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A printed circuit board (PCB) is a rigid board with electrical circuits known as traces. The present-day PCBs were first designed and produced around the 1930s however, in 1936 an Austrian inventor, Eisler Paul made the first printed circuit board to operate his radio system. This kind of printed circuit board (Rigid printed circuit board) can neither bend nor be forced out of its shape and is made with copper tracks. Alternatives of PCB are a wire wrap and point to pint construction. The board has lines and pads connecting different points. They were made through laborious point-to-point wiring which led to frequent wire failures and short circuits hence a significant advancing wire wrapping was made. A metal known as solder makes electrical connections between the PCB surface and electronic components since it’s a metal hence strong is composed of silkscreen, solder mask, copper, and substrate (FR4)
Silkscreen
- It’s applied on top of the solder mask layer and adds letters, numbers, and symbols to the PCB to allow easier assembly and ease human understanding of the board.
- The labels indicate each function of each pin, mostly the silkscreen is white though any ink color can be used.
Solder mask
- This is the layer on top of copper foil and gives the PCB its green color and is overlaid onto the copper layer to insulate the copper traces from coming into contact accidentally with other metal, solder, or conductive bits.
Copper –
- it’s laminated to the board with heat and adhesive. Double-sided PCBs copper has been applied on both sides of the substrates.
- the thickness of the copper is depended on the specified weight some PCBs that can handle very high power may use 2- or 3-ounce copper.
- They act in the same way as wire
Substrate (FR4)
- Its usual fiberglass and most historically and most common designator for this fiberglass is “FR4 which gives the PCB rigidity and thickness
- The designator for this fiberglass is “FR4”
Types of PCBs
- Single-sided PCB is the simplest and the lowest cost PCB and has been in existence since the 1950s and is only one single layer of the base substrate (fiberglass)and one single conductive layer which is made from copper.
- Double-sided PCB is a little and complex than single-sided PCBs as they have one single layer of the base substrate conductive layer on both sides of the board. The holes of electronic components have to be plated through for conductivity of both sides due to the double layers forming the circuit
- Multilayer PCB is a printed board with more than 2 layers and it must have 3 or more conductive layers whereby all these layers should be interconnected with copper-plated holes.
- High density interconnects (HDI) PCB –They take advantage of precision basing manufacturing technology to pack as much functionality small space through the use of many conductive layers.
Components of PCB
The transistor
- is a semiconductor device whose aim is to amplify electrical signals and power and are active components of integrated circuits.
- Transistors were invented in 1947-1948 by physicists John Bardeen, Walter H. Brattain, and William B. Shockley.
- It mainly works as both amplifier and a switch.
- The transistor works as an amplifier in the sense that it takes in a tiny electric current at a particular end and produces a bigger electric current through the output current by first boosting the current.
- Transistors are made from silicon which doesn’t conduct electricity as it’s a semiconductor.
Resistor
Its purpose is to monitor the flow of electrical current in the circuits which are mostly made from copper materials or carbon whose purpose is to make it hard for the electrical charges to flow through the circuit.
- The commonly used type of resistor is a carbon resistor which is suitable for lower-powered circuits.
- The resistors are used in protecting against voltage spikes as they ensure components receive proper voltage.
Inductor
It is also known as the coil and is a two-terminal electrical component for storing energy in magnetic when electric current flows through it.
- They are used as energy storage devices in switched-mode power devices to produce DC.it supplies energy to the circuits to maintain energy flow during the off-switching period.
- The capacity of inductors is controlled by the number of coils as the more the number of coils the more the inductance.
- The cross-sectional area of the coil whereby the more the area the more the inductance.
Capacitator
This is a device for storing electrical energy which consists of two conductors proximate and insulated from each other.
- They are mostly used in digital circuits so to store information in large computer memory is not lost during temporary power loss.
- Capacitator stores energy in the terminals hence when activated releases energy in a fraction of a second.
Light-emitting diode (LED)
This is a semiconductor light source emitting lite when current flows through it they convert electrical energy directly into the light and operates on a basic principle that electrons and holes in semiconductors recombine to emit protons under forwarding bias.
- It is applied in most cases due to its compact size, low consumption of energy, and extended lifetime.
- LEDs are used for TV backlighting it uses LEDs to give an efficient power reduction, using LEDs behind the display provides a better contrast hence it has resulted in them replacing CFLs and LCDs in the case of Tv backlighting.
- It is also used in the dimming of lights hence reduction of energy consumption
Potentiometer
This is a three-terminal resistor with a sliding contact forming an adjustable divider it is mostly used to measure the displacement in any direction it operates on a basic principle that the potential dropped across a segment of a wire of uniform cross-section carrying constant current is directly proportional to its length.
Electrical fuse
This is an electrical safety device operating to provide overcurrent protection of an electrical circuit it has a metal strip (wire) that melts when excess current flows through it, therefore, interrupting the current by stopping the flow of current. Fuses are of many types which include thermal fuses, mechanical fuses, blade fuses, expulsion fuses, and varistors.
