controlled By-products are not give off. Maintenance is very less and requires very less space for setting up.

6 87 (a) Temperature Controller With Universal Input (Model no: AOB508-A21) (b) K Type thermocouple with protective glass tube. (c) Quartz Heating Element (d) PP Tank installed with heater, heat sensor and air blower Fig. 3.4: Temperature controller, Thermocouple and Heating element

7 88 Table 3.2: Specifications of Infrared Quartz Heating Element (Source: Thermo measure) Infrared Quartz Heating Element Items Medium wave Diameter 18mm Max. overall length 3,500 mm 99.99% purity quartz which ensures high Quartz tube transparency, great shock heating resistance and high strength Ceramic base High heat-resistant and non-deformable Fe-Cr-Al or Ni-Cr Filament With special protective coating and is firmly burnt-in Filament temp. 600 C C Wave length μm Max. power 30 W/cm Average lifespan Response time Wire connection Voltage 20,000 hrs 1-3 min Two side connection for single tube 230V Electroplating Anode Bags The anode bag (fig. 3.5) is basically a filter that avoids Solid Anode Particles (SAPs) from entering into the electroplating solution. It is usually observed that SAPs in the electroplating solution will cause roughness on the plated parts [84]. Electroplating anode bags used in the study are made up of PP material procured from Keyan Reinforced Plastics, Bengaluru, India. These bags are double needle sewn at the top and bottom. Sides of the bags are also double stitched to prevent the bags from being torn by the rough action created by air agitation in the plating bath. PP

8 89 material has an excellent resistance towards alkalies, mineral acids, organic acids, organic solvents and oxidizing agents. The maximum safe temperature up to which they can be used in the electroplating bath is 93 o C. Fig. 3.5: Electroplating Anode Bags Used In Copper and Nickel Plating Copper and Nickel Anodes The Cu and Ni anodes [Figs. 3.6 (a-b)] are procured from Lakshmi Industries, Bengaluru, India. Cu anodes available with them are of two types viz, Electrolytic Copper (EC) and Phosphorous De- Oxidised (PDO). EC is a pure form of copper and finds its use in cyanide copper plating solutions. PDO anodes have low traces of phosphorus, on an average 0.05 % phosphorus. PDOs are important in acid Cu plating solutions that use organic additives. Since organic

They are usually available in strips or small pieces ('F' - flats, 'R' - rounds). Flat type of Ni anode is used in the study. 3.2.

9 90 additives are used in electroplating, the latter type of anode is used in the study. (a) Copper anode (b) Nickel anode Fig. 3.6: Copper and Nickel Anodes used in the study Electrolytic Ni anodes are used in the study. These are the purest type of Ni anodes and are usually less expensive. They are usually available in strips or small pieces ('F' - flats, 'R' - rounds). Flat type of Ni anode is used in the study Transformer The transformer used for electroplating, as shown in the fig. 3.7, has the following specifications: AC to DC variable transformer, Input 230V AC, single phase, output 0V to 230V DC, capacity 30 Amps, is procured from Universal Electricals, Bengaluru, India. The transformer is custom made, as the specifications depend on the size of the plating tank. The transformer is suitable for the research with precision amperage regulation. The control panel has an amp meter

10 91 and an on/off switch. The transformer is designed for continuous duty with solid state circuitry and full range of power. Fig. 3.7: Transformer used in the Study Some of the exclusive features of the built transformer are: Industrial grade, heavy duty, high output transformer. Oversized heat sinks and built-in cooling fans prevent overheating. Output current is 99% filtered assuring consistent results. Voltage is adjustable from 0 to 12 volts Demineralized water Fifty litres of demineralized water is supplied by Sri. Manjunatha Chemicals, Bengaluru, India. According to Subramanian Ramajayam and Ted Mooney [85], demineralised water

11 92 is generally used in all plating rinses, as hard water contains a large amount of dissolved solids. Also, the presence of iron, nitrate and large amount of chloride in the underground water may cause problems in plating. The water sample used in plating has to be analysed first, otherwise, plating problems like roughness, dullness, low cathode efficiency etc. may arise. But for post plating processes, soft water is generally preferred Chemicals for Preparation of Electrolytic Solution Chemicals like Copper sulphate salts, Chrome salts, Nickel salts, Sodium Hydroxide, Sodium Potassium Tartarate [figs. 3.8 (a-e)], Sulphuric acid, Hydrochloric acid, Silver Nitrate [fig. 3.8 (h)], Tin Chloride and Formaldehyde are purchased from Sri. Manjunatha Chemicals, Superchem Finishers and Lakshmi Industries, Bengaluru, India. Barium carbonate [fig. 3.8 (g)] for chrome flash is procured from M/s. Mehta Sons, Bengaluru, India. Brighteners 2793 and leveller 2794 [fig. 3.8 (f)] are supplied by Swathi chem-plast, Bengaluru, India.

12 93 (a) Copper Sulphate Salts (b) Chrome Salts (c) Nickel Salts (d) Sodium Hydroxide (e) Sodium potassium Tartarate (f) Brightener 2793 (left) and Leveller 2794 (right) Solutions (g) Barium Carbonate (h) Silver Nitrate Solution Fig. 3.8: Chemicals used in Electroplating process

NITEC CRYSTAL 1. Elektrolyt to achieve uniform and non reflective Nickel deposits

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