CHAPTER III EXPERIMENTAL TECHNIQUES

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CHAPTER III

EXPERIMENTAL TECHNIQUES

3.1 Electrodeposition Since electrodeposition is highly diverse in nature, no single universal

experimental procedure has been found satisfactory to cover all aspects of

electrodepositon of metals and alloys. However, it is very essential to select relevant

methods to correlate laboratory experiments with actual industrial operations [1-5].

Though absolute reproducibility is rather difficult to achieve due to several factors,

reproducibility with minimum error is of considerable importance.

3.1.1 Chemicals and materials used

Chemicals Make

Tri chloro ethylene Fischer, India

Agar-Agar CDH, India

Potassium chloride Ranbaxy, India

Sulfuric acid Fischer, India

Nitric acid Fischer, India

Hydrochloric acid Fischer, India

Sodium hydroxide ` Fischer, India

Sodium carbonate Fischer, India

Copper sulfate BDH, India

Copper carbonate (basic) S.d.fine chemicals, India

Methane sulphonic acid (100 %) Merck India

EDTA BDH, India

Lead carbonate Merck, India

Lead fluoborate Madras fluorine chemicals, Chennai

Hydrofluoric acid S.d.fine chemicals, India

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Boric acid Sarabhai chemicals, India

Sodium chloride Ranbaxy, India

Potassium ferry cyanide Ranbaxy, India

Peptone CDH, India

Gelatin CDH, India

Poly ethylene glycol (4000) Ranbaxy, India

Triton-X-100 Merck, India

Stannous oxide CDH, India

Tin fluoborate Madras fluorine chemicals, Chennai.

Iodine Merck, India

Potassium Iodide S.d.fine chemicals, India

Double distilled water was used for the preparation of experimental solutions.

All glassware and electrochemical apparatus were fabricated at Central

electrochemical research institute, Karaikudi, India. A single pan digital balance

(Afcoset Model ER-180A) was used for mass measurements to determine current

efficiency, throwing power, thickness etc.

The current and potential were measured using digital multimeters. The digital

power source (Aplab 0-2 A, 0-32 V) was employed as the DC power supply unit for

electrodeposition. Polarisation studies were carried out using a constant current regulator

(fabricated at Central electrochemical research institute, Karaikudi, India.)

3.2 Preparation and purification of electrolytes

3.2.1 Copper methane sulphonate bath

Required amount of basic copper carbonate was weighed and transferred into a

beaker. Required amount of methane sulphonic acid was added to this and the dissolved

in double distilled water. The suspended impurities present in the solution were removed

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by filtration. The organic and inorganic impurities were removed by treatment with

activated charcoal and dummy electrolysis respectively.

The amount of copper present in the electrolyte was estimated by complexometric

titration using EDTA. The basic bath compositions of copper methane sulphonate bath

used for the studies such as Hull-cell, current efficiency, throwing power measurements;

polarization, and samples preparation for testing mechanical properties and corrosion

studies is given in the table 3.1.

3.2.2 Copper sulphate bath

The sulphate based copper bath was prepared as and when required. A calculated

quantity of copper sulphate was exactly weighed and transferred into the beaker, with this

required volume of sulphuric acid was added slowly and made up with distilled water.

The suspended impurities present in the solution were removed by filtration. The organic

and inorganic impurities were removed by treatment with activated charcoal and dummy

electrolysis respectively.

The basic bath composition of copper sulphate bath used for the studies such as

Hull-cell, current efficiency, throwing power measurements; polarization, and samples

preparation for testing mechanical properties and corrosion studies is given in the table

3.1.

3.2.3 Lead methane sulphoante bath

Required amount of lead carbonate was weighed and transferred into a beaker. To

this the required amount of methane sulphonic acid was added and heated to 70-75oC,

After complete dissolution of the salt dissolved, the solution was made up to the required

volume with double distilled water. The suspended impurities present in the solution

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Table 3.1 Composition of baths studied

Bath Constituents

A Copper (as methane sulphonate) 0.70- 0.10 M

MSA 0.31–0.73 M

Temperature RT (30oC)

B Copper (as copper sulphate) 0.70- 0.10 M

Sulfuric acid 0.31 - 0.73 M


C Lead (as methane sulphonate) 0.24- 0.48 M

MSA 0.21- 0.63 M


D Lead (as fluoborate) 0.24- 0.48 M

Fluoboric acid 0.21- 0.63 M

Boric acid 0.48 M


E Tin (as methane sulphonate) 0.33 – 0.50 M

MSA 1.56 – 2.60 M


F Tin (as fluoborate) 0.33- 0.50 M

Fluoboric acid 1.56 –2.60M

Boric acid 0.48 M


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were removed by filtration. The organic and inorganic impurities were removed by

treatment with activated charcoal and dummy electrolysis respectively.

