Effect Of Dc Current And Ac Current Biology Essay

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For this project, the main objective is to study and do comparison between the effect of DC current and AC current electroplating techniques on electrodeposition process. An experiment setup has been realized in order to do research on DC and AC electrodeposition process.

DC current electroplating technique was firstly implemented to do research. This is because the electrodeposition process is normally carried out by using a DC current instead of an AC current. Therefore, one of the main objectives of this project is to observe how the AC current would make an effect in electrodeposition process. Resistance measurements results from the deposition plate will be obtained for difference electroplating conditions. Meanwhile, the observation on the surface morphology of deposition plate using AFM (atomic force microscopes) machine also will be performed.

The project started off by doing a detailed research on the basic theory, material used and setup method of electroplating. Firstly, chemical reactions in electrodeposition process are studied.

Based on research, material of this project used are copper plate and copper sulfate, CuSO4 solution in terms of low costs, low resistance and common used in current industry.

Other than that, the resistance measurement results will be obtained by interface of LabVIEW within those apparatus such as power supply, keithley 2000 multiammeter and keithley 6485 picoammeter. Meanwhile, DC current electroplating and AC curremt electroplating setup will have a difference on power supply apparatus used. It used DC power supply and function generator respectively.

Lastly, the comparison between AC current electrodeposition and DC current electrodeposition will be performed. These comparisons include their resistance and condition of plating surface morphology by AFM machine.

1.3 Motivation

Many experts believe that the expansion of the electronics industry will be increasingly dependent on new and innovative electroplating technology [1].The electronics industry and the needs to support the expansion of their underlying infrastructure continue to drive improvements worldwide in the electroplating industry [1]. However, how the AC current electroplating influences the electrodeposition process is not fully developed yet. Thus, it would be challenging and interesting to research and learn the basic theory of electrodeposition and some of the actual experiment. It would be a bonus if worked in the R&D field.

1.4 Purpose of Report

This project includes a comprehensive study on DC current electrodeposition process; but the focus is given on AC current electrodeposition process. This project is divided into two main aspects normally research and experiment.

The results for electrodeposition process will also be discussed in this report. The methodology and tools used to complete this project also will be provided in this report. All the progress will be discussed in details to provide understanding for all readers.

1.5 Thesis Organizations

This report consists of five chapters. Chapter 1 provides a brief description of the objectives and aims of this project. The motivation and overviews of the project are also discussed in this chapter.

In Chapter 2, theoretical background of DC current and AC current electroplating process, fundamental principles to implement this project and theory of measurement are provided.

Next in Chapter 3, an overview of the methodology applies in the project is provided. The hardware and software used and the steps in succeeding this project are described.

In Chapter 4, the data results of the experiment in the forms of line graph, figure and table are carried out. On the other hand, the further discussion of the results also will be provided.

Lastly in Chapter 5, conclusion of the project and some recommendations for potential future developments of the project are given.


2.1 History of Electroplating

The discovery of electroplating is an excellent invention. Without the brilliant scientific and researcher in few decades ago, electroplating techniques might not introduce today and electroplating techniques would not widen used in different way of applications. A chemist Luigi V. Brugnatelli from Italy had discovered the electroplating technique in 1805 [7]. However, those inventions were concealed by the French Academy of Sciences. Hence, general industry that time not used Brugnatelli's invention and all the works was anonymous outside of Italy.

Gold electroplating was introduced and developed at year 1800's to 1845. By the way, two types of gold electroplating dependently with costs were discovered. For low costs, very low concentration of gold chloride solution is used to coat thin layer of gold onto inexpensive objects. For precious objects required, higher gold chloride concentration used to deposit thick layer over a surface.

Scientists in Britain and Russia had independently come out a metal deposition processes that corresponded with Brugnatelli's copper electroplating of printing press plates in 1839 [2]. Presently, scientists from England named John Wright discovered that gold and silver electroplating can be invented using potassium cyanide as solution [7]. Wright's associates, George Elkington and Henry Elkington were awarded the first patents for electroplating in 1840 [7].

As fundamental principle of electrochemistry broadens, scope of the applicable area using electroplating processes was increased. The used of bright nickel, silver and zinc for electroplating process were accommodated in commercial purposes. With the exception of some technical improvements to direct current (d.c.) power supplies, the period from 1870 to 1940 was a quiet period, characterized by gradual improvements in manufacturing processes, anodic principles and plating bath formulas [7]. In the mid-1940, the betterment of electroplating technique was discovered due to the emergence of electronics industrial.

Based on the basis behaviors of electrochemical, development in chemical field has led to sophisticated plating bath formulas. Therefore, better plating thickness controlled with greater plating rate and high quality plating is enabled due to new chemical development. One the other band, the electroplating of exotic materials such as platinum, ruthenium and osmium are now finding broader usages on electronic connectors, circuit boards and contacts [1].

