Electronics Production

Group Assignment #2: Electronic Production

This week, we worked on Electronic Production group assignment. This assignment is about documenting what we learned in Electronics Production that includes PCB fabrication processes, PCB material, components, PCB assembly (including processes and tools). We have also documented how we used machining process for PCB, tools, what precautions need to be taken while operating the milling machine.

Objectives of this Group Assignment:

Understand PCBs, their types, fabrication processes, material and tools

Understand how to operate the PCB milling Machine

Learn safety precautions while operating this Machine

Characterize the design rules for your in-house PCB production process

What is PCB: A printed circuit board (PCB) is a laminated sandwich structure of conductive and insulating layers. PCBs have two complementary functions. The first is to affix electronic components in designated locations on the outer layers by means of soldering. The second is to provide reliable electrical connections (and also reliable open circuits) between the component's terminals in a controlled manner often referred to as PCB design.

PCBs mechanically support electronic components using conductive pads in the shape designed to accept the component's terminals, and also electrically connect them using traces, planes and other features etched from one or more sheet layers of copper laminated onto and/or between sheet layers of a non-conductive substrate.[1] Components are generally soldered onto the PCB to both electrically connect and mechanically fasten them to it. Printed circuit boards are used in nearly all electronic products and in some electrical products, such as passive switch boxes.

There are many types of PCBs like single layer PCB, Double layer PCB Multiple layer PCB, flexible PCB, rigid-flexible PCB, etc.

Types of PCBs

PCB Fabrication (Process, Material, Machine and Tools)

In this section, we are documenting machining (end milling) as process for PCB fabrication and required PCB material, machines and tools.

Machining (Milling) for PCB Fabrication

Printed circuit board milling (also: isolation milling) is the process of removing areas of copper from a sheet of printed circuit board material to recreate the pads, signal traces and structures according to patterns from a digital circuit board plan known as a layout file. Similar to the more common and well known chemical PCB etch process, the PCB milling process is subtractive: material is removed to create the electrical isolation and ground planes required. However, unlike the chemical etch process, PCB milling is typically a non-chemical process and as such it can be completed in a typical office or lab environment without exposure to hazardous chemicals. High quality circuit boards can be produced using either process. In the case of PCB milling, the quality of a circuit board is chiefly determined by the system's true, or weighted, milling accuracy and control as well as the condition (sharpness, temper) of the milling bits and their respective feed/rotational speeds. By contrast, in the chemical etch process, the quality of a circuit board depends on the accuracy and/or quality of the mask used to protect the copper from the chemicals and the state of the etching chemicals.

Material, Machine and Tools used in PCB Machining (Milling)

Material:

FR1-Phenolic paper is a material often used to make printed circuit board substrates (the flat board to which the components and traces are attached). It is a very tough board made of wood fibre and phenolic polymers. It is most commonly brown in colour, and is a fibre reinforced plastic. These PCB materials are known as FR-1 and FR-2.

Epoxy Film Electrical Tape with Thermosetting Acrylic Adhesive

- Electronic componets

Machine:

The mechanics behind a PCB milling machine are fairly straightforward and have their roots in CNC milling technology. A PCB milling system is similar to a miniature and highly accurate NC milling table. For machine control, positioning information and machine control commands are sent from the controlling software via a serial port or parallel port connection to the milling machine's on-board controller. The controller is then responsible for driving and monitoring the various positioning components which move the milling head and gantry and control the spindle speed.

e.g. Roland SRM-20 is a precision three-axis machining, including PCBs down to 0.25 mm feature size, and machineable wax to make tooling for molding and casting

Tools:

PCBs can be machined with conventional endmills. Flat end mills have many advantages. Their straight profiles and consistent diameters ensure that milled traces are of a consistent width, even if the FR-1 PCB blank used is not perfectly flat. Flat end mills are also great at clearing large areas of material, and large flat end mills can remove material very quickly.

Generate the tool path for tracing and cutting:

First, We downloaded the trace and cut layout PNG files for FabISP programmer.

Then, we opened mods project

Selected the trace PNG file first as shown in the picture below. We then set-up Zero for X, Y and Z absolute coordinate system.