The amount of lead present in the electrolyte was estimated by

complexometric titration using EDTA. The basic bath composition of lead methane

sulphonate used for the studies such as Hull-cell, current efficiency, throwing power

measurements; polarization, and samples preparation for testing mechanical properties

and corrosion studies is given in the table 3.1.

3.2.4 Preparation of fluoboric acid

Fluoboric acid was prepared by adding analar grade boric acid in small

increments with constant stirring to a chemically pure hydrofluoric acid (40 wt %) in the

stochiometric ratio as per the following equation

4 HF + H3BO3 HBF4 + 3 H2O

The presence of unreacted hydrofluoric acid was tested by the formation of white

precipitate with a sample of lead nitrate solution. The strength of fluoboric acid was

estimated by acid-base titration. The concentration of fluoboric acid was varied by

diluting this acid.

3.2.5 Lead fluoborate bath

Required amount of commercially available lead fluoborate solution

(approx.50%) was taken in a polyethylene beaker. To this, required quantities of

fluoboric acid and boric acid were added and then the solution made up to the required

volume with double distilled water. The suspended impurities present in the solution

were removed by filtration. The organic and inorganic impurities were removed by

treatment with activated charcoal and dummy electrolysis respectively.

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The amount of lead present in the electrolyte was estimated by complexometric

titration using EDTA. The basic bath composition of lead fluoborate used for the studies

such as Hull-cell, current efficiency, throwing power measurements; polarization and

samples preparation for testing mechanical properties and corrosion studies is given in

the table 3.1.Boric acid was added to avoid the hydrolysis of fluoboric acid.

3.2.6 Tin methane sulphonate bath

Required amount of stannous oxide was weighed and taken in a beaker. Required

amount of methane sulphonic acid was added and heated to 80oC. After complete

dissolution of the salt, the solution was filtered and made up with double distilled water.

The suspended impurities present in the solution were removed by filtration. The organic

and inorganic impurities were removed by treatment with activated charcoal and dummy

electrolysis

The amount of tin present in the electrolyte was estimated by iodometric

titration using starch as indicator. The basic bath composition of tin methane sulphonate

bath used for the studies such as Hull-cell, current efficiency, throwing power

measurements; polarization, and samples preparation for testing mechanical properties

and corrosion studies is given in the table 3.1.

3.2.7 Tin fluoborate electrolyte

Required amount of commercially available tin fluoborate solution (approx.50%)

was taken in a polyethylene container. Required quantity of fluoboric acid and boric acid

was added and then made up with double distilled water. The suspended impurities

present in the solution were removed by filtration. The organic and inorganic impurities

were removed by treatment with activated charcoal and dummy electrolysis respectively.

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The amount of tin present in the electrolyte was estimated by iodometric

titration using starch as indicator. The basic bath composition for tin fluoborate bath

used for the studies such as Hull-cell, current efficiency, throwing power measurements;

polarization, cyclic voltammetry, and samples preparation for testing mechanical

properties and corrosion studies is given in the table 3.1.

3.3 Electrodes and cells

3.3.1 Electrodes

Anodes Electrolytic copper (99.5 % pure)

Electrolytic lead (99.5 % pure)

Electrolytic tin (99.5 % pure)

Cathodes Mild steel (for tin, lead, deposition)

Brass (for copper deposition)

3.3.2 Hull Cell [6]

It is a small trapezoidal cell of accurate dimensions. Figure.3.1 shows the cross

sectional and over view of a Hull-cell. It is of different capacities, 1000 ml, 320 ml and

267 ml. Hull cell capacity of 267 ml was used in the present study. In this cell, the

cathode is positioned at an inclined angle to the anode so that the current density at each

point on the cathode is different.

The optimum current density range for obtaining quality deposits from the

selected plating bath was determined using Hull cell [7]. The experiments help in

determining the nature of deposits that could be obtained at different current densities in a

single experiment. Mechanically polished and degreased Brass/MS cathodes of 10.2 x

7.0 x 0.2 cm area and copper, lead, and tin anodes of 6.5 x 6.5 x 0.5 cm size were used

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for the experiment. Before starting experiments the backside of the cathode panels were

masked using duroflex lacquer. The cathode panels were subjected to electrochemical

surface treatment using the following solutions.