With more advances used of electroplating techniques, it was benefits the industrial nowadays. For example, automobiles industries use chromium plating to protecting steel component such as kettles, tower rails and car bumper. The figure 2.1 and 2.2 below shows applications of electroplating.

Figure 2.1: Kettles Figure 2.2: Tower Rails

For electronics industries application, interconnect in IC and electronics devices are enhanced by electroplating techniques to fill up the trenches and contact via. From the research, the electroplating technique used in the electronic semiconductor nowadays was DC current techniques.

Nowadays, development in electroplating techniques with DC power supplies is led in the electroplating usage with its achievement. Meanwhile, AC electroplating techniques also get attention due to better electroplating outcome is expected. However, research regards AC electroplating is still not fully development. More research and achievement using AC electroplating is needed to prove the outcome in terms of surface roughness, ability to fill via and uniformity plating is comparable with DC electroplating techniques.

2.2 Electroplating Process

In the recent decade, electroplating technique is undergoing development from an art to an exact science. Following improvement of technology, the ability to deposit very thin multilayer (less than a millionth of a cm) via electroplating represents yet a new avenue of producing new materials [2]. Therefore, electroplating has widening types of applications in technological areas such as electronic component and automobile industry (for example, it used chrome plating to protect metal component). One of the common reasons for electroplating is economy and convenience. However, DC current electroplating technique was common used in current technology instead of AC current electroplating technique. From research in recent works, AC current electroplating has gained high attention because of superior deposit properties may be obtained [4]. Meanwhile, many experts also believed that void free, low stress and very smooth deposition can only be achieved by the use of AC current plating [5].

Figure 2.3: Structure of an electroplating setup for plating metal "M" from a solution

of the metal salt "MA".

Electroplating is also called "electrodeposition" and these terms are interchangeable [3]. Electrodeposition is the process of producing a coating, usually metallic, on a surface by the action of electric current [6]. For further understanding of readers, figure 2.3 shows basic structure of an electroplating setup for plating metal "M" from a solution of the metal salt "MA". A wire from positive terminal of power supply is connected to anode metal while wire from negative terminal is connected to cathode metal. Then solution of the metal salt "MA" is filled to immerse the metal. The process of producing coating between cathode and anode would start to react under applied electric current. The equation 2.1 below shows reaction of electroplating process happened at cathode metal.

Mn+ + ne- = M (2.1)

On the other hand, this equation 2.2 below is shows reaction of electroplating process happened at anode metal.

M = Mn+ + ne- (2.2)

The cathode metal to be coated is connected to the negative terminal, negatively charge anions electron, ne- produced to attract cations, Mn+ deposited on cathode metal, M. At the anode plate, positively charge cations, Mn+ produced and migrated to cathode plate which attracted by anions, ne-. Therefore, cathode metal was coated by Mn+ and the reduction of metal occurred at anode metal.

2.3 Limitation

There are a few limitations using electroplating method. Firstly, the process electroplating is highly depending on the characteristic of metal to obtain uniform plating. Therefore, it is very important to conduct a proper study on the plating metal used. Furthermore, the surface cleaning method is applied to increase the plating rate to a satisfied level. Secondly, there is the limitation of resistance and current measurement due to measurement apparatus. Therefore, measurement using 4 point probe method with its high accuracy and stable characteristics were introduced. Lastly, the high sensitivity and high scale microscopes such as atomic force microscopes machine (AFM) are essential to study the condition of electroplating surface. This is because the deposited metal is micron to nanometre-scale of surface thickness on plating metal.

2.4 Material Used in Previous Work

According the research, various type of metal such as copper, zinc, argentums, gold, platinum and so on are widely used for electroplating. Most of the concerns regards metal used are in terms of cost, availability and its properties. Among those materials, applications of electroplating using copper were highly get attention by current researcher in industrial.

2.5 Surface Cleaning Method

Dust, contaminants and films on surface are the factor that causes the limitation of uniformity plating. However, method to remove those impurities on surfaces is important to avoid damage and scratch produced. Therefore, chemical and mechanical approach of surface cleaning method is studied to get uniformity surface plating.

2.5.1 Chemical Approach

Types of chemical approaches for surface cleaning are solvent degreasing, alkaline cleaning and acid cleaning. Solvent Degreasing

Solvent degreasing is using appropriate organic solvents to remove contaminants such as oil, grease and impurity organic materials. Table below shows three most common degreasing solvent used and their properties.

Table 2.1: Properties of Common Degreasing Solvent Used

Furthermore, solvent degreasing has two degreasing systems which are liquid phase degreasing and vapour phase degreasing. Alkaline Cleaning

Work pieces are immersed in tanks of hot alkaline cleaning solutions to remove dirt and solid soil [11]. There are few types of influenced can affect the alkaline cleaner such as type of basis metal, type and concentration of the cleaner, cleaner temperature and the time of immersion. Acid Cleaning

Acid cleaning can move heavy scale, heat-treat scale, oxide, and the like [11]. Sulphate acid and hydrochloric was the most common used acid for cleaning method. To be more effective, pickling is connected with current during acid cleaning process.

