Week-04

On the Wednesday of fourth week, Mr. Neil sir conducted our second global session. He took the random generator in first 90 minutes. He gave us overall explaination about week-04 which includes PCB (Printed Circuit Board) Fabrication. He tought us different concepts related to PCB fabrication process such as dead bug, etching, machining, fixturing, underlay, zeroing, priting methods including climb and conventional,etc. Also, he gave us brief explaination for choosing best material while priting such as FR4 and FR1, different assembly methods such as soldering, desoldering, stuffing,etc.
In this assignment, I have made documentation on-
Group Assignment
1. Characterize the design rules for your in-house PCB production process.
Individual Assignment
1. Make an in-circuit programmer that includes a microcontroller.
2. Mill and stuff the PCB.
3. Test it to verify that it works.

On the second day, Mr. Suhas sir conducted our online lecture to teach us about PCB milling process, conversion of ".png" images of traces and interior of PCB into G-Code using "Modes". After the online lecture my instructor Mr. Kiran sir conducted orientation of PCB Milling Machine physhically. He tought us the operation of PCB Milling software interface, precautions to be taken while operating machine and printing of architecture of PCB.
Before, starting PCB Milling we have to know about some basic concepts are as follows-
A. PCB Fabrication (Process, Material, Machine and Tools)
PCB Fabrication a process of manufacturing PCBs that transforms a circuit board design into a physhical structure based upon the specifications provided in the design package.
1) Etching for PCB Fabrication

Etching is the process of removing unwanted copper from a printed circuit board. Once all of the excess copper has been removed from the PCB, only the required circuit remains. Before the etching process begins, a layout for the board is generated. This desired layout for the board is transferred onto a PCB by process called photolithography. This forms the blueprint that decides which pieces of copper must be removed from the board. On the outer layer of PCB, the tin plating acts as the etch resist. However, in the inner layer, the photoresist is the etch resist. Basically, there are two types of etching are dry etching and wet etching. Dry etching is a process which uses plasma that activates chemical reactions between base and surface atoms of the laminate. This causes the unwanted copper to dissolve. On the other hand, Wet etching is the process uses solution that dissolves unwanted copper using chemical reactions. Depending on the etch material, acidic or alkaline chemical can be used here.
Click here to read more.
Some of the chemicals used in Etching
1. Citric acid = C6H8O7 Sour Salt dry powdered form
2. Acetic acid = CH3COOH (also written as CH3CO2H or C2H4O2) White Vinegar
3. Hydrochloric acid/ Muriatic acid = HCL Swimming Pools to reduce alkalinity
4. Hydrogen Peroxide = H2O2 first aid antiseptic solution, mild disinfectant for wounds
5. Copper sulphate = CuSO4
6. Sodium chloride = NaCl, the chemical name of salt
Precautions to be taken while Etching
1) Wear safety glasses and gloves during etching.
2) Etching can only be done under supervision.
3) Avoid inhalation of vapours.

2) Machining (Milling) for PCB Fabrication

PCB Milling is referred as the process of removing areas of copper from sheet of PCB material to recreate the signal traces, pads as well as structures based on patterns from a digital circuit board plan called a file of PCB layout. PCB milling is a non-chemical process, so it can be done in lab environment also. The milling accuracy and sharpness of the milling bits used for milling improves the quality of PCB.
Click here to know more.

Material used in PCB Milling
FR1-Phenolic paper is a type of material used to make printed circuit boards to which components and traces are attached. Basically, it is in brown colour appearance, made up of wood fibre and phenolic polymers. In short, it is a combination of paper and epoxy. Thus, it provides high mechanical strength to the circuit board which makes PCB withstand the load of components.
Machines used in PCB Milling
PCB Milling system is a single machine that can perform all of the required actions to create a prototype board, where components and traces are to be attached. PCB milling machines are basically roots in "CNC Milling Technology". The CNC Milling is a machining process that utilizes computarized controls to manage the movement and operation of multi-point rotary cutting tools.
Tools used in PCB Milling
Flat end mills tools are mostly used for PCB Milling. Their straigth profiles and consistent diameters gives great clearing large areas of material and it can remove material very quickly.

B. PCB Components and Assembly
There are two types of PCB components are as follows-

1. Through-hole technology
The name "Through-hole" itself refers that it is manufacturing method in which leads on the components are inserted through holes drilled in printed circuit boards and soldered to pads on the opposite side, either by manual assembly or by use of automated insertation process. It is the older form of PCB technology which often called as "PTH" (plated through hole) technology. It is the mounting process of mouting on the PCB components throungh plated holes.
2. Surface mount technology
Surface mounting generally called as planar mounting. It is the method in which the electrical components are mounted onto the surface of printed circuit board. Basically, it is component assembly technology used to attach and connect components on the surface of board.