Sodium carbonate 30 g/l

Sodium hydroxide 30 g/l

Anode Stainless steel

Current density 1.5 A/dm2, 4.5 A/dm2 (for brass)

Cathodic treatment 2 minutes

Anodic treatment 30 seconds.

Preliminary studies were carried out with Hull-cell using various electrolytes

under different conditions. After the experiments, the panels were washed, dried and the

results were expressed using codes to indicate the nature of deposits. By measuring the

distance from high current density and the distance of the points spanning the desired

deposit pattern, the value of current densities corresponding to those points and hence the

current density range for production of deposits of desired quality were determined. The

technique was also employed to identify a suitable addition agent that could be used to

improve the quality of deposits. The following formula enabled calculation of the current

density at a desired point on the Hull cell cathode.

Current density in A/dm2 at any point on the

inclined cathode = C (5.1-5.24logL)

Where C is the total current passing through the cell, ‘L’ is the distance in cm of

the point of interest from the nearer end of the cathode.

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All dimensions in mm

Figure 3.1 Cross section of Hull cell diagram

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3.3.3 Throwing power (Haring-Blum cell) [9]

Throwing power is regarded as one of the important characteristic properties of

any electroplating bath because it is a measure of the ability of the bath to cover the

surface or throw the metal uniformly over corners and in recesses. The throwing power

is commonly expressed as a percentage. After Field’s contribution to the plating scene,

the unit of percentage came to be expressed either as a positive (+ve) or a negative (-ve)

figure with 100 as the maximum. According to field the positive figures would represent

good performance of the baths and negative ones, their poor performance. He further

explained the poor performance in terms of non-uniform coverage and thickness of the

deposit.

It is a well-known fact that the alkaline baths are always associated with a high

(good) throwing power, probably because of the high over-potentials for metal deposition

is such solutions. In contrast, the throwing power is low or poor in the case of acid baths

due to low over-potentials.

The chief factors affecting throwing power are the extent to which the cathode

polarizes with increase in current density, the electrical conductivity of the electrolyte

and the relationship between cathode current efficiency and cathode current density.

The steeper the slope of the cathode polarization curve and greater the

conductivity of the electrolyte, the more uniform will be the current distribution and

hence the metal distribution over the cathode surface. If the cathode current efficiency

decreases with increase in current density, the uniformity of the metal distribution is

improved.

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Haring-Blum cell is used to determine throwing power. It is basically a

rectangular (15 x 5 x 5 cm) PVC box with an open top (Figure 3.2). Typically it has two

cathodes (5 x 5 x 0.2 cm) one at each end, with a single anode perforated of the same size

placed between them.

The studies on throwing power were carried out for different compositions of the

electrolytes of copper, lead, and tin under still and stirred conditions. Deposits were

produced on pre cleaned brass/steel cathodes, positioned at both ends of rectangular cell

with a distance ratio of 1:5 from the anode. The plating was carried out for 30 minutes at

1-10 A/dm2 for all the electrolytes. From the weight of the deposits obtained at the near

cathode (Cn) and far cathode (Cf) the throwing power was calculated. Under such

condition the electrolyte would behave in accordance with Ohm’s law and the metal

distribution would be proportional to the current distribution. In this hypothetical case

the current distribution is referred to as primary distribution. However, resistance at the

interface between the electrolyte and the cathode is high as compared with the resistance

of the electrolyte due to polarization and the resulting current distribution is known as

secondary distribution. Haring and Blum formula for determination of throwing power is

L-M Throwing power (%) = -------- x 100

L

In this expression C (Cn/Cf) is the metal distribution ratio, and K is the ratio of the

distance from the far cathode and the near cathode to the anode. Thus K is the current

distribution ratio and normally it is maintained at a value of 5. However, Field’s formula,

a modified term of Haring and Blum formula is the one greatly used, since the values it

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gives are more realistic and range from + 100 % to –100% irrespective of the value of K.

The Field’s formula is [10].

L-M Throwing power (%) = ---------- x 100

L+M – 2

Values of throwing power for different solutions were calculated with Field’s

formula.

3.4 Current efficiency

The studies on current efficiency and rate of build up were carried out for

different composition of the electrolytes under still and stirred condition. Experiments

were carried out in a 200 ml container containing 7.5(l) x 2.5 (b) x 0.5 (t) cm anodes

(copper, lead, tin,) with an exposed area of 2.5 (l) x 2.5 (b) cm and mild steel or brass

with exposed area of 2.5 (l) x 2.5 (b) cm by masking the unwanted portions by lacquer.