- The fuse plays a very vital role as it’s the cheapest form of maintenance. Its operations are automated and require less time compared to circuit breakers.
- Despise the fuse playing a very vital role it has several cons such as being time-consuming, especially when replacing a worn-out fuse after its operation.
How to design a layout of PCB
Don’t rush to use the auto-router
Most printed circuit board software designs have an autoroute feature that automatically does the routing for you unfortunately auto-routing is not perfect as routing for oneself. There are a few scenarios suitable for auto-routing which include:
- Upon placement of all your components, one can use the autoroute tool for checking one’s completion rating. If the rating is anything below 85%, then one needs to adjust component placement.
- if you don’t know how to begin routing or you get stuck at some point, auto-routing can be used as an inspiration source.
- In some cases, bottlenecks and other critical connection points can fall through the cracks when routing hence one can easily identify these through the autoroute feature.
Auto routing is not recommended as it ignores symmetry hence manual routing is advocated due to accuracy and reliability.
Use sufficient trace width
Since copper traces faces resistance from electrical current hence voltage drop which results in power resistance hence the generation of heat.
- To avoid excess heat in your circuit, one should reduce the amount of heat should increase the width of the traces.
- The width of the trace is calculated through a width calculator as far as the width is in line with your manufacturer’s stipulations, one can use a larger trace width than the ones specified by the calculator.
Know the manufacturer’s specifications
Preferred manufacturer’s specifications are very crucial before designing a PCB one should familiarize with the specifications such as trace width, number of board layers, and trace spacing beforehand to avoid the printed circuit board not being functional. This avoids the frustration of having to reroute the whole design at the final stages and working on it for extra hours.
Component planning
This is a success key factor as for one to place properly the components making up a circuit has to understand their characteristics as their components which should be placed close to others. Propper placement also enhances convenience. it’s advisable to place heat-sensitive electrolytic capacitors away from heat-generating diodes, inductors, and resistors.
Rules for designing
- Be mindful of components with more pins since they will require more space. It’s a joint mistake to pack components together, thereafter realize that there is no space left for routing traces.
- Take respectively component’s function and its relation to other workings into consideration before placement.
- Ensure that the components are placed in the same orientation since components usually have standard pin numbering to help with this.
Proper trace angles (45⁰)
45° is the sweet spot since 90° angles at the corners can be entrenched narrower than they should be. Trance angles make it easier to weave between pads and still produce a beautiful design.
Create a ground plane
The shared ground is aimed at gauging voltage to give all your traces a single orientation, particularly in analog circuits.
Designing a circuit board
Schematic capture
The schematics show things such as components that are used in your circuit board design, how components are connected, and the relationships between groups of components in various schematics.
- Not only is circuit interconnectivity easier to describe and control, but adapting a schematic to a board layout is much easier than designing directly on the board.
- However, one can design own schematic symbols and form a footprint.
Create a Blank PCB layout
After creating a schematic one should use a schematic capture tool to import components into a blank PCB layout.
- If PCBs shapes have already been determined one can set them.
- Schematic data is made obtainable for the PcbDoc by compiling the SchDoc the process verification of design and generation of several project documents that allows one to inspect and correct design before transfer to the PcbDoc
Synchronize Schematics to Your PCB
All the tools in Altium Designer work in a united strategy environment, where the schematic, printed circuit board layout, and BOM are interconnected and can be accessed instantaneously. Other programs force you to manually accumulate your schematic facts, but Altium Designer will do this for you automatically while you create your design.
Designing Your PCB Stackup
Upon transferring one schematic information to the PcbDoc the component footprints as shown in addition to the board outline specified.
- Once you are working on a high-frequency design you can use the built-in impedance profiler to ensure resistance regulator in your board.
- Routing style should be decided before you start calculating impedances despite using differential pair routing design the impedance solver in the layer enables differential pair of the solution not forgetting single-ended to determine both requirements while routing.
Defining PCB Plan Rules and DFM Requirements
There are various rules of PCB design hence there is no need to use all these available rules hence you can select and deselect various rules by clicking on the rules from the list in the PCB Rules and constraints editor whereby categories are divided into:
- Approvals between objects in the PCB design, such as between traces and pads
- High speed and signal integrity limits such as overshoot
- Board fabrication limits and clearances such as edge clearance
One can create ne design rules by following the rules of Altium designers design wizard which treats your custom design rules just like the built-in design rules. Upon placement of components, drill holes, and traces designer will automatically check out the layout against these rules and thereafter flag you visually upon notice of violation.
Place Components
Altium Designer provides a great deal of flexibility which allows quick placement of components on your circuit board the items can be arranged manually or automatically these options can be used jointly to take advantage of the speed of auto-placement and ensure that the board is laid according to good component placement rules.