2.5.2 Mechanical Approach

There are two types of mechanical approach used such as polishing and buffing. Polishing is to remove small amounts of metal by means of abrasives [11]. It produces a surface that is free of the larger imperfections left by grinding, and is a preliminary to buffing [11]. Buffing is similar to polishing, but uses finer abrasives to remove very little metal [11]. An extremely smooth surface was produce by buffing approach.

2.6 Measurement Method

Measurement method of electroplating is usually in terms of current, resistance to relate with studied of the surface morphology. Therefore, the electroplating process on surface can be proven from the measurement results and surface investigation process. In order to measure low resistivity of thin firm, 4 point probe method is introduced. For study the surface morphology, atomic force microscopy, AFM is introduced. More details theory of 4 point probe and AFM is introduced respectively as below.

2.6.1 Theory of 4 Point Probe Method

The purpose of four point probes used is to measure the sheet resistance of thin film or bulk resistance. Basically, there are two methods of resistance measurement which is 2 point probe and 4 point probe method. The difference between them is an additional 2 probe is used in 4 point method for measured the voltage potential of the surface. However, it also has weakness to using 2 point method measure the resistance. The weaknesses were the unwanted resistance such as contact resistance, Rc produced between probe and sample surface while spreading resistance, Rsp is produced during current flow into sample surface by the way resistance surface Rs is the only resistance to be concerned. Therefore, the total resistance obtained would be increased refer to equation 2.3.

Rtotal = Voltage, (V)/Current, (I) = 2Rc + 2Rsp + Rs (2.3)

With the used of additional 2 probe to measure voltage of sample surface in 4 point probe method, those unwanted resistance Rsp and Rc can be eliminated. Figure 2.4 below shows schematic of 4 point probe.

Figure 2.4: Schematic of 4 Point Probe

4 probes are connected to film in a row with "s" spacing. A high impedance current source is placed between two outer probes. On the other hand, voltmeter is placed between 2 inner probes. The measurement of 4 point probe is started with injected current through two outer probes; voltage is measure between two inner probes to determine the sample resistance and the using equation 2.4,

V2 = ρI/2πs (2.4)

Where "ρ" is the resistivity of a material, "I" is the current in the probe, and "s" is the distance between the voltage measurement and the current probe.

Using figure 2.2, the equation 2.5 used to measure voltage at probe 2, V2 is,

V2 = ρI/2π {(1/s1) - (1/ (s2+s3))} (2.5)

For the equation voltage at probe 3, V3 is,

V3 = ρI/2π {(1/ (s1+ s2)) - (1/s3)} (2.6)

Thus, the total voltage by subtract voltage at V2 with V3 is,

V = ρI/2π {(1/s1) + (1/s3) - (1/ s2+s3)) - (1/ (s1+s2))} (2.7)

Rearranging to get the resistivity,

ρ = 2π (V/I) / {(1/s1) + (1/s3) - (1/ (s2+s3)) - (1/(s1+s2))} (2.8)

However, if all probe spacing, s is equally, equation 2.8 is reduced to,

ρ= 2πs (V/I) (2.9)

Hence, with the fixed current and measurement of voltage, the resistance of material surface is obtained according the Ohm's law. This is resistance equation based Ohm's law,

R= (V/I) (2.10)

Where "R" is resistance (ohms, Ω), "V" is voltage (volts, V) and "I" is current (amperes, A).

Besides that, the configuration of current source and voltmeter will be changed dependently with resistance of sample to be measured. For high resistance sample, current need to reduce to avoid excessive large voltage at the contacts. On the other hand, the measurement is different for low resistance sample. Current is required to increase and the voltmeter is set to a lower scale.

Other than that, there also have limitations of measurement capability needed to be concerned. At first, the probes must be able to make ohmic contact with the material [12]. Secondly, only 100's of Angstroms up to 1 micron thickness of thin films can be measured. Next, current through the probe is best restricted to 10 mA because of heating effects and excessive current density at the probe tips [12]. Lastly, an unclean sample or a sample that has surface doping will lead to inaccurate figures due to an impeded ohmic contact or current leakage [12].

2.6.2 Theory of Atomic Force Microscopy (AFM)

The Atomic Force Microscopy, AFM is being applied to studies of phenomena such as abrasion, adhesion, cleaning, corrosion, etching, friction, lubrication, plating, and polishing. The purpose of using Atomic Force Microscopy, AFM is due to its ability to measure surface atoms that are extremely small. Besides that, atomic force microscope also able to provide topographic information from surface measured with 3 dimensional, 3D. From the figure 2.5 below, it shows how AFM works. Firstly, the AFM fine stylus is mounted on end of cantilever spring and move in Z direction to approach the sample. Meanwhile, detector which acts as light level sensor to detects the deflection of the cantilever. Then, force sensor and feedback control is required to measure the force and keep the "fixed" distance between tips and sample during scanning surface.