The cathodes were degreased and electrolytically cleaned in alkaline solution

prior to deposition. The specimens were weighed before and after deposition and the

cathodic current efficiency in each case was calculated using the relation

Weight of the deposit Cathode current efficiency = ------------------------- x 100 Theoretical weight

The theoretical amount of metal deposition was calculated using Faraday’s laws,

which states that gram equivalent weight of a metal deposited at the cathode requires

96,500 coulombs of electricity. The anodic dissolution efficiencies of copper, lead and tin

of above-mentioned dimensions were studied in their respective MSA baths and in

various concentration of pure MSA solution.

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The protective value of many electrodeposited coatings is determined mostly by

their thickness. It has been established that corrosion protection depends primarily on the

thickness or mass of the deposit [8]. In view of this, the thickness of the deposit and the

rate of deposition were calculated from the mass of the deposit obtained.

Mass of the deposit (gm) Thickness (micron) = --------------------------------- ----------- x 10 4

Density of the metal (g/cm3) x Area (cm 2)

3.5 Conductivity measurements

Solution of strong acids and bases are much better conductors than any other

aqueous solution and in electrolytic processes free acid or free alkali is often used to

improve the solution conductivity. It is very important that for an electroplating solution

being useful; conductivity should be adequate, avoiding the necessity of using higher

applied voltage and hence high energy-consumption.

Conductivity measurements were carried out for different compositions of the

electrolyte using Dot-tech digital conductivity meter (model Dot 466).

3.6 Polarization method

The cathodic polarizations were carried out in copper, lead, and tin electrolytes of

different compositions using three-electrode assembly under still and stirred condition.

Platinum foil of 1 cm2 area and saturated calomel electrode was used as the counter and

reference electrode respectively. Brass/steel of 1 cm2 area was used as a working

electrode. The anodic polarization of copper, lead, and tin, were also carried out in their

respective baths and in various concentration of pure MSA solution. Current steps were

applied using a constant current source and corresponding potentials were measured after

attaining steady state .

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Figure 3.2 Haring-Blum Throwing power cell

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3.7 Cyclic voltammetric studies

Potential sweep cyclic voltammetry is one of the most powerful electrochemical

techniques used as a means of obtaining a quick electrochemical spectrum of a charge

transfer system and also a method for the detailed examination of reaction mechanism. It

has also proved valuable in the study of surface processes, such as formation and

reduction of oxide layers on metal surfaces.

The electrochemical cell is made up of an all glass one-compartment cell with

three-electrode cell assembly.

For all the studies platinum foil of one square cm area was used as an auxiliary or

counter electrode (CE). The platinum disc electrode of specified area (0.003 cm2) was

used as a working electrode for copper and glassy carbon of specified area (0.196 cm2)

used as a working electrode for lead, tin systems. All the experiments were carried out

with saturated calomel electrode (Hg/HgCl2 filled with saturated potassium chloride) as a

reference electrode along with Agar-Agar-KCl salt bridge. The pretreatments of the

working electrode consisted of polishing with emery paper, degreasing using tri chloro

ethylene, washing and rinsing with distilled water.

For cyclic voltammetry experiments analytical grade chemicals and triple distilled

water were used for the preparation of solutions. The electrolytes were prepared by

mixing the appropriate solutions with stochiometric amounts of the reagents concerned.

The solution under study was deoxygenated for one hour using purified nitrogen.

The experimental arrangement consists of potentiostat (Wenking Model VSG 72)

and X-Y recorder (Rikadenki, Japan). The potential range for electrodeposition was

fixed after carrying out several experiments to get reproducible results in all the copper,

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lead, tin electrolytes. Cyclic voltammetry studies were carried out with various

electrolytes of the following compositions as given in the table 3.2

3.8 Corrosion resistance studies

One of the important properties of electrodeposited coatings is their corrosion

resistance. The porosity of electrodeposits is closely related to its corrosion behaviour.

Evaluation of corrosion resistance may be carried out by non-electrochemical and

electrochemical techniques. Corrosion data like corrosion current Icorr, corrosion potential

Ecorr and weight loss were found out using various techniques like potentiodynamic

polarization and weight loss method.