Insert Drill Holes
Drill holes are placed before rioting of traces. If the design is complicated there is a need to modify at least some of the via locations during trace routing, the preferences should be guided by the design for manufacturing (DFM) specifications of your PCB manufacturer.
Route Traces
Upon placement of component and mechanical elements, one is now in a position to route the traces. When routing aboard, one should arise with a strategy to finish significant routes first thereafter fill gaps with the remaining connections ss required. Among the important routes include power nets, impedance-controlled nets, and any noise-sensitive nets such as low-level analog signals
Add Labels and Identifiers
Addition of labels, identifiers, markings, or imagery to the board upon verification of circuit board. its good to also include reference designators for components as it assists in PCB assembly. The issue of polarity also should be kept into consideration for indication. The elements should be placed at the top overlay or bottom overlay layers in the PCB layout
Generate Design Output Files
This is done through a design rule check (DRC)for verification of circuit board layout which is done automatically by Altium Designer once the board has passed the final DRC there is a need to generate design files for the manufacturer to be clear on what to use. Using a systematic approthathich ensures that all aspects of your design are accounted for inherently whereby during the process there is minimal need to retrace the steps
Uses of PCB
- PCBs were used as insulating fluid in capacitors and transformers and also as hydraulic and lubricating fluids.
- They are also used in industrial electronics such as power equipment, Industrial Equipment, and control systems.
- They are mostly used in electronics and communication devices such as mobile, recording devices, entertainment systems, and computer electronics.
- In research and development, PCBs are used in testing machines, control boards, and scanning machines among others.
- In aerospace and defense, PCBs are used in monitoring types of equipment, security devices armored car satellites among others.
Mistakes to avoid in PCB design
The printed circuit board is the heart and soul of every electronic circuit it is the basic in the control of the cost of manufacturing costs can increase due to the mistakes made in the design phase some of the mistakes to be avoided include
Wrong trace geometry
The traces are responsible for the transmission of electrical signals between colorful factors of the circuit putting into consideration the speed, intensity, and frequency of the signal
Inadequate layout
Due to increased demand for small PCBs, the designers are forced to use components with smaller footprints and reduction of the distance between components. to ensure the desired functionality it’s important to adopt a layout suiting needs of particular circuits
Wrong position of decoupling capacitors
The capacitors are required on the PCB to supply power supply lines for a stable power supply free from transients to all the board components
Landing pattern errors
Landing pattern is the size of pads for each component which should have an area larger than the corresponding footprint even the slightest error in the pad-to-pad spacing can result in fatal soldering during the manufacturing process hence resulting in misalignments between components and PCB.
Over-reliance on the automatic routing
Automatic routing occupies a greater than desirable area of the PCB hence creating larger holes than those that could be achieved through manual routing.
Incorrect antenna layout
If PCB includes antennas for wireless communication should be very careful not to make layout mistakes hence impedance is adapted between the transceiver and the antenna.
Insufficient revision of the project
Periodic reviews of a project allow one to verify the conformity with the requirements of the project. this allows designers to avoid on advance errors that may fail the PCB
Advantages of the printed circuit board
PCBs are easy for diagnosing errors and repairs.
Compact size and saving of wire
PCBs have the capability of holding a large number of components which may be very small in size and therefore impossible to connect through wiring. PCBs help not only in connecting all the components through the copper tracks instead of wires hence making them intact.
Saves time by use of printed circuit board not only takes lesser time but also very convenient.
Ease in reparability in cases where PCB stops functioning correctly the problem is easily identified and repaired as all components are labeled using silkscreen.
It reduces the chances of short circuits the connections are made all through copper tracks hence a lesser chance of losing the connection that can result in short-circuiting the board.
There is less electronic noise is released in form of heat or radiation since the lengths are minimized since there is less emission of EM waves and radiation.
Lower cost since PCBs are mostly computerized systems hence saving layout of the schematic design.
Reliability PCBs ate very reliable as they are strictly checked for any errors as the process is fully automated.
Disadvantages of the printed circuit board
Damage is difficult to repair
Upon damage of PCBs, it’s nearly impossible to repair when damaged since there is only a single plate upon which all the parts are attached. It’s easier to replace a PCB rather than to repair it.
Not all machines can use them
A PCB should be designed in a way that should be compatible with the device since it is not automatic that the PCB will be compatible with the machine. They are also not for every situation or every type of device.
Etching is a great process for the board and is not eco-friendly hence not good for the planet as it uses chemicals hence producing negative effects on the environment.
In case one wants to modify the board after it is printed one is not able to and has to create a new board from the scratch.
It also uses a complex assembly process.
In the case of double-sided printed circuit boards are not ideal for conducting heavy current since the copper wires get heated up.
CONCLUSION
With the increased use of printed circuit boards, there is an increased need to familiarize ourselves with the basics of the PCBs as they are inclusive of various components such as resistors among others. In the design of PCB, the various stated factors should be kept into consideration for proper functionality. The impacts of the formation of PCBs should also be taken into consideration to avoid negative impacts.
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