Figure 2.5: Basic Principle of AFM

Other than that, AFM has 3 types operating mode of surface measuring techniques as figure 2.6 below shows.

Figure 2.6: Operating Mode of AFM

First operating mode was introduced is contact mode. During scanning the surface, the stylus is followed the topography of the surface. At the same time, an extremely low force (~10-9 N, interatomic force range) of the probe is kept constant [14]. However the weakness of contact mode is the excessive tracking forces applied by the probe to the sample might causes damage. Next, the non-contact mode is introduced to solve the contact mode's weakness. Stylus is move in the air during scanning the sample surface. Attractive Van der Waals forces acting between the tip and the sample are detected, and topographic images are constructed by scanning the tip above the surface. Lastly, tapping mode is introduced. AFM tip-cantilever taps the sample surface while rastering and only touch the sample at the bottom of each oscillation [14]. The advantages of tapping mode is can be performed on both wet and dry sample surfaces, prevents the tip from sticking to the surface and causing damage during scanning.


This chapter discusses about the methodology used and the experiment setup to accomplish this project. This project is mainly about research and experiment that divide into two parts. For part I, DC current electroplating experiment will be conducted and part II will conduct AC current electroplating experiment. Each part is doing same measurement such as electrical properties and study surface morphology. To succeed in realized this experiment; there exist 5 stages, which are:

3.1 Research

In order to implement a good experiment, research was the first step. Information about implementing the experiment was studied through reference books, journals and internet sources. Information that was studied includes pros and cons of different material used, current and resistance measurement during electroplating and the machine used to do investigation on surface morphology of electroplating. On the other hand, difference between DC current electroplating and AC electroplating setup were studied too. This information was important because they were the main criteria to accomplish this experiment.

3.2 Setting and Studied Materials, Software and Apparatus Usage to Implement

Electroplating Experiment

After sufficient research was done, materials and apparatus used to implement electroplating experiment were chosen and gathered. The materials used are copper metal, copper sulphate solution and sulphuric acid solution. Besides that, the apparatus used are DC power supply, function generator, Keithley 2000 multiammeter, keithley 6485 picoammeter and PH 5/6 meter. In order to connect apparatus and materials, software named LabView is used. By the way, those materials' characteristics are very important because chemical material is dangerous and harmful. Thus, precaution method during handle it can be implemented. Other than that, further studied on those apparatus' characteristics used are important too. Therefore, false connection that will causes the damage or malfunction on apparatus can be prevented.

3.2.1 Setting, Characteristic and Usage of Materials

The setting, characteristic and usage of materials were introduced respectively as below: Copper

Copper metal was chosen as electroplating metal due to its low resistance, low cost and good conductivity properties. The thickness of copper metal used is 0.05mm and considered as thin film. Solution Copper Sulphate, CuSo4 · 5H2O

Besides that, electrolyte solution used is copper sulphate, CuSO4· 5H2O. According the theory of electroplating, copper ion in electrolyte solution produced by action of current will be coated on cathode metal during process. On the other hand, copper ion coated on surface can provide good conductivity properties and it also easier to produce copper ion by applied lower current. Acid Cleaning, Sulphuric Acid, H2SO4

Acid cleaning is the cleaning method used to remove impurity on metal surface and enhance its plating rate. The common used of sulphuric acid, H2SO4 with 98% of concentration in acid cleaning were chosen. Firstly, 98% of sulphuric acid, H2SO4 is poured into 400ml of distill water. Then copper is immersed for 10 minutes to do the cleaning. Due to the acidic characteristic of sulphuric acid is hazard and able to cause severe burns, eye protector and glove needed to wear during handle it.

3.2.2 Setting, Characteristic and Usage of Software

The setting, characteristic and usage of software were introduced respectively as below: LabVIEW Software

LabVIEW is a graphic user interface, GUI software to make an interface between measurement device and plating sample for electroplating process. Therefore, simulated results during measurement can be obtained at the same time.

3.2.3 Setting, Characteristics and Usage of Apparatus

The setting, characteristic and usage of apparatus were introduced respectively as below: DC Power Supply

At part I, DC power supply in photo 3.1 shows act as source to perform DC electroplating experiment. The range of voltage provided by DC power supply is wide. However, 50mV is fixed as constant voltage for the experiment.

Photo 3.1: DC Power Supply Function Generator

For part II, AC current electroplating experiment is performed. Therefore, DC power supply source in experiment Part I is replaced by using function generator and 50mV voltage is still fixed for experiment. Besides that, two frequency parameters were set which is 50Hz and 125Hz parameter. Reason for setting frequency is to avoid noises produced during electroplating process and affected results. Photo 3.2 below shows function generator used in experiment.