3.8.1 Potentiodynamic polarization method

The earlier work of Wagner and Traud showed that there is a linear relationship

between potential and applied current at potentials only slightly removed from the

corrosion potential. They considered this relationship to be especially important because

low current polarization measurements combined with corrosion rate data permit

calculation of Tafel slopes. Since the measurements are carried out close to the corrosion

potential, only surface changes resulting from high current polarization are eliminated.

The slope of the linear portion will give the polarization resistance Rp = ∆E/∆t in

ohm.cm-1. I corr can be calculated by knowing the anodic and cathodic slopes ba and bc

respectively using the following equation.

ba bc I corr = ---------------- 2.303 Rp (ba + bc)

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Table 3.2 Composition of baths used for cyclic voltammetry studies

Bath Constituents

A1 Copper (as methane sulphonate) 0.70- 0.10 M

MSA 0.31–0.73 M


B1 Copper (as copper sulphate) 0.70- 0.10 M

Sulfuric acid 0.31 - 0.73 M


C1 Lead (as methane sulphonate) 0.24 -0.48 M

MSA 0.21- 0.62 M

Peptone 1.0 g/l


D1 Lead (as fluoborate) 0.24- 0.48 M

Fluoboric acid 0.21- 0.62 M

Boric acid 0.48 M

Peptone 1 .0 g/l


E1 Tin (as methane sulphonate) 0.34 - 0.50 M

MSA 1.56 - 2.60 M

Peptone 1.0 g/l


F1 Tin (as fluoborate) 0.34- 0.50 M

Fluoboric acid 1.56 –2.60M

Boric acid 0.48 M

Peptone 1.0 g/l


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The corrosion resistance studies of electrodeposited copper, lead, and tin,

of various thickness obtained from various electrolytes were carried out with polarization

technique. A three-electrode cell assembly was used in these polarization studies. The

electrodeposited copper, lead, and tin specimens were masked with lacquer to expose

only one square centimeter area on one side of the working electrode. A platinum foil and

saturated calomel electrode were employed as auxiliary and reference electrodes

respectively. Polarization studies were carried out with 5 % W/V neutral sodium chloride

solution for testing using Auto lab Ecochemie BSTR 10A system. The potentials were

scanned at the rate of 5-mV/sec up to 200 mV from the OCP value both in the cathodic

and on the anodic direction with suitable IR corrections. The intercepts of the linear

portions of the two polarization curves give I corr and E corr values.

3.8.2 Electrochemical impedance measurement method

Using the three electrode cell assembly, as used in potentiodynamic polarization

method, impedance measurements were carried out on copper, lead and tin deposits in 5

% sodium chloride solution at OCP using Solartron Model SI 1280 B. A circuit diagram

for the impedance study is shown in figure 3.3. Impedance measurements were carried

out at the OCP of the working electrode using the AC impedance system. AC signal of

amplitude 10 mV was impressed to the system with the frequencies ranging from 10 KHz

to 1 mHz. The values of solution resistance (Rs) and charge transfer resistance (Rt) have

been obtained from the Nyquist plot of real part (Z’) Vs imaginary part (Z’’).

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Figure 3.3 Circuit diagram for AC impedance measurement

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3.8.3 Self corrosion (weight loss) method

The corrosion rates can be expressed as variation in the weight per unit surface

area and unit time of penetration of the corrosion process into the metallic material in unit

time.

Weight loss experiments were carried out for copper, lead and tin anodes in

various concentrations of MSA. The anode area of (6.25cm2) was exposed for 7 days and

the corrosion products were removed and loss in weight was calculated [11].

3.9 Properties of electrodeposits

The characteristics of deposits mainly depend upon the nature of metals and

alloys. Properties of the electrodeposits were studied by measuring adhesion, porosity,

hardness and solderability.

3.9.1 Adhesion

A number of qualitative and quantitative tests have been developed for adhesion.

The qualitative tests are (a) bend test (b) twist test (c) heat cycling (d) burnishing (e)

scratching and chisting (f) impact tests and cupping. The qualitative tests are (1) peel test

(2) tensile test and (3) shear test.

In the present work bend test has been used for qualitatively assessing the deposit

adhesion [12]. The bend test comprises bending of the plated object to such as extent as

the specimen will permit. The test piece is held firmly by vise and bent as sharply as

possible. The bending is frequently reversed and repeated unit basis metal is fractured.

Any evidence of peeling, flaking of the deposit is taken as cause of rejection.

