Printed Circuit Boards Designing Process

Printed Circuit Board
Printed Circuit Board

The most vital element in electronic circuits and equipments is the Printed Circuit Board (PCB). It is also possible to build an electronic circuit with bread boards and zero boards, but the method is a low level and less efficient one wherein the designing circuit is prone to damage and the designing involves a complex process of placing the components of the circuit.

However, the invention of the PCB that supports physical electronic components and their wiring through the surface-mounted copper tracks is really remarkable. We can observe at least one PCB in any electronic gadgets ranging from cell phones to computers.

 

What is a Printed Circuit Board?

Electronic circuits in engineering and industry are normally manufactured by using printed circuit boards (PCBs). These boards are made up of special materials that do not conduct electricity such as fiber and glass. The circuits are designed on the boards with copper tracks instead of wires for the conduction of electricity between the electronic components.

The electronic components are fixed in their respective positions by drilling holes on the board, placing the components and then soldering them in appropriate positions so that the copper tracks and components together form a circuit. The printed circuit boards used in all electronic products such as automotives, wireless devices, Robotic applications, etc., offer quick functioning, access, control, monitoring and precise and exact results when compared to other wiring methods based devices The below figure shows how the circuit is arranged on a PCB with copper layer.

555 Timer PCB Circuit
555 Timer PCB Circuit

 

555 Timer Printed Circuit Board
555 Timer Printed Circuit Board

Designing Process of a PCB

Depend on printed circuit board manufacturer, there are numerous ways available for designing PCBs. This circuit board design can be manufactured as bulk using several machines in PCB fabrication industries including drilling, punching, plating and final fabrication processes that are performed through highly automated machines. Laser drilling with CNC machines, automatic plating machines, strip etching machines, and use of optical inspection equipments, flying probe testers for electrical testing of printed circuit board process result in high-quality PCBs (with a greater production yield).

For a reader to understand this concept at the basic level of printed circuit board design, the following step- by-step procedures of designing a PCB board at various levels will help and guide diligently.

Step1: Design the PCB circuit with a Software

Draw the schematic circuit diagram with the PCB layout software such as CAD software, Eagle and Multisim software. This type of PCB design software contains a library of components that can be used to build the circuit. It is also possible to change the circuit design’s position and then to modify according to your convenience and requirement. Here we have selected Eagle software to design the circuit and its procedure is as follows:

  • Open the Eagle circuit board design software.
  • A window with a menu bar appears.
  • Click on the file menu.
  • Select ‘new design’ from the drop-down menu.
  • Click on the library menu.
  • Select ‘pick devices/symbol’ from the drop-down menu.
  • Select a relevant comment by double clicking on it, so that the component appears on the window.
  • Add all the components and draw the circuit with proper connections as shown in the figure.

PCB cIircuit with a software

  • Enter the rating of each component according to the requirement.
  • Go to Command Toolbar and click Text editor varriages, click on the Varriages, and then close the window.
  • Next, a black screen appears which is of the layout or the film diagram of the circuit as shown in the below figure, and save this as an image format.
Printed circuit Layout
Printed circuit Layout

Step2: Film generation

The film is generated from the finalized circuit board diagram of the PCB layout software which is send to the manufacturing unit where the negative image or mask is printed out on a plastic sheet.

Film of Circuit
Film of Circuit

Step3: Select Raw Material

The bulk of the printed circuit board is made with an unbreakable glass or fiberglass having copper foil bonded unto one or both the sides of the board. Thus, the PCBs made from unbreakable paper phenolic with a bonded copper foil are less expensive and are often used in household electrical devices.
Mostly 0.059 industry standard thick, copper clad laminate, either single or double sided board is required. Panels may be sheared to contain May boards of different sizes.

Copper clad laminated boards
Copper clad laminated boards

Step4: Preparing Drill Holes

Machines and carbide drills are used to put holes on the printed circuit board. There are two types of machines available to drill the PCBs; they include hand machines and CNC machines. The hand machines require human intervention or effort to drill the holes, whereas CNC machines are computer-based machines that work-based on the machine timetables or programs that run both automatic as well as manually. The drilled pattern is stored in the computer like drill bit sizes, number of holes per panel, drilled stack, drilled time per load, etc. The PCB boards are placed into the CNC machine and the holes are drilled according to the determined pattern to place printed circuit board components.

Prepairing Drill Holes
Prepairing Drill Holes

Step5: Apply Image

The printed circuit layout can be printed in different ways on PCBs like manual pen, dry transfers, pen plotters and printers. The laser printers are a better way to print the layouts on printed circuit boards. The following steps are used to print the PCB layout through a laser printer:

Apply Image
Apply Image
  1. Take a clean and neat copper paper and place it on the laser printer.
  2. Next, store the designed layout film in the computer.
  3. A laser printer prints the designed circuit layout on a copper paper whenever it gets a print command from the computer.

Step6: Stripping and Etching

This process involves removing the unwired copper on the PCBs by using different types of chemicals like ferric chloride, ammonium per-sulphate, etc. Make the solvent by mixing 1% of sodium hydroxide and 10 grams of sodium hydroxide pellets to one liter of water and mix it until everything is dissolved. Next, the PCB is put on a chemical bowl and cleaned up with a brush. during this process, if the PCB is still greasy, due to applied sunflower or seed oil, the developing process may take about 1 minute.

Stripping and Etching
Stripping and Etching

Step7: Testing

After finishing the manufacturing process of the Printed Circuit Board, the Board undergoes a testing process to check whether the PCB is working properly. Nowadays many automatic testing equipments are available for the high volume testing of the PCBs.

The two different types of testing equipment available today that test your circuit boards include ATG test machines that are flying probe, fixtureless testers and in addition to a universal grid testing capability as well.

Testing
Testing

This is all about the PCB designing process with relevant images. Hope that you might have got some basic ideas of this topic by following it from the step one and then covering the step-by-step designing process. Furthermore, for any doubts on this topic or any technical assistance in the field of electronics, you can contact us by commenting below.

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