Photo 3.2: Function Generator

Before perform AC electroplating experiment, amplitude of function generator is set using oscilloscope. Function generator amplitude was set to 2V from peak to peak. Photo 3.3 oscilloscope shows the waveform that was set to 2V.

Photo 3.3: Oscilloscope Keithley 2000 Multiammeter

In order to measure the resistance of copper metal during electroplating process, Keithley 2000 multiammeter measurement device shows as figure 3.1 is chosen. Red circle shows on figure 3.1 is indicated four holes point where resistance is measured by 4 point probe method. This device can do measurement with fast, accuracy and highly stable condition.

Figure 3.1: Keithley 2000 Multiammeter Keithley 6485 Picoammeter

Besides doing measurement on resistance, current measurement also performed using keithley 6485 picoammeter as figure 3.2 showed. This measurement device has few characteristics such as low voltage burden, high accuracy current measurement up to nano-scale amperes and function of high speed auto range.

Figure 3.2: Keithley 6485 Picoammeter pH 5/6 & Ion 5/6 Meter

pH 5/6 & Ion 5/6 meter measurement as figure 3.3 shows is used to measure pH level of the electrolyte before electroplating and after electroplating process done. Measurement of electrolyte pH level is important to ensure concentration of solution unchanged. Hence, changes of concentration during electroplating that would cause inconsistently result obtained are avoided. This measurement device is economical and easy to use. The pH 5 indicates function of measures pH and temperature (oC) while the pH 6 is function of measures pH, mV and temperature [13]. Ion 5/6 allows ion concentration measurement of various ions (mono and divalence) and mV [13]. Besides Ion/mV modes, Ion 6 has pH and temperature (oC) measurement modes [13].

Figure 3.3: pH 5/6 & Ion 5/6 Meter device

3.3 Materials Preparation

Materials preparation is the following step after the apparatus setup ready.

3.3.1 Copper Preparation and Acid Cleaning

Firstly, small copper metal is cut into zigzag shape is shows as photo 3.4. This zigzag shape metal is act as cathode metal for the experiment. Main purpose of cutting the metal zigzag is to control its resistance according the theory of conductive resistance. Theory of conductive resistance is proven by equation 3.1 below shows.


Where "ρ" is a constant resistivity dependently with the material used. For copper, its resistivity is 1.678*10-8 ohm-centimetre (Ω-cm) [15]. Besides that, "l" is length of copper metal while "A" is the cross-sectional area of copper metal. From here, it indicated copper resistance is increase if the length is longer.

Photo 3.4: Zigzag Shape Metal

Next, a rectangular shape of copper is cut and acts as anode metal. Then, cathode copper metal and the anode copper metal cut were immersed into 34ml of 98% H2SO4 acidic in 250ml H2O for 10 minute. The metal were taken out and washed by distill water after 10 minute.

3.3.2 CuSO4 Solution Preparation

For solution preparation step, 80g of CuSO4· 5H2O powder is measured then poured into beaker contains 400ml of distilled water. The powder is dissolved in distilled water and stir with rod slowly. On the order hand, heater is set to 60 oC and it used to make sure powder form is fully dissolved in distilled water. The photo 3.5 below shows heater used during solution preparation.

Photo 3.5: Heater with Beaker contains Solution

3.3.3 Precaution during Material Preparation

During handling with material, there are some step is needed to precaution.

Wear eye protector

Wear the glove

No direct handling contact with material

Use tweeze to handling material

3.4 Experiment Procedures

Refer to the apparatus, characteristics and usages have been studied at previous step. The connection between apparatus and materials setup is showed as figure 3.4 below. Sample showed in the figure 3.4 are the materials used such as copper metal and copper sulphate solution. After the apparatus setting, solution preparation, material preparation and acid cleaning is performed, DC current electroplating experiment in Part I is implemented as figure 3.4 apparatus setup shows below. Firstly, LabVIEW software to make interface between measurement apparatus with sample is set. Secondly, voltage power supply is set to 50mV. Next, wire used for resistance measurement apparatus keithley 2000 multiammeter and current measurement apparatus keithley 6485 picoammeter is plugged in.

Figure 3.4: Connection of Apparatus with Materials Setup

Then, more detailed connection of apparatus with materials is showed as photo 3.6. After the apparatus and materials is prepared, cathode copper metal and anode copper metal is put in beaker. Positive terminal is connected to anode copper metal while negative terminal is connected to cathode copper metal. As showed, four point probes from keithley 2000 multiammeter are connected to cathode copper metal. Then, resistance of cathode copper metal is start measured after poured 40g CuSO4· 5H2O concentration of solution in beaker. Power supply is turn on for 40 minutes continuously. This step is repeated for 10g CuSO4· 5H2O concentration of solution. The measured data is collected.