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3.9.2 Porosity

Porosity of the electroplated metal coated over steel is detected by the Ferroxyl

test [13]. Special test papers were prepared by impregnating them in a solution containing

50 g/l sodium chloride solutions and then pressed against the electrodeposited panel and

left for 10 minutes. After removal the papers were immersed in a 10g/l solution of

potassium ferry cyanide. Blue marks developed in the paper in the region where steel is

exposed through discontinuities in the coating were counted by viewing the surface with

microscope. The porosity of the coating was expressed as the percentage of defective

area.

3.9.3 Micro hardness

The value of micro hardness of electrodeposits of copper, lead and tin obtained

from different electrolytes at different conditions were determined by using a HMV,

Shimadzu Micro hardness tester with a square base diamond pyramid, having an angle of

136o at the vertex between two opposite faces. The deposit should be of adequate

thickness so that the diamond pyramid does not penetrate it to a depth greater than 10 %

of its thickness. This can be readily ascertained since the penetration depth is equal to

1/7 of the indentation diagonal. For determining micro hardness of deposit, the diamond

pyramid was pressed into the deposit for 10 seconds and the indentation diagonal was

measured after the load was removed. The Vicker’s micro hardness of the deposit in

Kg/mm2 was determined in each case by using the formula

V = 1854 x P ------------ d2

Where P is the load applied in grams and d is the diagonal of the indent obtained

in micrometers.

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3.9.4 Solderability

In this method [14] fixed volume of solder was placed on the test specimen,

which was heated to 513 K on a hot plate. On heating the test specimen, the solder melt

and spread over the surface. Then the sample was cooled and the area of spread was

measured with a planimeter. Spread factor for a particular test surface is calculated by

using the equation.

D-H Percentage spread factor = ------- x 100

D

Where D- diameter of sphere having a volume equal to that of the solder used and

‘H’ is the height of the solder spot. If there is no effect from gravity, surface tension or

wetting of the solder, the solder drop will assume the shape of a sphere. As the

solderability increases the height of the solder spot decreases resulting in the increase of

the spread factor value.

3.10 Structural characterisation

3.10.1 X-ray diffraction studies

The copper, lead, and tin deposited samples obtained from various electrolytes

were subjected to x-ray diffraction studies using PAnalytical model X’per PRO to

identify the orientation. CuKα radiation was used.

3.10.2 Scanning Electron Microscopic studies

The morphology of the electrodeposits was examined under high magnification to

assess the grain size, deposit nature, heterogeneities and pores present in the deposits

using a scanning electron microscope. The scanning electron microscope that makes use

of reflected primary electrons and secondary electrons enables one to obtain information

from regions, which cannot be examined by other techniques. The plated specimens

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were cut into 1 X 1 Cm2 size and mounted suitably and examined under the microscope.

The SEM photographs were taken by using Hitachi model S-3000H l with an acceleration

voltage range of 20,000V and with the magnification range of 1000 and 2000.

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REFERENCES

1. A.K.Graham, ‘Electroplating Engineering Hand Book’, 3rd edition, Von Nostrand,

Reinhold publishing, Princeton (1971).

2. J.B Kushner, ‘Electroplating know-how’ Evansville, Indiana 47714 (1974).

3. W.Blum and B.H.George, ‘Principles of Electroplating and Electroforming’ 3rd

edition Mc Graw Hill book company New York (1949).

4. A.T.Vagramyan and Sulov Evaz A, ‘Technology of Electrodeposition’, Robert

Draper Ltd (1960).

5. A.G.Gray, ‘Modern Electroplating’ New York (1953).

6. N.O.Ruboa, Electroplating and Finishing 63 (1992) 43.

7. W.Nobse, ‘Investigation of Electroplating and Related Solution with the aid of

Hull cell’, Robert Draper Ltd, (1996).

8. E.Raub and K.Muller, ‘Fundamentals of Metal Deposition’ Elseveir publishing

co. New York (1967).

9. W.Nobse, ‘The Hull cell’ Robert Drapper Ltd (1966).

10. M.Mc.Cormick and Kuhn, Trans Inst. Metal Finish.71 (1993) 74.

11. Peterwolfram Wild, Modern analysis of Electroplating, finishing publishing Ltd.,

London.

12. P.Leisner and M.E.Benzon Trans. Inst.Metal Finish. 75 (1997) 88.

13. C.Bocking, Trans. Inst.Metal Finish 74 (1996) 182.

14. J.B.Mohler, Metal Finish. 71 (1973) 86.

CHAPTER III EXPERIMENTAL TECHNIQUES

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