Clicked 'WebSocket Print delete' and ''WebSocket device delete' buttons. We then added 'Save file'

We then connected output file of machine absolute coordinate to the 'save file button'.

Next, we clicked 'mill trace (1/64)' and changed 'offset number=-1'. Then 'offset number'= -1 got automatically reflected under 'mill raster 2D'. This -1 offset was given to remove all the material from the substrate except traces and paddings. Cutting speed for tracing was 4 mm/s.

We then clicked 'calculate' button under 'mill raster 2D'. Then tool path for tracing was generated and got downloaded automatically as shown in the picture below. We will use this tool path in VPanel controller to be sent to the milling machine to start tracing.

Lastly, after the XYZ coordinates on machine are set to Zero as mentioned in earlier steps, we browsed the toolpath file in VPanel controller through cut button.

We then deleted any previous paths and added new path. Selecting the newly added toolpath, I clicked on 'output' button to start the tracing operation inside the machine.

For cutting the board, once tracing was done, we moved the X and Y axis to its origin point, by clicking on the 'XY' button under 'to origin'. Once the X and Y axis are positioned, we inserted the 1/32 endmill into the collet the same way we did it with 1/64 endmill.

Finally, following are the pictures of our final board we cut to characterize the design rules for our in-house PCB production process.

Group Assignment Link

I milled the PCB with SRM-20 and programmed it to make an in-circuit programmer.

I have used Brian example for refernce.

Files from Brian:-

The files "Traces" and "Outline Cut" in png format with a resolution of 1000 dpi were downloaded from Brian

Fab modules:-

To edit the parameters and format of the png file, I utilised modifications CE. The following instructions were added:

Step1: Open modsproject link http://modsproject.org/.

Step2: Open Menu And Click Programs.

Step3: Then Select Open Programs.

Step4: and Select PCB Absolute.

Step5: Open Roland Monofab PCB System.

Step6: Click in-circuit programmer http://academy.cba.mit.edu/classes/electronics_production/index.html

Step7: Click Brian.

Step8: And Download traces file and outline cutout file.

Step9: Then Select Png File format And Upload traces File.

Step10: Select mill traces (1/64) and not change diameter.

Step11: change diameter x,y,z.

Step12: Right diameter x-0, y-0, z-0.

Step13: Then Delete Inputs File Box And Upload Save File Box.

Step14: Click modules.

Step15: Click Open mmodule.

Step16: Select File.

Step17: File Save Box Upload, And connect Output and Input.

Step18: Click calculate and not change diameter.

Step22: and then auto Download .rml file.

The image below shows the result tool path for traces file

Download .rml file

Traces File

Outline Cut File

The act of removing copper from a sheet of printed circuit board material to reconstruct pads, signal lines, and structures according to patterns from a digital circuit board plan known as a layout file is known as printed circuit board milling.

We have a Roland Modela SRM-20 in our lab. Brian's design is what I'm using for my FabISP.

SRM-20 machine Reference link https://www.rolanddga.com/products/3d/srm-20-small-milling-machine

SRM-20 machine Photo Reference Link.

Specifications and system requirements of SRM-20

Upload File Vpanel:

Step1: Download VPanel for SRM-20 VPanel Reference link

Step2 :VPanel Homepage.

Explain VPanel

Upload Cut File VPanel

Step1: Delete All File.

Step2: Then Click Add File.

Step3: Open Your File.

Step4: And Then Click Output.

This Tool use In Machin

Pre-prepartion for milling

Step1: Take copper coated board as you requied.

Step2: Take a level surfaced board(Don’t Use bended board).

Step3: Check Level of milling machine.

Step4: Now stick double side tape on bottom of board.

Step5: Set “Z” axis manual became zero.

Material Thickness Check

Use Bit

Photo Reference Link Link

1/64

Follows are processed with 1/64 bit since it is more slender and allows for the processing of small portions.

Cutting edges on the nose and sides of end mills remove material from a piece of stock's surface. They're used to make items with complex forms and features like slots, pockets, and grooves on CNC or manual milling machines.