PCB Assembly
A printed circuit board assembly describes the finished board after all the components have been soldered and installed on a printed circuit board. A circuit board assembler prepares printed circuit boards by soldering electronic components onto them. Reading wiring diagrams, selection of electronic components and finishing boards with hand tools are all includes in PCB assembly.
The first and most commonly used method for assembly is Soldering.

Soldering is a process used for joining metal parts to form mechanical or eletrical bond. Typically, it uses metal alloy having low melting point which is melted and applied to parts to be joined. Here, the iron is heated to create strong electrical bond.
Solder is a metal alloy used to create a permanent bond between metal workpieces. Solder which is used in making electrical connections also needs to have favourable electrical characteristics. Click here to know more.
There are different types of solder such as acid core solder, lead alloy solder, flux core solder, rosin core solder, silver alloy solder, etc. The most commonly used solder is "Tin-Lead solder", which is made up of 60% tin and 40% lead, has 180-190 deg.cel. melting point.

Solder paste is the mixture of the two main elements required to successfully solder together two pieces of metal i.e "powder" and "flux". Solder paste works as an adhesive material while soldering. It also provides electrical and thermal connection. The most common solder paste powder sizes for surface mount technology are type 3(T3), type 4(T4), type 5(T5). The lower the number, the larger the particle size within the solder powder.
Solder flux is a chemical compound that helps prepare the metal surfaces for soldering by removing oxides and enhancing the flow of solder. The most commonly used solder flux is natural rosin derived from pine tar resin.

Now, the next one process is Desoldering.
The name itself shows that it is the reverse process of soldering. Desoldering is the process of removal of solder and components mounted on circuit boards. The solder joint is removed using the desoldering process. In desoldering process, a small vacuum pump is used to remove solder from the plated through holes. The lead over which the desoldering tip was placed is moved in a circular motion for rounded leads and back and forth for flat leads.

Desoldering braid is pre-fluxed copper braid that is used to remove solder, which allows components to be replaced and excess solder to be removed. It is generally made from oxygen free copper.
Solder remover suction/vacuum pump is a manually-operated device which is used to remove solder from a printed circuit board. firstly you have to heat the solder joint using soldering iron until the solder melts. Then, position the tip of the desoldering pump close to that joint and press the button to activate the vacuum.

Hot air guns are used to heat up the solder joint, melts the solder and easily remove the components.
Soldering station is used to allows you to adjust the temperature of soldering iron. It help to enhancing the efficiency of soldering process. Soldering stations may include some accessories like holders and stands, soldering tip cleaners, hot air gun, soldering fume extractor and magnifying glass with light, etc.

Here is the picture of Soldering station and tools at Sanjivani Fab Lab.

Sanjivani Fab Lab owns Mill Drill Machine for PCB Drilling, Milling and Routing Application, manufactured by Interface Design Associates Pvt. Ltd., a local manufacturer in India. To operate this machine, manufacturer has given software named as WinMill which combines the power of SC06 with a user friendly application running under the Windows 7/8/8.1/10 32-bit system. The SC06 card has three axis CNC controller and its other specifications are-
1) 4 axis of digital numerical controller
2) G-Code and M-Code support
3) Multiple operations mode
4) Manual mode including jo, absolute, home, incremental
5) PLC interface available
6) 16 inputs and 16 outputs digital ports
We have operated our machine in Windows 7 operating system of standard PC. The movement of the nozzle can be controlled by using default software of the company i.e WinMill. It takes Gcode and operate according to the inserted Gcode.
On this day, our local instructor Mr. Kiran sir has taken the orientation of Milling Machine. He tought us to operate the machine, how to set Local Origin, clamping, base fixing, milling process of PCB, etc.

Now, after the orientation we started our Group Assignment.
Group Assignment
Firstly we have took the sheet of FR1 material. We have measure its thickness using vernier caliper measuring instrument. And setup the sheet on the base of machine using clamping.

Then, imported GCode file into the software for milling operation.

Here, we have set the local origin by setting X0, Y0 and Z0.

Here are the screenshots of software while milling process.

Here is the final PCB after milling. Click here to know more about my group assignment.

Now, moving towards my individual assignment.
Individual Assignment
Before, executing GCode in Milling machine, I have setup the new tool.