Photo 3.6: Connection of Apparatus with Materials

However, the experiment procedures for AC current electroplating experiment in Part II is repeated as described above during setup in experiment Part I . Besides that, the only one change which is the DC power supply during DC current electroplating is replaced with function generator to supply AC current during AC current electroplating experiment. The setting for function generator is set as described earlier. After performed the AC and DC current electroplating experiment, all resistance measurement data is gathered and graph is plotted.

3.5 Studied Surface Morphology Procedures

After electroplating experiment done, the cathode metal is taken out to do surface morphology studied by AFM. The AFM used is showed as photo 3.7 below.

Photo 3.7: Structure of AFM Machine

Firstly, solid frame pump is turned on in order to supports the entire AFM microscope. Meanwhile, it also can avoid vibration during scanned. Then, software named nanosuft easy scan2 is clicked to operate the AFM microscope. Next, cathode metal sample is cut into small pieces and placed on the glass. Following, the sample is placed on the stage and translator is adjusted to make the AFM head approached the surface sample. Now, "approach" is clicked and the translator would be adjusted until surface sample started reading as showed in photo 3.8. At imaging area, to get better resolution of image, image size "10µm", time/line 1 s, points/line "256" values is set respectively. The scanning surface process will stopped when scanning process ended. Results of scanning image are saved in bitmap format. The same steps are repeated for next samples.

Photo 3.8: Nanosurf Easy Scan2 Operating Software


4.1 DC Current Electroplating Results and Discussions

Refer to appendix A and B, the resistance difference, Rdifferent and surface roughness, Rq figure 4.1 as below shows is plotted. From the figure 4.1, the comparisons between the resistance difference, Rdifferent and surface roughness, Rq with different types of CuSO4· 5H2O / 400ml concentration is observed. Besides, it also showed a trend that surface roughness, Rq is increased when resistance different, Rdifferent increased. However, how resistance different, Rdifferent related between resistances before electroplating, R before and resistance after electroplating, R after would be explained more detailed.

*nm = x10-9m

*mm = x10-3m

Figure 4.1: Comparisons between Resistance Different, Rdifferent and Surface

Roughness, Rq with Different Types of Concentration

The method calculated the difference between resistances is showed at equation 4.1, where resistances before electroplating, R before subtract resistance after electroplating, R after. The value of resistance before and resistance after electroplating is referred to appendix A.

R different = R before - R after (4.1)

The resistance different is higher when higher resistances after electroplating, R after shows decreasing signs and much lower value than resistances before electroplating, R before is important to prove the coating on copper surface was obtained during deposition process. Lower the resistances obtained after electroplating, R after, higher the surface area. It is supported by theory of conductive resistance according equation 4.2.


Where "ρ" is a constant resistivity dependently with the material used. For copper, its resistivity is 1.678*10-8 ohm-centimetre (Ω-cm) [15]. Besides that, "l" is length of copper metal while "A" is the cross-sectional area of copper metal.

So, the trend from figure 4.1 is higher resistance different is showed at higher concentration, 40g of CuSO4· 5H2O / 400ml and theoretically the surface area also increased than low concentration, 10g of CuSO4· 5H2O / 400ml.

However, increasing area of plating surface is theoretical proven with refer to figure 4.1. For more detail, coating on copper surface can be observed using AFM. Figure 4.2 and 4.3 below shows the observation obtained from 10g of CuSO4· 5H2O /400ml surface sample while figure 4.4 and 4.5 below shows the observation obtained from 40g of CuSO4· 5H2O / 400ml surface sample.


Figure 4.2: 2D Images Scanned with Figure 4.3: Zoom In 3D Image From

10µm x 10µm Width Area Red Square Indicated at Figure 4.2 with

2.11µm x 2.11µm Width Area


Figure 4.4: 2D Images Scanned with Figure 4.5: Zoom In 3D Image From

10µm x 10µm Width Area Red Square Indicated at Figure 4.4

with 2.13µm x 2.13µm Width Area.

In order to observe more detailed coating surface, red square on 2D image scanned surface with 10µm x 10µm width area as figure 4.2 shows is zoom in with 2.11µm x 2.11µm width area using 3D image format as figure 4.3 shows. Figure 4.4 and figure 4.5 showed as above do the zoom in observation too.

Compare 2D image figure 4.2 with and 4.4, the copper plating on surface as sample from high concentration, 40g of CuSO4·5H2O/400ml, figure 4.4 showed bigger "dot" around the surface but it showed non-uniformity on surface is observed at figure 4.5(3D zoom in image). Meanwhile, sample from low concentration, 10g of CuSO4· 5H2O/ 400ml , as figure 4.2 showed small "dot" around the surface but the uniformity is observed at figure 4.3 (3D zoom in image).