1/32

use a 1/32” flat end mill to mill holes, and outlines.

sacrificial layer

A sacrificial layer is used to build complicated components, such as movable parts. For example, a suspended cantilever can be built by depositing and structuring a sacrificial layer, which is then selectively removed at the locations where the future beams must be attached to the substrate (i.e. the anchor points). A structural layer is then deposited on top of the polymer and structured to define the beams. Finally, the sacrificial layer is removed to release the beams, using a selective etch process that does not damage the structural layer.

Reference Link

Z-axis Set

Finally Cut My Design.

What is Solder?

Solder is a word that can be used in two ways. The term solder refers to an alloy (a substance made up of two or more metals) that is often sold in spools or tubes as a long, thin wire. Solder, as a verb, refers to the process of joining two pieces of metal in a solder junction.

Filler:

When the wire came into touch with the soldering iron, it melted and dried very instantly when it was placed on the PCB board. This conductive substance was used to secure the board and its components.

Flux:

The soldering process was aided by the chemical. I experimented with both liquid and solid flux.

Soldering Iron Rod:

Melt the filler with the rod at 330°C and insert it between the components and the board.When not in use, the rod was stored in the stand.

Hot Air Gun:

The filler was instantly melted by the extremely hot air. During desoldering, the equipment came in handy.

Exhaust Fan:

Filler gases were released during the melting process, and the fan drew them away.

Desolder Pump:

The filler was sucked out by the pump, which aided in the removal of the components from the board.

Twisers:

The twisers were really helpful in picking and placing the components.

Magnifying Glass:

The parts are labelled, however the printed words are very small. To read the specifications on the components, I used a magnifying lens.

Light lamp:

The light assisted in locating small circuit components and soldering gaps.

What is the FabISP?

An in-framework AVR microcontroller developer called the FabISP is created specifically for usage with FabLabs. It enables the programming of microcontrollers on various sheets.

Electronics Production is tasked with processing the board, packing it with components, and programming it. These software engineers will be used by us to programme different sheets that we develop throughout the course of the semester.

As best as I can understand, several individuals have revised the Basic FabISP numerous times throughout the years. The integrated circuits that power the ATtiny 44 and ATtiny 45 ISPs bear such names. I made use of ATtiny 45, made by BRIAN

Components of circuit:

1x ATtiny45 or ATtiny85

2x 1kΩ resistors

2x 499Ω resistors

2x 49Ω resistors

2x 3.3v zener diodes

1x red LED

1x green LED

1x 100nF capacitor

1x 2x3 pin header

Soldering Photo

Checked Circuit

I used a multimeter to test the connections between all of the components. Using the cathode and anode of a multimeter, verify connections at the ends of diodes, capacitors, LEDs, resistors, and integrated circuits (I.C).

Finally Soldering Complaint

I have used GNU AVR Toolchain for Windows 10 software.

Step1: Downloaded the Atmel Toolchain from Atmel’s site and run the installer.Extracted the files in C:\Program Files.

Installed GNU Make:

Gnu Make was downloaded and installed in the default location.

Updated Path:

Opened the Path setting in the local system:Control Home Panel>System> Advanced system settings> Environment Variables>Path

Edited Path to add the below 3 values:

C:\Program Files\avr8-gnu-toolchain\bin

C:\Program Files (x86)\GnuWin32\bin

C:\Program Files\avrdude

Step1: Open File Download Link http://fab.cba.mit.edu/classes/863.16/doc/projects/ftsmin/index.html

Step2: Click firmware source code And Download.

Step3: Open Download Folder.

Step4: and Extract all firmware source code.

Step5: Click firmware source code and Open this folder.

Step6: And press right click and Open git bash.

Step7: Open git bash Homepage

$ make
								
											
								

								
										$ make flash
								
											
								

								
										$ make fuses
								
										
								

								
										$ make rstdisbl
								
										
								

								
										Code Upload.
								

										
								

								
										Download Source Code:
										Source Code zip File

break 1/64 end mill

I broke the 1/64 bit because I kept the 1/64 bit out more.

Group Assignment