Here, I have inserted GCode into the milling machine through software.

Before importing GCode file into milling machine, I converted ".png" file into GCode format using Mods CE website.

Here are the steps for conversion-

By clicking on "calculate" option I got GCode file. I have added GCode file at the "Downloads" at the footer section where I changed G54 to G55.

Now, I wanted to import GCode file into the WinMill software which is default software given by manufacturer to operate Milling machine. Here is the interface of WinMill software-

Before starting the cycle, I have set local coordinates i.e X0, Y0 and Z0 using "setwcs" option.

Firstly, I imported GCode file of Quentorres Traces using "Load" option and starts the cycle.

After completing Traces file, I imported Interior GCode file of Quentorres and started the cycle again.

Finally, I got PCB Milling workpiece with proper finishing and cutting.

Pinout diagram of RP2040-

I completed soldering of all the SMD components under the guidance of my instructor Mr. Kiran sir in our fab lab.

Step 01- Open the Arduino program
In File>Preferences, we will add the URL of the additional boards. We need the Arduino-Pico by Earlephilhower.

Step 02- Boards manager
The next step is to download Pico in the boards manager. Tools>Board>Board manager.

Step 03- Configure the Arduino IDE for the Seeed Studio XIAO RP2040
we configure the Arduino IDE for the Seeed Studio XIAO RP2040. The Seeed Studio XIAO RP2040 will appear in the COM port, in my case in COM 3.

Step 04- Program the IC
I programmed the board to blink all the LEDs, and I also did programming to the push button to toggle the LEDs ON or OFF.

There are some programs that I used to program my board.
Program-01
//This code is written by Siddhi Bodhe #include
const int led1 = 0;
const int led2 = 1;
const int led3 = 26;
const int buttonPin = 27; // Replace with the actual button pin if different
int buttonState = LOW; // Initial button state
bool ledOn = false; // Flag to track LED state
void setup() {
// Set LED pins as outputs
pinMode(led1, OUTPUT);
pinMode(led2, OUTPUT);
pinMode(led3, OUTPUT);
// Set button pin as input with internal pull-up resistor
pinMode(buttonPin, INPUT_PULLUP);
// Initially turn off LEDs
digitalWrite(led1, HIGH);
digitalWrite(led2, HIGH);
digitalWrite(led3, HIGH);
}
void loop() {
// Read the button state
buttonState = digitalRead(buttonPin);
// Toggle LED state on button press (rising edge)
if (buttonState == LOW && !ledOn) {
ledOn = true;
digitalWrite(led1, LOW);
digitalWrite(led2, LOW);
digitalWrite(led3, LOW);
} else if (buttonState == HIGH && ledOn) {
ledOn = false;
digitalWrite(led1, HIGH);
digitalWrite(led2, HIGH);
digitalWrite(led3, HIGH);
}
}

Output-

Program-02
//This code is written by Siddhi Bodhe #include
const int ledPin = 26;
const int ledPin1 = 0;
const int ledPin2 = 1; // GPIO pin connected to the LED
void setup() {
// Set the LED pin as output
pinMode(ledPin, OUTPUT);
pinMode(ledPin1, OUTPUT);
pinMode(ledPin2, OUTPUT);
}
void loop() {
// Turn on the LED
digitalWrite(ledPin, LOW);
delay(50);
digitalWrite(ledPin1, HIGH);
delay(50);
digitalWrite(ledPin2, LOW);
// Wait for a second
delay(100);
// Turn off the LED
digitalWrite(ledPin, HIGH);
delay(50);
digitalWrite(ledPin1, LOW);
delay(50);
digitalWrite(ledPin2, HIGH);
// Wait for a second
delay(50);
}

Output-

Program-03
//This code is written by Siddhi Bodhe #include
const int ledPin = 26;
const int ledPin1 = 0;
const int ledPin2 = 1; // GPIO pin connected to the LED
void setup() {
// Set the LED pin as output
pinMode(ledPin, OUTPUT);
pinMode(ledPin1, OUTPUT);
pinMode(ledPin2, OUTPUT);
}
void loop() {
// Turn on the LED
digitalWrite(ledPin, LOW);
delay(50);
digitalWrite(ledPin1, HIGH);
delay(500);
digitalWrite(ledPin2, LOW);
// Wait for a second
delay(100);
// Turn off the LED
digitalWrite(ledPin, HIGH);
delay(500);
digitalWrite(ledPin1, LOW);
delay(500);
digitalWrite(ledPin2, HIGH);
// Wait for a second
delay(500);
}

Output-