Refer to figure 4.1, the resistance different, Rdifferent for 40g of CuSO4· 5H2O/ 400ml is higher than 10g of CuSO4· 5H2O/400ml concentration. Meanwhile, it also showed the surface roughness, Rq is slightly higher at high concentration, 40g of CuSO4·5H2O/400ml than low concentration, 10g of CuSO4·5H2O/400ml. It indicated that copper plating surface area by using high concentration solution, 40g of CuSO4·5H2O/400ml is increased compared with copper plating using low concentration solution, 10g of CuSO4· 5H2O/400ml after electroplating .

From the 3D zoom in width area at figure 4.3 and 4.5, it showed surface roughness and thickness of 40g of CuSO4·5H2O/400ml, figure 4.5 is higher than 10g of CuSO4·5H2O/400ml, figure 4.3 concentrations. Meanwhile, figure 4.5 also showed the height of deposition higher with non-uniform surface. Therefore, higher surface roughness does not indicate that surface is smoother. If the height of the surface is not uniform, it will cause the higher surface roughness too.

This is the surface roughness, Sq equation given,

Sq = Average Deviation of Profile y(x) from the mean line

= (4.3)

Figure 4.6: Parameter of Surface Roughness

At higher concentration, 40g CuSO4· 5H2O/400ml electroplating, polarization effect is occurs. Polarization means the rate of copper metal ion Cu2+ ­ reaction from solution is slower than rate of coating reaction at metal. Thus, the higher surface roughness and thickness surface with non-uniformity is obtained. The non-uniformity is due to the rate of copper metal ion Cu2+ ­ reaction from solution is high at the same time and led the high deposition process rate occurred. For low concentration, 10g CuSO4· 5H2O / 400ml solution, the electroplating reaction is followed the theory of polarization effect too. The deposition rate for 10g CuSO4· 5H2O/400ml, low concentration solution is slow compared with the 40g CuSO4· 5H2O/400ml, high concentration solution used. Hence the uniformity with low surface roughness and low surface thickness is obtained.

4.2 AC Current Electroplating Results and Discussions

For the AC current electroplating techniques, 2 sets of experiments are done. The same concepts between them are concentration types, fixed voltage supply while the sine wave frequency is varying variable in 50Hz and 125Hz during each experiment respectively. Refer to results appendix C, D and E, comparison of resistance different and surface roughness with different frequencies used is plotted as figure 4.7 below.

Figure 4.7: Comparison of Resistance Different and Surface Roughness with Different Frequencies used respectively

The figure 4.7 above showed 2 set of experiment also used 40g of CuSO4· 5H2O / 400ml concentration and 10g of CuSO4· 5H2O / 400ml concentration where the 50Hz and 125Hz of sine wave frequency is applied on each set experiment respectively. Besides that, first set experiment result using 50Hz showed a same trend as DC current electroplating experiment at figure 4.1 where surface roughness, Rq is increased when resistance different, Rdifferent increased. On the other hand, the trend for second set experiment result using 125Hz showed reversed trend compare with first set experiment and DC current electroplating experiment.

Same theoretical refer to equation 4.1 and 4.2 is applied during AC current electroplating experiment where higher the resistance different, lower the resistance after electroplating, Rafter would showed higher surface area. Therefore, the surface area is increased more during first set experiment with 50Hz frequency than second set experiment with 125Hz frequency.

However, this theory is just referring to theoretical equation 4.1 and 4.2 while surface morphology is observed to prove it.

This is the surface sample from first set experiment for 40g of CuSO4· 5H2O / 400ml using 50Hz sine wave. The figure 4.8 below showed the 2D image scanned with 10µm x 10µm width area on surface sample. Besides, more clear condition of plating surface from figure 4.9 is showed by zoom in 3D image scanned from position indicated at red square with 2.15µm x 2.15µm width area.


Figure 4.8: 2D Images Scanned with Figure 4.9: Zoom In 3D Image from

10µm x 10µm Width Area Red Square Indicated at Figure 4.8

with 2.15µm x 2.15µm Width Area.


Figure 4.10: 2D Images Scanned with Figure 4.11: Zoom In 3D Image from

10µm x 10µm Width Area Red Square Indicated at Figure 4.10

with 2.15µm x 2.15µm Width Area.

For the figure 4.10, it is the 2D image surface sample scanned from 10g of CuSO4· 5H2O /400ml using 50Hz Sine Wave with 10µm x 10µm width area. The figure 4.11 showed a zoom in 3D image scanned from position indicated at red square with 2.15µm x 2.15µm width area.

From the 2D image scanned at figure 4.8 and 4.10, both also showed big "dot" around the surface but the "dot" is more obviously seen from figure 4.8. Refer to figure 4.7, the resistance difference, Rdifferent and surface roughness, Rq is higher for high concentration, 40g of CuSO4· 5H2O / 400ml using 50Hz sine wave compared with low concentration, 10g of CuSO4· 5H2O / 400ml. So, the image here is proven the trend at figure 4.7. As 3D zoom in image showed at figure 4.9, it showed higher surface area which mean higher thickness with uniform surface for high concentration, 40g of CuSO4· 5H2O / 400ml. Meanwhile, 3D image figure 4.11 for low concentration, 10g of CuSO4· 5H2O / 400ml is showed lower surface thickness with slightly non-uniform on surface.

On the other hand, the 2D surface image for sample 40g of CuSO4· 5H2O / 400ml using 125Hz sine wave is scanned and showed as figure 4.12. The zoom in 3D image from red square indicated at figure 4.12 is showed as figure 4.13 below.


Figure 4.12: 2D Images Scanned with Figure 4.13: Zoom In 3D Image from

10µm x 10µm Width Area Red Square Indicated at Figure 4.12

with 2.15µm x 2.15µm Width Area


Figure 4.14: 2D Images Scanned with Figure 4.15: Zoom In 3D Image from

10µm x 10µm Width Area Red Square Indicated at Figure 4.14

with 2.15µm x 2.15µm Width Area

The same scanned image as previous step repeated for sample 10g of CuSO4· 5H2O / 400ml using 125Hz is showed at figure 4.14 which is 2D image and figure 4.15 which 3D zoom in image from figure 4.14.

From the 2D image figure 4.12 and 4.14, it show both small and big "dot" around the surface but not much quantity showed as 2D image figure 4.8 and 4.10 from first set experiment. Refer to figure 4.7, it showed inverse trend compared to first set experiment and DC current electroplating experiment (Refer to figure 4.1). With referring to equation 4.1 and 4.2, it showed the low concentration, 10g of CuSO4· 5H2O / 400ml sample plating area is higher than high concentration, 40g of CuSO4· 5H2O / 400ml sample.

With the 3D zoom in image figure 4.13 and 4.15, the surface roughness showed at low concentration, 10g of CuSO4· 5H2O / 400ml image figure 4.15, is higher than high concentration, 40g of CuSO4· 5H2O / 400ml image figure 4.13. Meanwhile, both "dot" surfaces are less compare to zoom in image from first experiment (3D figure 4.9 and 4.11). This inverse trend happened because the higher frequency (125Hz) used. When high frequency, 125Hz applied in low concentration, 10g of CuSO4· 5H2O / 400ml solution, it increased the resistance inside solution while due to the low concentration is using, the current still can pass through and electroplating is processed. On the other hand, high concentration 40g of CuSO4· 5H2O / 400ml solution contained high resistance and resistance is increased higher under high frequency, 125 Hz applied. Thus, the current flow through is decrease and electroplating process is slower rate compare with low concentration, 10g of CuSO4· 5H2O / 400ml.

For AC current electroplating, it showed an obviously changes at resistance different at low sine wave frequency, 50Hz compare to high sine wave frequency, 125Hz. From the first experiment with 50Hz frequency image figure 4.8-4.11, it showed uniform trend and the larger surface compare with second experiment with 125Hz frequency image figure 4.12-4.15. During low frequency, 50Hz AC current electroplating, high current can pass through and the polarization effect is occurred more frequently. Meanwhile, AC current electroplating can performed double deposition on surface and therefore the uniformity of surface and larger surface can be obtained.

From results of the DC and AC current electroplating experiment, it showed the better deposition on surface is performed at AC current electroplating with low frequency, 50Hz and high concentration, 40g of CuSO4· 5H2O / 400ml used. Besides that, uniformity plating surface and smoother surface can be obtained due to the double deposition reaction performed during low frequency, 50Hz AC current electroplating applied. Thus, it also increased the area of surface electroplating. Compare the surface roughness of DC current electroplating 3D figure 4.3 and 4.5 with low frequency, 50Hz AC current electroplating 3D figure 4.13 and 4.15, higher surface roughness results from DC current electroplating. However, the surface roughness higher doesn't mean the surface area is larger because it may contribute by non-uniform trend and different high height on the surface as what have been mentioned previously.


5.1: Conclusion

From the comparison between DC electroplating and AC electroplating outcome, it concluded that AC electroplating showed better deposition than DC electroplating technique from the resistance differences and image observed at same concentration. In addition, the thickness of the plating increased using AC electroplating and causes area increased. Meanwhile, the outcome also concluded that the surface roughness of AC plating sample is uniformity than DC plating sample. Lastly, frequency of AC electroplating is important to control the deposition rate and uniformity of surface.

However, there was a limitation during studied the composition of surface morphology. Results of copper plating surface might include the dust besides the metal ion salt. So, it was hard to confirmed that metal coating on surface is the metal ion salt.

Lastly, the project was successful as it was achieved the objectives of the projects.

5.2 Future Recommendation

Energy Dispersive X-ray Spectroscopy

The limitation of studied the composition of surface can be improve by using energy dispersive X-rap spectroscopy, EDX. The advantages usage of EDX is it able to characterize the elemental composition of the analyzed volume. Meanwhile, energy dispersive x-ray spectroscopy is also able to analyze the phases as small as 1μm or less.